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android / toolchain / jdk / jdk21 / HEAD / . / src / hotspot / share / opto / loopnode.cpp
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/*
* Copyright (c) 1998, 2023, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#include "precompiled.hpp"
#include "ci/ciMethodData.hpp"
#include "compiler/compileLog.hpp"
#include "gc/shared/barrierSet.hpp"
#include "gc/shared/c2/barrierSetC2.hpp"
#include "libadt/vectset.hpp"
#include "memory/allocation.inline.hpp"
#include "memory/resourceArea.hpp"
#include "opto/addnode.hpp"
#include "opto/arraycopynode.hpp"
#include "opto/callnode.hpp"
#include "opto/castnode.hpp"
#include "opto/connode.hpp"
#include "opto/convertnode.hpp"
#include "opto/divnode.hpp"
#include "opto/idealGraphPrinter.hpp"
#include "opto/loopnode.hpp"
#include "opto/movenode.hpp"
#include "opto/mulnode.hpp"
#include "opto/opaquenode.hpp"
#include "opto/rootnode.hpp"
#include "opto/runtime.hpp"
#include "opto/superword.hpp"
#include "runtime/sharedRuntime.hpp"
#include "utilities/powerOfTwo.hpp"
//=============================================================================
//--------------------------is_cloop_ind_var-----------------------------------
// Determine if a node is a counted loop induction variable.
// NOTE: The method is declared in "node.hpp".
bool Node::is_cloop_ind_var() const {
return (is_Phi() &&
as_Phi()->region()->is_CountedLoop() &&
as_Phi()->region()->as_CountedLoop()->phi() == this);
}
//=============================================================================
//------------------------------dump_spec--------------------------------------
// Dump special per-node info
#ifndef PRODUCT
void LoopNode::dump_spec(outputStream *st) const {
RegionNode::dump_spec(st);
if (is_inner_loop()) st->print( "inner " );
if (is_partial_peel_loop()) st->print( "partial_peel " );
if (partial_peel_has_failed()) st->print( "partial_peel_failed " );
}
#endif
//------------------------------is_valid_counted_loop-------------------------
bool LoopNode::is_valid_counted_loop(BasicType bt) const {
if (is_BaseCountedLoop() && as_BaseCountedLoop()->bt() == bt) {
BaseCountedLoopNode* l = as_BaseCountedLoop();
BaseCountedLoopEndNode* le = l->loopexit_or_null();
if (le != nullptr &&
le->proj_out_or_null(1 /* true */) == l->in(LoopNode::LoopBackControl)) {
Node* phi = l->phi();
Node* exit = le->proj_out_or_null(0 /* false */);
if (exit != nullptr && exit->Opcode() == Op_IfFalse &&
phi != nullptr && phi->is_Phi() &&
phi->in(LoopNode::LoopBackControl) == l->incr() &&
le->loopnode() == l && le->stride_is_con()) {
return true;
}
}
}
return false;
}
//------------------------------get_early_ctrl---------------------------------
// Compute earliest legal control
Node *PhaseIdealLoop::get_early_ctrl( Node *n ) {
assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" );
uint i;
Node *early;
if (n->in(0) && !n->is_expensive()) {
early = n->in(0);
if (!early->is_CFG()) // Might be a non-CFG multi-def
early = get_ctrl(early); // So treat input as a straight data input
i = 1;
} else {
early = get_ctrl(n->in(1));
i = 2;
}
uint e_d = dom_depth(early);
assert( early, "" );
for (; i < n->req(); i++) {
Node *cin = get_ctrl(n->in(i));
assert( cin, "" );
// Keep deepest dominator depth
uint c_d = dom_depth(cin);
if (c_d > e_d) { // Deeper guy?
early = cin; // Keep deepest found so far
e_d = c_d;
} else if (c_d == e_d && // Same depth?
early != cin) { // If not equal, must use slower algorithm
// If same depth but not equal, one _must_ dominate the other
// and we want the deeper (i.e., dominated) guy.
Node *n1 = early;
Node *n2 = cin;
while (1) {
n1 = idom(n1); // Walk up until break cycle
n2 = idom(n2);
if (n1 == cin || // Walked early up to cin
dom_depth(n2) < c_d)
break; // early is deeper; keep him
if (n2 == early || // Walked cin up to early
dom_depth(n1) < c_d) {
early = cin; // cin is deeper; keep him
break;
}
}
e_d = dom_depth(early); // Reset depth register cache
}
}
// Return earliest legal location
assert(early == find_non_split_ctrl(early), "unexpected early control");
if (n->is_expensive() && !_verify_only && !_verify_me) {
assert(n->in(0), "should have control input");
early = get_early_ctrl_for_expensive(n, early);
}
return early;
}
//------------------------------get_early_ctrl_for_expensive---------------------------------
// Move node up the dominator tree as high as legal while still beneficial
Node *PhaseIdealLoop::get_early_ctrl_for_expensive(Node *n, Node* earliest) {
assert(n->in(0) && n->is_expensive(), "expensive node with control input here");
assert(OptimizeExpensiveOps, "optimization off?");
Node* ctl = n->in(0);
assert(ctl->is_CFG(), "expensive input 0 must be cfg");
uint min_dom_depth = dom_depth(earliest);
#ifdef ASSERT
if (!is_dominator(ctl, earliest) && !is_dominator(earliest, ctl)) {
dump_bad_graph("Bad graph detected in get_early_ctrl_for_expensive", n, earliest, ctl);
assert(false, "Bad graph detected in get_early_ctrl_for_expensive");
}
#endif
if (dom_depth(ctl) < min_dom_depth) {
return earliest;
}
while (1) {
Node *next = ctl;
// Moving the node out of a loop on the projection of a If
// confuses loop predication. So once we hit a Loop in a If branch
// that doesn't branch to an UNC, we stop. The code that process
// expensive nodes will notice the loop and skip over it to try to
// move the node further up.
if (ctl->is_CountedLoop() && ctl->in(1) != nullptr && ctl->in(1)->in(0) != nullptr && ctl->in(1)->in(0)->is_If()) {
if (!ctl->in(1)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
break;
}
next = idom(ctl->in(1)->in(0));
} else if (ctl->is_Proj()) {
// We only move it up along a projection if the projection is
// the single control projection for its parent: same code path,
// if it's a If with UNC or fallthrough of a call.
Node* parent_ctl = ctl->in(0);
if (parent_ctl == nullptr) {
break;
} else if (parent_ctl->is_CountedLoopEnd() && parent_ctl->as_CountedLoopEnd()->loopnode() != nullptr) {
next = parent_ctl->as_CountedLoopEnd()->loopnode()->init_control();
} else if (parent_ctl->is_If()) {
if (!ctl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
break;
}
assert(idom(ctl) == parent_ctl, "strange");
next = idom(parent_ctl);
} else if (ctl->is_CatchProj()) {
if (ctl->as_Proj()->_con != CatchProjNode::fall_through_index) {
break;
}
assert(parent_ctl->in(0)->in(0)->is_Call(), "strange graph");
next = parent_ctl->in(0)->in(0)->in(0);
} else {
// Check if parent control has a single projection (this
// control is the only possible successor of the parent
// control). If so, we can try to move the node above the
// parent control.
int nb_ctl_proj = 0;
for (DUIterator_Fast imax, i = parent_ctl->fast_outs(imax); i < imax; i++) {
Node *p = parent_ctl->fast_out(i);
if (p->is_Proj() && p->is_CFG()) {
nb_ctl_proj++;
if (nb_ctl_proj > 1) {
break;
}
}
}
if (nb_ctl_proj > 1) {
break;
}
assert(parent_ctl->is_Start() || parent_ctl->is_MemBar() || parent_ctl->is_Call() ||
BarrierSet::barrier_set()->barrier_set_c2()->is_gc_barrier_node(parent_ctl), "unexpected node");
assert(idom(ctl) == parent_ctl, "strange");
next = idom(parent_ctl);
}
} else {
next = idom(ctl);
}
if (next->is_Root() || next->is_Start() || dom_depth(next) < min_dom_depth) {
break;
}
ctl = next;
}
if (ctl != n->in(0)) {
_igvn.replace_input_of(n, 0, ctl);
_igvn.hash_insert(n);
}
return ctl;
}
//------------------------------set_early_ctrl---------------------------------
// Set earliest legal control
void PhaseIdealLoop::set_early_ctrl(Node* n, bool update_body) {
Node *early = get_early_ctrl(n);
// Record earliest legal location
set_ctrl(n, early);
IdealLoopTree *loop = get_loop(early);
if (update_body && loop->_child == nullptr) {
loop->_body.push(n);
}
}
//------------------------------set_subtree_ctrl-------------------------------
// set missing _ctrl entries on new nodes
void PhaseIdealLoop::set_subtree_ctrl(Node* n, bool update_body) {
// Already set? Get out.
if (_loop_or_ctrl[n->_idx]) return;
// Recursively set _loop_or_ctrl array to indicate where the Node goes
uint i;
for (i = 0; i < n->req(); ++i) {
Node *m = n->in(i);
if (m && m != C->root()) {
set_subtree_ctrl(m, update_body);
}
}
// Fixup self
set_early_ctrl(n, update_body);
}
IdealLoopTree* PhaseIdealLoop::insert_outer_loop(IdealLoopTree* loop, LoopNode* outer_l, Node* outer_ift) {
IdealLoopTree* outer_ilt = new IdealLoopTree(this, outer_l, outer_ift);
IdealLoopTree* parent = loop->_parent;
IdealLoopTree* sibling = parent->_child;
if (sibling == loop) {
parent->_child = outer_ilt;
} else {
while (sibling->_next != loop) {
sibling = sibling->_next;
}
sibling->_next = outer_ilt;
}
outer_ilt->_next = loop->_next;
outer_ilt->_parent = parent;
outer_ilt->_child = loop;
outer_ilt->_nest = loop->_nest;
loop->_parent = outer_ilt;
loop->_next = nullptr;
loop->_nest++;
assert(loop->_nest <= SHRT_MAX, "sanity");
return outer_ilt;
}
// Create a skeleton strip mined outer loop: a Loop head before the
// inner strip mined loop, a safepoint and an exit condition guarded
// by an opaque node after the inner strip mined loop with a backedge
// to the loop head. The inner strip mined loop is left as it is. Only
// once loop optimizations are over, do we adjust the inner loop exit
// condition to limit its number of iterations, set the outer loop
// exit condition and add Phis to the outer loop head. Some loop
// optimizations that operate on the inner strip mined loop need to be
// aware of the outer strip mined loop: loop unswitching needs to
// clone the outer loop as well as the inner, unrolling needs to only
// clone the inner loop etc. No optimizations need to change the outer
// strip mined loop as it is only a skeleton.
IdealLoopTree* PhaseIdealLoop::create_outer_strip_mined_loop(BoolNode *test, Node *cmp, Node *init_control,
IdealLoopTree* loop, float cl_prob, float le_fcnt,
Node*& entry_control, Node*& iffalse) {
Node* outer_test = _igvn.intcon(0);
set_ctrl(outer_test, C->root());
Node *orig = iffalse;
iffalse = iffalse->clone();
_igvn.register_new_node_with_optimizer(iffalse);
set_idom(iffalse, idom(orig), dom_depth(orig));
IfNode *outer_le = new OuterStripMinedLoopEndNode(iffalse, outer_test, cl_prob, le_fcnt);
Node *outer_ift = new IfTrueNode (outer_le);
Node* outer_iff = orig;
_igvn.replace_input_of(outer_iff, 0, outer_le);
LoopNode *outer_l = new OuterStripMinedLoopNode(C, init_control, outer_ift);
entry_control = outer_l;
IdealLoopTree* outer_ilt = insert_outer_loop(loop, outer_l, outer_ift);
set_loop(iffalse, outer_ilt);
// When this code runs, loop bodies have not yet been populated.
const bool body_populated = false;
register_control(outer_le, outer_ilt, iffalse, body_populated);
register_control(outer_ift, outer_ilt, outer_le, body_populated);
set_idom(outer_iff, outer_le, dom_depth(outer_le));
_igvn.register_new_node_with_optimizer(outer_l);
set_loop(outer_l, outer_ilt);
set_idom(outer_l, init_control, dom_depth(init_control)+1);
return outer_ilt;
}
void PhaseIdealLoop::insert_loop_limit_check_predicate(ParsePredicateSuccessProj* loop_limit_check_parse_proj,
Node* cmp_limit, Node* bol) {
Node* new_predicate_proj = create_new_if_for_predicate(loop_limit_check_parse_proj, nullptr,
Deoptimization::Reason_loop_limit_check,
Op_If);
Node* iff = new_predicate_proj->in(0);
assert(iff->Opcode() == Op_If, "bad graph shape");
Node* conv = iff->in(1);
assert(conv->Opcode() == Op_Conv2B, "bad graph shape");
Node* opaq = conv->in(1);
assert(opaq->Opcode() == Op_Opaque1, "bad graph shape");
cmp_limit = _igvn.register_new_node_with_optimizer(cmp_limit);
bol = _igvn.register_new_node_with_optimizer(bol);
set_subtree_ctrl(bol, false);
_igvn.replace_input_of(iff, 1, bol);
#ifndef PRODUCT
// report that the loop predication has been actually performed
// for this loop
if (TraceLoopLimitCheck) {
tty->print_cr("Counted Loop Limit Check generated:");
debug_only( bol->dump(2); )
}
#endif
}
Node* PhaseIdealLoop::loop_exit_control(Node* x, IdealLoopTree* loop) {
// Counted loop head must be a good RegionNode with only 3 not null
// control input edges: Self, Entry, LoopBack.
if (x->in(LoopNode::Self) == nullptr || x->req() != 3 || loop->_irreducible) {
return nullptr;
}
Node *init_control = x->in(LoopNode::EntryControl);
Node *back_control = x->in(LoopNode::LoopBackControl);
if (init_control == nullptr || back_control == nullptr) { // Partially dead
return nullptr;
}
// Must also check for TOP when looking for a dead loop
if (init_control->is_top() || back_control->is_top()) {
return nullptr;
}
// Allow funny placement of Safepoint
if (back_control->Opcode() == Op_SafePoint) {
back_control = back_control->in(TypeFunc::Control);
}
// Controlling test for loop
Node *iftrue = back_control;
uint iftrue_op = iftrue->Opcode();
if (iftrue_op != Op_IfTrue &&
iftrue_op != Op_IfFalse) {
// I have a weird back-control. Probably the loop-exit test is in
// the middle of the loop and I am looking at some trailing control-flow
// merge point. To fix this I would have to partially peel the loop.
return nullptr; // Obscure back-control
}
// Get boolean guarding loop-back test
Node *iff = iftrue->in(0);
if (get_loop(iff) != loop || !iff->in(1)->is_Bool()) {
return nullptr;
}
return iftrue;
}
Node* PhaseIdealLoop::loop_exit_test(Node* back_control, IdealLoopTree* loop, Node*& incr, Node*& limit, BoolTest::mask& bt, float& cl_prob) {
Node* iftrue = back_control;
uint iftrue_op = iftrue->Opcode();
Node* iff = iftrue->in(0);
BoolNode* test = iff->in(1)->as_Bool();
bt = test->_test._test;
cl_prob = iff->as_If()->_prob;
if (iftrue_op == Op_IfFalse) {
bt = BoolTest(bt).negate();
cl_prob = 1.0 - cl_prob;
}
// Get backedge compare
Node* cmp = test->in(1);
if (!cmp->is_Cmp()) {
return nullptr;
}
// Find the trip-counter increment & limit. Limit must be loop invariant.
incr = cmp->in(1);
limit = cmp->in(2);
// ---------
// need 'loop()' test to tell if limit is loop invariant
// ---------
if (!is_member(loop, get_ctrl(incr))) { // Swapped trip counter and limit?
Node* tmp = incr; // Then reverse order into the CmpI
incr = limit;
limit = tmp;
bt = BoolTest(bt).commute(); // And commute the exit test
}
if (is_member(loop, get_ctrl(limit))) { // Limit must be loop-invariant
return nullptr;
}
if (!is_member(loop, get_ctrl(incr))) { // Trip counter must be loop-variant
return nullptr;
}
return cmp;
}
Node* PhaseIdealLoop::loop_iv_incr(Node* incr, Node* x, IdealLoopTree* loop, Node*& phi_incr) {
if (incr->is_Phi()) {
if (incr->as_Phi()->region() != x || incr->req() != 3) {
return nullptr; // Not simple trip counter expression
}
phi_incr = incr;
incr = phi_incr->in(LoopNode::LoopBackControl); // Assume incr is on backedge of Phi
if (!is_member(loop, get_ctrl(incr))) { // Trip counter must be loop-variant
return nullptr;
}
}
return incr;
}
Node* PhaseIdealLoop::loop_iv_stride(Node* incr, IdealLoopTree* loop, Node*& xphi) {
assert(incr->Opcode() == Op_AddI || incr->Opcode() == Op_AddL, "caller resp.");
// Get merge point
xphi = incr->in(1);
Node *stride = incr->in(2);
if (!stride->is_Con()) { // Oops, swap these
if (!xphi->is_Con()) { // Is the other guy a constant?
return nullptr; // Nope, unknown stride, bail out
}
Node *tmp = xphi; // 'incr' is commutative, so ok to swap
xphi = stride;
stride = tmp;
}
return stride;
}
PhiNode* PhaseIdealLoop::loop_iv_phi(Node* xphi, Node* phi_incr, Node* x, IdealLoopTree* loop) {
if (!xphi->is_Phi()) {
return nullptr; // Too much math on the trip counter
}
if (phi_incr != nullptr && phi_incr != xphi) {
return nullptr;
}
PhiNode *phi = xphi->as_Phi();
// Phi must be of loop header; backedge must wrap to increment
if (phi->region() != x) {
return nullptr;
}
return phi;
}
static int check_stride_overflow(jlong final_correction, const TypeInteger* limit_t, BasicType bt) {
if (final_correction > 0) {
if (limit_t->lo_as_long() > (max_signed_integer(bt) - final_correction)) {
return -1;
}
if (limit_t->hi_as_long() > (max_signed_integer(bt) - final_correction)) {
return 1;
}
} else {
if (limit_t->hi_as_long() < (min_signed_integer(bt) - final_correction)) {
return -1;
}
if (limit_t->lo_as_long() < (min_signed_integer(bt) - final_correction)) {
return 1;
}
}
return 0;
}
static bool condition_stride_ok(BoolTest::mask bt, jlong stride_con) {
// If the condition is inverted and we will be rolling
// through MININT to MAXINT, then bail out.
if (bt == BoolTest::eq || // Bail out, but this loop trips at most twice!
// Odd stride
(bt == BoolTest::ne && stride_con != 1 && stride_con != -1) ||
// Count down loop rolls through MAXINT
((bt == BoolTest::le || bt == BoolTest::lt) && stride_con < 0) ||
// Count up loop rolls through MININT
((bt == BoolTest::ge || bt == BoolTest::gt) && stride_con > 0)) {
return false; // Bail out
}
return true;
}
Node* PhaseIdealLoop::loop_nest_replace_iv(Node* iv_to_replace, Node* inner_iv, Node* outer_phi, Node* inner_head,
BasicType bt) {
Node* iv_as_long;
if (bt == T_LONG) {
iv_as_long = new ConvI2LNode(inner_iv, TypeLong::INT);
register_new_node(iv_as_long, inner_head);
} else {
iv_as_long = inner_iv;
}
Node* iv_replacement = AddNode::make(outer_phi, iv_as_long, bt);
register_new_node(iv_replacement, inner_head);
for (DUIterator_Last imin, i = iv_to_replace->last_outs(imin); i >= imin;) {
Node* u = iv_to_replace->last_out(i);
#ifdef ASSERT
if (!is_dominator(inner_head, ctrl_or_self(u))) {
assert(u->is_Phi(), "should be a Phi");
for (uint j = 1; j < u->req(); j++) {
if (u->in(j) == iv_to_replace) {
assert(is_dominator(inner_head, u->in(0)->in(j)), "iv use above loop?");
}
}
}
#endif
_igvn.rehash_node_delayed(u);
int nb = u->replace_edge(iv_to_replace, iv_replacement, &_igvn);
i -= nb;
}
return iv_replacement;
}
// Add a Parse Predicate with an uncommon trap on the failing/false path. Normal control will continue on the true path.
void PhaseIdealLoop::add_parse_predicate(Deoptimization::DeoptReason reason, Node* inner_head, IdealLoopTree* loop,
SafePointNode* sfpt) {
if (!C->too_many_traps(reason)) {
Node* cont = _igvn.intcon(1);
Node* opaq = new Opaque1Node(C, cont);
_igvn.register_new_node_with_optimizer(opaq);
Node* bol = new Conv2BNode(opaq);
_igvn.register_new_node_with_optimizer(bol);
set_subtree_ctrl(bol, false);
ParsePredicateNode* iff = new ParsePredicateNode(inner_head->in(LoopNode::EntryControl), bol, reason);
register_control(iff, loop, inner_head->in(LoopNode::EntryControl));
Node* if_false = new IfFalseNode(iff);
register_control(if_false, _ltree_root, iff);
Node* if_true = new IfTrueNode(iff);
register_control(if_true, loop, iff);
C->add_parse_predicate_opaq(opaq);
int trap_request = Deoptimization::make_trap_request(reason, Deoptimization::Action_maybe_recompile);
address call_addr = SharedRuntime::uncommon_trap_blob()->entry_point();
const TypePtr* no_memory_effects = nullptr;
JVMState* jvms = sfpt->jvms();
CallNode* unc = new CallStaticJavaNode(OptoRuntime::uncommon_trap_Type(), call_addr, "uncommon_trap",
no_memory_effects);
Node* mem = nullptr;
Node* i_o = nullptr;
if (sfpt->is_Call()) {
mem = sfpt->proj_out(TypeFunc::Memory);
i_o = sfpt->proj_out(TypeFunc::I_O);
} else {
mem = sfpt->memory();
i_o = sfpt->i_o();
}
Node *frame = new ParmNode(C->start(), TypeFunc::FramePtr);
register_new_node(frame, C->start());
Node *ret = new ParmNode(C->start(), TypeFunc::ReturnAdr);
register_new_node(ret, C->start());
unc->init_req(TypeFunc::Control, if_false);
unc->init_req(TypeFunc::I_O, i_o);
unc->init_req(TypeFunc::Memory, mem); // may gc ptrs
unc->init_req(TypeFunc::FramePtr, frame);
unc->init_req(TypeFunc::ReturnAdr, ret);
unc->init_req(TypeFunc::Parms+0, _igvn.intcon(trap_request));
unc->set_cnt(PROB_UNLIKELY_MAG(4));
unc->copy_call_debug_info(&_igvn, sfpt);
for (uint i = TypeFunc::Parms; i < unc->req(); i++) {
set_subtree_ctrl(unc->in(i), false);
}
register_control(unc, _ltree_root, if_false);
Node* ctrl = new ProjNode(unc, TypeFunc::Control);
register_control(ctrl, _ltree_root, unc);
Node* halt = new HaltNode(ctrl, frame, "uncommon trap returned which should never happen" PRODUCT_ONLY(COMMA /*reachable*/false));
register_control(halt, _ltree_root, ctrl);
_igvn.add_input_to(C->root(), halt);
_igvn.replace_input_of(inner_head, LoopNode::EntryControl, if_true);
set_idom(inner_head, if_true, dom_depth(inner_head));
}
}
// Find a safepoint node that dominates the back edge. We need a
// SafePointNode so we can use its jvm state to create empty
// predicates.
static bool no_side_effect_since_safepoint(Compile* C, Node* x, Node* mem, MergeMemNode* mm, PhaseIdealLoop* phase) {
SafePointNode* safepoint = nullptr;
for (DUIterator_Fast imax, i = x->fast_outs(imax); i < imax; i++) {
Node* u = x->fast_out(i);
if (u->is_Phi() && u->bottom_type() == Type::MEMORY) {
Node* m = u->in(LoopNode::LoopBackControl);
if (u->adr_type() == TypePtr::BOTTOM) {
if (m->is_MergeMem() && mem->is_MergeMem()) {
if (m != mem DEBUG_ONLY(|| true)) {
// MergeMemStream can modify m, for example to adjust the length to mem.
// This is unfortunate, and probably unnecessary. But as it is, we need
// to add m to the igvn worklist, else we may have a modified node that
// is not on the igvn worklist.
phase->igvn()._worklist.push(m);
for (MergeMemStream mms(m->as_MergeMem(), mem->as_MergeMem()); mms.next_non_empty2(); ) {
if (!mms.is_empty()) {
if (mms.memory() != mms.memory2()) {
return false;
}
#ifdef ASSERT
if (mms.alias_idx() != Compile::AliasIdxBot) {
mm->set_memory_at(mms.alias_idx(), mem->as_MergeMem()->base_memory());
}
#endif
}
}
}
} else if (mem->is_MergeMem()) {
if (m != mem->as_MergeMem()->base_memory()) {
return false;
}
} else {
return false;
}
} else {
if (mem->is_MergeMem()) {
if (m != mem->as_MergeMem()->memory_at(C->get_alias_index(u->adr_type()))) {
return false;
}
#ifdef ASSERT
mm->set_memory_at(C->get_alias_index(u->adr_type()), mem->as_MergeMem()->base_memory());
#endif
} else {
if (m != mem) {
return false;
}
}
}
}
}
return true;
}
SafePointNode* PhaseIdealLoop::find_safepoint(Node* back_control, Node* x, IdealLoopTree* loop) {
IfNode* exit_test = back_control->in(0)->as_If();
SafePointNode* safepoint = nullptr;
if (exit_test->in(0)->is_SafePoint() && exit_test->in(0)->outcnt() == 1) {
safepoint = exit_test->in(0)->as_SafePoint();
} else {
Node* c = back_control;
while (c != x && c->Opcode() != Op_SafePoint) {
c = idom(c);
}
if (c->Opcode() == Op_SafePoint) {
safepoint = c->as_SafePoint();
}
if (safepoint == nullptr) {
return nullptr;
}
Node* mem = safepoint->in(TypeFunc::Memory);
// We can only use that safepoint if there's no side effect between the backedge and the safepoint.
// mm is used for book keeping
MergeMemNode* mm = nullptr;
#ifdef ASSERT
if (mem->is_MergeMem()) {
mm = mem->clone()->as_MergeMem();
_igvn._worklist.push(mm);
for (MergeMemStream mms(mem->as_MergeMem()); mms.next_non_empty(); ) {
if (mms.alias_idx() != Compile::AliasIdxBot && loop != get_loop(ctrl_or_self(mms.memory()))) {
mm->set_memory_at(mms.alias_idx(), mem->as_MergeMem()->base_memory());
}
}
}
#endif
if (!no_side_effect_since_safepoint(C, x, mem, mm, this)) {
safepoint = nullptr;
} else {
assert(mm == nullptr|| _igvn.transform(mm) == mem->as_MergeMem()->base_memory(), "all memory state should have been processed");
}
#ifdef ASSERT
if (mm != nullptr) {
_igvn.remove_dead_node(mm);
}
#endif
}
return safepoint;
}
// If the loop has the shape of a counted loop but with a long
// induction variable, transform the loop in a loop nest: an inner
// loop that iterates for at most max int iterations with an integer
// induction variable and an outer loop that iterates over the full
// range of long values from the initial loop in (at most) max int
// steps. That is:
//
// x: for (long phi = init; phi < limit; phi += stride) {
// // phi := Phi(L, init, incr)
// // incr := AddL(phi, longcon(stride))
// long incr = phi + stride;
// ... use phi and incr ...
// }
//
// OR:
//
// x: for (long phi = init; (phi += stride) < limit; ) {
// // phi := Phi(L, AddL(init, stride), incr)
// // incr := AddL(phi, longcon(stride))
// long incr = phi + stride;
// ... use phi and (phi + stride) ...
// }
//
// ==transform=>
//
// const ulong inner_iters_limit = INT_MAX - stride - 1; //near 0x7FFFFFF0
// assert(stride <= inner_iters_limit); // else abort transform
// assert((extralong)limit + stride <= LONG_MAX); // else deopt
// outer_head: for (long outer_phi = init;;) {
// // outer_phi := Phi(outer_head, init, AddL(outer_phi, I2L(inner_phi)))
// ulong inner_iters_max = (ulong) MAX(0, ((extralong)limit + stride - outer_phi));
// long inner_iters_actual = MIN(inner_iters_limit, inner_iters_max);
// assert(inner_iters_actual == (int)inner_iters_actual);
// int inner_phi, inner_incr;
// x: for (inner_phi = 0;; inner_phi = inner_incr) {
// // inner_phi := Phi(x, intcon(0), inner_incr)
// // inner_incr := AddI(inner_phi, intcon(stride))
// inner_incr = inner_phi + stride;
// if (inner_incr < inner_iters_actual) {
// ... use phi=>(outer_phi+inner_phi) ...
// continue;
// }
// else break;
// }
// if ((outer_phi+inner_phi) < limit) //OR (outer_phi+inner_incr) < limit
// continue;
// else break;
// }
//
// The same logic is used to transform an int counted loop that contains long range checks into a loop nest of 2 int
// loops with long range checks transformed to int range checks in the inner loop.
bool PhaseIdealLoop::create_loop_nest(IdealLoopTree* loop, Node_List &old_new) {
Node* x = loop->_head;
// Only for inner loops
if (loop->_child != nullptr || !x->is_BaseCountedLoop() || x->as_Loop()->is_loop_nest_outer_loop()) {
return false;
}
if (x->is_CountedLoop() && !x->as_CountedLoop()->is_main_loop() && !x->as_CountedLoop()->is_normal_loop()) {
return false;
}
BaseCountedLoopNode* head = x->as_BaseCountedLoop();
BasicType bt = x->as_BaseCountedLoop()->bt();
check_counted_loop_shape(loop, x, bt);
#ifndef PRODUCT
if (bt == T_LONG) {
Atomic::inc(&_long_loop_candidates);
}
#endif
jlong stride_con_long = head->stride_con();
assert(stride_con_long != 0, "missed some peephole opt");
// We can't iterate for more than max int at a time.
if (stride_con_long != (jint)stride_con_long || stride_con_long == min_jint) {
assert(bt == T_LONG, "only for long loops");
return false;
}
jint stride_con = checked_cast<jint>(stride_con_long);
// The number of iterations for the integer count loop: guarantee no
// overflow: max_jint - stride_con max. -1 so there's no need for a
// loop limit check if the exit test is <= or >=.
int iters_limit = max_jint - ABS(stride_con) - 1;
#ifdef ASSERT
if (bt == T_LONG && StressLongCountedLoop > 0) {
iters_limit = iters_limit / StressLongCountedLoop;
}
#endif
// At least 2 iterations so counted loop construction doesn't fail
if (iters_limit/ABS(stride_con) < 2) {
return false;
}
PhiNode* phi = head->phi()->as_Phi();
Node* incr = head->incr();
Node* back_control = head->in(LoopNode::LoopBackControl);
// data nodes on back branch not supported
if (back_control->outcnt() > 1) {
return false;
}
Node* limit = head->limit();
// We'll need to use the loop limit before the inner loop is entered
if (!is_dominator(get_ctrl(limit), x)) {
return false;
}
IfNode* exit_test = head->loopexit();
assert(back_control->Opcode() == Op_IfTrue, "wrong projection for back edge");
Node_List range_checks;
iters_limit = extract_long_range_checks(loop, stride_con, iters_limit, phi, range_checks);
if (bt == T_INT) {
// The only purpose of creating a loop nest is to handle long range checks. If there are none, do not proceed further.
if (range_checks.size() == 0) {
return false;
}
}
// Take what we know about the number of iterations of the long counted loop into account when computing the limit of
// the inner loop.
const Node* init = head->init_trip();
const TypeInteger* lo = _igvn.type(init)->is_integer(bt);
const TypeInteger* hi = _igvn.type(limit)->is_integer(bt);
if (stride_con < 0) {
swap(lo, hi);
}
if (hi->hi_as_long() <= lo->lo_as_long()) {
// not a loop after all
return false;
}
julong orig_iters = (julong)hi->hi_as_long() - lo->lo_as_long();
iters_limit = checked_cast<int>(MIN2((julong)iters_limit, orig_iters));
// We need a safepoint to insert Parse Predicates for the inner loop.
SafePointNode* safepoint;
if (bt == T_INT && head->as_CountedLoop()->is_strip_mined()) {
// Loop is strip mined: use the safepoint of the outer strip mined loop
OuterStripMinedLoopNode* outer_loop = head->as_CountedLoop()->outer_loop();
assert(outer_loop != nullptr, "no outer loop");
safepoint = outer_loop->outer_safepoint();
outer_loop->transform_to_counted_loop(&_igvn, this);
exit_test = head->loopexit();
} else {
safepoint = find_safepoint(back_control, x, loop);
}
Node* exit_branch = exit_test->proj_out(false);
Node* entry_control = head->in(LoopNode::EntryControl);
// Clone the control flow of the loop to build an outer loop
Node* outer_back_branch = back_control->clone();
Node* outer_exit_test = new IfNode(exit_test->in(0), exit_test->in(1), exit_test->_prob, exit_test->_fcnt);
Node* inner_exit_branch = exit_branch->clone();
LoopNode* outer_head = new LoopNode(entry_control, outer_back_branch);
IdealLoopTree* outer_ilt = insert_outer_loop(loop, outer_head, outer_back_branch);
const bool body_populated = true;
register_control(outer_head, outer_ilt, entry_control, body_populated);
_igvn.register_new_node_with_optimizer(inner_exit_branch);
set_loop(inner_exit_branch, outer_ilt);
set_idom(inner_exit_branch, exit_test, dom_depth(exit_branch));
outer_exit_test->set_req(0, inner_exit_branch);
register_control(outer_exit_test, outer_ilt, inner_exit_branch, body_populated);
_igvn.replace_input_of(exit_branch, 0, outer_exit_test);
set_idom(exit_branch, outer_exit_test, dom_depth(exit_branch));
outer_back_branch->set_req(0, outer_exit_test);
register_control(outer_back_branch, outer_ilt, outer_exit_test, body_populated);
_igvn.replace_input_of(x, LoopNode::EntryControl, outer_head);
set_idom(x, outer_head, dom_depth(x));
// add an iv phi to the outer loop and use it to compute the inner
// loop iteration limit
Node* outer_phi = phi->clone();
outer_phi->set_req(0, outer_head);
register_new_node(outer_phi, outer_head);
Node* inner_iters_max = nullptr;
if (stride_con > 0) {
inner_iters_max = MaxNode::max_diff_with_zero(limit, outer_phi, TypeInteger::bottom(bt), _igvn);
} else {
inner_iters_max = MaxNode::max_diff_with_zero(outer_phi, limit, TypeInteger::bottom(bt), _igvn);
}
Node* inner_iters_limit = _igvn.integercon(iters_limit, bt);
// inner_iters_max may not fit in a signed integer (iterating from
// Long.MIN_VALUE to Long.MAX_VALUE for instance). Use an unsigned
// min.
Node* inner_iters_actual = MaxNode::unsigned_min(inner_iters_max, inner_iters_limit, TypeInteger::make(0, iters_limit, Type::WidenMin, bt), _igvn);
Node* inner_iters_actual_int;
if (bt == T_LONG) {
inner_iters_actual_int = new ConvL2INode(inner_iters_actual);
_igvn.register_new_node_with_optimizer(inner_iters_actual_int);
} else {
inner_iters_actual_int = inner_iters_actual;
}
Node* int_zero = _igvn.intcon(0);
set_ctrl(int_zero, C->root());
if (stride_con < 0) {
inner_iters_actual_int = new SubINode(int_zero, inner_iters_actual_int);
_igvn.register_new_node_with_optimizer(inner_iters_actual_int);
}
// Clone the iv data nodes as an integer iv
Node* int_stride = _igvn.intcon(stride_con);
set_ctrl(int_stride, C->root());
Node* inner_phi = new PhiNode(x->in(0), TypeInt::INT);
Node* inner_incr = new AddINode(inner_phi, int_stride);
Node* inner_cmp = nullptr;
inner_cmp = new CmpINode(inner_incr, inner_iters_actual_int);
Node* inner_bol = new BoolNode(inner_cmp, exit_test->in(1)->as_Bool()->_test._test);
inner_phi->set_req(LoopNode::EntryControl, int_zero);
inner_phi->set_req(LoopNode::LoopBackControl, inner_incr);
register_new_node(inner_phi, x);
register_new_node(inner_incr, x);
register_new_node(inner_cmp, x);
register_new_node(inner_bol, x);
_igvn.replace_input_of(exit_test, 1, inner_bol);
// Clone inner loop phis to outer loop
for (uint i = 0; i < head->outcnt(); i++) {
Node* u = head->raw_out(i);
if (u->is_Phi() && u != inner_phi && u != phi) {
assert(u->in(0) == head, "inconsistent");
Node* clone = u->clone();
clone->set_req(0, outer_head);
register_new_node(clone, outer_head);
_igvn.replace_input_of(u, LoopNode::EntryControl, clone);
}
}
// Replace inner loop long iv phi as inner loop int iv phi + outer
// loop iv phi
Node* iv_add = loop_nest_replace_iv(phi, inner_phi, outer_phi, head, bt);
set_subtree_ctrl(inner_iters_actual_int, body_populated);
LoopNode* inner_head = create_inner_head(loop, head, exit_test);
// Summary of steps from initial loop to loop nest:
//
// == old IR nodes =>
//
// entry_control: {...}
// x:
// for (long phi = init;;) {
// // phi := Phi(x, init, incr)
// // incr := AddL(phi, longcon(stride))
// exit_test:
// if (phi < limit)
// back_control: fallthrough;
// else
// exit_branch: break;
// long incr = phi + stride;
// ... use phi and incr ...
// phi = incr;
// }
//
// == new IR nodes (just before final peel) =>
//
// entry_control: {...}
// long adjusted_limit = limit + stride; //because phi_incr != nullptr
// assert(!limit_check_required || (extralong)limit + stride == adjusted_limit); // else deopt
// ulong inner_iters_limit = max_jint - ABS(stride) - 1; //near 0x7FFFFFF0
// outer_head:
// for (long outer_phi = init;;) {
// // outer_phi := phi->clone(), in(0):=outer_head, => Phi(outer_head, init, incr)
// // REPLACE phi => AddL(outer_phi, I2L(inner_phi))
// // REPLACE incr => AddL(outer_phi, I2L(inner_incr))
// // SO THAT outer_phi := Phi(outer_head, init, AddL(outer_phi, I2L(inner_incr)))
// ulong inner_iters_max = (ulong) MAX(0, ((extralong)adjusted_limit - outer_phi) * SGN(stride));
// int inner_iters_actual_int = (int) MIN(inner_iters_limit, inner_iters_max) * SGN(stride);
// inner_head: x: //in(1) := outer_head
// int inner_phi;
// for (inner_phi = 0;;) {
// // inner_phi := Phi(x, intcon(0), inner_phi + stride)
// int inner_incr = inner_phi + stride;
// bool inner_bol = (inner_incr < inner_iters_actual_int);
// exit_test: //exit_test->in(1) := inner_bol;
// if (inner_bol) // WAS (phi < limit)
// back_control: fallthrough;
// else
// inner_exit_branch: break; //exit_branch->clone()
// ... use phi=>(outer_phi+inner_phi) ...
// inner_phi = inner_phi + stride; // inner_incr
// }
// outer_exit_test: //exit_test->clone(), in(0):=inner_exit_branch
// if ((outer_phi+inner_phi) < limit) // WAS (phi < limit)
// outer_back_branch: fallthrough; //back_control->clone(), in(0):=outer_exit_test
// else
// exit_branch: break; //in(0) := outer_exit_test
// }
if (bt == T_INT) {
outer_phi = new ConvI2LNode(outer_phi);
register_new_node(outer_phi, outer_head);
}
transform_long_range_checks(stride_con, range_checks, outer_phi, inner_iters_actual_int,
inner_phi, iv_add, inner_head);
// Peel one iteration of the loop and use the safepoint at the end
// of the peeled iteration to insert Parse Predicates. If no well
// positioned safepoint peel to guarantee a safepoint in the outer
// loop.
if (safepoint != nullptr || !loop->_has_call) {
old_new.clear();
do_peeling(loop, old_new);
} else {
C->set_major_progress();
}
if (safepoint != nullptr) {
SafePointNode* cloned_sfpt = old_new[safepoint->_idx]->as_SafePoint();
if (UseLoopPredicate) {
add_parse_predicate(Deoptimization::Reason_predicate, inner_head, outer_ilt, cloned_sfpt);
}
if (UseProfiledLoopPredicate) {
add_parse_predicate(Deoptimization::Reason_profile_predicate, inner_head, outer_ilt, cloned_sfpt);
}
add_parse_predicate(Deoptimization::Reason_loop_limit_check, inner_head, outer_ilt, cloned_sfpt);
}
#ifndef PRODUCT
if (bt == T_LONG) {
Atomic::inc(&_long_loop_nests);
}
#endif
inner_head->mark_loop_nest_inner_loop();
outer_head->mark_loop_nest_outer_loop();
return true;
}
int PhaseIdealLoop::extract_long_range_checks(const IdealLoopTree* loop, jint stride_con, int iters_limit, PhiNode* phi,
Node_List& range_checks) {
const jlong min_iters = 2;
jlong reduced_iters_limit = iters_limit;
jlong original_iters_limit = iters_limit;
for (uint i = 0; i < loop->_body.size(); i++) {
Node* c = loop->_body.at(i);
if (c->is_IfProj() && c->in(0)->is_RangeCheck()) {
IfProjNode* if_proj = c->as_IfProj();
CallStaticJavaNode* call = if_proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
if (call != nullptr) {
Node* range = nullptr;
Node* offset = nullptr;
jlong scale = 0;
if (loop->is_range_check_if(if_proj, this, T_LONG, phi, range, offset, scale) &&
loop->is_invariant(range) && loop->is_invariant(offset) &&
scale != min_jlong &&
original_iters_limit / ABS(scale) >= min_iters * ABS(stride_con)) {
assert(scale == (jint)scale, "scale should be an int");
reduced_iters_limit = MIN2(reduced_iters_limit, original_iters_limit/ABS(scale));
range_checks.push(c);
}
}
}
}
return checked_cast<int>(reduced_iters_limit);
}
// One execution of the inner loop covers a sub-range of the entire iteration range of the loop: [A,Z), aka [A=init,
// Z=limit). If the loop has at least one trip (which is the case here), the iteration variable i always takes A as its
// first value, followed by A+S (S is the stride), next A+2S, etc. The limit is exclusive, so that the final value B of
// i is never Z. It will be B=Z-1 if S=1, or B=Z+1 if S=-1.
// If |S|>1 the formula for the last value B would require a floor operation, specifically B=floor((Z-sgn(S)-A)/S)*S+A,
// which is B=Z-sgn(S)U for some U in [1,|S|]. So when S>0, i ranges as i:[A,Z) or i:[A,B=Z-U], or else (in reverse)
// as i:(Z,A] or i:[B=Z+U,A]. It will become important to reason about this inclusive range [A,B] or [B,A].
// Within the loop there may be many range checks. Each such range check (R.C.) is of the form 0 <= i*K+L < R, where K
// is a scale factor applied to the loop iteration variable i, and L is some offset; K, L, and R are loop-invariant.
// Because R is never negative (see below), this check can always be simplified to an unsigned check i*K+L <u R.
// When a long loop over a 64-bit variable i (outer_iv) is decomposed into a series of shorter sub-loops over a 32-bit
// variable j (inner_iv), j ranges over a shorter interval j:[0,B_2] or [0,Z_2) (assuming S > 0), where the limit is
// chosen to prevent various cases of 32-bit overflow (including multiplications j*K below). In the sub-loop the
// logical value i is offset from j by a 64-bit constant C, so i ranges in i:C+[0,Z_2).
// For S<0, j ranges (in reverse!) through j:[-|B_2|,0] or (-|Z_2|,0]. For either sign of S, we can say i=j+C and j
// ranges through 32-bit ranges [A_2,B_2] or [B_2,A_2] (A_2=0 of course).
// The disjoint union of all the C+[A_2,B_2] ranges from the sub-loops must be identical to the whole range [A,B].
// Assuming S>0, the first C must be A itself, and the next C value is the previous C+B_2, plus S. If |S|=1, the next
// C value is also the previous C+Z_2. In each sub-loop, j counts from j=A_2=0 and i counts from C+0 and exits at
// j=B_2 (i=C+B_2), just before it gets to i=C+Z_2. Both i and j count up (from C and 0) if S>0; otherwise they count
// down (from C and 0 again).
// Returning to range checks, we see that each i*K+L <u R expands to (C+j)*K+L <u R, or j*K+Q <u R, where Q=(C*K+L).
// (Recall that K and L and R are loop-invariant scale, offset and range values for a particular R.C.) This is still a
// 64-bit comparison, so the range check elimination logic will not apply to it. (The R.C.E. transforms operate only on
// 32-bit indexes and comparisons, because they use 64-bit temporary values to avoid overflow; see
// PhaseIdealLoop::add_constraint.)
// We must transform this comparison so that it gets the same answer, but by means of a 32-bit R.C. (using j not i) of
// the form j*K+L_2 <u32 R_2. Note that L_2 and R_2 must be loop-invariant, but only with respect to the sub-loop. Thus, the
// problem reduces to computing values for L_2 and R_2 (for each R.C. in the loop) in the loop header for the sub-loop.
// Then the standard R.C.E. transforms can take those as inputs and further compute the necessary minimum and maximum
// values for the 32-bit counter j within which the range checks can be eliminated.
// So, given j*K+Q <u R, we need to find some j*K+L_2 <u32 R_2, where L_2 and R_2 fit in 32 bits, and the 32-bit operations do
// not overflow. We also need to cover the cases where i*K+L (= j*K+Q) overflows to a 64-bit negative, since that is
// allowed as an input to the R.C., as long as the R.C. as a whole fails.
// If 32-bit multiplication j*K might overflow, we adjust the sub-loop limit Z_2 closer to zero to reduce j's range.
// For each R.C. j*K+Q <u32 R, the range of mathematical values of j*K+Q in the sub-loop is [Q_min, Q_max], where
// Q_min=Q and Q_max=B_2*K+Q (if S>0 and K>0), Q_min=A_2*K+Q and Q_max=Q (if S<0 and K>0),
// Q_min=B_2*K+Q and Q_max=Q if (S>0 and K<0), Q_min=Q and Q_max=A_2*K+Q (if S<0 and K<0)
// Note that the first R.C. value is always Q=(S*K>0 ? Q_min : Q_max). Also Q_{min,max} = Q + {min,max}(A_2*K,B_2*K).
// If S*K>0 then, as the loop iterations progress, each R.C. value i*K+L = j*K+Q goes up from Q=Q_min towards Q_max.
// If S*K<0 then j*K+Q starts at Q=Q_max and goes down towards Q_min.
// Case A: Some Negatives (but no overflow).
// Number line:
// |s64_min . . . 0 . . . s64_max|
// | . Q_min..Q_max . 0 . . . . | s64 negative
// | . . . . R=0 R< R< R< R< | (against R values)
// | . . . Q_min..0..Q_max . . . | small mixed
// | . . . . R R R< R< R< | (against R values)
//
// R values which are out of range (>Q_max+1) are reduced to max(0,Q_max+1). They are marked on the number line as R<.
//
// So, if Q_min <s64 0, then use this test:
// j*K + s32_trunc(Q_min) <u32 clamp(R, 0, Q_max+1) if S*K>0 (R.C.E. steps upward)
// j*K + s32_trunc(Q_max) <u32 clamp(R, 0, Q_max+1) if S*K<0 (R.C.E. steps downward)
// Both formulas reduce to adding j*K to the 32-bit truncated value of the first R.C. expression value, Q:
// j*K + s32_trunc(Q) <u32 clamp(R, 0, Q_max+1) for all S,K
// If the 32-bit truncation loses information, no harm is done, since certainly the clamp also will return R_2=zero.
// Case B: No Negatives.
// Number line:
// |s64_min . . . 0 . . . s64_max|
// | . . . . 0 Q_min..Q_max . . | small positive
// | . . . . R> R R R< R< | (against R values)
// | . . . . 0 . Q_min..Q_max . | s64 positive
// | . . . . R> R> R R R< | (against R values)
//
// R values which are out of range (<Q_min or >Q_max+1) are reduced as marked: R> up to Q_min, R< down to Q_max+1.
// Then the whole comparison is shifted left by Q_min, so it can take place at zero, which is a nice 32-bit value.
//
// So, if both Q_min, Q_max+1 >=s64 0, then use this test:
// j*K + 0 <u32 clamp(R, Q_min, Q_max+1) - Q_min if S*K>0
// More generally:
// j*K + Q - Q_min <u32 clamp(R, Q_min, Q_max+1) - Q_min for all S,K
// Case C: Overflow in the 64-bit domain
// Number line:
// |..Q_max-2^64 . . 0 . . . Q_min..| s64 overflow
// | . . . . R> R> R> R> R | (against R values)
//
// In this case, Q_min >s64 Q_max+1, even though the mathematical values of Q_min and Q_max+1 are correctly ordered.
// The formulas from the previous case can be used, except that the bad upper bound Q_max is replaced by max_jlong.
// (In fact, we could use any replacement bound from R to max_jlong inclusive, as the input to the clamp function.)
//
// So if Q_min >=s64 0 but Q_max+1 <s64 0, use this test:
// j*K + 0 <u32 clamp(R, Q_min, max_jlong) - Q_min if S*K>0
// More generally:
// j*K + Q - Q_min <u32 clamp(R, Q_min, max_jlong) - Q_min for all S,K
//
// Dropping the bad bound means only Q_min is used to reduce the range of R:
// j*K + Q - Q_min <u32 max(Q_min, R) - Q_min for all S,K
//
// Here the clamp function is a 64-bit min/max that reduces the dynamic range of its R operand to the required [L,H]:
// clamp(X, L, H) := max(L, min(X, H))
// When degenerately L > H, it returns L not H.
//
// All of the formulas above can be merged into a single one:
// L_clamp = Q_min < 0 ? 0 : Q_min --whether and how far to left-shift
// H_clamp = Q_max+1 < Q_min ? max_jlong : Q_max+1
// = Q_max+1 < 0 && Q_min >= 0 ? max_jlong : Q_max+1
// Q_first = Q = (S*K>0 ? Q_min : Q_max) = (C*K+L)
// R_clamp = clamp(R, L_clamp, H_clamp) --reduced dynamic range
// replacement R.C.:
// j*K + Q_first - L_clamp <u32 R_clamp - L_clamp
// or equivalently:
// j*K + L_2 <u32 R_2
// where
// L_2 = Q_first - L_clamp
// R_2 = R_clamp - L_clamp
//
// Note on why R is never negative:
//
// Various details of this transformation would break badly if R could be negative, so this transformation only
// operates after obtaining hard evidence that R<0 is impossible. For example, if R comes from a LoadRange node, we
// know R cannot be negative. For explicit checks (of both int and long) a proof is constructed in
// inline_preconditions_checkIndex, which triggers an uncommon trap if R<0, then wraps R in a ConstraintCastNode with a
// non-negative type. Later on, when IdealLoopTree::is_range_check_if looks for an optimizable R.C., it checks that
// the type of that R node is non-negative. Any "wild" R node that could be negative is not treated as an optimizable
// R.C., but R values from a.length and inside checkIndex are good to go.
//
void PhaseIdealLoop::transform_long_range_checks(int stride_con, const Node_List &range_checks, Node* outer_phi,
Node* inner_iters_actual_int, Node* inner_phi,
Node* iv_add, LoopNode* inner_head) {
Node* long_zero = _igvn.longcon(0);
set_ctrl(long_zero, C->root());
Node* int_zero = _igvn.intcon(0);
set_ctrl(int_zero, this->C->root());
Node* long_one = _igvn.longcon(1);
set_ctrl(long_one, this->C->root());
Node* int_stride = _igvn.intcon(checked_cast<int>(stride_con));
set_ctrl(int_stride, this->C->root());
for (uint i = 0; i < range_checks.size(); i++) {
ProjNode* proj = range_checks.at(i)->as_Proj();
ProjNode* unc_proj = proj->other_if_proj();
RangeCheckNode* rc = proj->in(0)->as_RangeCheck();
jlong scale = 0;
Node* offset = nullptr;
Node* rc_bol = rc->in(1);
Node* rc_cmp = rc_bol->in(1);
if (rc_cmp->Opcode() == Op_CmpU) {
// could be shared and have already been taken care of
continue;
}
bool short_scale = false;
bool ok = is_scaled_iv_plus_offset(rc_cmp->in(1), iv_add, T_LONG, &scale, &offset, &short_scale);
assert(ok, "inconsistent: was tested before");
Node* range = rc_cmp->in(2);
Node* c = rc->in(0);
Node* entry_control = inner_head->in(LoopNode::EntryControl);
Node* R = range;
Node* K = _igvn.longcon(scale);
set_ctrl(K, this->C->root());
Node* L = offset;
if (short_scale) {
// This converts:
// (int)i*K + L <u64 R
// with K an int into:
// i*(long)K + L <u64 unsigned_min((long)max_jint + L + 1, R)
// to protect against an overflow of (int)i*K
//
// Because if (int)i*K overflows, there are K,L where:
// (int)i*K + L <u64 R is false because (int)i*K+L overflows to a negative which becomes a huge u64 value.
// But if i*(long)K + L is >u64 (long)max_jint and still is <u64 R, then
// i*(long)K + L <u64 R is true.
//
// As a consequence simply converting i*K + L <u64 R to i*(long)K + L <u64 R could cause incorrect execution.
//
// It's always true that:
// (int)i*K <u64 (long)max_jint + 1
// which implies (int)i*K + L <u64 (long)max_jint + 1 + L
// As a consequence:
// i*(long)K + L <u64 unsigned_min((long)max_jint + L + 1, R)
// is always false in case of overflow of i*K
//
// Note, there are also K,L where i*K overflows and
// i*K + L <u64 R is true, but
// i*(long)K + L <u64 unsigned_min((long)max_jint + L + 1, R) is false
// So this transformation could cause spurious deoptimizations and failed range check elimination
// (but not incorrect execution) for unlikely corner cases with overflow.
// If this causes problems in practice, we could maybe direct execution to a post-loop, instead of deoptimizing.
Node* max_jint_plus_one_long = _igvn.longcon((jlong)max_jint + 1);
set_ctrl(max_jint_plus_one_long, C->root());
Node* max_range = new AddLNode(max_jint_plus_one_long, L);
register_new_node(max_range, entry_control);
R = MaxNode::unsigned_min(R, max_range, TypeLong::POS, _igvn);
set_subtree_ctrl(R, true);
}
Node* C = outer_phi;
// Start with 64-bit values:
// i*K + L <u64 R
// (C+j)*K + L <u64 R
// j*K + Q <u64 R where Q = Q_first = C*K+L
Node* Q_first = new MulLNode(C, K);
register_new_node(Q_first, entry_control);
Q_first = new AddLNode(Q_first, L);
register_new_node(Q_first, entry_control);
// Compute endpoints of the range of values j*K + Q.
// Q_min = (j=0)*K + Q; Q_max = (j=B_2)*K + Q
Node* Q_min = Q_first;
// Compute the exact ending value B_2 (which is really A_2 if S < 0)
Node* B_2 = new LoopLimitNode(this->C, int_zero, inner_iters_actual_int, int_stride);
register_new_node(B_2, entry_control);
B_2 = new SubINode(B_2, int_stride);
register_new_node(B_2, entry_control);
B_2 = new ConvI2LNode(B_2);
register_new_node(B_2, entry_control);
Node* Q_max = new MulLNode(B_2, K);
register_new_node(Q_max, entry_control);
Q_max = new AddLNode(Q_max, Q_first);
register_new_node(Q_max, entry_control);
if (scale * stride_con < 0) {
swap(Q_min, Q_max);
}
// Now, mathematically, Q_max > Q_min, and they are close enough so that (Q_max-Q_min) fits in 32 bits.
// L_clamp = Q_min < 0 ? 0 : Q_min
Node* Q_min_cmp = new CmpLNode(Q_min, long_zero);
register_new_node(Q_min_cmp, entry_control);
Node* Q_min_bool = new BoolNode(Q_min_cmp, BoolTest::lt);
register_new_node(Q_min_bool, entry_control);
Node* L_clamp = new CMoveLNode(Q_min_bool, Q_min, long_zero, TypeLong::LONG);
register_new_node(L_clamp, entry_control);
// (This could also be coded bitwise as L_clamp = Q_min & ~(Q_min>>63).)
Node* Q_max_plus_one = new AddLNode(Q_max, long_one);
register_new_node(Q_max_plus_one, entry_control);
// H_clamp = Q_max+1 < Q_min ? max_jlong : Q_max+1
// (Because Q_min and Q_max are close, the overflow check could also be encoded as Q_max+1 < 0 & Q_min >= 0.)
Node* max_jlong_long = _igvn.longcon(max_jlong);
set_ctrl(max_jlong_long, this->C->root());
Node* Q_max_cmp = new CmpLNode(Q_max_plus_one, Q_min);
register_new_node(Q_max_cmp, entry_control);
Node* Q_max_bool = new BoolNode(Q_max_cmp, BoolTest::lt);
register_new_node(Q_max_bool, entry_control);
Node* H_clamp = new CMoveLNode(Q_max_bool, Q_max_plus_one, max_jlong_long, TypeLong::LONG);
register_new_node(H_clamp, entry_control);
// (This could also be coded bitwise as H_clamp = ((Q_max+1)<<1 | M)>>>1 where M = (Q_max+1)>>63 & ~Q_min>>63.)
// R_2 = clamp(R, L_clamp, H_clamp) - L_clamp
// that is: R_2 = clamp(R, L_clamp=0, H_clamp=Q_max) if Q_min < 0
// or else: R_2 = clamp(R, L_clamp, H_clamp) - Q_min if Q_min >= 0
// and also: R_2 = clamp(R, L_clamp, Q_max+1) - L_clamp if Q_min < Q_max+1 (no overflow)
// or else: R_2 = clamp(R, L_clamp, *no limit*)- L_clamp if Q_max+1 < Q_min (overflow)
Node* R_2 = clamp(R, L_clamp, H_clamp);
R_2 = new SubLNode(R_2, L_clamp);
register_new_node(R_2, entry_control);
R_2 = new ConvL2INode(R_2, TypeInt::POS);
register_new_node(R_2, entry_control);
// L_2 = Q_first - L_clamp
// We are subtracting L_clamp from both sides of the <u32 comparison.
// If S*K>0, then Q_first == 0 and the R.C. expression at -L_clamp and steps upward to Q_max-L_clamp.
// If S*K<0, then Q_first != 0 and the R.C. expression starts high and steps downward to Q_min-L_clamp.
Node* L_2 = new SubLNode(Q_first, L_clamp);
register_new_node(L_2, entry_control);
L_2 = new ConvL2INode(L_2, TypeInt::INT);
register_new_node(L_2, entry_control);
// Transform the range check using the computed values L_2/R_2
// from: i*K + L <u64 R
// to: j*K + L_2 <u32 R_2
// that is:
// (j*K + Q_first) - L_clamp <u32 clamp(R, L_clamp, H_clamp) - L_clamp
K = _igvn.intcon(checked_cast<int>(scale));
set_ctrl(K, this->C->root());
Node* scaled_iv = new MulINode(inner_phi, K);
register_new_node(scaled_iv, c);
Node* scaled_iv_plus_offset = new AddINode(scaled_iv, L_2);
register_new_node(scaled_iv_plus_offset, c);
Node* new_rc_cmp = new CmpUNode(scaled_iv_plus_offset, R_2);
register_new_node(new_rc_cmp, c);
_igvn.replace_input_of(rc_bol, 1, new_rc_cmp);
}
}
Node* PhaseIdealLoop::clamp(Node* R, Node* L, Node* H) {
Node* min = MaxNode::signed_min(R, H, TypeLong::LONG, _igvn);
set_subtree_ctrl(min, true);
Node* max = MaxNode::signed_max(L, min, TypeLong::LONG, _igvn);
set_subtree_ctrl(max, true);
return max;
}
LoopNode* PhaseIdealLoop::create_inner_head(IdealLoopTree* loop, BaseCountedLoopNode* head,
IfNode* exit_test) {
LoopNode* new_inner_head = new LoopNode(head->in(1), head->in(2));
IfNode* new_inner_exit = new IfNode(exit_test->in(0), exit_test->in(1), exit_test->_prob, exit_test->_fcnt);
_igvn.register_new_node_with_optimizer(new_inner_head);
_igvn.register_new_node_with_optimizer(new_inner_exit);
loop->_body.push(new_inner_head);
loop->_body.push(new_inner_exit);
loop->_body.yank(head);
loop->_body.yank(exit_test);
set_loop(new_inner_head, loop);
set_loop(new_inner_exit, loop);
set_idom(new_inner_head, idom(head), dom_depth(head));
set_idom(new_inner_exit, idom(exit_test), dom_depth(exit_test));
lazy_replace(head, new_inner_head);
lazy_replace(exit_test, new_inner_exit);
loop->_head = new_inner_head;
return new_inner_head;
}
#ifdef ASSERT
void PhaseIdealLoop::check_counted_loop_shape(IdealLoopTree* loop, Node* x, BasicType bt) {
Node* back_control = loop_exit_control(x, loop);
assert(back_control != nullptr, "no back control");
BoolTest::mask mask = BoolTest::illegal;
float cl_prob = 0;
Node* incr = nullptr;
Node* limit = nullptr;
Node* cmp = loop_exit_test(back_control, loop, incr, limit, mask, cl_prob);
assert(cmp != nullptr && cmp->Opcode() == Op_Cmp(bt), "no exit test");
Node* phi_incr = nullptr;
incr = loop_iv_incr(incr, x, loop, phi_incr);
assert(incr != nullptr && incr->Opcode() == Op_Add(bt), "no incr");
Node* xphi = nullptr;
Node* stride = loop_iv_stride(incr, loop, xphi);
assert(stride != nullptr, "no stride");
PhiNode* phi = loop_iv_phi(xphi, phi_incr, x, loop);
assert(phi != nullptr && phi->in(LoopNode::LoopBackControl) == incr, "No phi");
jlong stride_con = stride->get_integer_as_long(bt);
assert(condition_stride_ok(mask, stride_con), "illegal condition");
assert(mask != BoolTest::ne, "unexpected condition");
assert(phi_incr == nullptr, "bad loop shape");
assert(cmp->in(1) == incr, "bad exit test shape");
// Safepoint on backedge not supported
assert(x->in(LoopNode::LoopBackControl)->Opcode() != Op_SafePoint, "no safepoint on backedge");
}
#endif
#ifdef ASSERT
// convert an int counted loop to a long counted to stress handling of
// long counted loops
bool PhaseIdealLoop::convert_to_long_loop(Node* cmp, Node* phi, IdealLoopTree* loop) {
Unique_Node_List iv_nodes;
Node_List old_new;
iv_nodes.push(cmp);
bool failed = false;
for (uint i = 0; i < iv_nodes.size() && !failed; i++) {
Node* n = iv_nodes.at(i);
switch(n->Opcode()) {
case Op_Phi: {
Node* clone = new PhiNode(n->in(0), TypeLong::LONG);
old_new.map(n->_idx, clone);
break;
}
case Op_CmpI: {
Node* clone = new CmpLNode(nullptr, nullptr);
old_new.map(n->_idx, clone);
break;
}
case Op_AddI: {
Node* clone = new AddLNode(nullptr, nullptr);
old_new.map(n->_idx, clone);
break;
}
case Op_CastII: {
failed = true;
break;
}
default:
DEBUG_ONLY(n->dump());
fatal("unexpected");
}
for (uint i = 1; i < n->req(); i++) {
Node* in = n->in(i);
if (in == nullptr) {
continue;
}
if (loop->is_member(get_loop(get_ctrl(in)))) {
iv_nodes.push(in);
}
}
}
if (failed) {
for (uint i = 0; i < iv_nodes.size(); i++) {
Node* n = iv_nodes.at(i);
Node* clone = old_new[n->_idx];
if (clone != nullptr) {
_igvn.remove_dead_node(clone);
}
}
return false;
}
for (uint i = 0; i < iv_nodes.size(); i++) {
Node* n = iv_nodes.at(i);
Node* clone = old_new[n->_idx];
for (uint i = 1; i < n->req(); i++) {
Node* in = n->in(i);
if (in == nullptr) {
continue;
}
Node* in_clone = old_new[in->_idx];
if (in_clone == nullptr) {
assert(_igvn.type(in)->isa_int(), "");
in_clone = new ConvI2LNode(in);
_igvn.register_new_node_with_optimizer(in_clone);
set_subtree_ctrl(in_clone, false);
}
if (in_clone->in(0) == nullptr) {
in_clone->set_req(0, C->top());
clone->set_req(i, in_clone);
in_clone->set_req(0, nullptr);
} else {
clone->set_req(i, in_clone);
}
}
_igvn.register_new_node_with_optimizer(clone);
}
set_ctrl(old_new[phi->_idx], phi->in(0));
for (uint i = 0; i < iv_nodes.size(); i++) {
Node* n = iv_nodes.at(i);
Node* clone = old_new[n->_idx];
set_subtree_ctrl(clone, false);
Node* m = n->Opcode() == Op_CmpI ? clone : nullptr;
for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
Node* u = n->fast_out(i);
if (iv_nodes.member(u)) {
continue;
}
if (m == nullptr) {
m = new ConvL2INode(clone);
_igvn.register_new_node_with_optimizer(m);
set_subtree_ctrl(m, false);
}
_igvn.rehash_node_delayed(u);
int nb = u->replace_edge(n, m, &_igvn);
--i, imax -= nb;
}
}
return true;
}
#endif
//------------------------------is_counted_loop--------------------------------
bool PhaseIdealLoop::is_counted_loop(Node* x, IdealLoopTree*&loop, BasicType iv_bt) {
PhaseGVN *gvn = &_igvn;
Node* back_control = loop_exit_control(x, loop);
if (back_control == nullptr) {
return false;
}
BoolTest::mask bt = BoolTest::illegal;
float cl_prob = 0;
Node* incr = nullptr;
Node* limit = nullptr;
Node* cmp = loop_exit_test(back_control, loop, incr, limit, bt, cl_prob);
if (cmp == nullptr || cmp->Opcode() != Op_Cmp(iv_bt)) {
return false; // Avoid pointer & float & 64-bit compares
}
// Trip-counter increment must be commutative & associative.
if (incr->Opcode() == Op_Cast(iv_bt)) {
incr = incr->in(1);
}
Node* phi_incr = nullptr;
incr = loop_iv_incr(incr, x, loop, phi_incr);
if (incr == nullptr) {
return false;
}
Node* trunc1 = nullptr;
Node* trunc2 = nullptr;
const TypeInteger* iv_trunc_t = nullptr;
Node* orig_incr = incr;
if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t, iv_bt))) {
return false; // Funny increment opcode
}
assert(incr->Opcode() == Op_Add(iv_bt), "wrong increment code");
Node* xphi = nullptr;
Node* stride = loop_iv_stride(incr, loop, xphi);
if (stride == nullptr) {
return false;
}
if (xphi->Opcode() == Op_Cast(iv_bt)) {
xphi = xphi->in(1);
}
// Stride must be constant
jlong stride_con = stride->get_integer_as_long(iv_bt);
assert(stride_con != 0, "missed some peephole opt");
PhiNode* phi = loop_iv_phi(xphi, phi_incr, x, loop);
if (phi == nullptr ||
(trunc1 == nullptr && phi->in(LoopNode::LoopBackControl) != incr) ||
(trunc1 != nullptr && phi->in(LoopNode::LoopBackControl) != trunc1)) {
return false;
}
Node* iftrue = back_control;
uint iftrue_op = iftrue->Opcode();
Node* iff = iftrue->in(0);
BoolNode* test = iff->in(1)->as_Bool();
const TypeInteger* limit_t = gvn->type(limit)->is_integer(iv_bt);
if (trunc1 != nullptr) {
// When there is a truncation, we must be sure that after the truncation
// the trip counter will end up higher than the limit, otherwise we are looking
// at an endless loop. Can happen with range checks.
// Example:
// int i = 0;
// while (true)
// sum + = array[i];
// i++;
// i = i && 0x7fff;
// }
//
// If the array is shorter than 0x8000 this exits through a AIOOB
// - Counted loop transformation is ok
// If the array is longer then this is an endless loop
// - No transformation can be done.
const TypeInteger* incr_t = gvn->type(orig_incr)->is_integer(iv_bt);
if (limit_t->hi_as_long() > incr_t->hi_as_long()) {
// if the limit can have a higher value than the increment (before the phi)
return false;
}
}
Node *init_trip = phi->in(LoopNode::EntryControl);
// If iv trunc type is smaller than int, check for possible wrap.
if (!TypeInteger::bottom(iv_bt)->higher_equal(iv_trunc_t)) {
assert(trunc1 != nullptr, "must have found some truncation");
// Get a better type for the phi (filtered thru if's)
const TypeInteger* phi_ft = filtered_type(phi);
// Can iv take on a value that will wrap?
//
// Ensure iv's limit is not within "stride" of the wrap value.
//
// Example for "short" type
// Truncation ensures value is in the range -32768..32767 (iv_trunc_t)
// If the stride is +10, then the last value of the induction
// variable before the increment (phi_ft->_hi) must be
// <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to
// ensure no truncation occurs after the increment.
if (stride_con > 0) {
if (iv_trunc_t->hi_as_long() - phi_ft->hi_as_long() < stride_con ||
iv_trunc_t->lo_as_long() > phi_ft->lo_as_long()) {
return false; // truncation may occur
}
} else if (stride_con < 0) {
if (iv_trunc_t->lo_as_long() - phi_ft->lo_as_long() > stride_con ||
iv_trunc_t->hi_as_long() < phi_ft->hi_as_long()) {
return false; // truncation may occur
}
}
// No possibility of wrap so truncation can be discarded
// Promote iv type to Int
} else {
assert(trunc1 == nullptr && trunc2 == nullptr, "no truncation for int");
}
if (!condition_stride_ok(bt, stride_con)) {
return false;
}
const TypeInteger* init_t = gvn->type(init_trip)->is_integer(iv_bt);
if (stride_con > 0) {
if (init_t->lo_as_long() > max_signed_integer(iv_bt) - stride_con) {
return false; // cyclic loop
}
} else {
if (init_t->hi_as_long() < min_signed_integer(iv_bt) - stride_con) {
return false; // cyclic loop
}
}
if (phi_incr != nullptr && bt != BoolTest::ne) {
// check if there is a possibility of IV overflowing after the first increment
if (stride_con > 0) {
if (init_t->hi_as_long() > max_signed_integer(iv_bt) - stride_con) {
return false;
}
} else {
if (init_t->lo_as_long() < min_signed_integer(iv_bt) - stride_con) {
return false;
}
}
}
// =================================================
// ---- SUCCESS! Found A Trip-Counted Loop! -----
//
assert(x->Opcode() == Op_Loop || x->Opcode() == Op_LongCountedLoop, "regular loops only");
C->print_method(PHASE_BEFORE_CLOOPS, 3);
// ===================================================
// We can only convert this loop to a counted loop if we can guarantee that the iv phi will never overflow at runtime.
// This is an implicit assumption taken by some loop optimizations. We therefore must ensure this property at all cost.
// At this point, we've already excluded some trivial cases where an overflow could have been proven statically.
// But even though we cannot prove that an overflow will *not* happen, we still want to speculatively convert this loop
// to a counted loop. This can be achieved by adding additional iv phi overflow checks before the loop. If they fail,
// we trap and resume execution before the loop without having executed any iteration of the loop, yet.
//
// These additional iv phi overflow checks can be inserted as Loop Limit Check Predicates above the Loop Limit Check
// Parse Predicate which captures a JVM state just before the entry of the loop. If there is no such Parse Predicate,
// we cannot generate a Loop Limit Check Predicate and thus cannot speculatively convert the loop to a counted loop.
//
// In the following, we only focus on int loops with stride > 0 to keep things simple. The argumentation and proof
// for stride < 0 is analogously. For long loops, we would replace max_int with max_long.
//
//
// The loop to be converted does not always need to have the often used shape:
//
// i = init
// i = init loop:
// do { ...
// // ... equivalent i+=stride
// i+=stride <==> if (i < limit)
// } while (i < limit); goto loop
// exit:
// ...
//
// where the loop exit check uses the post-incremented iv phi and a '<'-operator.
//
// We could also have '<='-operator (or '>='-operator for negative strides) or use the pre-incremented iv phi value
// in the loop exit check:
//
// i = init
// loop:
// ...
// if (i <= limit)
// i+=stride
// goto loop
// exit:
// ...
//
// Let's define the following terms:
// - iv_pre_i: The pre-incremented iv phi before the i-th iteration.
// - iv_post_i: The post-incremented iv phi after the i-th iteration.
//
// The iv_pre_i and iv_post_i have the following relation:
// iv_pre_i + stride = iv_post_i
//
// When converting a loop to a counted loop, we want to have a canonicalized loop exit check of the form:
// iv_post_i < adjusted_limit
//
// If that is not the case, we need to canonicalize the loop exit check by using different values for adjusted_limit:
// (LE1) iv_post_i < limit: Already canonicalized. We can directly use limit as adjusted_limit.
// -> adjusted_limit = limit.
// (LE2) iv_post_i <= limit:
// iv_post_i < limit + 1
// -> adjusted limit = limit + 1
// (LE3) iv_pre_i < limit:
// iv_pre_i + stride < limit + stride
// iv_post_i < limit + stride
// -> adjusted_limit = limit + stride
// (LE4) iv_pre_i <= limit:
// iv_pre_i < limit + 1
// iv_pre_i + stride < limit + stride + 1
// iv_post_i < limit + stride + 1
// -> adjusted_limit = limit + stride + 1
//
// Note that:
// (AL) limit <= adjusted_limit.
//
// The following loop invariant has to hold for counted loops with n iterations (i.e. loop exit check true after n-th
// loop iteration) and a canonicalized loop exit check to guarantee that no iv_post_i over- or underflows:
// (INV) For i = 1..n, min_int <= iv_post_i <= max_int
//
// To prove (INV), we require the following two conditions/assumptions:
// (i): adjusted_limit - 1 + stride <= max_int
// (ii): init < limit
//
// If we can prove (INV), we know that there can be no over- or underflow of any iv phi value. We prove (INV) by
// induction by assuming (i) and (ii).
//
// Proof by Induction
// ------------------
// > Base case (i = 1): We show that (INV) holds after the first iteration:
// min_int <= iv_post_1 = init + stride <= max_int
// Proof:
// First, we note that (ii) implies
// (iii) init <= limit - 1
// max_int >= adjusted_limit - 1 + stride [using (i)]
// >= limit - 1 + stride [using (AL)]
// >= init + stride [using (iii)]
// >= min_int [using stride > 0, no underflow]
// Thus, no overflow happens after the first iteration and (INV) holds for i = 1.
//
// Note that to prove the base case we need (i) and (ii).
//
// > Induction Hypothesis (i = j, j > 1): Assume that (INV) holds after the j-th iteration:
// min_int <= iv_post_j <= max_int
// > Step case (i = j + 1): We show that (INV) also holds after the j+1-th iteration:
// min_int <= iv_post_{j+1} = iv_post_j + stride <= max_int
// Proof:
// If iv_post_j >= adjusted_limit:
// We exit the loop after the j-th iteration, and we don't execute the j+1-th iteration anymore. Thus, there is
// also no iv_{j+1}. Since (INV) holds for iv_j, there is nothing left to prove.
// If iv_post_j < adjusted_limit:
// First, we note that:
// (iv) iv_post_j <= adjusted_limit - 1
// max_int >= adjusted_limit - 1 + stride [using (i)]
// >= iv_post_j + stride [using (iv)]
// >= min_int [using stride > 0, no underflow]
//
// Note that to prove the step case we only need (i).
//
// Thus, by assuming (i) and (ii), we proved (INV).
//
//
// It is therefore enough to add the following two Loop Limit Check Predicates to check assumptions (i) and (ii):
//
// (1) Loop Limit Check Predicate for (i):
// Using (i): adjusted_limit - 1 + stride <= max_int
//
// This condition is now restated to use limit instead of adjusted_limit:
//
// To prevent an overflow of adjusted_limit -1 + stride itself, we rewrite this check to
// max_int - stride + 1 >= adjusted_limit
// We can merge the two constants into
// canonicalized_correction = stride - 1
// which gives us
// max_int - canonicalized_correction >= adjusted_limit
//
// To directly use limit instead of adjusted_limit in the predicate condition, we split adjusted_limit into:
// adjusted_limit = limit + limit_correction
// Since stride > 0 and limit_correction <= stride + 1, we can restate this with no over- or underflow into:
// max_int - canonicalized_correction - limit_correction >= limit
// Since canonicalized_correction and limit_correction are both constants, we can replace them with a new constant:
// final_correction = canonicalized_correction + limit_correction
// which gives us:
//
// Final predicate condition:
// max_int - final_correction >= limit
//
// (2) Loop Limit Check Predicate for (ii):
// Using (ii): init < limit
//
// This Loop Limit Check Predicate is not required if we can prove at compile time that either:
// (2.1) type(init) < type(limit)
// In this case, we know:
// all possible values of init < all possible values of limit
// and we can skip the predicate.
//
// (2.2) init < limit is already checked before (i.e. found as a dominating check)
// In this case, we do not need to re-check the condition and can skip the predicate.
// This is often found for while- and for-loops which have the following shape:
//
// if (init < limit) { // Dominating test. Do not need the Loop Limit Check Predicate below.
// i = init;
// if (init >= limit) { trap(); } // Here we would insert the Loop Limit Check Predicate
// do {
// i += stride;
// } while (i < limit);
// }
//
// (2.3) init + stride <= max_int
// In this case, there is no overflow of the iv phi after the first loop iteration.
// In the proof of the base case above we showed that init + stride <= max_int by using assumption (ii):
// init < limit
// In the proof of the step case above, we did not need (ii) anymore. Therefore, if we already know at
// compile time that init + stride <= max_int then we have trivially proven the base case and that
// there is no overflow of the iv phi after the first iteration. In this case, we don't need to check (ii)
// again and can skip the predicate.
// Accounting for (LE3) and (LE4) where we use pre-incremented phis in the loop exit check.
const jlong limit_correction_for_pre_iv_exit_check = (phi_incr != nullptr) ? stride_con : 0;
// Accounting for (LE2) and (LE4) where we use <= or >= in the loop exit check.
const bool includes_limit = (bt == BoolTest::le || bt == BoolTest::ge);
const jlong limit_correction_for_le_ge_exit_check = (includes_limit ? (stride_con > 0 ? 1 : -1) : 0);
const jlong limit_correction = limit_correction_for_pre_iv_exit_check + limit_correction_for_le_ge_exit_check;
const jlong canonicalized_correction = stride_con + (stride_con > 0 ? -1 : 1);
const jlong final_correction = canonicalized_correction + limit_correction;
int sov = check_stride_overflow(final_correction, limit_t, iv_bt);
Node* init_control = x->in(LoopNode::EntryControl);
// If sov==0, limit's type always satisfies the condition, for
// example, when it is an array length.
if (sov != 0) {
if (sov < 0) {
return false; // Bailout: integer overflow is certain.
}
// (1) Loop Limit Check Predicate is required because we could not statically prove that
// limit + final_correction = adjusted_limit - 1 + stride <= max_int
assert(!x->as_Loop()->is_loop_nest_inner_loop(), "loop was transformed");
if (!ParsePredicates::is_loop_limit_check_predicate_proj(init_control)) {
// The Loop Limit Check Parse Predicate is not generated if this method trapped here before.
#ifdef ASSERT
if (TraceLoopLimitCheck) {
tty->print("Missing Loop Limit Check Parse Predicate:");
loop->dump_head();
x->dump(1);
}
#endif
return false;
}
ParsePredicateSuccessProj* loop_limit_check_parse_predicate_proj = init_control->as_IfTrue();
ParsePredicateNode* parse_predicate = loop_limit_check_parse_predicate_proj->in(0)->as_ParsePredicate();
if (!is_dominator(get_ctrl(limit), parse_predicate->in(0))) {
return false;
}
Node* cmp_limit;
Node* bol;
if (stride_con > 0) {
cmp_limit = CmpNode::make(limit, _igvn.integercon(max_signed_integer(iv_bt) - final_correction, iv_bt), iv_bt);
bol = new BoolNode(cmp_limit, BoolTest::le);
} else {
cmp_limit = CmpNode::make(limit, _igvn.integercon(min_signed_integer(iv_bt) - final_correction, iv_bt), iv_bt);
bol = new BoolNode(cmp_limit, BoolTest::ge);
}
insert_loop_limit_check_predicate(loop_limit_check_parse_predicate_proj, cmp_limit, bol);
}
// (2.3)
const bool init_plus_stride_could_overflow =
(stride_con > 0 && init_t->hi_as_long() > max_signed_integer(iv_bt) - stride_con) ||
(stride_con < 0 && init_t->lo_as_long() < min_signed_integer(iv_bt) - stride_con);
// (2.1)
const bool init_gte_limit = (stride_con > 0 && init_t->hi_as_long() >= limit_t->lo_as_long()) ||
(stride_con < 0 && init_t->lo_as_long() <= limit_t->hi_as_long());
if (init_gte_limit && // (2.1)
((bt == BoolTest::ne || init_plus_stride_could_overflow) && // (2.3)
!has_dominating_loop_limit_check(init_trip, limit, stride_con, iv_bt, init_control))) { // (2.2)
// (2) Iteration Loop Limit Check Predicate is required because neither (2.1), (2.2), nor (2.3) holds.
// We use the following condition:
// - stride > 0: init < limit
// - stride < 0: init > limit
//
// This predicate is always required if we have a non-equal-operator in the loop exit check (where stride = 1 is
// a requirement). We transform the loop exit check by using a less-than-operator. By doing so, we must always
// check that init < limit. Otherwise, we could have a different number of iterations at runtime.
if (!ParsePredicates::is_loop_limit_check_predicate_proj(init_control)) {
// The Loop Limit Check Parse Predicate is not generated if this method trapped here before.
#ifdef ASSERT
if (TraceLoopLimitCheck) {
tty->print("Missing Loop Limit Check Parse Predicate:");
loop->dump_head();
x->dump(1);
}
#endif
return false;
}
ParsePredicateSuccessProj* loop_limit_check_parse_predicate_proj = init_control->as_IfTrue();
ParsePredicateNode* parse_predicate = init_control->in(0)->as_ParsePredicate();
if (!is_dominator(get_ctrl(limit), parse_predicate->in(0)) ||
!is_dominator(get_ctrl(init_trip), parse_predicate->in(0))) {
return false;
}
Node* cmp_limit;
Node* bol;
if (stride_con > 0) {
cmp_limit = CmpNode::make(init_trip, limit, iv_bt);
bol = new BoolNode(cmp_limit, BoolTest::lt);
} else {
cmp_limit = CmpNode::make(init_trip, limit, iv_bt);
bol = new BoolNode(cmp_limit, BoolTest::gt);
}
insert_loop_limit_check_predicate(loop_limit_check_parse_predicate_proj, cmp_limit, bol);
}
if (bt == BoolTest::ne) {
// Now we need to canonicalize the loop condition if it is 'ne'.
assert(stride_con == 1 || stride_con == -1, "simple increment only - checked before");
if (stride_con > 0) {
// 'ne' can be replaced with 'lt' only when init < limit. This is ensured by the inserted predicate above.
bt = BoolTest::lt;
} else {
assert(stride_con < 0, "must be");
// 'ne' can be replaced with 'gt' only when init > limit. This is ensured by the inserted predicate above.
bt = BoolTest::gt;
}
}
Node* sfpt = nullptr;
if (loop->_child == nullptr) {
sfpt = find_safepoint(back_control, x, loop);
} else {
sfpt = iff->in(0);
if (sfpt->Opcode() != Op_SafePoint) {
sfpt = nullptr;
}
}
if (x->in(LoopNode::LoopBackControl)->Opcode() == Op_SafePoint) {
Node* backedge_sfpt = x->in(LoopNode::LoopBackControl);
if (((iv_bt == T_INT && LoopStripMiningIter != 0) ||
iv_bt == T_LONG) &&
sfpt == nullptr) {
// Leaving the safepoint on the backedge and creating a
// CountedLoop will confuse optimizations. We can't move the
// safepoint around because its jvm state wouldn't match a new
// location. Give up on that loop.
return false;
}
if (is_deleteable_safept(backedge_sfpt)) {
lazy_replace(backedge_sfpt, iftrue);
if (loop->_safepts != nullptr) {
loop->_safepts->yank(backedge_sfpt);
}
loop->_tail = iftrue;
}
}
#ifdef ASSERT
if (iv_bt == T_INT &&
!x->as_Loop()->is_loop_nest_inner_loop() &&
StressLongCountedLoop > 0 &&
trunc1 == nullptr &&
convert_to_long_loop(cmp, phi, loop)) {
return false;
}
#endif
Node* adjusted_limit = limit;
if (phi_incr != nullptr) {
// If compare points directly to the phi we need to adjust
// the compare so that it points to the incr. Limit have
// to be adjusted to keep trip count the same and we
// should avoid int overflow.
//
// i = init; do {} while(i++ < limit);
// is converted to
// i = init; do {} while(++i < limit+1);
//
adjusted_limit = gvn->transform(AddNode::make(limit, stride, iv_bt));
}
if (includes_limit) {
// The limit check guaranties that 'limit <= (max_jint - stride)' so
// we can convert 'i <= limit' to 'i < limit+1' since stride != 0.
//
Node* one = (stride_con > 0) ? gvn->integercon( 1, iv_bt) : gvn->integercon(-1, iv_bt);
adjusted_limit = gvn->transform(AddNode::make(adjusted_limit, one, iv_bt));
if (bt == BoolTest::le)
bt = BoolTest::lt;
else if (bt == BoolTest::ge)
bt = BoolTest::gt;
else
ShouldNotReachHere();
}
set_subtree_ctrl(adjusted_limit, false);
// Build a canonical trip test.
// Clone code, as old values may be in use.
incr = incr->clone();
incr->set_req(1,phi);
incr->set_req(2,stride);
incr = _igvn.register_new_node_with_optimizer(incr);
set_early_ctrl(incr, false);
_igvn.rehash_node_delayed(phi);
phi->set_req_X( LoopNode::LoopBackControl, incr, &_igvn );
// If phi type is more restrictive than Int, raise to
// Int to prevent (almost) infinite recursion in igvn
// which can only handle integer types for constants or minint..maxint.
if (!TypeInteger::bottom(iv_bt)->higher_equal(phi->bottom_type())) {
Node* nphi = PhiNode::make(phi->in(0), phi->in(LoopNode::EntryControl), TypeInteger::bottom(iv_bt));
nphi->set_req(LoopNode::LoopBackControl, phi->in(LoopNode::LoopBackControl));
nphi = _igvn.register_new_node_with_optimizer(nphi);
set_ctrl(nphi, get_ctrl(phi));
_igvn.replace_node(phi, nphi);
phi = nphi->as_Phi();
}
cmp = cmp->clone();
cmp->set_req(1,incr);
cmp->set_req(2, adjusted_limit);
cmp = _igvn.register_new_node_with_optimizer(cmp);
set_ctrl(cmp, iff->in(0));
test = test->clone()->as_Bool();
(*(BoolTest*)&test->_test)._test = bt;
test->set_req(1,cmp);
_igvn.register_new_node_with_optimizer(test);
set_ctrl(test, iff->in(0));
// Replace the old IfNode with a new LoopEndNode
Node *lex = _igvn.register_new_node_with_optimizer(BaseCountedLoopEndNode::make(iff->in(0), test, cl_prob, iff->as_If()->_fcnt, iv_bt));
IfNode *le = lex->as_If();
uint dd = dom_depth(iff);
set_idom(le, le->in(0), dd); // Update dominance for loop exit
set_loop(le, loop);
// Get the loop-exit control
Node *iffalse = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue));
// Need to swap loop-exit and loop-back control?
if (iftrue_op == Op_IfFalse) {
Node *ift2=_igvn.register_new_node_with_optimizer(new IfTrueNode (le));
Node *iff2=_igvn.register_new_node_with_optimizer(new IfFalseNode(le));
loop->_tail = back_control = ift2;
set_loop(ift2, loop);
set_loop(iff2, get_loop(iffalse));
// Lazy update of 'get_ctrl' mechanism.
lazy_replace(iffalse, iff2);
lazy_replace(iftrue, ift2);
// Swap names
iffalse = iff2;
iftrue = ift2;
} else {
_igvn.rehash_node_delayed(iffalse);
_igvn.rehash_node_delayed(iftrue);
iffalse->set_req_X( 0, le, &_igvn );
iftrue ->set_req_X( 0, le, &_igvn );
}
set_idom(iftrue, le, dd+1);
set_idom(iffalse, le, dd+1);
assert(iff->outcnt() == 0, "should be dead now");
lazy_replace( iff, le ); // fix 'get_ctrl'
Node* entry_control = init_control;
bool strip_mine_loop = iv_bt == T_INT &&
loop->_child == nullptr &&
sfpt != nullptr &&
!loop->_has_call &&
is_deleteable_safept(sfpt);
IdealLoopTree* outer_ilt = nullptr;
if (strip_mine_loop) {
outer_ilt = create_outer_strip_mined_loop(test, cmp, init_control, loop,
cl_prob, le->_fcnt, entry_control,
iffalse);
}
// Now setup a new CountedLoopNode to replace the existing LoopNode
BaseCountedLoopNode *l = BaseCountedLoopNode::make(entry_control, back_control, iv_bt);
l->set_unswitch_count(x->as_Loop()->unswitch_count()); // Preserve
// The following assert is approximately true, and defines the intention
// of can_be_counted_loop. It fails, however, because phase->type
// is not yet initialized for this loop and its parts.
//assert(l->can_be_counted_loop(this), "sanity");
_igvn.register_new_node_with_optimizer(l);
set_loop(l, loop);
loop->_head = l;
// Fix all data nodes placed at the old loop head.
// Uses the lazy-update mechanism of 'get_ctrl'.
lazy_replace( x, l );
set_idom(l, entry_control, dom_depth(entry_control) + 1);
if (iv_bt == T_INT && (LoopStripMiningIter == 0 || strip_mine_loop)) {
// Check for immediately preceding SafePoint and remove
if (sfpt != nullptr && (strip_mine_loop || is_deleteable_safept(sfpt))) {
if (strip_mine_loop) {
Node* outer_le = outer_ilt->_tail->in(0);
Node* sfpt_clone = sfpt->clone();
sfpt_clone->set_req(0, iffalse);
outer_le->set_req(0, sfpt_clone);
Node* polladdr = sfpt_clone->in(TypeFunc::Parms);
if (polladdr != nullptr && polladdr->is_Load()) {
// Polling load should be pinned outside inner loop.
Node* new_polladdr = polladdr->clone();
new_polladdr->set_req(0, iffalse);
_igvn.register_new_node_with_optimizer(new_polladdr, polladdr);
set_ctrl(new_polladdr, iffalse);
sfpt_clone->set_req(TypeFunc::Parms, new_polladdr);
}
// When this code runs, loop bodies have not yet been populated.
const bool body_populated = false;
register_control(sfpt_clone, outer_ilt, iffalse, body_populated);
set_idom(outer_le, sfpt_clone, dom_depth(sfpt_clone));
}
lazy_replace(sfpt, sfpt->in(TypeFunc::Control));
if (loop->_safepts != nullptr) {
loop->_safepts->yank(sfpt);
}
}
}
#ifdef ASSERT
assert(l->is_valid_counted_loop(iv_bt), "counted loop shape is messed up");
assert(l == loop->_head && l->phi() == phi && l->loopexit_or_null() == lex, "" );
#endif
#ifndef PRODUCT
if (TraceLoopOpts) {
tty->print("Counted ");
loop->dump_head();
}
#endif
C->print_method(PHASE_AFTER_CLOOPS, 3);
// Capture bounds of the loop in the induction variable Phi before
// subsequent transformation (iteration splitting) obscures the
// bounds
l->phi()->as_Phi()->set_type(l->phi()->Value(&_igvn));
if (strip_mine_loop) {
l->mark_strip_mined();
l->verify_strip_mined(1);
outer_ilt->_head->as_Loop()->verify_strip_mined(1);
loop = outer_ilt;
}
#ifndef PRODUCT
if (x->as_Loop()->is_loop_nest_inner_loop() && iv_bt == T_LONG) {
Atomic::inc(&_long_loop_counted_loops);
}
#endif
if (iv_bt == T_LONG && x->as_Loop()->is_loop_nest_outer_loop()) {
l->mark_loop_nest_outer_loop();
}
return true;
}
// Check if there is a dominating loop limit check of the form 'init < limit' starting at the loop entry.
// If there is one, then we do not need to create an additional Loop Limit Check Predicate.
bool PhaseIdealLoop::has_dominating_loop_limit_check(Node* init_trip, Node* limit, const jlong stride_con,
const BasicType iv_bt, Node* loop_entry) {
// Eagerly call transform() on the Cmp and Bool node to common them up if possible. This is required in order to
// successfully find a dominated test with the If node below.
Node* cmp_limit;
Node* bol;
if (stride_con > 0) {
cmp_limit = _igvn.transform(CmpNode::make(init_trip, limit, iv_bt));
bol = _igvn.transform(new BoolNode(cmp_limit, BoolTest::lt));
} else {
cmp_limit = _igvn.transform(CmpNode::make(init_trip, limit, iv_bt));
bol = _igvn.transform(new BoolNode(cmp_limit, BoolTest::gt));
}
// Check if there is already a dominating init < limit check. If so, we do not need a Loop Limit Check Predicate.
IfNode* iff = new IfNode(loop_entry, bol, PROB_MIN, COUNT_UNKNOWN);
// Also add fake IfProj nodes in order to call transform() on the newly created IfNode.
IfFalseNode* if_false = new IfFalseNode(iff);
IfTrueNode* if_true = new IfTrueNode(iff);
Node* dominated_iff = _igvn.transform(iff);
// ConI node? Found dominating test (IfNode::dominated_by() returns a ConI node).
const bool found_dominating_test = dominated_iff != nullptr && dominated_iff->is_ConI();
// Kill the If with its projections again in the next IGVN round by cutting it off from the graph.
_igvn.replace_input_of(iff, 0, C->top());
_igvn.replace_input_of(iff, 1, C->top());
return found_dominating_test;
}
//----------------------exact_limit-------------------------------------------
Node* PhaseIdealLoop::exact_limit( IdealLoopTree *loop ) {
assert(loop->_head->is_CountedLoop(), "");
CountedLoopNode *cl = loop->_head->as_CountedLoop();
assert(cl->is_valid_counted_loop(T_INT), "");
if (ABS(cl->stride_con()) == 1 ||
cl->limit()->Opcode() == Op_LoopLimit) {
// Old code has exact limit (it could be incorrect in case of int overflow).
// Loop limit is exact with stride == 1. And loop may already have exact limit.
return cl->limit();
}
Node *limit = nullptr;
#ifdef ASSERT
BoolTest::mask bt = cl->loopexit()->test_trip();
assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
#endif
if (cl->has_exact_trip_count()) {
// Simple case: loop has constant boundaries.
// Use jlongs to avoid integer overflow.
int stride_con = cl->stride_con();
jlong init_con = cl->init_trip()->get_int();
jlong limit_con = cl->limit()->get_int();
julong trip_cnt = cl->trip_count();
jlong final_con = init_con + trip_cnt*stride_con;
int final_int = (int)final_con;
// The final value should be in integer range since the loop
// is counted and the limit was checked for overflow.
assert(final_con == (jlong)final_int, "final value should be integer");
limit = _igvn.intcon(final_int);
} else {
// Create new LoopLimit node to get exact limit (final iv value).
limit = new LoopLimitNode(C, cl->init_trip(), cl->limit(), cl->stride());
register_new_node(limit, cl->in(LoopNode::EntryControl));
}
assert(limit != nullptr, "sanity");
return limit;
}
//------------------------------Ideal------------------------------------------
// Return a node which is more "ideal" than the current node.
// Attempt to convert into a counted-loop.
Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
if (!can_be_counted_loop(phase) && !is_OuterStripMinedLoop()) {
phase->C->set_major_progress();
}
return RegionNode::Ideal(phase, can_reshape);
}
#ifdef ASSERT
void LoopNode::verify_strip_mined(int expect_skeleton) const {
const OuterStripMinedLoopNode* outer = nullptr;
const CountedLoopNode* inner = nullptr;
if (is_strip_mined()) {
if (!is_valid_counted_loop(T_INT)) {
return; // Skip malformed counted loop
}
assert(is_CountedLoop(), "no Loop should be marked strip mined");
inner = as_CountedLoop();
outer = inner->in(LoopNode::EntryControl)->as_OuterStripMinedLoop();
} else if (is_OuterStripMinedLoop()) {
outer = this->as_OuterStripMinedLoop();
inner = outer->unique_ctrl_out()->as_CountedLoop();
assert(inner->is_valid_counted_loop(T_INT) && inner->is_strip_mined(), "OuterStripMinedLoop should have been removed");
assert(!is_strip_mined(), "outer loop shouldn't be marked strip mined");
}
if (inner != nullptr || outer != nullptr) {
assert(inner != nullptr && outer != nullptr, "missing loop in strip mined nest");
Node* outer_tail = outer->in(LoopNode::LoopBackControl);
Node* outer_le = outer_tail->in(0);
assert(outer_le->Opcode() == Op_OuterStripMinedLoopEnd, "tail of outer loop should be an If");
Node* sfpt = outer_le->in(0);
assert(sfpt->Opcode() == Op_SafePoint, "where's the safepoint?");
Node* inner_out = sfpt->in(0);
CountedLoopEndNode* cle = inner_out->in(0)->as_CountedLoopEnd();
assert(cle == inner->loopexit_or_null(), "mismatch");
bool has_skeleton = outer_le->in(1)->bottom_type()->singleton() && outer_le->in(1)->bottom_type()->is_int()->get_con() == 0;
if (has_skeleton) {
assert(expect_skeleton == 1 || expect_skeleton == -1, "unexpected skeleton node");
assert(outer->outcnt() == 2, "only control nodes");
} else {
assert(expect_skeleton == 0 || expect_skeleton == -1, "no skeleton node?");
uint phis = 0;
uint be_loads = 0;
Node* be = inner->in(LoopNode::LoopBackControl);
for (DUIterator_Fast imax, i = inner->fast_outs(imax); i < imax; i++) {
Node* u = inner->fast_out(i);
if (u->is_Phi()) {
phis++;
for (DUIterator_Fast jmax, j = be->fast_outs(jmax); j < jmax; j++) {
Node* n = be->fast_out(j);
if (n->is_Load()) {
assert(n->in(0) == be || n->find_prec_edge(be) > 0, "should be on the backedge");
do {
n = n->raw_out(0);
} while (!n->is_Phi());
if (n == u) {
be_loads++;
break;
}
}
}
}
}
assert(be_loads <= phis, "wrong number phis that depends on a pinned load");
for (DUIterator_Fast imax, i = outer->fast_outs(imax); i < imax; i++) {
Node* u = outer->fast_out(i);
assert(u == outer || u == inner || u->is_Phi(), "nothing between inner and outer loop");
}
uint stores = 0;
for (DUIterator_Fast imax, i = inner_out->fast_outs(imax); i < imax; i++) {
Node* u = inner_out->fast_out(i);
if (u->is_Store()) {
stores++;
}
}
// Late optimization of loads on backedge can cause Phi of outer loop to be eliminated but Phi of inner loop is
// not guaranteed to be optimized out.
assert(outer->outcnt() >= phis + 2 - be_loads && outer->outcnt() <= phis + 2 + stores + 1, "only phis");
}
assert(sfpt->outcnt() == 1, "no data node");
assert(outer_tail->outcnt() == 1 || !has_skeleton, "no data node");
}
}
#endif
//=============================================================================
//------------------------------Ideal------------------------------------------
// Return a node which is more "ideal" than the current node.
// Attempt to convert into a counted-loop.
Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
return RegionNode::Ideal(phase, can_reshape);
}
//------------------------------dump_spec--------------------------------------
// Dump special per-node info
#ifndef PRODUCT
void CountedLoopNode::dump_spec(outputStream *st) const {
LoopNode::dump_spec(st);
if (stride_is_con()) {
st->print("stride: %d ",stride_con());
}
if (is_pre_loop ()) st->print("pre of N%d" , _main_idx);
if (is_main_loop()) st->print("main of N%d", _idx);
if (is_post_loop()) st->print("post of N%d", _main_idx);
if (is_strip_mined()) st->print(" strip mined");
}
#endif
//=============================================================================
jlong BaseCountedLoopEndNode::stride_con() const {
return stride()->bottom_type()->is_integer(bt())->get_con_as_long(bt());
}
BaseCountedLoopEndNode* BaseCountedLoopEndNode::make(Node* control, Node* test, float prob, float cnt, BasicType bt) {
if (bt == T_INT) {
return new CountedLoopEndNode(control, test, prob, cnt);
}
assert(bt == T_LONG, "unsupported");
return new LongCountedLoopEndNode(control, test, prob, cnt);
}
//=============================================================================
//------------------------------Value-----------------------------------------
const Type* LoopLimitNode::Value(PhaseGVN* phase) const {
const Type* init_t = phase->type(in(Init));
const Type* limit_t = phase->type(in(Limit));
const Type* stride_t = phase->type(in(Stride));
// Either input is TOP ==> the result is TOP
if (init_t == Type::TOP) return Type::TOP;
if (limit_t == Type::TOP) return Type::TOP;
if (stride_t == Type::TOP) return Type::TOP;
int stride_con = stride_t->is_int()->get_con();
if (stride_con == 1)
return bottom_type(); // Identity
if (init_t->is_int()->is_con() && limit_t->is_int()->is_con()) {
// Use jlongs to avoid integer overflow.
jlong init_con = init_t->is_int()->get_con();
jlong limit_con = limit_t->is_int()->get_con();
int stride_m = stride_con - (stride_con > 0 ? 1 : -1);
jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
jlong final_con = init_con + stride_con*trip_count;
int final_int = (int)final_con;
// The final value should be in integer range since the loop
// is counted and the limit was checked for overflow.
// Assert checks for overflow only if all input nodes are ConINodes, as during CCP
// there might be a temporary overflow from PhiNodes see JDK-8309266
assert((in(Init)->is_ConI() && in(Limit)->is_ConI() && in(Stride)->is_ConI()) ? final_con == (jlong)final_int : true, "final value should be integer");
if (final_con == (jlong)final_int) {
return TypeInt::make(final_int);
} else {
return bottom_type();
}
}
return bottom_type(); // TypeInt::INT
}
//------------------------------Ideal------------------------------------------
// Return a node which is more "ideal" than the current node.
Node *LoopLimitNode::Ideal(PhaseGVN *phase, bool can_reshape) {
if (phase->type(in(Init)) == Type::TOP ||
phase->type(in(Limit)) == Type::TOP ||
phase->type(in(Stride)) == Type::TOP)
return nullptr; // Dead
int stride_con = phase->type(in(Stride))->is_int()->get_con();
if (stride_con == 1)
return nullptr; // Identity
if (in(Init)->is_Con() && in(Limit)->is_Con())
return nullptr; // Value
// Delay following optimizations until all loop optimizations
// done to keep Ideal graph simple.
if (!can_reshape || !phase->C->post_loop_opts_phase()) {
return nullptr;
}
const TypeInt* init_t = phase->type(in(Init) )->is_int();
const TypeInt* limit_t = phase->type(in(Limit))->is_int();
int stride_p;
jlong lim, ini;
julong max;
if (stride_con > 0) {
stride_p = stride_con;
lim = limit_t->_hi;
ini = init_t->_lo;
max = (julong)max_jint;
} else {
stride_p = -stride_con;
lim = init_t->_hi;
ini = limit_t->_lo;
max = (julong)min_jint;
}
julong range = lim - ini + stride_p;
if (range <= max) {
// Convert to integer expression if it is not overflow.
Node* stride_m = phase->intcon(stride_con - (stride_con > 0 ? 1 : -1));
Node *range = phase->transform(new SubINode(in(Limit), in(Init)));
Node *bias = phase->transform(new AddINode(range, stride_m));
Node *trip = phase->transform(new DivINode(0, bias, in(Stride)));
Node *span = phase->transform(new MulINode(trip, in(Stride)));
return new AddINode(span, in(Init)); // exact limit
}
if (is_power_of_2(stride_p) || // divisor is 2^n
!Matcher::has_match_rule(Op_LoopLimit)) { // or no specialized Mach node?
// Convert to long expression to avoid integer overflow
// and let igvn optimizer convert this division.
//
Node* init = phase->transform( new ConvI2LNode(in(Init)));
Node* limit = phase->transform( new ConvI2LNode(in(Limit)));
Node* stride = phase->longcon(stride_con);
Node* stride_m = phase->longcon(stride_con - (stride_con > 0 ? 1 : -1));
Node *range = phase->transform(new SubLNode(limit, init));
Node *bias = phase->transform(new AddLNode(range, stride_m));
Node *span;
if (stride_con > 0 && is_power_of_2(stride_p)) {
// bias >= 0 if stride >0, so if stride is 2^n we can use &(-stride)
// and avoid generating rounding for division. Zero trip guard should
// guarantee that init < limit but sometimes the guard is missing and
// we can get situation when init > limit. Note, for the empty loop
// optimization zero trip guard is generated explicitly which leaves
// only RCE predicate where exact limit is used and the predicate
// will simply fail forcing recompilation.
Node* neg_stride = phase->longcon(-stride_con);
span = phase->transform(new AndLNode(bias, neg_stride));
} else {
Node *trip = phase->transform(new DivLNode(0, bias, stride));
span = phase->transform(new MulLNode(trip, stride));
}
// Convert back to int
Node *span_int = phase->transform(new ConvL2INode(span));
return new AddINode(span_int, in(Init)); // exact limit
}
return nullptr; // No progress
}
//------------------------------Identity---------------------------------------
// If stride == 1 return limit node.
Node* LoopLimitNode::Identity(PhaseGVN* phase) {
int stride_con = phase->type(in(Stride))->is_int()->get_con();
if (stride_con == 1 || stride_con == -1)
return in(Limit);
return this;
}
//=============================================================================
//----------------------match_incr_with_optional_truncation--------------------
// Match increment with optional truncation:
// CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16
// Return null for failure. Success returns the increment node.
Node* CountedLoopNode::match_incr_with_optional_truncation(Node* expr, Node** trunc1, Node** trunc2,
const TypeInteger** trunc_type,
BasicType bt) {
// Quick cutouts:
if (expr == nullptr || expr->req() != 3) return nullptr;
Node *t1 = nullptr;
Node *t2 = nullptr;
Node* n1 = expr;
int n1op = n1->Opcode();
const TypeInteger* trunc_t = TypeInteger::bottom(bt);
if (bt == T_INT) {
// Try to strip (n1 & M) or (n1 << N >> N) from n1.
if (n1op == Op_AndI &&
n1->in(2)->is_Con() &&
n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) {
// %%% This check should match any mask of 2**K-1.
t1 = n1;
n1 = t1->in(1);
n1op = n1->Opcode();
trunc_t = TypeInt::CHAR;
} else if (n1op == Op_RShiftI &&
n1->in(1) != nullptr &&
n1->in(1)->Opcode() == Op_LShiftI &&
n1->in(2) == n1->in(1)->in(2) &&
n1->in(2)->is_Con()) {
jint shift = n1->in(2)->bottom_type()->is_int()->get_con();
// %%% This check should match any shift in [1..31].
if (shift == 16 || shift == 8) {
t1 = n1;
t2 = t1->in(1);
n1 = t2->in(1);
n1op = n1->Opcode();
if (shift == 16) {
trunc_t = TypeInt::SHORT;
} else if (shift == 8) {
trunc_t = TypeInt::BYTE;
}
}
}
}
// If (maybe after stripping) it is an AddI, we won:
if (n1op == Op_Add(bt)) {
*trunc1 = t1;
*trunc2 = t2;
*trunc_type = trunc_t;
return n1;
}
// failed
return nullptr;
}
LoopNode* CountedLoopNode::skip_strip_mined(int expect_skeleton) {
if (is_strip_mined() && in(EntryControl) != nullptr && in(EntryControl)->is_OuterStripMinedLoop()) {
verify_strip_mined(expect_skeleton);
return in(EntryControl)->as_Loop();
}
return this;
}
OuterStripMinedLoopNode* CountedLoopNode::outer_loop() const {
assert(is_strip_mined(), "not a strip mined loop");
Node* c = in(EntryControl);
if (c == nullptr || c->is_top() || !c->is_OuterStripMinedLoop()) {
return nullptr;
}
return c->as_OuterStripMinedLoop();
}
IfTrueNode* OuterStripMinedLoopNode::outer_loop_tail() const {
Node* c = in(LoopBackControl);
if (c == nullptr || c->is_top()) {
return nullptr;
}
return c->as_IfTrue();
}
IfTrueNode* CountedLoopNode::outer_loop_tail() const {
LoopNode* l = outer_loop();
if (l == nullptr) {
return nullptr;
}
return l->outer_loop_tail();
}
OuterStripMinedLoopEndNode* OuterStripMinedLoopNode::outer_loop_end() const {
IfTrueNode* proj = outer_loop_tail();
if (proj == nullptr) {
return nullptr;
}
Node* c = proj->in(0);
if (c == nullptr || c->is_top() || c->outcnt() != 2) {
return nullptr;
}
return c->as_OuterStripMinedLoopEnd();
}
OuterStripMinedLoopEndNode* CountedLoopNode::outer_loop_end() const {
LoopNode* l = outer_loop();
if (l == nullptr) {
return nullptr;
}
return l->outer_loop_end();
}
IfFalseNode* OuterStripMinedLoopNode::outer_loop_exit() const {
IfNode* le = outer_loop_end();
if (le == nullptr) {
return nullptr;
}
Node* c = le->proj_out_or_null(false);
if (c == nullptr) {
return nullptr;
}
return c->as_IfFalse();
}
IfFalseNode* CountedLoopNode::outer_loop_exit() const {
LoopNode* l = outer_loop();
if (l == nullptr) {
return nullptr;
}
return l->outer_loop_exit();
}
SafePointNode* OuterStripMinedLoopNode::outer_safepoint() const {
IfNode* le = outer_loop_end();
if (le == nullptr) {
return nullptr;
}
Node* c = le->in(0);
if (c == nullptr || c->is_top()) {
return nullptr;
}
assert(c->Opcode() == Op_SafePoint, "broken outer loop");
return c->as_SafePoint();
}
SafePointNode* CountedLoopNode::outer_safepoint() const {
LoopNode* l = outer_loop();
if (l == nullptr) {
return nullptr;
}
return l->outer_safepoint();
}
Node* CountedLoopNode::skip_predicates_from_entry(Node* ctrl) {
while (ctrl != nullptr && ctrl->is_Proj() && ctrl->in(0) != nullptr && ctrl->in(0)->is_If() &&
!is_zero_trip_guard_if(ctrl->in(0)->as_If()) &&
(ctrl->in(0)->as_If()->proj_out_or_null(1-ctrl->as_Proj()->_con) == nullptr ||
(ctrl->in(0)->as_If()->proj_out(1-ctrl->as_Proj()->_con)->outcnt() == 1 &&
ctrl->in(0)->as_If()->proj_out(1-ctrl->as_Proj()->_con)->unique_out()->Opcode() == Op_Halt))) {
ctrl = ctrl->in(0)->in(0);
}
return ctrl;
}
bool CountedLoopNode::is_zero_trip_guard_if(const IfNode* iff) {
if (iff->in(1) == nullptr || !iff->in(1)->is_Bool()) {
return false;
}
if (iff->in(1)->in(1) == nullptr || iff->in(1)->in(1)->Opcode() != Op_CmpI) {
return false;
}
if (iff->in(1)->in(1)->in(1) != nullptr && iff->in(1)->in(1)->in(1)->Opcode() == Op_OpaqueZeroTripGuard) {
return true;
}
if (iff->in(1)->in(1)->in(2) != nullptr && iff->in(1)->in(1)->in(2)->Opcode() == Op_OpaqueZeroTripGuard) {
return true;
}
return false;
}
Node* CountedLoopNode::skip_predicates() {
Node* ctrl = in(LoopNode::EntryControl);
if (is_main_loop()) {
ctrl = skip_strip_mined()->in(LoopNode::EntryControl);
}
if (is_main_loop() || is_post_loop()) {
return skip_predicates_from_entry(ctrl);
}
return ctrl;
}
int CountedLoopNode::stride_con() const {
CountedLoopEndNode* cle = loopexit_or_null();
return cle != nullptr ? cle->stride_con() : 0;
}
BaseCountedLoopNode* BaseCountedLoopNode::make(Node* entry, Node* backedge, BasicType bt) {
if (bt == T_INT) {
return new CountedLoopNode(entry, backedge);
}
assert(bt == T_LONG, "unsupported");
return new LongCountedLoopNode(entry, backedge);
}
void OuterStripMinedLoopNode::fix_sunk_stores(CountedLoopEndNode* inner_cle, LoopNode* inner_cl, PhaseIterGVN* igvn,
PhaseIdealLoop* iloop) {
Node* cle_out = inner_cle->proj_out(false);
Node* cle_tail = inner_cle->proj_out(true);
if (cle_out->outcnt() > 1) {
// Look for chains of stores that were sunk
// out of the inner loop and are in the outer loop
for (DUIterator_Fast imax, i = cle_out->fast_outs(imax); i < imax; i++) {
Node* u = cle_out->fast_out(i);
if (u->is_Store()) {
int alias_idx = igvn->C->get_alias_index(u->adr_type());
Node* first = u;
for (;;) {
Node* next = first->in(MemNode::Memory);
if (!next->is_Store() || next->in(0) != cle_out) {
break;
}
assert(igvn->C->get_alias_index(next->adr_type()) == alias_idx, "");
first = next;
}
Node* last = u;
for (;;) {
Node* next = nullptr;
for (DUIterator_Fast jmax, j = last->fast_outs(jmax); j < jmax; j++) {
Node* uu = last->fast_out(j);
if (uu->is_Store() && uu->in(0) == cle_out) {
assert(next == nullptr, "only one in the outer loop");
next = uu;
assert(igvn->C->get_alias_index(next->adr_type()) == alias_idx, "");
}
}
if (next == nullptr) {
break;
}
last = next;
}
Node* phi = nullptr;
for (DUIterator_Fast jmax, j = inner_cl->fast_outs(jmax); j < jmax; j++) {
Node* uu = inner_cl->fast_out(j);
if (uu->is_Phi()) {
Node* be = uu->in(LoopNode::LoopBackControl);
if (be->is_Store() && be->in(0) == inner_cl->in(LoopNode::LoopBackControl)) {
assert(igvn->C->get_alias_index(uu->adr_type()) != alias_idx && igvn->C->get_alias_index(uu->adr_type()) != Compile::AliasIdxBot, "unexpected store");
}
if (be == last || be == first->in(MemNode::Memory)) {
assert(igvn->C->get_alias_index(uu->adr_type()) == alias_idx || igvn->C->get_alias_index(uu->adr_type()) == Compile::AliasIdxBot, "unexpected alias");
assert(phi == nullptr, "only one phi");
phi = uu;
}
}
}
#ifdef ASSERT
for (DUIterator_Fast jmax, j = inner_cl->fast_outs(jmax); j < jmax; j++) {
Node* uu = inner_cl->fast_out(j);
if (uu->is_Phi() && uu->bottom_type() == Type::MEMORY) {
if (uu->adr_type() == igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type()))) {
assert(phi == uu, "what's that phi?");
} else if (uu->adr_type() == TypePtr::BOTTOM) {
Node* n = uu->in(LoopNode::LoopBackControl);
uint limit = igvn->C->live_nodes();
uint i = 0;
while (n != uu) {
i++;
assert(i < limit, "infinite loop");
if (n->is_Proj()) {
n = n->in(0);
} else if (n->is_SafePoint() || n->is_MemBar()) {
n = n->in(TypeFunc::Memory);
} else if (n->is_Phi()) {
n = n->in(1);
} else if (n->is_MergeMem()) {
n = n->as_MergeMem()->memory_at(igvn->C->get_alias_index(u->adr_type()));
} else if (n->is_Store() || n->is_LoadStore() || n->is_ClearArray()) {
n = n->in(MemNode::Memory);
} else {
n->dump();
ShouldNotReachHere();
}
}
}
}
}
#endif
if (phi == nullptr) {
// If an entire chains was sunk, the
// inner loop has no phi for that memory
// slice, create one for the outer loop
phi = PhiNode::make(inner_cl, first->in(MemNode::Memory), Type::MEMORY,
igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type())));
phi->set_req(LoopNode::LoopBackControl, last);
phi = register_new_node(phi, inner_cl, igvn, iloop);
igvn->replace_input_of(first, MemNode::Memory, phi);
} else {
// Or fix the outer loop fix to include
// that chain of stores.
Node* be = phi->in(LoopNode::LoopBackControl);
assert(!(be->is_Store() && be->in(0) == inner_cl->in(LoopNode::LoopBackControl)), "store on the backedge + sunk stores: unsupported");
if (be == first->in(MemNode::Memory)) {
if (be == phi->in(LoopNode::LoopBackControl)) {
igvn->replace_input_of(phi, LoopNode::LoopBackControl, last);
} else {
igvn->replace_input_of(be, MemNode::Memory, last);
}
} else {
#ifdef ASSERT
if (be == phi->in(LoopNode::LoopBackControl)) {
assert(phi->in(LoopNode::LoopBackControl) == last, "");
} else {
assert(be->in(MemNode::Memory) == last, "");
}
#endif
}
}
}
}
}
}
void OuterStripMinedLoopNode::adjust_strip_mined_loop(PhaseIterGVN* igvn) {
// Look for the outer & inner strip mined loop, reduce number of
// iterations of the inner loop, set exit condition of outer loop,
// construct required phi nodes for outer loop.
CountedLoopNode* inner_cl = unique_ctrl_out()->as_CountedLoop();
assert(inner_cl->is_strip_mined(), "inner loop should be strip mined");
if (LoopStripMiningIter == 0) {
remove_outer_loop_and_safepoint(igvn);
return;
}
if (LoopStripMiningIter == 1) {
transform_to_counted_loop(igvn, nullptr);
return;
}
Node* inner_iv_phi = inner_cl->phi();
if (inner_iv_phi == nullptr) {
IfNode* outer_le = outer_loop_end();
Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
igvn->replace_node(outer_le, iff);
inner_cl->clear_strip_mined();
return;
}
CountedLoopEndNode* inner_cle = inner_cl->loopexit();
int stride = inner_cl->stride_con();
jlong scaled_iters_long = ((jlong)LoopStripMiningIter) * ABS(stride);
int scaled_iters = (int)scaled_iters_long;
int short_scaled_iters = LoopStripMiningIterShortLoop* ABS(stride);
const TypeInt* inner_iv_t = igvn->type(inner_iv_phi)->is_int();
jlong iter_estimate = (jlong)inner_iv_t->_hi - (jlong)inner_iv_t->_lo;
assert(iter_estimate > 0, "broken");
if ((jlong)scaled_iters != scaled_iters_long || iter_estimate <= short_scaled_iters) {
// Remove outer loop and safepoint (too few iterations)
remove_outer_loop_and_safepoint(igvn);
return;
}
if (iter_estimate <= scaled_iters_long) {
// We would only go through one iteration of
// the outer loop: drop the outer loop but
// keep the safepoint so we don't run for
// too long without a safepoint
IfNode* outer_le = outer_loop_end();
Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
igvn->replace_node(outer_le, iff);
inner_cl->clear_strip_mined();
return;
}
Node* cle_tail = inner_cle->proj_out(true);
ResourceMark rm;
Node_List old_new;
if (cle_tail->outcnt() > 1) {
// Look for nodes on backedge of inner loop and clone them
Unique_Node_List backedge_nodes;
for (DUIterator_Fast imax, i = cle_tail->fast_outs(imax); i < imax; i++) {
Node* u = cle_tail->fast_out(i);
if (u != inner_cl) {
assert(!u->is_CFG(), "control flow on the backedge?");
backedge_nodes.push(u);
}
}
uint last = igvn->C->unique();
for (uint next = 0; next < backedge_nodes.size(); next++) {
Node* n = backedge_nodes.at(next);
old_new.map(n->_idx, n->clone());
for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
Node* u = n->fast_out(i);
assert(!u->is_CFG(), "broken");
if (u->_idx >= last) {
continue;
}
if (!u->is_Phi()) {
backedge_nodes.push(u);
} else {
assert(u->in(0) == inner_cl, "strange phi on the backedge");
}
}
}
// Put the clones on the outer loop backedge
Node* le_tail = outer_loop_tail();
for (uint next = 0; next < backedge_nodes.size(); next++) {
Node *n = old_new[backedge_nodes.at(next)->_idx];
for (uint i = 1; i < n->req(); i++) {
if (n->in(i) != nullptr && old_new[n->in(i)->_idx] != nullptr) {
n->set_req(i, old_new[n->in(i)->_idx]);
}
}
if (n->in(0) != nullptr && n->in(0) == cle_tail) {
n->set_req(0, le_tail);
}
igvn->register_new_node_with_optimizer(n);
}
}
Node* iv_phi = nullptr;
// Make a clone of each phi in the inner loop
// for the outer loop
for (uint i = 0; i < inner_cl->outcnt(); i++) {
Node* u = inner_cl->raw_out(i);
if (u->is_Phi()) {
assert(u->in(0) == inner_cl, "inconsistent");
Node* phi = u->clone();
phi->set_req(0, this);
Node* be = old_new[phi->in(LoopNode::LoopBackControl)->_idx];
if (be != nullptr) {
phi->set_req(LoopNode::LoopBackControl, be);
}
phi = igvn->transform(phi);
igvn->replace_input_of(u, LoopNode::EntryControl, phi);
if (u == inner_iv_phi) {
iv_phi = phi;
}
}
}
if (iv_phi != nullptr) {
// Now adjust the inner loop's exit condition
Node* limit = inner_cl->limit();
// If limit < init for stride > 0 (or limit > init for stride < 0),
// the loop body is run only once. Given limit - init (init - limit resp.)
// would be negative, the unsigned comparison below would cause
// the loop body to be run for LoopStripMiningIter.
Node* max = nullptr;
if (stride > 0) {
max = MaxNode::max_diff_with_zero(limit, iv_phi, TypeInt::INT, *igvn);
} else {
max = MaxNode::max_diff_with_zero(iv_phi, limit, TypeInt::INT, *igvn);
}
// sub is positive and can be larger than the max signed int
// value. Use an unsigned min.
Node* const_iters = igvn->intcon(scaled_iters);
Node* min = MaxNode::unsigned_min(max, const_iters, TypeInt::make(0, scaled_iters, Type::WidenMin), *igvn);
// min is the number of iterations for the next inner loop execution:
// unsigned_min(max(limit - iv_phi, 0), scaled_iters) if stride > 0
// unsigned_min(max(iv_phi - limit, 0), scaled_iters) if stride < 0
Node* new_limit = nullptr;
if (stride > 0) {
new_limit = igvn->transform(new AddINode(min, iv_phi));
} else {
new_limit = igvn->transform(new SubINode(iv_phi, min));
}
Node* inner_cmp = inner_cle->cmp_node();
Node* inner_bol = inner_cle->in(CountedLoopEndNode::TestValue);
Node* outer_bol = inner_bol;
// cmp node for inner loop may be shared
inner_cmp = inner_cmp->clone();
inner_cmp->set_req(2, new_limit);
inner_bol = inner_bol->clone();
inner_bol->set_req(1, igvn->transform(inner_cmp));
igvn->replace_input_of(inner_cle, CountedLoopEndNode::TestValue, igvn->transform(inner_bol));
// Set the outer loop's exit condition too
igvn->replace_input_of(outer_loop_end(), 1, outer_bol);
} else {
assert(false, "should be able to adjust outer loop");
IfNode* outer_le = outer_loop_end();
Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
igvn->replace_node(outer_le, iff);
inner_cl->clear_strip_mined();
}
}
void OuterStripMinedLoopNode::transform_to_counted_loop(PhaseIterGVN* igvn, PhaseIdealLoop* iloop) {
CountedLoopNode* inner_cl = unique_ctrl_out()->as_CountedLoop();
CountedLoopEndNode* cle = inner_cl->loopexit();
Node* inner_test = cle->in(1);
IfNode* outer_le = outer_loop_end();
CountedLoopEndNode* inner_cle = inner_cl->loopexit();
Node* safepoint = outer_safepoint();
fix_sunk_stores(inner_cle, inner_cl, igvn, iloop);
// make counted loop exit test always fail
ConINode* zero = igvn->intcon(0);
if (iloop != nullptr) {
iloop->set_ctrl(zero, igvn->C->root());
}
igvn->replace_input_of(cle, 1, zero);
// replace outer loop end with CountedLoopEndNode with formers' CLE's exit test
Node* new_end = new CountedLoopEndNode(outer_le->in(0), inner_test, cle->_prob, cle->_fcnt);
register_control(new_end, inner_cl, outer_le->in(0), igvn, iloop);
if (iloop == nullptr) {
igvn->replace_node(outer_le, new_end);
} else {
iloop->lazy_replace(outer_le, new_end);
}
// the backedge of the inner loop must be rewired to the new loop end
Node* backedge = cle->proj_out(true);
igvn->replace_input_of(backedge, 0, new_end);
if (iloop != nullptr) {
iloop->set_idom(backedge, new_end, iloop->dom_depth(new_end) + 1);
}
// make the outer loop go away
igvn->replace_input_of(in(LoopBackControl), 0, igvn->C->top());
igvn->replace_input_of(this, LoopBackControl, igvn->C->top());
inner_cl->clear_strip_mined();
if (iloop != nullptr) {
Unique_Node_List wq;
wq.push(safepoint);
IdealLoopTree* outer_loop_ilt = iloop->get_loop(this);
IdealLoopTree* loop = iloop->get_loop(inner_cl);
for (uint i = 0; i < wq.size(); i++) {
Node* n = wq.at(i);
for (uint j = 0; j < n->req(); ++j) {
Node* in = n->in(j);
if (in == nullptr || in->is_CFG()) {
continue;
}
if (iloop->get_loop(iloop->get_ctrl(in)) != outer_loop_ilt) {
continue;
}
assert(!loop->_body.contains(in), "");
loop->_body.push(in);
wq.push(in);
}
}
iloop->set_loop(safepoint, loop);
loop->_body.push(safepoint);
iloop->set_loop(safepoint->in(0), loop);
loop->_body.push(safepoint->in(0));
outer_loop_ilt->_tail = igvn->C->top();
}
}
void OuterStripMinedLoopNode::remove_outer_loop_and_safepoint(PhaseIterGVN* igvn) const {
CountedLoopNode* inner_cl = unique_ctrl_out()->as_CountedLoop();
Node* outer_sfpt = outer_safepoint();
Node* outer_out = outer_loop_exit();
igvn->replace_node(outer_out, outer_sfpt->in(0));
igvn->replace_input_of(outer_sfpt, 0, igvn->C->top());
inner_cl->clear_strip_mined();
}
Node* OuterStripMinedLoopNode::register_new_node(Node* node, LoopNode* ctrl, PhaseIterGVN* igvn, PhaseIdealLoop* iloop) {
if (iloop == nullptr) {
return igvn->transform(node);
}
iloop->register_new_node(node, ctrl);
return node;
}
Node* OuterStripMinedLoopNode::register_control(Node* node, Node* loop, Node* idom, PhaseIterGVN* igvn,
PhaseIdealLoop* iloop) {
if (iloop == nullptr) {
return igvn->transform(node);
}
iloop->register_control(node, iloop->get_loop(loop), idom);
return node;
}
const Type* OuterStripMinedLoopEndNode::Value(PhaseGVN* phase) const {
if (!in(0)) return Type::TOP;
if (phase->type(in(0)) == Type::TOP)
return Type::TOP;
// Until expansion, the loop end condition is not set so this should not constant fold.
if (is_expanded(phase)) {
return IfNode::Value(phase);
}
return TypeTuple::IFBOTH;
}
bool OuterStripMinedLoopEndNode::is_expanded(PhaseGVN *phase) const {
// The outer strip mined loop head only has Phi uses after expansion
if (phase->is_IterGVN()) {
Node* backedge = proj_out_or_null(true);
if (backedge != nullptr) {
Node* head = backedge->unique_ctrl_out_or_null();
if (head != nullptr && head->is_OuterStripMinedLoop()) {
if (head->find_out_with(Op_Phi) != nullptr) {
return true;
}
}
}
}
return false;
}
Node *OuterStripMinedLoopEndNode::Ideal(PhaseGVN *phase, bool can_reshape) {
if (remove_dead_region(phase, can_reshape)) return this;
return nullptr;
}
//------------------------------filtered_type--------------------------------
// Return a type based on condition control flow
// A successful return will be a type that is restricted due
// to a series of dominating if-tests, such as:
// if (i < 10) {
// if (i > 0) {
// here: "i" type is [1..10)
// }
// }
// or a control flow merge
// if (i < 10) {
// do {
// phi( , ) -- at top of loop type is [min_int..10)
// i = ?
// } while ( i < 10)
//
const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) {
assert(n && n->bottom_type()->is_int(), "must be int");
const TypeInt* filtered_t = nullptr;
if (!n->is_Phi()) {
assert(n_ctrl != nullptr || n_ctrl == C->top(), "valid control");
filtered_t = filtered_type_from_dominators(n, n_ctrl);
} else {
Node* phi = n->as_Phi();
Node* region = phi->in(0);
assert(n_ctrl == nullptr || n_ctrl == region, "ctrl parameter must be region");
if (region && region != C->top()) {
for (uint i = 1; i < phi->req(); i++) {
Node* val = phi->in(i);
Node* use_c = region->in(i);
const TypeInt* val_t = filtered_type_from_dominators(val, use_c);
if (val_t != nullptr) {
if (filtered_t == nullptr) {
filtered_t = val_t;
} else {
filtered_t = filtered_t->meet(val_t)->is_int();
}
}
}
}
}
const TypeInt* n_t = _igvn.type(n)->is_int();
if (filtered_t != nullptr) {
n_t = n_t->join(filtered_t)->is_int();
}
return n_t;
}
//------------------------------filtered_type_from_dominators--------------------------------
// Return a possibly more restrictive type for val based on condition control flow of dominators
const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) {
if (val->is_Con()) {
return val->bottom_type()->is_int();
}
uint if_limit = 10; // Max number of dominating if's visited
const TypeInt* rtn_t = nullptr;
if (use_ctrl && use_ctrl != C->top()) {
Node* val_ctrl = get_ctrl(val);
uint val_dom_depth = dom_depth(val_ctrl);
Node* pred = use_ctrl;
uint if_cnt = 0;
while (if_cnt < if_limit) {
if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) {
if_cnt++;
const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred);
if (if_t != nullptr) {
if (rtn_t == nullptr) {
rtn_t = if_t;
} else {
rtn_t = rtn_t->join(if_t)->is_int();
}
}
}
pred = idom(pred);
if (pred == nullptr || pred == C->top()) {
break;
}
// Stop if going beyond definition block of val
if (dom_depth(pred) < val_dom_depth) {
break;
}
}
}
return rtn_t;
}
//------------------------------dump_spec--------------------------------------
// Dump special per-node info
#ifndef PRODUCT
void CountedLoopEndNode::dump_spec(outputStream *st) const {
if( in(TestValue) != nullptr && in(TestValue)->is_Bool() ) {
BoolTest bt( test_trip()); // Added this for g++.
st->print("[");
bt.dump_on(st);
st->print("]");
}
st->print(" ");
IfNode::dump_spec(st);
}
#endif
//=============================================================================
//------------------------------is_member--------------------------------------
// Is 'l' a member of 'this'?
bool IdealLoopTree::is_member(const IdealLoopTree *l) const {
while( l->_nest > _nest ) l = l->_parent;
return l == this;
}
//------------------------------set_nest---------------------------------------
// Set loop tree nesting depth. Accumulate _has_call bits.
int IdealLoopTree::set_nest( uint depth ) {
assert(depth <= SHRT_MAX, "sanity");
_nest = depth;
int bits = _has_call;
if( _child ) bits |= _child->set_nest(depth+1);
if( bits ) _has_call = 1;
if( _next ) bits |= _next ->set_nest(depth );
return bits;
}
//------------------------------split_fall_in----------------------------------
// Split out multiple fall-in edges from the loop header. Move them to a
// private RegionNode before the loop. This becomes the loop landing pad.
void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) {
PhaseIterGVN &igvn = phase->_igvn;
uint i;
// Make a new RegionNode to be the landing pad.
RegionNode* landing_pad = new RegionNode(fall_in_cnt + 1);
phase->set_loop(landing_pad,_parent);
// If _head was irreducible loop entry, landing_pad may now be too
landing_pad->set_loop_status(_head->as_Region()->loop_status());
// Gather all the fall-in control paths into the landing pad
uint icnt = fall_in_cnt;
uint oreq = _head->req();
for( i = oreq-1; i>0; i-- )
if( !phase->is_member( this, _head->in(i) ) )
landing_pad->set_req(icnt--,_head->in(i));
// Peel off PhiNode edges as well
for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
Node *oj = _head->fast_out(j);
if( oj->is_Phi() ) {
PhiNode* old_phi = oj->as_Phi();
assert( old_phi->region() == _head, "" );
igvn.hash_delete(old_phi); // Yank from hash before hacking edges
Node *p = PhiNode::make_blank(landing_pad, old_phi);
uint icnt = fall_in_cnt;
for( i = oreq-1; i>0; i-- ) {
if( !phase->is_member( this, _head->in(i) ) ) {
p->init_req(icnt--, old_phi->in(i));
// Go ahead and clean out old edges from old phi
old_phi->del_req(i);
}
}
// Search for CSE's here, because ZKM.jar does a lot of
// loop hackery and we need to be a little incremental
// with the CSE to avoid O(N^2) node blow-up.
Node *p2 = igvn.hash_find_insert(p); // Look for a CSE
if( p2 ) { // Found CSE
p->destruct(&igvn); // Recover useless new node
p = p2; // Use old node
} else {
igvn.register_new_node_with_optimizer(p, old_phi);
}
// Make old Phi refer to new Phi.
old_phi->add_req(p);
// Check for the special case of making the old phi useless and
// disappear it. In JavaGrande I have a case where this useless
// Phi is the loop limit and prevents recognizing a CountedLoop
// which in turn prevents removing an empty loop.
Node *id_old_phi = old_phi->Identity(&igvn);
if( id_old_phi != old_phi ) { // Found a simple identity?
// Note that I cannot call 'replace_node' here, because
// that will yank the edge from old_phi to the Region and
// I'm mid-iteration over the Region's uses.
for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) {
Node* use = old_phi->last_out(i);
igvn.rehash_node_delayed(use);
uint uses_found = 0;
for (uint j = 0; j < use->len(); j++) {
if (use->in(j) == old_phi) {
if (j < use->req()) use->set_req (j, id_old_phi);
else use->set_prec(j, id_old_phi);
uses_found++;
}
}
i -= uses_found; // we deleted 1 or more copies of this edge
}
}
igvn._worklist.push(old_phi);
}
}
// Finally clean out the fall-in edges from the RegionNode
for( i = oreq-1; i>0; i-- ) {
if( !phase->is_member( this, _head->in(i) ) ) {
_head->del_req(i);
}
}
igvn.rehash_node_delayed(_head);
// Transform landing pad
igvn.register_new_node_with_optimizer(landing_pad, _head);
// Insert landing pad into the header
_head->add_req(landing_pad);
}
//------------------------------split_outer_loop-------------------------------
// Split out the outermost loop from this shared header.
void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) {
PhaseIterGVN &igvn = phase->_igvn;
// Find index of outermost loop; it should also be my tail.
uint outer_idx = 1;
while( _head->in(outer_idx) != _tail ) outer_idx++;
// Make a LoopNode for the outermost loop.
Node *ctl = _head->in(LoopNode::EntryControl);
Node *outer = new LoopNode( ctl, _head->in(outer_idx) );
outer = igvn.register_new_node_with_optimizer(outer, _head);
phase->set_created_loop_node();
// Outermost loop falls into '_head' loop
_head->set_req(LoopNode::EntryControl, outer);
_head->del_req(outer_idx);
// Split all the Phis up between '_head' loop and 'outer' loop.
for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
Node *out = _head->fast_out(j);
if( out->is_Phi() ) {
PhiNode *old_phi = out->as_Phi();
assert( old_phi->region() == _head, "" );
Node *phi = PhiNode::make_blank(outer, old_phi);
phi->init_req(LoopNode::EntryControl, old_phi->in(LoopNode::EntryControl));
phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx));
phi = igvn.register_new_node_with_optimizer(phi, old_phi);
// Make old Phi point to new Phi on the fall-in path
igvn.replace_input_of(old_phi, LoopNode::EntryControl, phi);
old_phi->del_req(outer_idx);
}
}
// Use the new loop head instead of the old shared one
_head = outer;
phase->set_loop(_head, this);
}
//------------------------------fix_parent-------------------------------------
static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) {
loop->_parent = parent;
if( loop->_child ) fix_parent( loop->_child, loop );
if( loop->_next ) fix_parent( loop->_next , parent );
}
//------------------------------estimate_path_freq-----------------------------
static float estimate_path_freq( Node *n ) {
// Try to extract some path frequency info
IfNode *iff;
for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests
uint nop = n->Opcode();
if( nop == Op_SafePoint ) { // Skip any safepoint
n = n->in(0);
continue;
}
if( nop == Op_CatchProj ) { // Get count from a prior call
// Assume call does not always throw exceptions: means the call-site
// count is also the frequency of the fall-through path.
assert( n->is_CatchProj(), "" );
if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index )
return 0.0f; // Assume call exception path is rare
Node *call = n->in(0)->in(0)->in(0);
assert( call->is_Call(), "expect a call here" );
const JVMState *jvms = ((CallNode*)call)->jvms();
ciMethodData* methodData = jvms->method()->method_data();
if (!methodData->is_mature()) return 0.0f; // No call-site data
ciProfileData* data = methodData->bci_to_data(jvms->bci());
if ((data == nullptr) || !data->is_CounterData()) {
// no call profile available, try call's control input
n = n->in(0);
continue;
}
return data->as_CounterData()->count()/FreqCountInvocations;
}
// See if there's a gating IF test
Node *n_c = n->in(0);
if( !n_c->is_If() ) break; // No estimate available
iff = n_c->as_If();
if( iff->_fcnt != COUNT_UNKNOWN ) // Have a valid count?
// Compute how much count comes on this path
return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt;
// Have no count info. Skip dull uncommon-trap like branches.
if( (nop == Op_IfTrue && iff->_prob < PROB_LIKELY_MAG(5)) ||
(nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) )
break;
// Skip through never-taken branch; look for a real loop exit.
n = iff->in(0);
}
return 0.0f; // No estimate available
}
//------------------------------merge_many_backedges---------------------------
// Merge all the backedges from the shared header into a private Region.
// Feed that region as the one backedge to this loop.
void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) {
uint i;
// Scan for the top 2 hottest backedges
float hotcnt = 0.0f;
float warmcnt = 0.0f;
uint hot_idx = 0;
// Loop starts at 2 because slot 1 is the fall-in path
for( i = 2; i < _head->req(); i++ ) {
float cnt = estimate_path_freq(_head->in(i));
if( cnt > hotcnt ) { // Grab hottest path
warmcnt = hotcnt;
hotcnt = cnt;
hot_idx = i;
} else if( cnt > warmcnt ) { // And 2nd hottest path
warmcnt = cnt;
}
}
// See if the hottest backedge is worthy of being an inner loop
// by being much hotter than the next hottest backedge.
if( hotcnt <= 0.0001 ||
hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge
// Peel out the backedges into a private merge point; peel
// them all except optionally hot_idx.
PhaseIterGVN &igvn = phase->_igvn;
Node *hot_tail = nullptr;
// Make a Region for the merge point
Node *r = new RegionNode(1);
for( i = 2; i < _head->req(); i++ ) {
if( i != hot_idx )
r->add_req( _head->in(i) );
else hot_tail = _head->in(i);
}
igvn.register_new_node_with_optimizer(r, _head);
// Plug region into end of loop _head, followed by hot_tail
while( _head->req() > 3 ) _head->del_req( _head->req()-1 );
igvn.replace_input_of(_head, 2, r);
if( hot_idx ) _head->add_req(hot_tail);
// Split all the Phis up between '_head' loop and the Region 'r'
for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
Node *out = _head->fast_out(j);
if( out->is_Phi() ) {
PhiNode* n = out->as_Phi();
igvn.hash_delete(n); // Delete from hash before hacking edges
Node *hot_phi = nullptr;
Node *phi = new PhiNode(r, n->type(), n->adr_type());
// Check all inputs for the ones to peel out
uint j = 1;
for( uint i = 2; i < n->req(); i++ ) {
if( i != hot_idx )
phi->set_req( j++, n->in(i) );
else hot_phi = n->in(i);
}
// Register the phi but do not transform until whole place transforms
igvn.register_new_node_with_optimizer(phi, n);
// Add the merge phi to the old Phi
while( n->req() > 3 ) n->del_req( n->req()-1 );
igvn.replace_input_of(n, 2, phi);
if( hot_idx ) n->add_req(hot_phi);
}
}
// Insert a new IdealLoopTree inserted below me. Turn it into a clone
// of self loop tree. Turn self into a loop headed by _head and with
// tail being the new merge point.
IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail );
phase->set_loop(_tail,ilt); // Adjust tail
_tail = r; // Self's tail is new merge point
phase->set_loop(r,this);
ilt->_child = _child; // New guy has my children
_child = ilt; // Self has new guy as only child
ilt->_parent = this; // new guy has self for parent
ilt->_nest = _nest; // Same nesting depth (for now)
// Starting with 'ilt', look for child loop trees using the same shared
// header. Flatten these out; they will no longer be loops in the end.
IdealLoopTree **pilt = &_child;
while( ilt ) {
if( ilt->_head == _head ) {
uint i;
for( i = 2; i < _head->req(); i++ )
if( _head->in(i) == ilt->_tail )
break; // Still a loop
if( i == _head->req() ) { // No longer a loop
// Flatten ilt. Hang ilt's "_next" list from the end of
// ilt's '_child' list. Move the ilt's _child up to replace ilt.
IdealLoopTree **cp = &ilt->_child;
while( *cp ) cp = &(*cp)->_next; // Find end of child list
*cp = ilt->_next; // Hang next list at end of child list
*pilt = ilt->_child; // Move child up to replace ilt
ilt->_head = nullptr; // Flag as a loop UNIONED into parent
ilt = ilt->_child; // Repeat using new ilt
continue; // do not advance over ilt->_child
}
assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" );
phase->set_loop(_head,ilt);
}
pilt = &ilt->_child; // Advance to next
ilt = *pilt;
}
if( _child ) fix_parent( _child, this );
}
//------------------------------beautify_loops---------------------------------
// Split shared headers and insert loop landing pads.
// Insert a LoopNode to replace the RegionNode.
// Return TRUE if loop tree is structurally changed.
bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) {
bool result = false;
// Cache parts in locals for easy
PhaseIterGVN &igvn = phase->_igvn;
igvn.hash_delete(_head); // Yank from hash before hacking edges
// Check for multiple fall-in paths. Peel off a landing pad if need be.
int fall_in_cnt = 0;
for( uint i = 1; i < _head->req(); i++ )
if( !phase->is_member( this, _head->in(i) ) )
fall_in_cnt++;
assert( fall_in_cnt, "at least 1 fall-in path" );
if( fall_in_cnt > 1 ) // Need a loop landing pad to merge fall-ins
split_fall_in( phase, fall_in_cnt );
// Swap inputs to the _head and all Phis to move the fall-in edge to
// the left.
fall_in_cnt = 1;
while( phase->is_member( this, _head->in(fall_in_cnt) ) )
fall_in_cnt++;
if( fall_in_cnt > 1 ) {
// Since I am just swapping inputs I do not need to update def-use info
Node *tmp = _head->in(1);
igvn.rehash_node_delayed(_head);
_head->set_req( 1, _head->in(fall_in_cnt) );
_head->set_req( fall_in_cnt, tmp );
// Swap also all Phis
for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) {
Node* phi = _head->fast_out(i);
if( phi->is_Phi() ) {
igvn.rehash_node_delayed(phi); // Yank from hash before hacking edges
tmp = phi->in(1);
phi->set_req( 1, phi->in(fall_in_cnt) );
phi->set_req( fall_in_cnt, tmp );
}
}
}
assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" );
assert( phase->is_member( this, _head->in(2) ), "right edge is loop" );
// If I am a shared header (multiple backedges), peel off the many
// backedges into a private merge point and use the merge point as
// the one true backedge.
if (_head->req() > 3) {
// Merge the many backedges into a single backedge but leave
// the hottest backedge as separate edge for the following peel.
if (!_irreducible) {
merge_many_backedges( phase );
}
// When recursively beautify my children, split_fall_in can change
// loop tree structure when I am an irreducible loop. Then the head
// of my children has a req() not bigger than 3. Here we need to set
// result to true to catch that case in order to tell the caller to
// rebuild loop tree. See issue JDK-8244407 for details.
result = true;
}
// If I have one hot backedge, peel off myself loop.
// I better be the outermost loop.
if (_head->req() > 3 && !_irreducible) {
split_outer_loop( phase );
result = true;
} else if (!_head->is_Loop() && !_irreducible) {
// Make a new LoopNode to replace the old loop head
Node *l = new LoopNode( _head->in(1), _head->in(2) );
l = igvn.register_new_node_with_optimizer(l, _head);
phase->set_created_loop_node();
// Go ahead and replace _head
phase->_igvn.replace_node( _head, l );
_head = l;
phase->set_loop(_head, this);
}
// Now recursively beautify nested loops
if( _child ) result |= _child->beautify_loops( phase );
if( _next ) result |= _next ->beautify_loops( phase );
return result;
}
//------------------------------allpaths_check_safepts----------------------------
// Allpaths backwards scan from loop tail, terminating each path at first safepoint
// encountered. Helper for check_safepts.
void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) {
assert(stack.size() == 0, "empty stack");
stack.push(_tail);
visited.clear();
visited.set(_tail->_idx);
while (stack.size() > 0) {
Node* n = stack.pop();
if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
// Terminate this path
} else if (n->Opcode() == Op_SafePoint) {
if (_phase->get_loop(n) != this) {
if (_required_safept == nullptr) _required_safept = new Node_List();
_required_safept->push(n); // save the one closest to the tail
}
// Terminate this path
} else {
uint start = n->is_Region() ? 1 : 0;
uint end = n->is_Region() && !n->is_Loop() ? n->req() : start + 1;
for (uint i = start; i < end; i++) {
Node* in = n->in(i);
assert(in->is_CFG(), "must be");
if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) {
stack.push(in);
}
}
}
}
}
//------------------------------check_safepts----------------------------
// Given dominators, try to find loops with calls that must always be
// executed (call dominates loop tail). These loops do not need non-call
// safepoints (ncsfpt).
//
// A complication is that a safepoint in a inner loop may be needed
// by an outer loop. In the following, the inner loop sees it has a
// call (block 3) on every path from the head (block 2) to the
// backedge (arc 3->2). So it deletes the ncsfpt (non-call safepoint)
// in block 2, _but_ this leaves the outer loop without a safepoint.
//
// entry 0
// |
// v
// outer 1,2 +->1
// | |
// | v
// | 2<---+ ncsfpt in 2
// |_/|\ |
// | v |
// inner 2,3 / 3 | call in 3
// / | |
// v +--+
// exit 4
//
//
// This method creates a list (_required_safept) of ncsfpt nodes that must
// be protected is created for each loop. When a ncsfpt maybe deleted, it
// is first looked for in the lists for the outer loops of the current loop.
//
// The insights into the problem:
// A) counted loops are okay
// B) innermost loops are okay (only an inner loop can delete
// a ncsfpt needed by an outer loop)
// C) a loop is immune from an inner loop deleting a safepoint
// if the loop has a call on the idom-path
// D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the
// idom-path that is not in a nested loop
// E) otherwise, an ncsfpt on the idom-path that is nested in an inner
// loop needs to be prevented from deletion by an inner loop
//
// There are two analyses:
// 1) The first, and cheaper one, scans the loop body from
// tail to head following the idom (immediate dominator)
// chain, looking for the cases (C,D,E) above.
// Since inner loops are scanned before outer loops, there is summary
// information about inner loops. Inner loops can be skipped over
// when the tail of an inner loop is encountered.
//
// 2) The second, invoked if the first fails to find a call or ncsfpt on
// the idom path (which is rare), scans all predecessor control paths
// from the tail to the head, terminating a path when a call or sfpt
// is encountered, to find the ncsfpt's that are closest to the tail.
//
void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) {
// Bottom up traversal
IdealLoopTree* ch = _child;
if (_child) _child->check_safepts(visited, stack);
if (_next) _next ->check_safepts(visited, stack);
if (!_head->is_CountedLoop() && !_has_sfpt && _parent != nullptr && !_irreducible) {
bool has_call = false; // call on dom-path
bool has_local_ncsfpt = false; // ncsfpt on dom-path at this loop depth
Node* nonlocal_ncsfpt = nullptr; // ncsfpt on dom-path at a deeper depth
// Scan the dom-path nodes from tail to head
for (Node* n = tail(); n != _head; n = _phase->idom(n)) {
if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
has_call = true;
_has_sfpt = 1; // Then no need for a safept!
break;
} else if (n->Opcode() == Op_SafePoint) {
if (_phase->get_loop(n) == this) {
has_local_ncsfpt = true;
break;
}
if (nonlocal_ncsfpt == nullptr) {
nonlocal_ncsfpt = n; // save the one closest to the tail
}
} else {
IdealLoopTree* nlpt = _phase->get_loop(n);
if (this != nlpt) {
// If at an inner loop tail, see if the inner loop has already
// recorded seeing a call on the dom-path (and stop.) If not,
// jump to the head of the inner loop.
assert(is_member(nlpt), "nested loop");
Node* tail = nlpt->_tail;
if (tail->in(0)->is_If()) tail = tail->in(0);
if (n == tail) {
// If inner loop has call on dom-path, so does outer loop
if (nlpt->_has_sfpt) {
has_call = true;
_has_sfpt = 1;
break;
}
// Skip to head of inner loop
assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head");
n = nlpt->_head;
if (_head == n) {
// this and nlpt (inner loop) have the same loop head. This should not happen because
// during beautify_loops we call merge_many_backedges. However, infinite loops may not
// have been attached to the loop-tree during build_loop_tree before beautify_loops,
// but then attached in the build_loop_tree afterwards, and so still have unmerged
// backedges. Check if we are indeed in an infinite subgraph, and terminate the scan,
// since we have reached the loop head of this.
assert(_head->as_Region()->is_in_infinite_subgraph(),
"only expect unmerged backedges in infinite loops");
break;
}
}
}
}
}
// Record safept's that this loop needs preserved when an
// inner loop attempts to delete it's safepoints.
if (_child != nullptr && !has_call && !has_local_ncsfpt) {
if (nonlocal_ncsfpt != nullptr) {
if (_required_safept == nullptr) _required_safept = new Node_List();
_required_safept->push(nonlocal_ncsfpt);
} else {
// Failed to find a suitable safept on the dom-path. Now use
// an all paths walk from tail to head, looking for safepoints to preserve.
allpaths_check_safepts(visited, stack);
}
}
}
}
//---------------------------is_deleteable_safept----------------------------
// Is safept not required by an outer loop?
bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) {
assert(sfpt->Opcode() == Op_SafePoint, "");
IdealLoopTree* lp = get_loop(sfpt)->_parent;
while (lp != nullptr) {
Node_List* sfpts = lp->_required_safept;
if (sfpts != nullptr) {
for (uint i = 0; i < sfpts->size(); i++) {
if (sfpt == sfpts->at(i))
return false;
}
}
lp = lp->_parent;
}
return true;
}
//---------------------------replace_parallel_iv-------------------------------
// Replace parallel induction variable (parallel to trip counter)
void PhaseIdealLoop::replace_parallel_iv(IdealLoopTree *loop) {
assert(loop->_head->is_CountedLoop(), "");
CountedLoopNode *cl = loop->_head->as_CountedLoop();
if (!cl->is_valid_counted_loop(T_INT)) {
return; // skip malformed counted loop
}
Node *incr = cl->incr();
if (incr == nullptr) {
return; // Dead loop?
}
Node *init = cl->init_trip();
Node *phi = cl->phi();
int stride_con = cl->stride_con();
// Visit all children, looking for Phis
for (DUIterator i = cl->outs(); cl->has_out(i); i++) {
Node *out = cl->out(i);
// Look for other phis (secondary IVs). Skip dead ones
if (!out->is_Phi() || out == phi || !has_node(out)) {
continue;
}
PhiNode* phi2 = out->as_Phi();
Node* incr2 = phi2->in(LoopNode::LoopBackControl);
// Look for induction variables of the form: X += constant
if (phi2->region() != loop->_head ||
incr2->req() != 3 ||
incr2->in(1)->uncast() != phi2 ||
incr2 == incr ||
incr2->Opcode() != Op_AddI ||
!incr2->in(2)->is_Con()) {
continue;
}
if (incr2->in(1)->is_ConstraintCast() &&
!(incr2->in(1)->in(0)->is_IfProj() && incr2->in(1)->in(0)->in(0)->is_RangeCheck())) {
// Skip AddI->CastII->Phi case if CastII is not controlled by local RangeCheck
continue;
}
// Check for parallel induction variable (parallel to trip counter)
// via an affine function. In particular, count-down loops with
// count-up array indices are common. We only RCE references off
// the trip-counter, so we need to convert all these to trip-counter
// expressions.
Node* init2 = phi2->in(LoopNode::EntryControl);
int stride_con2 = incr2->in(2)->get_int();
// The ratio of the two strides cannot be represented as an int
// if stride_con2 is min_int and stride_con is -1.
if (stride_con2 == min_jint && stride_con == -1) {
continue;
}
// The general case here gets a little tricky. We want to find the
// GCD of all possible parallel IV's and make a new IV using this
// GCD for the loop. Then all possible IVs are simple multiples of
// the GCD. In practice, this will cover very few extra loops.
// Instead we require 'stride_con2' to be a multiple of 'stride_con',
// where +/-1 is the common case, but other integer multiples are
// also easy to handle.
int ratio_con = stride_con2/stride_con;
if ((ratio_con * stride_con) == stride_con2) { // Check for exact
#ifndef PRODUCT
if (TraceLoopOpts) {
tty->print("Parallel IV: %d ", phi2->_idx);
loop->dump_head();
}
#endif
// Convert to using the trip counter. The parallel induction
// variable differs from the trip counter by a loop-invariant
// amount, the difference between their respective initial values.
// It is scaled by the 'ratio_con'.
Node* ratio = _igvn.intcon(ratio_con);
set_ctrl(ratio, C->root());
Node* ratio_init = new MulINode(init, ratio);
_igvn.register_new_node_with_optimizer(ratio_init, init);
set_early_ctrl(ratio_init, false);
Node* diff = new SubINode(init2, ratio_init);
_igvn.register_new_node_with_optimizer(diff, init2);
set_early_ctrl(diff, false);
Node* ratio_idx = new MulINode(phi, ratio);
_igvn.register_new_node_with_optimizer(ratio_idx, phi);
set_ctrl(ratio_idx, cl);
Node* add = new AddINode(ratio_idx, diff);
_igvn.register_new_node_with_optimizer(add);
set_ctrl(add, cl);
_igvn.replace_node( phi2, add );
// Sometimes an induction variable is unused
if (add->outcnt() == 0) {
_igvn.remove_dead_node(add);
}
--i; // deleted this phi; rescan starting with next position
continue;
}
}
}
void IdealLoopTree::remove_safepoints(PhaseIdealLoop* phase, bool keep_one) {
Node* keep = nullptr;
if (keep_one) {
// Look for a safepoint on the idom-path.
for (Node* i = tail(); i != _head; i = phase->idom(i)) {
if (i->Opcode() == Op_SafePoint && phase->get_loop(i) == this) {
keep = i;
break; // Found one
}
}
}
// Don't remove any safepoints if it is requested to keep a single safepoint and
// no safepoint was found on idom-path. It is not safe to remove any safepoint
// in this case since there's no safepoint dominating all paths in the loop body.
bool prune = !keep_one || keep != nullptr;
// Delete other safepoints in this loop.
Node_List* sfpts = _safepts;
if (prune && sfpts != nullptr) {
assert(keep == nullptr || keep->Opcode() == Op_SafePoint, "not safepoint");
for (uint i = 0; i < sfpts->size(); i++) {
Node* n = sfpts->at(i);
assert(phase->get_loop(n) == this, "");
if (n != keep && phase->is_deleteable_safept(n)) {
phase->lazy_replace(n, n->in(TypeFunc::Control));
}
}
}
}
//------------------------------counted_loop-----------------------------------
// Convert to counted loops where possible
void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) {
// For grins, set the inner-loop flag here
if (!_child) {
if (_head->is_Loop()) _head->as_Loop()->set_inner_loop();
}
IdealLoopTree* loop = this;
if (_head->is_CountedLoop() ||
phase->is_counted_loop(_head, loop, T_INT)) {
if (LoopStripMiningIter == 0 || _head->as_CountedLoop()->is_strip_mined()) {
// Indicate we do not need a safepoint here
_has_sfpt = 1;
}
// Remove safepoints
bool keep_one_sfpt = !(_has_call || _has_sfpt);
remove_safepoints(phase, keep_one_sfpt);
// Look for induction variables
phase->replace_parallel_iv(this);
} else if (_head->is_LongCountedLoop() ||
phase->is_counted_loop(_head, loop, T_LONG)) {
remove_safepoints(phase, true);
} else {
assert(!_head->is_Loop() || !_head->as_Loop()->is_loop_nest_inner_loop(), "transformation to counted loop should not fail");
if (_parent != nullptr && !_irreducible) {
// Not a counted loop. Keep one safepoint.
bool keep_one_sfpt = true;
remove_safepoints(phase, keep_one_sfpt);
}
}
// Recursively
assert(loop->_child != this || (loop->_head->as_Loop()->is_OuterStripMinedLoop() && _head->as_CountedLoop()->is_strip_mined()), "what kind of loop was added?");
assert(loop->_child != this || (loop->_child->_child == nullptr && loop->_child->_next == nullptr), "would miss some loops");
if (loop->_child && loop->_child != this) loop->_child->counted_loop(phase);
if (loop->_next) loop->_next ->counted_loop(phase);
}
// The Estimated Loop Clone Size:
// CloneFactor * (~112% * BodySize + BC) + CC + FanOutTerm,
// where BC and CC are totally ad-hoc/magic "body" and "clone" constants,
// respectively, used to ensure that the node usage estimates made are on the
// safe side, for the most part. The FanOutTerm is an attempt to estimate the
// possible additional/excessive nodes generated due to data and control flow
// merging, for edges reaching outside the loop.
uint IdealLoopTree::est_loop_clone_sz(uint factor) const {
precond(0 < factor && factor < 16);
uint const bc = 13;
uint const cc = 17;
uint const sz = _body.size() + (_body.size() + 7) / 2;
uint estimate = factor * (sz + bc) + cc;
assert((estimate - cc) / factor == sz + bc, "overflow");
return estimate + est_loop_flow_merge_sz();
}
// The Estimated Loop (full-) Unroll Size:
// UnrollFactor * (~106% * BodySize) + CC + FanOutTerm,
// where CC is a (totally) ad-hoc/magic "clone" constant, used to ensure that
// node usage estimates made are on the safe side, for the most part. This is
// a "light" version of the loop clone size calculation (above), based on the
// assumption that most of the loop-construct overhead will be unraveled when
// (fully) unrolled. Defined for unroll factors larger or equal to one (>=1),
// including an overflow check and returning UINT_MAX in case of an overflow.
uint IdealLoopTree::est_loop_unroll_sz(uint factor) const {
precond(factor > 0);
// Take into account that after unroll conjoined heads and tails will fold.
uint const b0 = _body.size() - EMPTY_LOOP_SIZE;
uint const cc = 7;
uint const sz = b0 + (b0 + 15) / 16;
uint estimate = factor * sz + cc;
if ((estimate - cc) / factor != sz) {
return UINT_MAX;
}
return estimate + est_loop_flow_merge_sz();
}
// Estimate the growth effect (in nodes) of merging control and data flow when
// cloning a loop body, based on the amount of control and data flow reaching
// outside of the (current) loop body.
uint IdealLoopTree::est_loop_flow_merge_sz() const {
uint ctrl_edge_out_cnt = 0;
uint data_edge_out_cnt = 0;
for (uint i = 0; i < _body.size(); i++) {
Node* node = _body.at(i);
uint outcnt = node->outcnt();
for (uint k = 0; k < outcnt; k++) {
Node* out = node->raw_out(k);
if (out == nullptr) continue;
if (out->is_CFG()) {
if (!is_member(_phase->get_loop(out))) {
ctrl_edge_out_cnt++;
}
} else if (_phase->has_ctrl(out)) {
Node* ctrl = _phase->get_ctrl(out);
assert(ctrl != nullptr, "must be");
assert(ctrl->is_CFG(), "must be");
if (!is_member(_phase->get_loop(ctrl))) {
data_edge_out_cnt++;
}
}
}
}
// Use data and control count (x2.0) in estimate iff both are > 0. This is
// a rather pessimistic estimate for the most part, in particular for some
// complex loops, but still not enough to capture all loops.
if (ctrl_edge_out_cnt > 0 && data_edge_out_cnt > 0) {
return 2 * (ctrl_edge_out_cnt + data_edge_out_cnt);
}
return 0;
}
#ifndef PRODUCT
//------------------------------dump_head--------------------------------------
// Dump 1 liner for loop header info
void IdealLoopTree::dump_head() {
tty->sp(2 * _nest);
tty->print("Loop: N%d/N%d ", _head->_idx, _tail->_idx);
if (_irreducible) tty->print(" IRREDUCIBLE");
Node* entry = _head->is_Loop() ? _head->as_Loop()->skip_strip_mined(-1)->in(LoopNode::EntryControl)
: _head->in(LoopNode::EntryControl);
ParsePredicates parse_predicates(entry);
if (parse_predicates.loop_limit_check_predicate_proj() != nullptr) {
tty->print(" limit_check");
}
if (UseProfiledLoopPredicate && parse_predicates.profiled_loop_predicate_proj() != nullptr) {
tty->print(" profile_predicated");
}
if (UseLoopPredicate && parse_predicates.loop_predicate_proj() != nullptr) {
tty->print(" predicated");
}
if (_head->is_CountedLoop()) {
CountedLoopNode *cl = _head->as_CountedLoop();
tty->print(" counted");
Node* init_n = cl->init_trip();
if (init_n != nullptr && init_n->is_Con())
tty->print(" [%d,", cl->init_trip()->get_int());
else
tty->print(" [int,");
Node* limit_n = cl->limit();
if (limit_n != nullptr && limit_n->is_Con())
tty->print("%d),", cl->limit()->get_int());
else
tty->print("int),");
int stride_con = cl->stride_con();
if (stride_con > 0) tty->print("+");
tty->print("%d", stride_con);
tty->print(" (%0.f iters) ", cl->profile_trip_cnt());
if (cl->is_pre_loop ()) tty->print(" pre" );
if (cl->is_main_loop()) tty->print(" main");
if (cl->is_post_loop()) tty->print(" post");
if (cl->is_vectorized_loop()) tty->print(" vector");
if (range_checks_present()) tty->print(" rc ");
if (cl->is_multiversioned()) tty->print(" multi ");
}
if (_has_call) tty->print(" has_call");
if (_has_sfpt) tty->print(" has_sfpt");
if (_rce_candidate) tty->print(" rce");
if (_safepts != nullptr && _safepts->size() > 0) {
tty->print(" sfpts={"); _safepts->dump_simple(); tty->print(" }");
}
if (_required_safept != nullptr && _required_safept->size() > 0) {
tty->print(" req={"); _required_safept->dump_simple(); tty->print(" }");
}
if (Verbose) {
tty->print(" body={"); _body.dump_simple(); tty->print(" }");
}
if (_head->is_Loop() && _head->as_Loop()->is_strip_mined()) {
tty->print(" strip_mined");
}
tty->cr();
}
//------------------------------dump-------------------------------------------
// Dump loops by loop tree
void IdealLoopTree::dump() {
dump_head();
if (_child) _child->dump();
if (_next) _next ->dump();
}
#endif
static void log_loop_tree_helper(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) {
if (loop == root) {
if (loop->_child != nullptr) {
log->begin_head("loop_tree");
log->end_head();
log_loop_tree_helper(root, loop->_child, log);
log->tail("loop_tree");
assert(loop->_next == nullptr, "what?");
}
} else if (loop != nullptr) {
Node* head = loop->_head;
log->begin_head("loop");
log->print(" idx='%d' ", head->_idx);
if (loop->_irreducible) log->print("irreducible='1' ");
if (head->is_Loop()) {
if (head->as_Loop()->is_inner_loop()) log->print("inner_loop='1' ");
if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' ");
} else if (head->is_CountedLoop()) {
CountedLoopNode* cl = head->as_CountedLoop();
if (cl->is_pre_loop()) log->print("pre_loop='%d' ", cl->main_idx());
if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx);
if (cl->is_post_loop()) log->print("post_loop='%d' ", cl->main_idx());
}
log->end_head();
log_loop_tree_helper(root, loop->_child, log);
log->tail("loop");
log_loop_tree_helper(root, loop->_next, log);
}
}
void PhaseIdealLoop::log_loop_tree() {
if (C->log() != nullptr) {
log_loop_tree_helper(_ltree_root, _ltree_root, C->log());
}
}
//---------------------collect_potentially_useful_predicates-----------------------
// Helper function to collect potentially useful predicates to prevent them from
// being eliminated by PhaseIdealLoop::eliminate_useless_predicates
void PhaseIdealLoop::collect_potentially_useful_predicates(IdealLoopTree* loop, Unique_Node_List &useful_predicates) {
if (loop->_child) { // child
collect_potentially_useful_predicates(loop->_child, useful_predicates);
}
// self (only loops that we can apply loop predication may use their predicates)
if (loop->_head->is_Loop() &&
!loop->_irreducible &&
!loop->tail()->is_top()) {
LoopNode* lpn = loop->_head->as_Loop();
Node* entry = lpn->in(LoopNode::EntryControl);
ParsePredicates parse_predicates(entry);
ProjNode* predicate_proj = parse_predicates.loop_limit_check_predicate_proj();
if (predicate_proj != nullptr) { // right pattern that can be used by loop predication
assert(predicate_proj->in(0)->in(1)->in(1)->Opcode() == Op_Opaque1, "must be");
useful_predicates.push(predicate_proj->in(0)->in(1)->in(1)); // good one
}
if (UseProfiledLoopPredicate) {
predicate_proj = parse_predicates.profiled_loop_predicate_proj();
if (predicate_proj != nullptr) { // right pattern that can be used by loop predication
useful_predicates.push(predicate_proj->in(0)->in(1)->in(1)); // good one
get_assertion_predicates(predicate_proj, useful_predicates, true);
}
}
if (UseLoopPredicate) {
predicate_proj = parse_predicates.loop_predicate_proj();
if (predicate_proj != nullptr) { // right pattern that can be used by loop predication
useful_predicates.push(predicate_proj->in(0)->in(1)->in(1)); // good one
get_assertion_predicates(predicate_proj, useful_predicates, true);
}
}
}
if (loop->_next) { // sibling
collect_potentially_useful_predicates(loop->_next, useful_predicates);
}
}
//------------------------eliminate_useless_predicates-----------------------------
// Eliminate all inserted predicates if they could not be used by loop predication.
// Note: it will also eliminates loop limits check predicate since it also uses
// Opaque1 node (see Parse::add_predicate()).
void PhaseIdealLoop::eliminate_useless_predicates() {
if (C->parse_predicate_count() == 0 && C->template_assertion_predicate_count() == 0) {
return; // no predicate left
}
Unique_Node_List useful_predicates; // to store useful predicates
if (C->has_loops()) {
collect_potentially_useful_predicates(_ltree_root->_child, useful_predicates);
}
for (int i = C->parse_predicate_count(); i > 0; i--) {
Node* n = C->parse_predicate_opaque1_node(i - 1);
assert(n->Opcode() == Op_Opaque1, "must be");
if (!useful_predicates.member(n)) { // not in the useful list
_igvn.replace_node(n, n->in(1));
}
}
for (int i = C->template_assertion_predicate_count(); i > 0; i--) {
Node* n = C->template_assertion_predicate_opaq_node(i - 1);
assert(n->Opcode() == Op_Opaque4, "must be");
if (!useful_predicates.member(n)) { // not in the useful list
_igvn.replace_node(n, n->in(2));
}
}
}
// If a post or main loop is removed due to an assert predicate, the opaque that guards the loop is not needed anymore
void PhaseIdealLoop::eliminate_useless_zero_trip_guard() {
if (_zero_trip_guard_opaque_nodes.size() == 0) {
return;
}
Unique_Node_List useful_zero_trip_guard_opaques_nodes;
for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
IdealLoopTree* lpt = iter.current();
if (lpt->_child == nullptr && lpt->is_counted()) {
CountedLoopNode* head = lpt->_head->as_CountedLoop();
Node* opaque = head->is_canonical_loop_entry();
if (opaque != nullptr) {
useful_zero_trip_guard_opaques_nodes.push(opaque);
}
}
}
for (uint i = 0; i < _zero_trip_guard_opaque_nodes.size(); ++i) {
OpaqueZeroTripGuardNode* opaque = ((OpaqueZeroTripGuardNode*)_zero_trip_guard_opaque_nodes.at(i));
DEBUG_ONLY(CountedLoopNode* guarded_loop = opaque->guarded_loop());
if (!useful_zero_trip_guard_opaques_nodes.member(opaque)) {
IfNode* iff = opaque->if_node();
IdealLoopTree* loop = get_loop(iff);
while (loop != _ltree_root && loop != nullptr) {
loop = loop->_parent;
}
if (loop == nullptr) {
// unreachable from _ltree_root: zero trip guard is in a newly discovered infinite loop.
// We can't tell if the opaque node is useful or not
assert(guarded_loop == nullptr || guarded_loop->is_in_infinite_subgraph(), "");
} else {
assert(guarded_loop == nullptr, "");
this->_igvn.replace_node(opaque, opaque->in(1));
}
} else {
assert(guarded_loop != nullptr, "");
}
}
}
//------------------------process_expensive_nodes-----------------------------
// Expensive nodes have their control input set to prevent the GVN
// from commoning them and as a result forcing the resulting node to
// be in a more frequent path. Use CFG information here, to change the
// control inputs so that some expensive nodes can be commoned while
// not executed more frequently.
bool PhaseIdealLoop::process_expensive_nodes() {
assert(OptimizeExpensiveOps, "optimization off?");
// Sort nodes to bring similar nodes together
C->sort_expensive_nodes();
bool progress = false;
for (int i = 0; i < C->expensive_count(); ) {
Node* n = C->expensive_node(i);
int start = i;
// Find nodes similar to n
i++;
for (; i < C->expensive_count() && Compile::cmp_expensive_nodes(n, C->expensive_node(i)) == 0; i++);
int end = i;
// And compare them two by two
for (int j = start; j < end; j++) {
Node* n1 = C->expensive_node(j);
if (is_node_unreachable(n1)) {
continue;
}
for (int k = j+1; k < end; k++) {
Node* n2 = C->expensive_node(k);
if (is_node_unreachable(n2)) {
continue;
}
assert(n1 != n2, "should be pair of nodes");
Node* c1 = n1->in(0);
Node* c2 = n2->in(0);
Node* parent_c1 = c1;
Node* parent_c2 = c2;
// The call to get_early_ctrl_for_expensive() moves the
// expensive nodes up but stops at loops that are in a if
// branch. See whether we can exit the loop and move above the
// If.
if (c1->is_Loop()) {
parent_c1 = c1->in(1);
}
if (c2->is_Loop()) {
parent_c2 = c2->in(1);
}
if (parent_c1 == parent_c2) {
_igvn._worklist.push(n1);
_igvn._worklist.push(n2);
continue;
}
// Look for identical expensive node up the dominator chain.
if (is_dominator(c1, c2)) {
c2 = c1;
} else if (is_dominator(c2, c1)) {
c1 = c2;
} else if (parent_c1->is_Proj() && parent_c1->in(0)->is_If() &&
parent_c2->is_Proj() && parent_c1->in(0) == parent_c2->in(0)) {
// Both branches have the same expensive node so move it up
// before the if.
c1 = c2 = idom(parent_c1->in(0));
}
// Do the actual moves
if (n1->in(0) != c1) {
_igvn.replace_input_of(n1, 0, c1);
progress = true;
}
if (n2->in(0) != c2) {
_igvn.replace_input_of(n2, 0, c2);
progress = true;
}
}
}
}
return progress;
}
#ifdef ASSERT
// Goes over all children of the root of the loop tree. Check if any of them have a path
// down to Root, that does not go via a NeverBranch exit.
bool PhaseIdealLoop::only_has_infinite_loops() {
ResourceMark rm;
Unique_Node_List worklist;
// start traversal at all loop heads of first-level loops
for (IdealLoopTree* l = _ltree_root->_child; l != nullptr; l = l->_next) {
Node* head = l->_head;
assert(head->is_Region(), "");
worklist.push(head);
}
return RegionNode::are_all_nodes_in_infinite_subgraph(worklist);
}
#endif
//=============================================================================
//----------------------------build_and_optimize-------------------------------
// Create a PhaseLoop. Build the ideal Loop tree. Map each Ideal Node to
// its corresponding LoopNode. If 'optimize' is true, do some loop cleanups.
void PhaseIdealLoop::build_and_optimize() {
assert(!C->post_loop_opts_phase(), "no loop opts allowed");
bool do_split_ifs = (_mode == LoopOptsDefault);
bool skip_loop_opts = (_mode == LoopOptsNone);
bool do_max_unroll = (_mode == LoopOptsMaxUnroll);
int old_progress = C->major_progress();
uint orig_worklist_size = _igvn._worklist.size();
// Reset major-progress flag for the driver's heuristics
C->clear_major_progress();
#ifndef PRODUCT
// Capture for later assert
uint unique = C->unique();
_loop_invokes++;
_loop_work += unique;
#endif
// True if the method has at least 1 irreducible loop
_has_irreducible_loops = false;
_created_loop_node = false;
VectorSet visited;
// Pre-grow the mapping from Nodes to IdealLoopTrees.
_loop_or_ctrl.map(C->unique(), nullptr);
memset(_loop_or_ctrl.adr(), 0, wordSize * C->unique());
// Pre-build the top-level outermost loop tree entry
_ltree_root = new IdealLoopTree( this, C->root(), C->root() );
// Do not need a safepoint at the top level
_ltree_root->_has_sfpt = 1;
// Initialize Dominators.
// Checked in clone_loop_predicate() during beautify_loops().
_idom_size = 0;
_idom = nullptr;
_dom_depth = nullptr;
_dom_stk = nullptr;
// Empty pre-order array
allocate_preorders();
// Build a loop tree on the fly. Build a mapping from CFG nodes to
// IdealLoopTree entries. Data nodes are NOT walked.
build_loop_tree();
// Check for bailout, and return
if (C->failing()) {
return;
}
// Verify that the has_loops() flag set at parse time is consistent
// with the just built loop tree. With infinite loops, it could be
// that one pass of loop opts only finds infinite loops, clears the
// has_loops() flag but adds NeverBranch nodes so the next loop opts
// verification pass finds a non empty loop tree. When the back edge
// is an exception edge, parsing doesn't set has_loops().
assert(_ltree_root->_child == nullptr || C->has_loops() || only_has_infinite_loops() || C->has_exception_backedge(), "parsing found no loops but there are some");
// No loops after all
if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false);
// There should always be an outer loop containing the Root and Return nodes.
// If not, we have a degenerate empty program. Bail out in this case.
if (!has_node(C->root())) {
if (!_verify_only) {
C->clear_major_progress();
assert(false, "empty program detected during loop optimization");
C->record_method_not_compilable("empty program detected during loop optimization");
}
return;
}
BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
// Nothing to do, so get out
bool stop_early = !C->has_loops() && !skip_loop_opts && !do_split_ifs && !do_max_unroll && !_verify_me &&
!_verify_only && !bs->is_gc_specific_loop_opts_pass(_mode);
bool do_expensive_nodes = C->should_optimize_expensive_nodes(_igvn);
bool strip_mined_loops_expanded = bs->strip_mined_loops_expanded(_mode);
if (stop_early && !do_expensive_nodes) {
return;
}
// Set loop nesting depth
_ltree_root->set_nest( 0 );
// Split shared headers and insert loop landing pads.
// Do not bother doing this on the Root loop of course.
if( !_verify_me && !_verify_only && _ltree_root->_child ) {
C->print_method(PHASE_BEFORE_BEAUTIFY_LOOPS, 3);
if( _ltree_root->_child->beautify_loops( this ) ) {
// Re-build loop tree!
_ltree_root->_child = nullptr;
_loop_or_ctrl.clear();
reallocate_preorders();
build_loop_tree();
// Check for bailout, and return
if (C->failing()) {
return;
}
// Reset loop nesting depth
_ltree_root->set_nest( 0 );
C->print_method(PHASE_AFTER_BEAUTIFY_LOOPS, 3);
}
}
// Build Dominators for elision of null checks & loop finding.
// Since nodes do not have a slot for immediate dominator, make
// a persistent side array for that info indexed on node->_idx.
_idom_size = C->unique();
_idom = NEW_RESOURCE_ARRAY( Node*, _idom_size );
_dom_depth = NEW_RESOURCE_ARRAY( uint, _idom_size );
_dom_stk = nullptr; // Allocated on demand in recompute_dom_depth
memset( _dom_depth, 0, _idom_size * sizeof(uint) );
Dominators();
if (!_verify_only) {
// As a side effect, Dominators removed any unreachable CFG paths
// into RegionNodes. It doesn't do this test against Root, so
// we do it here.
for( uint i = 1; i < C->root()->req(); i++ ) {
if (!_loop_or_ctrl[C->root()->in(i)->_idx]) { // Dead path into Root?
_igvn.delete_input_of(C->root(), i);
i--; // Rerun same iteration on compressed edges
}
}
// Given dominators, try to find inner loops with calls that must
// always be executed (call dominates loop tail). These loops do
// not need a separate safepoint.
Node_List cisstack;
_ltree_root->check_safepts(visited, cisstack);
}
// Walk the DATA nodes and place into loops. Find earliest control
// node. For CFG nodes, the _loop_or_ctrl array starts out and remains
// holding the associated IdealLoopTree pointer. For DATA nodes, the
// _loop_or_ctrl array holds the earliest legal controlling CFG node.
// Allocate stack with enough space to avoid frequent realloc
int stack_size = (C->live_nodes() >> 1) + 16; // (live_nodes>>1)+16 from Java2D stats
Node_Stack nstack(stack_size);
visited.clear();
Node_List worklist;
// Don't need C->root() on worklist since
// it will be processed among C->top() inputs
worklist.push(C->top());
visited.set(C->top()->_idx); // Set C->top() as visited now
build_loop_early( visited, worklist, nstack );
// Given early legal placement, try finding counted loops. This placement
// is good enough to discover most loop invariants.
if (!_verify_me && !_verify_only && !strip_mined_loops_expanded) {
_ltree_root->counted_loop( this );
}
// Find latest loop placement. Find ideal loop placement.
visited.clear();
init_dom_lca_tags();
// Need C->root() on worklist when processing outs
worklist.push(C->root());
NOT_PRODUCT( C->verify_graph_edges(); )
worklist.push(C->top());
build_loop_late( visited, worklist, nstack );
if (C->failing()) { return; }
if (_verify_only) {
C->restore_major_progress(old_progress);
assert(C->unique() == unique, "verification _mode made Nodes? ? ?");
assert(_igvn._worklist.size() == orig_worklist_size, "shouldn't push anything");
return;
}
// clear out the dead code after build_loop_late
while (_deadlist.size()) {
_igvn.remove_globally_dead_node(_deadlist.pop());
}
eliminate_useless_zero_trip_guard();
if (stop_early) {
assert(do_expensive_nodes, "why are we here?");
if (process_expensive_nodes()) {
// If we made some progress when processing expensive nodes then
// the IGVN may modify the graph in a way that will allow us to
// make some more progress: we need to try processing expensive
// nodes again.
C->set_major_progress();
}
return;
}
// Some parser-inserted loop predicates could never be used by loop
// predication or they were moved away from loop during some optimizations.
// For example, peeling. Eliminate them before next loop optimizations.
eliminate_useless_predicates();
#ifndef PRODUCT
C->verify_graph_edges();
if (_verify_me) { // Nested verify pass?
// Check to see if the verify _mode is broken
assert(C->unique() == unique, "non-optimize _mode made Nodes? ? ?");
return;
}
DEBUG_ONLY( if (VerifyLoopOptimizations) { verify(); } );
if (TraceLoopOpts && C->has_loops()) {
_ltree_root->dump();
}
#endif
if (skip_loop_opts) {
C->restore_major_progress(old_progress);
return;
}
if (do_max_unroll) {
for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
IdealLoopTree* lpt = iter.current();
if (lpt->is_innermost() && lpt->_allow_optimizations && !lpt->_has_call && lpt->is_counted()) {
lpt->compute_trip_count(this);
if (!lpt->do_one_iteration_loop(this) &&
!lpt->do_remove_empty_loop(this)) {
AutoNodeBudget node_budget(this);
if (lpt->_head->as_CountedLoop()->is_normal_loop() &&
lpt->policy_maximally_unroll(this)) {
memset( worklist.adr(), 0, worklist.max()*sizeof(Node*) );
do_maximally_unroll(lpt, worklist);
}
}
}
}
C->restore_major_progress(old_progress);
return;
}
if (bs->optimize_loops(this, _mode, visited, nstack, worklist)) {
return;
}
if (ReassociateInvariants && !C->major_progress()) {
// Reassociate invariants and prep for split_thru_phi
for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
IdealLoopTree* lpt = iter.current();
if (!lpt->is_loop()) {
continue;
}
Node* head = lpt->_head;
if (!head->is_BaseCountedLoop() || !lpt->is_innermost()) continue;
// check for vectorized loops, any reassociation of invariants was already done
if (head->is_CountedLoop()) {
if (head->as_CountedLoop()->is_unroll_only()) {
continue;
} else {
AutoNodeBudget node_budget(this);
lpt->reassociate_invariants(this);
}
}
// Because RCE opportunities can be masked by split_thru_phi,
// look for RCE candidates and inhibit split_thru_phi
// on just their loop-phi's for this pass of loop opts
if (SplitIfBlocks && do_split_ifs &&
head->as_BaseCountedLoop()->is_valid_counted_loop(head->as_BaseCountedLoop()->bt()) &&
(lpt->policy_range_check(this, true, T_LONG) ||
(head->is_CountedLoop() && lpt->policy_range_check(this, true, T_INT)))) {
lpt->_rce_candidate = 1; // = true
}
}
}
// Check for aggressive application of split-if and other transforms
// that require basic-block info (like cloning through Phi's)
if (!C->major_progress() && SplitIfBlocks && do_split_ifs) {
visited.clear();
split_if_with_blocks( visited, nstack);
DEBUG_ONLY( if (VerifyLoopOptimizations) { verify(); } );
}
if (!C->major_progress() && do_expensive_nodes && process_expensive_nodes()) {
C->set_major_progress();
}
// Perform loop predication before iteration splitting
if (C->has_loops() && !C->major_progress() && (C->parse_predicate_count() > 0)) {
_ltree_root->_child->loop_predication(this);
}
if (OptimizeFill && UseLoopPredicate && C->has_loops() && !C->major_progress()) {
if (do_intrinsify_fill()) {
C->set_major_progress();
}
}
// Perform iteration-splitting on inner loops. Split iterations to avoid
// range checks or one-shot null checks.
// If split-if's didn't hack the graph too bad (no CFG changes)
// then do loop opts.
if (C->has_loops() && !C->major_progress()) {
memset( worklist.adr(), 0, worklist.max()*sizeof(Node*) );
_ltree_root->_child->iteration_split( this, worklist );
// No verify after peeling! GCM has hoisted code out of the loop.
// After peeling, the hoisted code could sink inside the peeled area.
// The peeling code does not try to recompute the best location for
// all the code before the peeled area, so the verify pass will always
// complain about it.
}
// Check for bailout, and return
if (C->failing()) {
return;
}
// Do verify graph edges in any case
NOT_PRODUCT( C->verify_graph_edges(); );
if (!do_split_ifs) {
// We saw major progress in Split-If to get here. We forced a
// pass with unrolling and not split-if, however more split-if's
// might make progress. If the unrolling didn't make progress
// then the major-progress flag got cleared and we won't try
// another round of Split-If. In particular the ever-common
// instance-of/check-cast pattern requires at least 2 rounds of
// Split-If to clear out.
C->set_major_progress();
}
// Repeat loop optimizations if new loops were seen
if (created_loop_node()) {
C->set_major_progress();
}
// Keep loop predicates and perform optimizations with them
// until no more loop optimizations could be done.
// After that switch predicates off and do more loop optimizations.
if (!C->major_progress() && (C->parse_predicate_count() > 0)) {
C->cleanup_parse_predicates(_igvn);
if (TraceLoopOpts) {
tty->print_cr("PredicatesOff");
}
C->set_major_progress();
}
// Convert scalar to superword operations at the end of all loop opts.
if (UseSuperWord && C->has_loops() && !C->major_progress()) {
// SuperWord transform
SuperWord sw(this);
for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
IdealLoopTree* lpt = iter.current();
if (lpt->is_counted()) {
CountedLoopNode *cl = lpt->_head->as_CountedLoop();
if (cl->is_rce_post_loop() && !cl->is_vectorized_loop()) {
assert(PostLoopMultiversioning, "multiversioning must be enabled");
// Check that the rce'd post loop is encountered first, multiversion after all
// major main loop optimization are concluded
if (!C->major_progress()) {
IdealLoopTree *lpt_next = lpt->_next;
if (lpt_next && lpt_next->is_counted()) {
CountedLoopNode *cl = lpt_next->_head->as_CountedLoop();
if (cl->is_post_loop() && lpt_next->range_checks_present()) {
if (!cl->is_multiversioned()) {
if (multi_version_post_loops(lpt, lpt_next) == false) {
// Cause the rce loop to be optimized away if we fail
cl->mark_is_multiversioned();
cl->set_slp_max_unroll(0);
poison_rce_post_loop(lpt);
}
}
}
}
sw.transform_loop(lpt, true);
}
} else if (cl->is_main_loop()) {
if (!sw.transform_loop(lpt, true)) {
// Instigate more unrolling for optimization when vectorization fails.
if (cl->has_passed_slp()) {
C->set_major_progress();
cl->set_notpassed_slp();
cl->mark_do_unroll_only();
}
}
}
}
}
}
// Move UnorderedReduction out of counted loop. Can be introduced by SuperWord.
if (C->has_loops() && !C->major_progress()) {
for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
IdealLoopTree* lpt = iter.current();
if (lpt->is_counted() && lpt->is_innermost()) {
move_unordered_reduction_out_of_loop(lpt);
}
}
}
}
#ifndef PRODUCT
//------------------------------print_statistics-------------------------------
int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes
int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique
volatile int PhaseIdealLoop::_long_loop_candidates=0; // Number of long loops seen
volatile int PhaseIdealLoop::_long_loop_nests=0; // Number of long loops successfully transformed to a nest
volatile int PhaseIdealLoop::_long_loop_counted_loops=0; // Number of long loops successfully transformed to a counted loop
void PhaseIdealLoop::print_statistics() {
tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d, long loops=%d/%d/%d", _loop_invokes, _loop_work, _long_loop_counted_loops, _long_loop_nests, _long_loop_candidates);
}
#endif
#ifdef ASSERT
// Build a verify-only PhaseIdealLoop, and see that it agrees with "this".
void PhaseIdealLoop::verify() const {
ResourceMark rm;
int old_progress = C->major_progress();
bool success = true;
PhaseIdealLoop phase_verify(_igvn, this);
if (C->failing()) return;
// Verify ctrl and idom of every node.
success &= verify_idom_and_nodes(C->root(), &phase_verify);
// Verify loop-tree.
success &= _ltree_root->verify_tree(phase_verify._ltree_root);
assert(success, "VerifyLoopOptimizations failed");
// Major progress was cleared by creating a verify version of PhaseIdealLoop.
C->restore_major_progress(old_progress);
}
// Perform a BFS starting at n, through all inputs.
// Call verify_idom and verify_node on all nodes of BFS traversal.
bool PhaseIdealLoop::verify_idom_and_nodes(Node* root, const PhaseIdealLoop* phase_verify) const {
Unique_Node_List worklist;
worklist.push(root);
bool success = true;
for (uint i = 0; i < worklist.size(); i++) {
Node* n = worklist.at(i);
// process node
success &= verify_idom(n, phase_verify);
success &= verify_loop_ctrl(n, phase_verify);
// visit inputs
for (uint j = 0; j < n->req(); j++) {
if (n->in(j) != nullptr) {
worklist.push(n->in(j));
}
}
}
return success;
}
// Verify dominator structure (IDOM).
bool PhaseIdealLoop::verify_idom(Node* n, const PhaseIdealLoop* phase_verify) const {
// Verify IDOM for all CFG nodes (except root).
if (!n->is_CFG() || n->is_Root()) {
return true; // pass
}
if (n->_idx >= _idom_size) {
tty->print("CFG Node with no idom: ");
n->dump();
return false; // fail
}
Node* id = idom_no_update(n);
Node* id_verify = phase_verify->idom_no_update(n);
if (id != id_verify) {
tty->print("Mismatching idom for node: ");
n->dump();
tty->print(" We have idom: ");
id->dump();
tty->print(" Verify has idom: ");
id_verify->dump();
tty->cr();
return false; // fail
}
return true; // pass
}
// Verify "_loop_or_ctrl": control and loop membership.
// (0) _loop_or_ctrl[i] == nullptr -> node not reachable.
// (1) has_ctrl -> check lowest bit. 1 -> data node. 0 -> ctrl node.
// (2) has_ctrl true: get_ctrl_no_update returns ctrl of data node.
// (3) has_ctrl false: get_loop_idx returns IdealLoopTree for ctrl node.
bool PhaseIdealLoop::verify_loop_ctrl(Node* n, const PhaseIdealLoop* phase_verify) const {
const uint i = n->_idx;
// The loop-tree was built from def to use (top-down).
// The verification happens from use to def (bottom-up).
// We may thus find nodes during verification that are not in the loop-tree.
if (_loop_or_ctrl[i] == nullptr || phase_verify->_loop_or_ctrl[i] == nullptr) {
if (_loop_or_ctrl[i] != nullptr || phase_verify->_loop_or_ctrl[i] != nullptr) {
tty->print_cr("Was reachable in only one. this %d, verify %d.",
_loop_or_ctrl[i] != nullptr, phase_verify->_loop_or_ctrl[i] != nullptr);
n->dump();
return false; // fail
}
// Not reachable for both.
return true; // pass
}
if (n->is_CFG() == has_ctrl(n)) {
tty->print_cr("Exactly one should be true: %d for is_CFG, %d for has_ctrl.", n->is_CFG(), has_ctrl(n));
n->dump();
return false; // fail
}
if (has_ctrl(n) != phase_verify->has_ctrl(n)) {
tty->print_cr("Mismatch has_ctrl: %d for this, %d for verify.", has_ctrl(n), phase_verify->has_ctrl(n));
n->dump();
return false; // fail
} else if (has_ctrl(n)) {
assert(phase_verify->has_ctrl(n), "sanity");
// n is a data node.
// Verify that its ctrl is the same.
// Broken part of VerifyLoopOptimizations (A)
// Reason:
// BUG, wrong control set for example in
// PhaseIdealLoop::split_if_with_blocks
// at "set_ctrl(x, new_ctrl);"
/*
if( _loop_or_ctrl[i] != loop_verify->_loop_or_ctrl[i] &&
get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) {
tty->print("Mismatched control setting for: ");
n->dump();
if( fail++ > 10 ) return;
Node *c = get_ctrl_no_update(n);
tty->print("We have it as: ");
if( c->in(0) ) c->dump();
else tty->print_cr("N%d",c->_idx);
tty->print("Verify thinks: ");
if( loop_verify->has_ctrl(n) )
loop_verify->get_ctrl_no_update(n)->dump();
else
loop_verify->get_loop_idx(n)->dump();
tty->cr();
}
*/
return true; // pass
} else {
assert(!phase_verify->has_ctrl(n), "sanity");
// n is a ctrl node.
// Verify that not has_ctrl, and that get_loop_idx is the same.
// Broken part of VerifyLoopOptimizations (B)
// Reason:
// NeverBranch node for example is added to loop outside its scope.
// Once we run build_loop_tree again, it is added to the correct loop.
/*
if (!C->major_progress()) {
// Loop selection can be messed up if we did a major progress
// operation, like split-if. Do not verify in that case.
IdealLoopTree *us = get_loop_idx(n);
IdealLoopTree *them = loop_verify->get_loop_idx(n);
if( us->_head != them->_head || us->_tail != them->_tail ) {
tty->print("Unequals loops for: ");
n->dump();
if( fail++ > 10 ) return;
tty->print("We have it as: ");
us->dump();
tty->print("Verify thinks: ");
them->dump();
tty->cr();
}
}
*/
return true; // pass
}
}
int compare_tree(IdealLoopTree* const& a, IdealLoopTree* const& b) {
assert(a != nullptr && b != nullptr, "must be");
return a->_head->_idx - b->_head->_idx;
}
GrowableArray<IdealLoopTree*> IdealLoopTree::collect_sorted_children() const {
GrowableArray<IdealLoopTree*> children;
IdealLoopTree* child = _child;
while (child != nullptr) {
assert(child->_parent == this, "all must be children of this");
children.insert_sorted<compare_tree>(child);
child = child->_next;
}
return children;
}
// Verify that tree structures match. Because the CFG can change, siblings
// within the loop tree can be reordered. We attempt to deal with that by
// reordering the verify's loop tree if possible.
bool IdealLoopTree::verify_tree(IdealLoopTree* loop_verify) const {
assert(_head == loop_verify->_head, "mismatched loop head");
assert(this->_parent != nullptr || this->_next == nullptr, "is_root_loop implies has_no_sibling");
// Collect the children
GrowableArray<IdealLoopTree*> children = collect_sorted_children();
GrowableArray<IdealLoopTree*> children_verify = loop_verify->collect_sorted_children();
bool success = true;
// Compare the two children lists
for (int i = 0, j = 0; i < children.length() || j < children_verify.length(); ) {
IdealLoopTree* child = nullptr;
IdealLoopTree* child_verify = nullptr;
// Read from both lists, if possible.
if (i < children.length()) {
child = children.at(i);
}
if (j < children_verify.length()) {
child_verify = children_verify.at(j);
}
assert(child != nullptr || child_verify != nullptr, "must find at least one");
if (child != nullptr && child_verify != nullptr && child->_head != child_verify->_head) {
// We found two non-equal children. Select the smaller one.
if (child->_head->_idx < child_verify->_head->_idx) {
child_verify = nullptr;
} else {
child = nullptr;
}
}
// Process the two children, or potentially log the failure if we only found one.
if (child_verify == nullptr) {
if (child->_irreducible && Compile::current()->major_progress()) {
// Irreducible loops can pick a different header (one of its entries).
} else {
tty->print_cr("We have a loop that verify does not have");
child->dump();
success = false;
}
i++; // step for this
} else if (child == nullptr) {
if (child_verify->_irreducible && Compile::current()->major_progress()) {
// Irreducible loops can pick a different header (one of its entries).
} else if (child_verify->_head->as_Region()->is_in_infinite_subgraph()) {
// Infinite loops do not get attached to the loop-tree on their first visit.
// "this" runs before "loop_verify". It is thus possible that we find the
// infinite loop only for "child_verify". Only finding it with "child" would
// mean that we lost it, which is not ok.
} else {
tty->print_cr("Verify has a loop that we do not have");
child_verify->dump();
success = false;
}
j++; // step for verify
} else {
assert(child->_head == child_verify->_head, "We have both and they are equal");
success &= child->verify_tree(child_verify); // Recursion
i++; // step for this
j++; // step for verify
}
}
// Broken part of VerifyLoopOptimizations (D)
// Reason:
// split_if has to update the _tail, if it is modified. But that is done by
// checking to what loop the iff belongs to. That info can be wrong, and then
// we do not update the _tail correctly.
/*
Node *tail = _tail; // Inline a non-updating version of
while( !tail->in(0) ) // the 'tail()' call.
tail = tail->in(1);
assert( tail == loop->_tail, "mismatched loop tail" );
*/
if (_head->is_CountedLoop()) {
CountedLoopNode *cl = _head->as_CountedLoop();
Node* ctrl = cl->init_control();
Node* back = cl->back_control();
assert(ctrl != nullptr && ctrl->is_CFG(), "sane loop in-ctrl");
assert(back != nullptr && back->is_CFG(), "sane loop backedge");
cl->loopexit(); // assert implied
}
// Broken part of VerifyLoopOptimizations (E)
// Reason:
// PhaseIdealLoop::split_thru_region creates new nodes for loop that are not added
// to the loop body. Or maybe they are not added to the correct loop.
// at "Node* x = n->clone();"
/*
// Innermost loops need to verify loop bodies,
// but only if no 'major_progress'
int fail = 0;
if (!Compile::current()->major_progress() && _child == nullptr) {
for( uint i = 0; i < _body.size(); i++ ) {
Node *n = _body.at(i);
if (n->outcnt() == 0) continue; // Ignore dead
uint j;
for( j = 0; j < loop->_body.size(); j++ )
if( loop->_body.at(j) == n )
break;
if( j == loop->_body.size() ) { // Not found in loop body
// Last ditch effort to avoid assertion: Its possible that we
// have some users (so outcnt not zero) but are still dead.
// Try to find from root.
if (Compile::current()->root()->find(n->_idx)) {
fail++;
tty->print("We have that verify does not: ");
n->dump();
}
}
}
for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) {
Node *n = loop->_body.at(i2);
if (n->outcnt() == 0) continue; // Ignore dead
uint j;
for( j = 0; j < _body.size(); j++ )
if( _body.at(j) == n )
break;
if( j == _body.size() ) { // Not found in loop body
// Last ditch effort to avoid assertion: Its possible that we
// have some users (so outcnt not zero) but are still dead.
// Try to find from root.
if (Compile::current()->root()->find(n->_idx)) {
fail++;
tty->print("Verify has that we do not: ");
n->dump();
}
}
}
assert( !fail, "loop body mismatch" );
}
*/
return success;
}
#endif
//------------------------------set_idom---------------------------------------
void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) {
uint idx = d->_idx;
if (idx >= _idom_size) {
uint newsize = next_power_of_2(idx);
_idom = REALLOC_RESOURCE_ARRAY( Node*, _idom,_idom_size,newsize);
_dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize);
memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) );
_idom_size = newsize;
}
_idom[idx] = n;
_dom_depth[idx] = dom_depth;
}
//------------------------------recompute_dom_depth---------------------------------------
// The dominator tree is constructed with only parent pointers.
// This recomputes the depth in the tree by first tagging all
// nodes as "no depth yet" marker. The next pass then runs up
// the dom tree from each node marked "no depth yet", and computes
// the depth on the way back down.
void PhaseIdealLoop::recompute_dom_depth() {
uint no_depth_marker = C->unique();
uint i;
// Initialize depth to "no depth yet" and realize all lazy updates
for (i = 0; i < _idom_size; i++) {
// Only indices with a _dom_depth has a Node* or null (otherwise uninitialized).
if (_dom_depth[i] > 0 && _idom[i] != nullptr) {
_dom_depth[i] = no_depth_marker;
// heal _idom if it has a fwd mapping in _loop_or_ctrl
if (_idom[i]->in(0) == nullptr) {
idom(i);
}
}
}
if (_dom_stk == nullptr) {
uint init_size = C->live_nodes() / 100; // Guess that 1/100 is a reasonable initial size.
if (init_size < 10) init_size = 10;
_dom_stk = new GrowableArray<uint>(init_size);
}
// Compute new depth for each node.
for (i = 0; i < _idom_size; i++) {
uint j = i;
// Run up the dom tree to find a node with a depth
while (_dom_depth[j] == no_depth_marker) {
_dom_stk->push(j);
j = _idom[j]->_idx;
}
// Compute the depth on the way back down this tree branch
uint dd = _dom_depth[j] + 1;
while (_dom_stk->length() > 0) {
uint j = _dom_stk->pop();
_dom_depth[j] = dd;
dd++;
}
}
}
//------------------------------sort-------------------------------------------
// Insert 'loop' into the existing loop tree. 'innermost' is a leaf of the
// loop tree, not the root.
IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) {
if( !innermost ) return loop; // New innermost loop
int loop_preorder = get_preorder(loop->_head); // Cache pre-order number
assert( loop_preorder, "not yet post-walked loop" );
IdealLoopTree **pp = &innermost; // Pointer to previous next-pointer
IdealLoopTree *l = *pp; // Do I go before or after 'l'?
// Insert at start of list
while( l ) { // Insertion sort based on pre-order
if( l == loop ) return innermost; // Already on list!
int l_preorder = get_preorder(l->_head); // Cache pre-order number
assert( l_preorder, "not yet post-walked l" );
// Check header pre-order number to figure proper nesting
if( loop_preorder > l_preorder )
break; // End of insertion
// If headers tie (e.g., shared headers) check tail pre-order numbers.
// Since I split shared headers, you'd think this could not happen.
// BUT: I must first do the preorder numbering before I can discover I
// have shared headers, so the split headers all get the same preorder
// number as the RegionNode they split from.
if( loop_preorder == l_preorder &&
get_preorder(loop->_tail) < get_preorder(l->_tail) )
break; // Also check for shared headers (same pre#)
pp = &l->_parent; // Chain up list
l = *pp;
}
// Link into list
// Point predecessor to me
*pp = loop;
// Point me to successor
IdealLoopTree *p = loop->_parent;
loop->_parent = l; // Point me to successor
if( p ) sort( p, innermost ); // Insert my parents into list as well
return innermost;
}
//------------------------------build_loop_tree--------------------------------
// I use a modified Vick/Tarjan algorithm. I need pre- and a post- visit
// bits. The _loop_or_ctrl[] array is mapped by Node index and holds a null for
// not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the
// tightest enclosing IdealLoopTree for post-walked.
//
// During my forward walk I do a short 1-layer lookahead to see if I can find
// a loop backedge with that doesn't have any work on the backedge. This
// helps me construct nested loops with shared headers better.
//
// Once I've done the forward recursion, I do the post-work. For each child
// I check to see if there is a backedge. Backedges define a loop! I
// insert an IdealLoopTree at the target of the backedge.
//
// During the post-work I also check to see if I have several children
// belonging to different loops. If so, then this Node is a decision point
// where control flow can choose to change loop nests. It is at this
// decision point where I can figure out how loops are nested. At this
// time I can properly order the different loop nests from my children.
// Note that there may not be any backedges at the decision point!
//
// Since the decision point can be far removed from the backedges, I can't
// order my loops at the time I discover them. Thus at the decision point
// I need to inspect loop header pre-order numbers to properly nest my
// loops. This means I need to sort my childrens' loops by pre-order.
// The sort is of size number-of-control-children, which generally limits
// it to size 2 (i.e., I just choose between my 2 target loops).
void PhaseIdealLoop::build_loop_tree() {
// Allocate stack of size C->live_nodes()/2 to avoid frequent realloc
GrowableArray <Node *> bltstack(C->live_nodes() >> 1);
Node *n = C->root();
bltstack.push(n);
int pre_order = 1;
int stack_size;
while ( ( stack_size = bltstack.length() ) != 0 ) {
n = bltstack.top(); // Leave node on stack
if ( !is_visited(n) ) {
// ---- Pre-pass Work ----
// Pre-walked but not post-walked nodes need a pre_order number.
set_preorder_visited( n, pre_order ); // set as visited
// ---- Scan over children ----
// Scan first over control projections that lead to loop headers.
// This helps us find inner-to-outer loops with shared headers better.
// Scan children's children for loop headers.
for ( int i = n->outcnt() - 1; i >= 0; --i ) {
Node* m = n->raw_out(i); // Child
if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children
// Scan over children's children to find loop
for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
Node* l = m->fast_out(j);
if( is_visited(l) && // Been visited?
!is_postvisited(l) && // But not post-visited
get_preorder(l) < pre_order ) { // And smaller pre-order
// Found! Scan the DFS down this path before doing other paths
bltstack.push(m);
break;
}
}
}
}
pre_order++;
}
else if ( !is_postvisited(n) ) {
// Note: build_loop_tree_impl() adds out edges on rare occasions,
// such as com.sun.rsasign.am::a.
// For non-recursive version, first, process current children.
// On next iteration, check if additional children were added.
for ( int k = n->outcnt() - 1; k >= 0; --k ) {
Node* u = n->raw_out(k);
if ( u->is_CFG() && !is_visited(u) ) {
bltstack.push(u);
}
}
if ( bltstack.length() == stack_size ) {
// There were no additional children, post visit node now
(void)bltstack.pop(); // Remove node from stack
pre_order = build_loop_tree_impl( n, pre_order );
// Check for bailout
if (C->failing()) {
return;
}
// Check to grow _preorders[] array for the case when
// build_loop_tree_impl() adds new nodes.
check_grow_preorders();
}
}
else {
(void)bltstack.pop(); // Remove post-visited node from stack
}
}
DEBUG_ONLY(verify_regions_in_irreducible_loops();)
}
//------------------------------build_loop_tree_impl---------------------------
int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) {
// ---- Post-pass Work ----
// Pre-walked but not post-walked nodes need a pre_order number.
// Tightest enclosing loop for this Node
IdealLoopTree *innermost = nullptr;
// For all children, see if any edge is a backedge. If so, make a loop
// for it. Then find the tightest enclosing loop for the self Node.
for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
Node* m = n->fast_out(i); // Child
if( n == m ) continue; // Ignore control self-cycles
if( !m->is_CFG() ) continue;// Ignore non-CFG edges
IdealLoopTree *l; // Child's loop
if( !is_postvisited(m) ) { // Child visited but not post-visited?
// Found a backedge
assert( get_preorder(m) < pre_order, "should be backedge" );
// Check for the RootNode, which is already a LoopNode and is allowed
// to have multiple "backedges".
if( m == C->root()) { // Found the root?
l = _ltree_root; // Root is the outermost LoopNode
} else { // Else found a nested loop
// Insert a LoopNode to mark this loop.
l = new IdealLoopTree(this, m, n);
} // End of Else found a nested loop
if( !has_loop(m) ) // If 'm' does not already have a loop set
set_loop(m, l); // Set loop header to loop now
} else { // Else not a nested loop
if (!_loop_or_ctrl[m->_idx]) continue; // Dead code has no loop
l = get_loop(m); // Get previously determined loop
// If successor is header of a loop (nest), move up-loop till it
// is a member of some outer enclosing loop. Since there are no
// shared headers (I've split them already) I only need to go up
// at most 1 level.
while( l && l->_head == m ) // Successor heads loop?
l = l->_parent; // Move up 1 for me
// If this loop is not properly parented, then this loop
// has no exit path out, i.e. its an infinite loop.
if( !l ) {
// Make loop "reachable" from root so the CFG is reachable. Basically
// insert a bogus loop exit that is never taken. 'm', the loop head,
// points to 'n', one (of possibly many) fall-in paths. There may be
// many backedges as well.
// Here I set the loop to be the root loop. I could have, after
// inserting a bogus loop exit, restarted the recursion and found my
// new loop exit. This would make the infinite loop a first-class
// loop and it would then get properly optimized. What's the use of
// optimizing an infinite loop?
l = _ltree_root; // Oops, found infinite loop
if (!_verify_only) {
// Insert the NeverBranch between 'm' and it's control user.
NeverBranchNode *iff = new NeverBranchNode( m );
_igvn.register_new_node_with_optimizer(iff);
set_loop(iff, l);
Node *if_t = new CProjNode( iff, 0 );
_igvn.register_new_node_with_optimizer(if_t);
set_loop(if_t, l);
Node* cfg = nullptr; // Find the One True Control User of m
for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
Node* x = m->fast_out(j);
if (x->is_CFG() && x != m && x != iff)
{ cfg = x; break; }
}
assert(cfg != nullptr, "must find the control user of m");
uint k = 0; // Probably cfg->in(0)
while( cfg->in(k) != m ) k++; // But check in case cfg is a Region
_igvn.replace_input_of(cfg, k, if_t); // Now point to NeverBranch
// Now create the never-taken loop exit
Node *if_f = new CProjNode( iff, 1 );
_igvn.register_new_node_with_optimizer(if_f);
set_loop(if_f, l);
// Find frame ptr for Halt. Relies on the optimizer
// V-N'ing. Easier and quicker than searching through
// the program structure.
Node *frame = new ParmNode( C->start(), TypeFunc::FramePtr );
_igvn.register_new_node_with_optimizer(frame);
// Halt & Catch Fire
Node* halt = new HaltNode(if_f, frame, "never-taken loop exit reached");
_igvn.register_new_node_with_optimizer(halt);
set_loop(halt, l);
_igvn.add_input_to(C->root(), halt);
}
set_loop(C->root(), _ltree_root);
}
}
if (is_postvisited(l->_head)) {
// We are currently visiting l, but its head has already been post-visited.
// l is irreducible: we just found a second entry m.
_has_irreducible_loops = true;
RegionNode* secondary_entry = m->as_Region();
DEBUG_ONLY(secondary_entry->verify_can_be_irreducible_entry();)
// Walk up the loop-tree, mark all loops that are already post-visited as irreducible
// Since m is a secondary entry to them all.
while( is_postvisited(l->_head) ) {
l->_irreducible = 1; // = true
RegionNode* head = l->_head->as_Region();
DEBUG_ONLY(head->verify_can_be_irreducible_entry();)
l = l->_parent;
// Check for bad CFG here to prevent crash, and bailout of compile
if (l == nullptr) {
#ifndef PRODUCT
if (TraceLoopOpts) {
tty->print_cr("bailout: unhandled CFG: infinite irreducible loop");
m->dump();
}
#endif
// This is a rare case that we do not want to handle in C2.
C->record_method_not_compilable("unhandled CFG detected during loop optimization");
return pre_order;
}
}
}
if (!_verify_only) {
C->set_has_irreducible_loop(_has_irreducible_loops);
}
// This Node might be a decision point for loops. It is only if
// it's children belong to several different loops. The sort call
// does a trivial amount of work if there is only 1 child or all
// children belong to the same loop. If however, the children
// belong to different loops, the sort call will properly set the
// _parent pointers to show how the loops nest.
//
// In any case, it returns the tightest enclosing loop.
innermost = sort( l, innermost );
}
// Def-use info will have some dead stuff; dead stuff will have no
// loop decided on.
// Am I a loop header? If so fix up my parent's child and next ptrs.
if( innermost && innermost->_head == n ) {
assert( get_loop(n) == innermost, "" );
IdealLoopTree *p = innermost->_parent;
IdealLoopTree *l = innermost;
while( p && l->_head == n ) {
l->_next = p->_child; // Put self on parents 'next child'
p->_child = l; // Make self as first child of parent
l = p; // Now walk up the parent chain
p = l->_parent;
}
} else {
// Note that it is possible for a LoopNode to reach here, if the
// backedge has been made unreachable (hence the LoopNode no longer
// denotes a Loop, and will eventually be removed).
// Record tightest enclosing loop for self. Mark as post-visited.
set_loop(n, innermost);
// Also record has_call flag early on
if( innermost ) {
if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) {
// Do not count uncommon calls
if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) {
Node *iff = n->in(0)->in(0);
// No any calls for vectorized loops.
if( UseSuperWord || !iff->is_If() ||
(n->in(0)->Opcode() == Op_IfFalse &&
(1.0 - iff->as_If()->_prob) >= 0.01) ||
(iff->as_If()->_prob >= 0.01) )
innermost->_has_call = 1;
}
} else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) {
// Disable loop optimizations if the loop has a scalar replaceable
// allocation. This disabling may cause a potential performance lost
// if the allocation is not eliminated for some reason.
innermost->_allow_optimizations = false;
innermost->_has_call = 1; // = true
} else if (n->Opcode() == Op_SafePoint) {
// Record all safepoints in this loop.
if (innermost->_safepts == nullptr) innermost->_safepts = new Node_List();
innermost->_safepts->push(n);
}
}
}
// Flag as post-visited now
set_postvisited(n);
return pre_order;
}
#ifdef ASSERT
//--------------------------verify_regions_in_irreducible_loops----------------
// Iterate down from Root through CFG, verify for every region:
// if it is in an irreducible loop it must be marked as such
void PhaseIdealLoop::verify_regions_in_irreducible_loops() {
ResourceMark rm;
if (!_has_irreducible_loops) {
// last build_loop_tree has not found any irreducible loops
// hence no region has to be marked is_in_irreduible_loop
return;
}
RootNode* root = C->root();
Unique_Node_List worklist; // visit all nodes once
worklist.push(root);
bool failure = false;
for (uint i = 0; i < worklist.size(); i++) {
Node* n = worklist.at(i);
if (n->is_Region()) {
RegionNode* region = n->as_Region();
if (is_in_irreducible_loop(region) &&
region->loop_status() == RegionNode::LoopStatus::Reducible) {
failure = true;
tty->print("irreducible! ");
region->dump();
}
}
for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
Node* use = n->fast_out(j);
if (use->is_CFG()) {
worklist.push(use); // push if was not pushed before
}
}
}
assert(!failure, "region in irreducible loop was marked as reducible");
}
//---------------------------is_in_irreducible_loop-------------------------
// Analogous to ciTypeFlow::Block::is_in_irreducible_loop
bool PhaseIdealLoop::is_in_irreducible_loop(RegionNode* region) {
if (!_has_irreducible_loops) {
return false; // no irreducible loop in graph
}
IdealLoopTree* l = get_loop(region); // l: innermost loop that contains region
do {
if (l->_irreducible) {
return true; // found it
}
if (l == _ltree_root) {
return false; // reached root, terimnate
}
l = l->_parent;
} while (l != nullptr);
assert(region->is_in_infinite_subgraph(), "must be in infinite subgraph");
// We have "l->_parent == nullptr", which happens only for infinite loops,
// where no parent is attached to the loop. We did not find any irreducible
// loop from this block out to lp. Thus lp only has one entry, and no exit
// (it is infinite and reducible). We can always rewrite an infinite loop
// that is nested inside other loops:
// while(condition) { infinite_loop; }
// with an equivalent program where the infinite loop is an outermost loop
// that is not nested in any loop:
// while(condition) { break; } infinite_loop;
// Thus, we can understand lp as an outermost loop, and can terminate and
// conclude: this block is in no irreducible loop.
return false;
}
#endif
//------------------------------build_loop_early-------------------------------
// Put Data nodes into some loop nest, by setting the _loop_or_ctrl[]->loop mapping.
// First pass computes the earliest controlling node possible. This is the
// controlling input with the deepest dominating depth.
void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
while (worklist.size() != 0) {
// Use local variables nstack_top_n & nstack_top_i to cache values
// on nstack's top.
Node *nstack_top_n = worklist.pop();
uint nstack_top_i = 0;
//while_nstack_nonempty:
while (true) {
// Get parent node and next input's index from stack's top.
Node *n = nstack_top_n;
uint i = nstack_top_i;
uint cnt = n->req(); // Count of inputs
if (i == 0) { // Pre-process the node.
if( has_node(n) && // Have either loop or control already?
!has_ctrl(n) ) { // Have loop picked out already?
// During "merge_many_backedges" we fold up several nested loops
// into a single loop. This makes the members of the original
// loop bodies pointing to dead loops; they need to move up
// to the new UNION'd larger loop. I set the _head field of these
// dead loops to null and the _parent field points to the owning
// loop. Shades of UNION-FIND algorithm.
IdealLoopTree *ilt;
while( !(ilt = get_loop(n))->_head ) {
// Normally I would use a set_loop here. But in this one special
// case, it is legal (and expected) to change what loop a Node
// belongs to.
_loop_or_ctrl.map(n->_idx, (Node*)(ilt->_parent));
}
// Remove safepoints ONLY if I've already seen I don't need one.
// (the old code here would yank a 2nd safepoint after seeing a
// first one, even though the 1st did not dominate in the loop body
// and thus could be avoided indefinitely)
if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint &&
is_deleteable_safept(n)) {
Node *in = n->in(TypeFunc::Control);
lazy_replace(n,in); // Pull safepoint now
if (ilt->_safepts != nullptr) {
ilt->_safepts->yank(n);
}
// Carry on with the recursion "as if" we are walking
// only the control input
if( !visited.test_set( in->_idx ) ) {
worklist.push(in); // Visit this guy later, using worklist
}
// Get next node from nstack:
// - skip n's inputs processing by setting i > cnt;
// - we also will not call set_early_ctrl(n) since
// has_node(n) == true (see the condition above).
i = cnt + 1;
}
}
} // if (i == 0)
// Visit all inputs
bool done = true; // Assume all n's inputs will be processed
while (i < cnt) {
Node *in = n->in(i);
++i;
if (in == nullptr) continue;
if (in->pinned() && !in->is_CFG())
set_ctrl(in, in->in(0));
int is_visited = visited.test_set( in->_idx );
if (!has_node(in)) { // No controlling input yet?
assert( !in->is_CFG(), "CFG Node with no controlling input?" );
assert( !is_visited, "visit only once" );
nstack.push(n, i); // Save parent node and next input's index.
nstack_top_n = in; // Process current input now.
nstack_top_i = 0;
done = false; // Not all n's inputs processed.
break; // continue while_nstack_nonempty;
} else if (!is_visited) {
// This guy has a location picked out for him, but has not yet
// been visited. Happens to all CFG nodes, for instance.
// Visit him using the worklist instead of recursion, to break
// cycles. Since he has a location already we do not need to
// find his location before proceeding with the current Node.
worklist.push(in); // Visit this guy later, using worklist
}
}
if (done) {
// All of n's inputs have been processed, complete post-processing.
// Compute earliest point this Node can go.
// CFG, Phi, pinned nodes already know their controlling input.
if (!has_node(n)) {
// Record earliest legal location
set_early_ctrl(n, false);
}
if (nstack.is_empty()) {
// Finished all nodes on stack.
// Process next node on the worklist.
break;
}
// Get saved parent node and next input's index.
nstack_top_n = nstack.node();
nstack_top_i = nstack.index();
nstack.pop();
}
} // while (true)
}
}
//------------------------------dom_lca_internal--------------------------------
// Pair-wise LCA
Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const {
if( !n1 ) return n2; // Handle null original LCA
assert( n1->is_CFG(), "" );
assert( n2->is_CFG(), "" );
// find LCA of all uses
uint d1 = dom_depth(n1);
uint d2 = dom_depth(n2);
while (n1 != n2) {
if (d1 > d2) {
n1 = idom(n1);
d1 = dom_depth(n1);
} else if (d1 < d2) {
n2 = idom(n2);
d2 = dom_depth(n2);
} else {
// Here d1 == d2. Due to edits of the dominator-tree, sections
// of the tree might have the same depth. These sections have
// to be searched more carefully.
// Scan up all the n1's with equal depth, looking for n2.
Node *t1 = idom(n1);
while (dom_depth(t1) == d1) {
if (t1 == n2) return n2;
t1 = idom(t1);
}
// Scan up all the n2's with equal depth, looking for n1.
Node *t2 = idom(n2);
while (dom_depth(t2) == d2) {
if (t2 == n1) return n1;
t2 = idom(t2);
}
// Move up to a new dominator-depth value as well as up the dom-tree.
n1 = t1;
n2 = t2;
d1 = dom_depth(n1);
d2 = dom_depth(n2);
}
}
return n1;
}
//------------------------------compute_idom-----------------------------------
// Locally compute IDOM using dom_lca call. Correct only if the incoming
// IDOMs are correct.
Node *PhaseIdealLoop::compute_idom( Node *region ) const {
assert( region->is_Region(), "" );
Node *LCA = nullptr;
for( uint i = 1; i < region->req(); i++ ) {
if( region->in(i) != C->top() )
LCA = dom_lca( LCA, region->in(i) );
}
return LCA;
}
bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) {
bool had_error = false;
#ifdef ASSERT
if (early != C->root()) {
// Make sure that there's a dominance path from LCA to early
Node* d = LCA;
while (d != early) {
if (d == C->root()) {
dump_bad_graph("Bad graph detected in compute_lca_of_uses", n, early, LCA);
tty->print_cr("*** Use %d isn't dominated by def %d ***", use->_idx, n->_idx);
had_error = true;
break;
}
d = idom(d);
}
}
#endif
return had_error;
}
Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) {
// Compute LCA over list of uses
bool had_error = false;
Node *LCA = nullptr;
for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) {
Node* c = n->fast_out(i);
if (_loop_or_ctrl[c->_idx] == nullptr)
continue; // Skip the occasional dead node
if( c->is_Phi() ) { // For Phis, we must land above on the path
for( uint j=1; j<c->req(); j++ ) {// For all inputs
if( c->in(j) == n ) { // Found matching input?
Node *use = c->in(0)->in(j);
if (_verify_only && use->is_top()) continue;
LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
}
}
} else {
// For CFG data-users, use is in the block just prior
Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0);
LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
}
}
assert(!had_error, "bad dominance");
return LCA;
}
// Check the shape of the graph at the loop entry. In some cases,
// the shape of the graph does not match the shape outlined below.
// That is caused by the Opaque1 node "protecting" the shape of
// the graph being removed by, for example, the IGVN performed
// in PhaseIdealLoop::build_and_optimize().
//
// After the Opaque1 node has been removed, optimizations (e.g., split-if,
// loop unswitching, and IGVN, or a combination of them) can freely change
// the graph's shape. As a result, the graph shape outlined below cannot
// be guaranteed anymore.
Node* CountedLoopNode::is_canonical_loop_entry() {
if (!is_main_loop() && !is_post_loop()) {
return nullptr;
}
Node* ctrl = skip_predicates();
if (ctrl == nullptr || (!ctrl->is_IfTrue() && !ctrl->is_IfFalse())) {
return nullptr;
}
Node* iffm = ctrl->in(0);
if (iffm == nullptr || iffm->Opcode() != Op_If) {
return nullptr;
}
Node* bolzm = iffm->in(1);
if (bolzm == nullptr || !bolzm->is_Bool()) {
return nullptr;
}
Node* cmpzm = bolzm->in(1);
if (cmpzm == nullptr || !cmpzm->is_Cmp()) {
return nullptr;
}
uint input = is_main_loop() ? 2 : 1;
if (input >= cmpzm->req() || cmpzm->in(input) == nullptr) {
return nullptr;
}
bool res = cmpzm->in(input)->Opcode() == Op_OpaqueZeroTripGuard;
#ifdef ASSERT
bool found_opaque = false;
for (uint i = 1; i < cmpzm->req(); i++) {
Node* opnd = cmpzm->in(i);
if (opnd && opnd->is_Opaque1()) {
found_opaque = true;
break;
}
}
assert(found_opaque == res, "wrong pattern");
#endif
return res ? cmpzm->in(input) : nullptr;
}
//------------------------------get_late_ctrl----------------------------------
// Compute latest legal control.
Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
assert(early != nullptr, "early control should not be null");
Node* LCA = compute_lca_of_uses(n, early);
#ifdef ASSERT
if (LCA == C->root() && LCA != early) {
// def doesn't dominate uses so print some useful debugging output
compute_lca_of_uses(n, early, true);
}
#endif
if (n->is_Load() && LCA != early) {
LCA = get_late_ctrl_with_anti_dep(n->as_Load(), early, LCA);
}
assert(LCA == find_non_split_ctrl(LCA), "unexpected late control");
return LCA;
}
// if this is a load, check for anti-dependent stores
// We use a conservative algorithm to identify potential interfering
// instructions and for rescheduling the load. The users of the memory
// input of this load are examined. Any use which is not a load and is
// dominated by early is considered a potentially interfering store.
// This can produce false positives.
Node* PhaseIdealLoop::get_late_ctrl_with_anti_dep(LoadNode* n, Node* early, Node* LCA) {
int load_alias_idx = C->get_alias_index(n->adr_type());
if (C->alias_type(load_alias_idx)->is_rewritable()) {
Unique_Node_List worklist;
Node* mem = n->in(MemNode::Memory);
for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
Node* s = mem->fast_out(i);
worklist.push(s);
}
for (uint i = 0; i < worklist.size() && LCA != early; i++) {
Node* s = worklist.at(i);
if (s->is_Load() || s->Opcode() == Op_SafePoint ||
(s->is_CallStaticJava() && s->as_CallStaticJava()->uncommon_trap_request() != 0) ||
s->is_Phi()) {
continue;
} else if (s->is_MergeMem()) {
for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
Node* s1 = s->fast_out(i);
worklist.push(s1);
}
} else {
Node* sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
assert(sctrl != nullptr || !s->is_reachable_from_root(), "must have control");
if (sctrl != nullptr && !sctrl->is_top() && is_dominator(early, sctrl)) {
const TypePtr* adr_type = s->adr_type();
if (s->is_ArrayCopy()) {
// Copy to known instance needs destination type to test for aliasing
const TypePtr* dest_type = s->as_ArrayCopy()->_dest_type;
if (dest_type != TypeOopPtr::BOTTOM) {
adr_type = dest_type;
}
}
if (C->can_alias(adr_type, load_alias_idx)) {
LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n);
} else if (s->is_CFG() && s->is_Multi()) {
// Look for the memory use of s (that is the use of its memory projection)
for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
Node* s1 = s->fast_out(i);
assert(s1->is_Proj(), "projection expected");
if (_igvn.type(s1) == Type::MEMORY) {
for (DUIterator_Fast jmax, j = s1->fast_outs(jmax); j < jmax; j++) {
Node* s2 = s1->fast_out(j);
worklist.push(s2);
}
}
}
}
}
}
}
// For Phis only consider Region's inputs that were reached by following the memory edges
if (LCA != early) {
for (uint i = 0; i < worklist.size(); i++) {
Node* s = worklist.at(i);
if (s->is_Phi() && C->can_alias(s->adr_type(), load_alias_idx)) {
Node* r = s->in(0);
for (uint j = 1; j < s->req(); j++) {
Node* in = s->in(j);
Node* r_in = r->in(j);
// We can't reach any node from a Phi because we don't enqueue Phi's uses above
if (((worklist.member(in) && !in->is_Phi()) || in == mem) && is_dominator(early, r_in)) {
LCA = dom_lca_for_get_late_ctrl(LCA, r_in, n);
}
}
}
}
}
}
return LCA;
}
// true if CFG node d dominates CFG node n
bool PhaseIdealLoop::is_dominator(Node *d, Node *n) {
if (d == n)
return true;
assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes");
uint dd = dom_depth(d);
while (dom_depth(n) >= dd) {
if (n == d)
return true;
n = idom(n);
}
return false;
}
//------------------------------dom_lca_for_get_late_ctrl_internal-------------
// Pair-wise LCA with tags.
// Tag each index with the node 'tag' currently being processed
// before advancing up the dominator chain using idom().
// Later calls that find a match to 'tag' know that this path has already
// been considered in the current LCA (which is input 'n1' by convention).
// Since get_late_ctrl() is only called once for each node, the tag array
// does not need to be cleared between calls to get_late_ctrl().
// Algorithm trades a larger constant factor for better asymptotic behavior
//
Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal(Node *n1, Node *n2, Node *tag_node) {
uint d1 = dom_depth(n1);
uint d2 = dom_depth(n2);
jlong tag = tag_node->_idx | (((jlong)_dom_lca_tags_round) << 32);
do {
if (d1 > d2) {
// current lca is deeper than n2
_dom_lca_tags.at_put_grow(n1->_idx, tag);
n1 = idom(n1);
d1 = dom_depth(n1);
} else if (d1 < d2) {
// n2 is deeper than current lca
jlong memo = _dom_lca_tags.at_grow(n2->_idx, 0);
if (memo == tag) {
return n1; // Return the current LCA
}
_dom_lca_tags.at_put_grow(n2->_idx, tag);
n2 = idom(n2);
d2 = dom_depth(n2);
} else {
// Here d1 == d2. Due to edits of the dominator-tree, sections
// of the tree might have the same depth. These sections have
// to be searched more carefully.
// Scan up all the n1's with equal depth, looking for n2.
_dom_lca_tags.at_put_grow(n1->_idx, tag);
Node *t1 = idom(n1);
while (dom_depth(t1) == d1) {
if (t1 == n2) return n2;
_dom_lca_tags.at_put_grow(t1->_idx, tag);
t1 = idom(t1);
}
// Scan up all the n2's with equal depth, looking for n1.
_dom_lca_tags.at_put_grow(n2->_idx, tag);
Node *t2 = idom(n2);
while (dom_depth(t2) == d2) {
if (t2 == n1) return n1;
_dom_lca_tags.at_put_grow(t2->_idx, tag);
t2 = idom(t2);
}
// Move up to a new dominator-depth value as well as up the dom-tree.
n1 = t1;
n2 = t2;
d1 = dom_depth(n1);
d2 = dom_depth(n2);
}
} while (n1 != n2);
return n1;
}
//------------------------------init_dom_lca_tags------------------------------
// Tag could be a node's integer index, 32bits instead of 64bits in some cases
// Intended use does not involve any growth for the array, so it could
// be of fixed size.
void PhaseIdealLoop::init_dom_lca_tags() {
uint limit = C->unique() + 1;
_dom_lca_tags.at_grow(limit, 0);
_dom_lca_tags_round = 0;
#ifdef ASSERT
for (uint i = 0; i < limit; ++i) {
assert(_dom_lca_tags.at(i) == 0, "Must be distinct from each node pointer");
}
#endif // ASSERT
}
//------------------------------build_loop_late--------------------------------
// Put Data nodes into some loop nest, by setting the _loop_or_ctrl[]->loop mapping.
// Second pass finds latest legal placement, and ideal loop placement.
void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
while (worklist.size() != 0) {
Node *n = worklist.pop();
// Only visit once
if (visited.test_set(n->_idx)) continue;
uint cnt = n->outcnt();
uint i = 0;
while (true) {
assert(_loop_or_ctrl[n->_idx], "no dead nodes");
// Visit all children
if (i < cnt) {
Node* use = n->raw_out(i);
++i;
// Check for dead uses. Aggressively prune such junk. It might be
// dead in the global sense, but still have local uses so I cannot
// easily call 'remove_dead_node'.
if (_loop_or_ctrl[use->_idx] != nullptr || use->is_top()) { // Not dead?
// Due to cycles, we might not hit the same fixed point in the verify
// pass as we do in the regular pass. Instead, visit such phis as
// simple uses of the loop head.
if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) {
if( !visited.test(use->_idx) )
worklist.push(use);
} else if( !visited.test_set(use->_idx) ) {
nstack.push(n, i); // Save parent and next use's index.
n = use; // Process all children of current use.
cnt = use->outcnt();
i = 0;
}
} else {
// Do not visit around the backedge of loops via data edges.
// push dead code onto a worklist
_deadlist.push(use);
}
} else {
// All of n's children have been processed, complete post-processing.
build_loop_late_post(n);
if (C->failing()) { return; }
if (nstack.is_empty()) {
// Finished all nodes on stack.
// Process next node on the worklist.
break;
}
// Get saved parent node and next use's index. Visit the rest of uses.
n = nstack.node();
cnt = n->outcnt();
i = nstack.index();
nstack.pop();
}
}
}
}
// Verify that no data node is scheduled in the outer loop of a strip
// mined loop.
void PhaseIdealLoop::verify_strip_mined_scheduling(Node *n, Node* least) {
#ifdef ASSERT
if (get_loop(least)->_nest == 0) {
return;
}
IdealLoopTree* loop = get_loop(least);
Node* head = loop->_head;
if (head->is_OuterStripMinedLoop() &&
// Verification can't be applied to fully built strip mined loops
head->as_Loop()->outer_loop_end()->in(1)->find_int_con(-1) == 0) {
Node* sfpt = head->as_Loop()->outer_safepoint();
ResourceMark rm;
Unique_Node_List wq;
wq.push(sfpt);
for (uint i = 0; i < wq.size(); i++) {
Node *m = wq.at(i);
for (uint i = 1; i < m->req(); i++) {
Node* nn = m->in(i);
if (nn == n) {
return;
}
if (nn != nullptr && has_ctrl(nn) && get_loop(get_ctrl(nn)) == loop) {
wq.push(nn);
}
}
}
ShouldNotReachHere();
}
#endif
}
//------------------------------build_loop_late_post---------------------------
// Put Data nodes into some loop nest, by setting the _loop_or_ctrl[]->loop mapping.
// Second pass finds latest legal placement, and ideal loop placement.
void PhaseIdealLoop::build_loop_late_post(Node *n) {
build_loop_late_post_work(n, true);
}
void PhaseIdealLoop::build_loop_late_post_work(Node *n, bool pinned) {
if (n->req() == 2 && (n->Opcode() == Op_ConvI2L || n->Opcode() == Op_CastII) && !C->major_progress() && !_verify_only) {
_igvn._worklist.push(n); // Maybe we'll normalize it, if no more loops.
}
#ifdef ASSERT
if (_verify_only && !n->is_CFG()) {
// Check def-use domination.
compute_lca_of_uses(n, get_ctrl(n), true /* verify */);
}
#endif
// CFG and pinned nodes already handled
if( n->in(0) ) {
if( n->in(0)->is_top() ) return; // Dead?
// We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads
// _must_ be pinned (they have to observe their control edge of course).
// Unlike Stores (which modify an unallocable resource, the memory
// state), Mods/Loads can float around. So free them up.
switch( n->Opcode() ) {
case Op_DivI:
case Op_DivF:
case Op_DivD:
case Op_ModI:
case Op_ModF:
case Op_ModD:
case Op_LoadB: // Same with Loads; they can sink
case Op_LoadUB: // during loop optimizations.
case Op_LoadUS:
case Op_LoadD:
case Op_LoadF:
case Op_LoadI:
case Op_LoadKlass:
case Op_LoadNKlass:
case Op_LoadL:
case Op_LoadS:
case Op_LoadP:
case Op_LoadN:
case Op_LoadRange:
case Op_LoadD_unaligned:
case Op_LoadL_unaligned:
case Op_StrComp: // Does a bunch of load-like effects
case Op_StrEquals:
case Op_StrIndexOf:
case Op_StrIndexOfChar:
case Op_AryEq:
case Op_VectorizedHashCode:
case Op_CountPositives:
pinned = false;
}
if (n->is_CMove() || n->is_ConstraintCast()) {
pinned = false;
}
if( pinned ) {
IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n));
if( !chosen_loop->_child ) // Inner loop?
chosen_loop->_body.push(n); // Collect inner loops
return;
}
} else { // No slot zero
if( n->is_CFG() ) { // CFG with no slot 0 is dead
_loop_or_ctrl.map(n->_idx,0); // No block setting, it's globally dead
return;
}
assert(!n->is_CFG() || n->outcnt() == 0, "");
}
// Do I have a "safe range" I can select over?
Node *early = get_ctrl(n);// Early location already computed
// Compute latest point this Node can go
Node *LCA = get_late_ctrl( n, early );
// LCA is null due to uses being dead
if( LCA == nullptr ) {
#ifdef ASSERT
for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) {
assert(_loop_or_ctrl[n->out(i1)->_idx] == nullptr, "all uses must also be dead");
}
#endif
_loop_or_ctrl.map(n->_idx, 0); // This node is useless
_deadlist.push(n);
return;
}
assert(LCA != nullptr && !LCA->is_top(), "no dead nodes");
Node *legal = LCA; // Walk 'legal' up the IDOM chain
Node *least = legal; // Best legal position so far
while( early != legal ) { // While not at earliest legal
if (legal->is_Start() && !early->is_Root()) {
#ifdef ASSERT
// Bad graph. Print idom path and fail.
dump_bad_graph("Bad graph detected in build_loop_late", n, early, LCA);
assert(false, "Bad graph detected in build_loop_late");
#endif
C->record_method_not_compilable("Bad graph detected in build_loop_late");
return;
}
// Find least loop nesting depth
legal = idom(legal); // Bump up the IDOM tree
// Check for lower nesting depth
if( get_loop(legal)->_nest < get_loop(least)->_nest )
least = legal;
}
assert(early == legal || legal != C->root(), "bad dominance of inputs");
if (least != early) {
// Move the node above predicates as far up as possible so a
// following pass of loop predication doesn't hoist a predicate
// that depends on it above that node.
Node* new_ctrl = least;
for (;;) {
if (!new_ctrl->is_Proj()) {
break;
}
CallStaticJavaNode* call = new_ctrl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
if (call == nullptr) {
break;
}
int req = call->uncommon_trap_request();
Deoptimization::DeoptReason trap_reason = Deoptimization::trap_request_reason(req);
if (trap_reason != Deoptimization::Reason_loop_limit_check &&
trap_reason != Deoptimization::Reason_predicate &&
trap_reason != Deoptimization::Reason_profile_predicate) {
break;
}
Node* c = new_ctrl->in(0)->in(0);
if (is_dominator(c, early) && c != early) {
break;
}
new_ctrl = c;
}
least = new_ctrl;
}
// Try not to place code on a loop entry projection
// which can inhibit range check elimination.
if (least != early && !BarrierSet::barrier_set()->barrier_set_c2()->is_gc_specific_loop_opts_pass(_mode)) {
Node* ctrl_out = least->unique_ctrl_out_or_null();
if (ctrl_out != nullptr && ctrl_out->is_Loop() &&
least == ctrl_out->in(LoopNode::EntryControl) &&
(ctrl_out->is_CountedLoop() || ctrl_out->is_OuterStripMinedLoop())) {
Node* least_dom = idom(least);
if (get_loop(least_dom)->is_member(get_loop(least))) {
least = least_dom;
}
}
}
// Don't extend live ranges of raw oops
if (least != early && n->is_ConstraintCast() && n->in(1)->bottom_type()->isa_rawptr() &&
!n->bottom_type()->isa_rawptr()) {
least = early;
}
#ifdef ASSERT
// Broken part of VerifyLoopOptimizations (F)
// Reason:
// _verify_me->get_ctrl_no_update(n) seems to return wrong result
/*
// If verifying, verify that 'verify_me' has a legal location
// and choose it as our location.
if( _verify_me ) {
Node *v_ctrl = _verify_me->get_ctrl_no_update(n);
Node *legal = LCA;
while( early != legal ) { // While not at earliest legal
if( legal == v_ctrl ) break; // Check for prior good location
legal = idom(legal) ;// Bump up the IDOM tree
}
// Check for prior good location
if( legal == v_ctrl ) least = legal; // Keep prior if found
}
*/
#endif
// Assign discovered "here or above" point
least = find_non_split_ctrl(least);
verify_strip_mined_scheduling(n, least);
set_ctrl(n, least);
// Collect inner loop bodies
IdealLoopTree *chosen_loop = get_loop(least);
if( !chosen_loop->_child ) // Inner loop?
chosen_loop->_body.push(n);// Collect inner loops
if (!_verify_only && n->Opcode() == Op_OpaqueZeroTripGuard) {
_zero_trip_guard_opaque_nodes.push(n);
}
}
#ifdef ASSERT
void PhaseIdealLoop::dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA) {
tty->print_cr("%s", msg);
tty->print("n: "); n->dump();
tty->print("early(n): "); early->dump();
if (n->in(0) != nullptr && !n->in(0)->is_top() &&
n->in(0) != early && !n->in(0)->is_Root()) {
tty->print("n->in(0): "); n->in(0)->dump();
}
for (uint i = 1; i < n->req(); i++) {
Node* in1 = n->in(i);
if (in1 != nullptr && in1 != n && !in1->is_top()) {
tty->print("n->in(%d): ", i); in1->dump();
Node* in1_early = get_ctrl(in1);
tty->print("early(n->in(%d)): ", i); in1_early->dump();
if (in1->in(0) != nullptr && !in1->in(0)->is_top() &&
in1->in(0) != in1_early && !in1->in(0)->is_Root()) {
tty->print("n->in(%d)->in(0): ", i); in1->in(0)->dump();
}
for (uint j = 1; j < in1->req(); j++) {
Node* in2 = in1->in(j);
if (in2 != nullptr && in2 != n && in2 != in1 && !in2->is_top()) {
tty->print("n->in(%d)->in(%d): ", i, j); in2->dump();
Node* in2_early = get_ctrl(in2);
tty->print("early(n->in(%d)->in(%d)): ", i, j); in2_early->dump();
if (in2->in(0) != nullptr && !in2->in(0)->is_top() &&
in2->in(0) != in2_early && !in2->in(0)->is_Root()) {
tty->print("n->in(%d)->in(%d)->in(0): ", i, j); in2->in(0)->dump();
}
}
}
}
}
tty->cr();
tty->print("LCA(n): "); LCA->dump();
for (uint i = 0; i < n->outcnt(); i++) {
Node* u1 = n->raw_out(i);
if (u1 == n)
continue;
tty->print("n->out(%d): ", i); u1->dump();
if (u1->is_CFG()) {
for (uint j = 0; j < u1->outcnt(); j++) {
Node* u2 = u1->raw_out(j);
if (u2 != u1 && u2 != n && u2->is_CFG()) {
tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
}
}
} else {
Node* u1_later = get_ctrl(u1);
tty->print("later(n->out(%d)): ", i); u1_later->dump();
if (u1->in(0) != nullptr && !u1->in(0)->is_top() &&
u1->in(0) != u1_later && !u1->in(0)->is_Root()) {
tty->print("n->out(%d)->in(0): ", i); u1->in(0)->dump();
}
for (uint j = 0; j < u1->outcnt(); j++) {
Node* u2 = u1->raw_out(j);
if (u2 == n || u2 == u1)
continue;
tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
if (!u2->is_CFG()) {
Node* u2_later = get_ctrl(u2);
tty->print("later(n->out(%d)->out(%d)): ", i, j); u2_later->dump();
if (u2->in(0) != nullptr && !u2->in(0)->is_top() &&
u2->in(0) != u2_later && !u2->in(0)->is_Root()) {
tty->print("n->out(%d)->in(0): ", i); u2->in(0)->dump();
}
}
}
}
}
dump_idoms(early, LCA);
tty->cr();
}
// Class to compute the real LCA given an early node and a wrong LCA in a bad graph.
class RealLCA {
const PhaseIdealLoop* _phase;
Node* _early;
Node* _wrong_lca;
uint _early_index;
int _wrong_lca_index;
// Given idom chains of early and wrong LCA: Walk through idoms starting at StartNode and find the first node which
// is different: Return the previously visited node which must be the real LCA.
// The node lists also contain _early and _wrong_lca, respectively.
Node* find_real_lca(Unique_Node_List& early_with_idoms, Unique_Node_List& wrong_lca_with_idoms) {
int early_index = early_with_idoms.size() - 1;
int wrong_lca_index = wrong_lca_with_idoms.size() - 1;
bool found_difference = false;
do {
if (early_with_idoms[early_index] != wrong_lca_with_idoms[wrong_lca_index]) {
// First time early and wrong LCA idoms differ. Real LCA must be at the previous index.
found_difference = true;
break;
}
early_index--;
wrong_lca_index--;
} while (wrong_lca_index >= 0);
assert(early_index >= 0, "must always find an LCA - cannot be early");
_early_index = early_index;
_wrong_lca_index = wrong_lca_index;
Node* real_lca = early_with_idoms[_early_index + 1]; // Plus one to skip _early.
assert(found_difference || real_lca == _wrong_lca, "wrong LCA dominates early and is therefore the real LCA");
return real_lca;
}
void dump(Node* real_lca) {
tty->cr();
tty->print_cr("idoms of early \"%d %s\":", _early->_idx, _early->Name());
_phase->dump_idom(_early, _early_index + 1);
tty->cr();
tty->print_cr("idoms of (wrong) LCA \"%d %s\":", _wrong_lca->_idx, _wrong_lca->Name());
_phase->dump_idom(_wrong_lca, _wrong_lca_index + 1);
tty->cr();
tty->print("Real LCA of early \"%d %s\" (idom[%d]) and wrong LCA \"%d %s\"",
_early->_idx, _early->Name(), _early_index, _wrong_lca->_idx, _wrong_lca->Name());
if (_wrong_lca_index >= 0) {
tty->print(" (idom[%d])", _wrong_lca_index);
}
tty->print_cr(":");
real_lca->dump();
}
public:
RealLCA(const PhaseIdealLoop* phase, Node* early, Node* wrong_lca)
: _phase(phase), _early(early), _wrong_lca(wrong_lca), _early_index(0), _wrong_lca_index(0) {
assert(!wrong_lca->is_Start(), "StartNode is always a common dominator");
}
void compute_and_dump() {
ResourceMark rm;
Unique_Node_List early_with_idoms;
Unique_Node_List wrong_lca_with_idoms;
early_with_idoms.push(_early);
wrong_lca_with_idoms.push(_wrong_lca);
_phase->get_idoms(_early, 10000, early_with_idoms);
_phase->get_idoms(_wrong_lca, 10000, wrong_lca_with_idoms);
Node* real_lca = find_real_lca(early_with_idoms, wrong_lca_with_idoms);
dump(real_lca);
}
};
// Dump the idom chain of early, of the wrong LCA and dump the real LCA of early and wrong LCA.
void PhaseIdealLoop::dump_idoms(Node* early, Node* wrong_lca) {
assert(!is_dominator(early, wrong_lca), "sanity check that early does not dominate wrong lca");
assert(!has_ctrl(early) && !has_ctrl(wrong_lca), "sanity check, no data nodes");
RealLCA real_lca(this, early, wrong_lca);
real_lca.compute_and_dump();
}
#endif // ASSERT
#ifndef PRODUCT
//------------------------------dump-------------------------------------------
void PhaseIdealLoop::dump() const {
ResourceMark rm;
Node_Stack stack(C->live_nodes() >> 2);
Node_List rpo_list;
VectorSet visited;
visited.set(C->top()->_idx);
rpo(C->root(), stack, visited, rpo_list);
// Dump root loop indexed by last element in PO order
dump(_ltree_root, rpo_list.size(), rpo_list);
}
void PhaseIdealLoop::dump(IdealLoopTree* loop, uint idx, Node_List &rpo_list) const {
loop->dump_head();
// Now scan for CFG nodes in the same loop
for (uint j = idx; j > 0; j--) {
Node* n = rpo_list[j-1];
if (!_loop_or_ctrl[n->_idx]) // Skip dead nodes
continue;
if (get_loop(n) != loop) { // Wrong loop nest
if (get_loop(n)->_head == n && // Found nested loop?
get_loop(n)->_parent == loop)
dump(get_loop(n), rpo_list.size(), rpo_list); // Print it nested-ly
continue;
}
// Dump controlling node
tty->sp(2 * loop->_nest);
tty->print("C");
if (n == C->root()) {
n->dump();
} else {
Node* cached_idom = idom_no_update(n);
Node* computed_idom = n->in(0);
if (n->is_Region()) {
computed_idom = compute_idom(n);
// computed_idom() will return n->in(0) when idom(n) is an IfNode (or
// any MultiBranch ctrl node), so apply a similar transform to
// the cached idom returned from idom_no_update.
cached_idom = find_non_split_ctrl(cached_idom);
}
tty->print(" ID:%d", computed_idom->_idx);
n->dump();
if (cached_idom != computed_idom) {
tty->print_cr("*** BROKEN IDOM! Computed as: %d, cached as: %d",
computed_idom->_idx, cached_idom->_idx);
}
}
// Dump nodes it controls
for (uint k = 0; k < _loop_or_ctrl.max(); k++) {
// (k < C->unique() && get_ctrl(find(k)) == n)
if (k < C->unique() && _loop_or_ctrl[k] == (Node*)((intptr_t)n + 1)) {
Node* m = C->root()->find(k);
if (m && m->outcnt() > 0) {
if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) {
tty->print_cr("*** BROKEN CTRL ACCESSOR! _loop_or_ctrl[k] is %p, ctrl is %p",
_loop_or_ctrl[k], has_ctrl(m) ? get_ctrl_no_update(m) : nullptr);
}
tty->sp(2 * loop->_nest + 1);
m->dump();
}
}
}
}
}
void PhaseIdealLoop::dump_idom(Node* n, const uint count) const {
if (has_ctrl(n)) {
tty->print_cr("No idom for data nodes");
} else {
ResourceMark rm;
Unique_Node_List idoms;
get_idoms(n, count, idoms);
dump_idoms_in_reverse(n, idoms);
}
}
void PhaseIdealLoop::get_idoms(Node* n, const uint count, Unique_Node_List& idoms) const {
Node* next = n;
for (uint i = 0; !next->is_Start() && i < count; i++) {
next = idom(next);
assert(!idoms.member(next), "duplicated idom is not possible");
idoms.push(next);
}
}
void PhaseIdealLoop::dump_idoms_in_reverse(const Node* n, const Node_List& idom_list) const {
Node* next;
uint padding = 3;
uint node_index_padding_width = static_cast<int>(log10(static_cast<double>(C->unique()))) + 1;
for (int i = idom_list.size() - 1; i >= 0; i--) {
if (i == 9 || i == 99) {
padding++;
}
next = idom_list[i];
tty->print_cr("idom[%d]:%*c%*d %s", i, padding, ' ', node_index_padding_width, next->_idx, next->Name());
}
tty->print_cr("n: %*c%*d %s", padding, ' ', node_index_padding_width, n->_idx, n->Name());
}
#endif // NOT PRODUCT
// Collect a R-P-O for the whole CFG.
// Result list is in post-order (scan backwards for RPO)
void PhaseIdealLoop::rpo(Node* start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list) const {
stk.push(start, 0);
visited.set(start->_idx);
while (stk.is_nonempty()) {
Node* m = stk.node();
uint idx = stk.index();
if (idx < m->outcnt()) {
stk.set_index(idx + 1);
Node* n = m->raw_out(idx);
if (n->is_CFG() && !visited.test_set(n->_idx)) {
stk.push(n, 0);
}
} else {
rpo_list.push(m);
stk.pop();
}
}
}
//=============================================================================
//------------------------------LoopTreeIterator-------------------------------
// Advance to next loop tree using a preorder, left-to-right traversal.
void LoopTreeIterator::next() {
assert(!done(), "must not be done.");
if (_curnt->_child != nullptr) {
_curnt = _curnt->_child;
} else if (_curnt->_next != nullptr) {
_curnt = _curnt->_next;
} else {
while (_curnt != _root && _curnt->_next == nullptr) {
_curnt = _curnt->_parent;
}
if (_curnt == _root) {
_curnt = nullptr;
assert(done(), "must be done.");
} else {
assert(_curnt->_next != nullptr, "must be more to do");
_curnt = _curnt->_next;
}
}
}