bolt/lib/Passes/ValidateInternalCalls.cpp - toolchain/llvm-project - Git at Google

 //===- bolt/Passes/ValidateInternalCalls.cpp ------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the ValidateInternalCalls class.
 //
 //===----------------------------------------------------------------------===//

 #include "bolt/Passes/ValidateInternalCalls.h"
 #include "bolt/Core/BinaryBasicBlock.h"
 #include "bolt/Passes/DataflowInfoManager.h"
 #include "bolt/Passes/FrameAnalysis.h"
 #include "llvm/MC/MCInstPrinter.h"
 #include <optional>
 #include <queue>

 #define DEBUG_TYPE "bolt-internalcalls"

 namespace llvm {
 namespace bolt {

 namespace {

 // Helper used to extract the target basic block used in an internal call.
 // Return nullptr if this is not an internal call target.
 BinaryBasicBlock *getInternalCallTarget(BinaryFunction &Function,
                                         const MCInst &Inst) {
   const BinaryContext &BC = Function.getBinaryContext();
   if (!BC.MIB->isCall(Inst) || MCPlus::getNumPrimeOperands(Inst) != 1 ||
       !Inst.getOperand(0).isExpr())
     return nullptr;

   return Function.getBasicBlockForLabel(BC.MIB->getTargetSymbol(Inst));
 }

 // A special StackPointerTracking that considers internal calls
 class StackPointerTrackingForInternalCalls
     : public StackPointerTrackingBase<StackPointerTrackingForInternalCalls> {
   friend class DataflowAnalysis<StackPointerTrackingForInternalCalls,
                                 std::pair<int, int>>;

   std::optional<unsigned> AnnotationIndex;

 protected:
   // We change the starting state to only consider the first block as an
   // entry point, otherwise the analysis won't converge (there will be two valid
   // stack offsets, one for an external call and another for an internal call).
   std::pair<int, int> getStartingStateAtBB(const BinaryBasicBlock &BB) {
     if (&BB == &*Func.begin())
       return std::make_pair(-8, getEmpty());
     return std::make_pair(getEmpty(), getEmpty());
   }

   // Here we decrement SP for internal calls too, in addition to the regular
   // StackPointerTracking processing.
   std::pair<int, int> computeNext(const MCInst &Point,
                                   const std::pair<int, int> &Cur) {
     std::pair<int, int> Res = StackPointerTrackingBase<
         StackPointerTrackingForInternalCalls>::computeNext(Point, Cur);
     if (Res.first == StackPointerTracking::SUPERPOSITION ||
         Res.first == StackPointerTracking::EMPTY)
       return Res;

     if (BC.MIB->isReturn(Point)) {
       Res.first += 8;
       return Res;
     }

     BinaryBasicBlock *Target = getInternalCallTarget(Func, Point);
     if (!Target)
       return Res;

     Res.first -= 8;
     return Res;
   }

   StringRef getAnnotationName() const {
     return StringRef("StackPointerTrackingForInternalCalls");
   }

 public:
   StackPointerTrackingForInternalCalls(BinaryFunction &BF)
       : StackPointerTrackingBase<StackPointerTrackingForInternalCalls>(BF) {}

   void run() {
     StackPointerTrackingBase<StackPointerTrackingForInternalCalls>::run();
   }
 };

 } // end anonymous namespace

 void ValidateInternalCalls::fixCFGForPIC(BinaryFunction &Function) const {
   std::queue<BinaryBasicBlock *> Work;
   for (BinaryBasicBlock &BB : Function)
     Work.emplace(&BB);

   while (!Work.empty()) {
     BinaryBasicBlock &BB = *Work.front();
     Work.pop();

     // Search for the next internal call.
     const BinaryBasicBlock::iterator InternalCall =
         llvm::find_if(BB, [&](const MCInst &Inst) {
           return getInternalCallTarget(Function, Inst) != nullptr;
         });

     // No internal call? Done with this block.
     if (InternalCall == BB.end())
       continue;

     BinaryBasicBlock *Target = getInternalCallTarget(Function, *InternalCall);
     InstructionListType MovedInsts = BB.splitInstructions(&*InternalCall);
     if (!MovedInsts.empty()) {
       // Split this block at the call instruction.
       std::unique_ptr<BinaryBasicBlock> NewBB = Function.createBasicBlock();
       NewBB->addInstructions(MovedInsts.begin(), MovedInsts.end());
       BB.moveAllSuccessorsTo(NewBB.get());

       Work.emplace(NewBB.get());
       std::vector<std::unique_ptr<BinaryBasicBlock>> NewBBs;
       NewBBs.emplace_back(std::move(NewBB));
       Function.insertBasicBlocks(&BB, std::move(NewBBs));
     }
     // Update successors
     BB.removeAllSuccessors();
     BB.addSuccessor(Target, BB.getExecutionCount(), 0ULL);
   }
 }

 bool ValidateInternalCalls::fixCFGForIC(BinaryFunction &Function) const {
   const BinaryContext &BC = Function.getBinaryContext();
   // Track SP value
   StackPointerTrackingForInternalCalls SPTIC(Function);
   SPTIC.run();

   // Track instructions reaching a given point of the CFG to answer
   // "There is a path from entry to point A that contains instruction B"
   ReachingInsns<false> RI(Function);
   RI.run();

   // We use the InsnToBB map that DataflowInfoManager provides us
   DataflowInfoManager Info(Function, nullptr, nullptr);

   bool Updated = false;

   auto processReturns = [&](BinaryBasicBlock &BB, MCInst &Return) {
     // Check all reaching internal calls
     for (auto I = RI.expr_begin(Return), E = RI.expr_end(); I != E; ++I) {
       MCInst &ReachingInst = **I;
       if (!getInternalCallTarget(Function, ReachingInst) ||
           BC.MIB->hasAnnotation(ReachingInst, getProcessedICTag()))
         continue;

       // Stack pointer matching
       int SPAtCall = SPTIC.getStateAt(ReachingInst)->first;
       int SPAtRet = SPTIC.getStateAt(Return)->first;
       if (SPAtCall != StackPointerTracking::SUPERPOSITION &&
           SPAtRet != StackPointerTracking::SUPERPOSITION &&
           SPAtCall != SPAtRet - 8)
         continue;

       Updated = true;

       // Mark this call as processed, so we don't try to analyze it as a
       // PIC-computation internal call.
       BC.MIB->addAnnotation(ReachingInst, getProcessedICTag(), 0U);

       // Connect this block with the returning block of the caller
       BinaryBasicBlock *CallerBlock = Info.getInsnToBBMap()[&ReachingInst];
       BinaryBasicBlock *ReturnDestBlock =
           Function.getLayout().getBasicBlockAfter(CallerBlock);
       BB.addSuccessor(ReturnDestBlock, BB.getExecutionCount(), 0);
     }
   };

   // This will connect blocks terminated with RETs to their respective
   // internal caller return block. A note here: this is overly conservative
   // because in nested calls, or unrelated calls, it will create edges
   // connecting RETs to potentially unrelated internal calls. This is safe
   // and if this causes a problem to recover the stack offsets properly, we
   // will fail later.
   for (BinaryBasicBlock &BB : Function) {
     for (MCInst &Inst : BB) {
       if (!BC.MIB->isReturn(Inst))
         continue;

       processReturns(BB, Inst);
     }
   }
   return Updated;
 }

 bool ValidateInternalCalls::hasTailCallsInRange(
     BinaryFunction &Function) const {
   const BinaryContext &BC = Function.getBinaryContext();
   for (BinaryBasicBlock &BB : Function)
     for (MCInst &Inst : BB)
       if (BC.MIB->isTailCall(Inst))
         return true;
   return false;
 }

 bool ValidateInternalCalls::analyzeFunction(BinaryFunction &Function) const {
   fixCFGForPIC(Function);
   while (fixCFGForIC(Function)) {
   }

   BinaryContext &BC = Function.getBinaryContext();
   RegAnalysis RA = RegAnalysis(BC, nullptr, nullptr);
   RA.setConservativeStrategy(RegAnalysis::ConservativeStrategy::CLOBBERS_NONE);
   bool HasTailCalls = hasTailCallsInRange(Function);

   for (BinaryBasicBlock &BB : Function) {
     for (MCInst &Inst : BB) {
       BinaryBasicBlock *Target = getInternalCallTarget(Function, Inst);
       if (!Target || BC.MIB->hasAnnotation(Inst, getProcessedICTag()))
         continue;

       if (HasTailCalls) {
         LLVM_DEBUG(dbgs() << Function
                           << " has tail calls and internal calls.\n");
         return false;
       }

       FrameIndexEntry FIE;
       int32_t SrcImm = 0;
       MCPhysReg Reg = 0;
       int64_t StackOffset = 0;
       bool IsIndexed = false;
       MCInst *TargetInst = ProgramPoint::getFirstPointAt(*Target).getInst();
       if (!BC.MIB->isStackAccess(*TargetInst, FIE.IsLoad, FIE.IsStore,
                                  FIE.IsStoreFromReg, Reg, SrcImm,
                                  FIE.StackPtrReg, StackOffset, FIE.Size,
                                  FIE.IsSimple, IsIndexed)) {
         LLVM_DEBUG({
           dbgs() << "Frame analysis failed - not simple: " << Function << "\n";
           Function.dump();
         });
         return false;
       }
       if (!FIE.IsLoad || FIE.StackPtrReg != BC.MIB->getStackPointer() ||
           StackOffset != 0) {
         LLVM_DEBUG({
           dbgs() << "Target instruction does not fetch return address - not "
                     "simple: "
                  << Function << "\n";
           Function.dump();
         });
         return false;
       }
       // Now track how the return address is used by tracking uses of Reg
       ReachingDefOrUse</*Def=*/false> RU =
           ReachingDefOrUse<false>(RA, Function, Reg);
       RU.run();

       int64_t Offset = static_cast<int64_t>(Target->getInputOffset());
       bool UseDetected = false;
       for (auto I = RU.expr_begin(*RU.getStateBefore(*TargetInst)),
                 E = RU.expr_end();
            I != E; ++I) {
         MCInst &Use = **I;
         BitVector UsedRegs = BitVector(BC.MRI->getNumRegs(), false);
         BC.MIB->getTouchedRegs(Use, UsedRegs);
         if (!UsedRegs[Reg])
           continue;
         UseDetected = true;
         int64_t Output;
         std::pair<MCPhysReg, int64_t> Input1 = std::make_pair(Reg, 0);
         std::pair<MCPhysReg, int64_t> Input2 = std::make_pair(0, 0);
         if (!BC.MIB->evaluateStackOffsetExpr(Use, Output, Input1, Input2)) {
           LLVM_DEBUG(dbgs() << "Evaluate stack offset expr failed.\n");
           return false;
         }
         if (Offset + Output < 0 ||
             Offset + Output > static_cast<int64_t>(Function.getSize())) {
           LLVM_DEBUG({
             dbgs() << "Detected out-of-range PIC reference in " << Function
                    << "\nReturn address load: ";
             BC.dump(*TargetInst);
             dbgs() << "Use: ";
             BC.dump(Use);
             Function.dump();
           });
           return false;
         }
         LLVM_DEBUG({
           dbgs() << "Validated access: ";
           BC.dump(Use);
         });
       }
       if (!UseDetected) {
         LLVM_DEBUG(dbgs() << "No use detected.\n");
         return false;
       }
     }
   }
   return true;
 }

 Error ValidateInternalCalls::runOnFunctions(BinaryContext &BC) {
   // Look for functions that need validation. This should be pretty rare.
   std::set<BinaryFunction *> NeedsValidation;
   for (auto &BFI : BC.getBinaryFunctions()) {
     BinaryFunction &Function = BFI.second;
     for (BinaryBasicBlock &BB : Function) {
       for (MCInst &Inst : BB) {
         if (getInternalCallTarget(Function, Inst)) {
           BC.errs() << "BOLT-WARNING: internal call detected in function "
                     << Function << '\n';
           NeedsValidation.insert(&Function);
           Function.setSimple(false);
           Function.setPreserveNops(true);
           break;
         }
       }
     }
   }

   if (!BC.isX86())
     return Error::success();

   // Skip validation for non-relocation mode
   if (!BC.HasRelocations)
     return Error::success();

   // Since few functions need validation, we can work with our most expensive
   // algorithms here. Fix the CFG treating internal calls as unconditional
   // jumps. This optimistically assumes this call is a PIC trick to get the PC
   // value, so it is not really a call, but a jump. If we find that it's not the
   // case, we mark this function as non-simple and stop processing it.
   std::set<BinaryFunction *> Invalid;
   for (BinaryFunction *Function : NeedsValidation) {
     LLVM_DEBUG(dbgs() << "Validating " << *Function << "\n");
     if (!analyzeFunction(*Function))
       Invalid.insert(Function);
     clearAnnotations(*Function);
   }

   if (!Invalid.empty()) {
     BC.errs()
         << "BOLT-WARNING: will skip the following function(s) as unsupported"
            " internal calls were detected:\n";
     for (BinaryFunction *Function : Invalid) {
       BC.errs() << "              " << *Function << "\n";
       Function->setIgnored();
     }
   }
   return Error::success();
 }

 } // namespace bolt
 } // namespace llvm
	//===- bolt/Passes/ValidateInternalCalls.cpp ------------------------------===//
	//
	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
	// See https://llvm.org/LICENSE.txt for license information.
	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
	//
	//===----------------------------------------------------------------------===//
	//
	// This file implements the ValidateInternalCalls class.
	//
	//===----------------------------------------------------------------------===//

	#include "bolt/Passes/ValidateInternalCalls.h"
	#include "bolt/Core/BinaryBasicBlock.h"
	#include "bolt/Passes/DataflowInfoManager.h"
	#include "bolt/Passes/FrameAnalysis.h"
	#include "llvm/MC/MCInstPrinter.h"
	#include <optional>
	#include <queue>

	#define DEBUG_TYPE "bolt-internalcalls"

	namespace llvm {
	namespace bolt {

	namespace {

	// Helper used to extract the target basic block used in an internal call.
	// Return nullptr if this is not an internal call target.
	BinaryBasicBlock *getInternalCallTarget(BinaryFunction &Function,
	const MCInst &Inst) {
	const BinaryContext &BC = Function.getBinaryContext();
	if (!BC.MIB->isCall(Inst) \|\| MCPlus::getNumPrimeOperands(Inst) != 1 \|\|
	!Inst.getOperand(0).isExpr())
	return nullptr;

	return Function.getBasicBlockForLabel(BC.MIB->getTargetSymbol(Inst));
	}

	// A special StackPointerTracking that considers internal calls
	class StackPointerTrackingForInternalCalls
	: public StackPointerTrackingBase<StackPointerTrackingForInternalCalls> {
	friend class DataflowAnalysis<StackPointerTrackingForInternalCalls,
	std::pair<int, int>>;

	std::optional<unsigned> AnnotationIndex;

	protected:
	// We change the starting state to only consider the first block as an
	// entry point, otherwise the analysis won't converge (there will be two valid
	// stack offsets, one for an external call and another for an internal call).
	std::pair<int, int> getStartingStateAtBB(const BinaryBasicBlock &BB) {
	if (&BB == &*Func.begin())
	return std::make_pair(-8, getEmpty());
	return std::make_pair(getEmpty(), getEmpty());
	}

	// Here we decrement SP for internal calls too, in addition to the regular
	// StackPointerTracking processing.
	std::pair<int, int> computeNext(const MCInst &Point,
	const std::pair<int, int> &Cur) {
	std::pair<int, int> Res = StackPointerTrackingBase<
	StackPointerTrackingForInternalCalls>::computeNext(Point, Cur);
	if (Res.first == StackPointerTracking::SUPERPOSITION \|\|
	Res.first == StackPointerTracking::EMPTY)
	return Res;

	if (BC.MIB->isReturn(Point)) {
	Res.first += 8;
	return Res;
	}

	BinaryBasicBlock *Target = getInternalCallTarget(Func, Point);
	if (!Target)
	return Res;

	Res.first -= 8;
	return Res;
	}

	StringRef getAnnotationName() const {
	return StringRef("StackPointerTrackingForInternalCalls");
	}

	public:
	StackPointerTrackingForInternalCalls(BinaryFunction &BF)
	: StackPointerTrackingBase<StackPointerTrackingForInternalCalls>(BF) {}

	void run() {
	StackPointerTrackingBase<StackPointerTrackingForInternalCalls>::run();
	}
	};

	} // end anonymous namespace

	void ValidateInternalCalls::fixCFGForPIC(BinaryFunction &Function) const {
	std::queue<BinaryBasicBlock *> Work;
	for (BinaryBasicBlock &BB : Function)
	Work.emplace(&BB);

	while (!Work.empty()) {
	BinaryBasicBlock &BB = *Work.front();
	Work.pop();

	// Search for the next internal call.
	const BinaryBasicBlock::iterator InternalCall =
	llvm::find_if(BB, [&](const MCInst &Inst) {
	return getInternalCallTarget(Function, Inst) != nullptr;
	});

	// No internal call? Done with this block.
	if (InternalCall == BB.end())
	continue;

	BinaryBasicBlock Target = getInternalCallTarget(Function, InternalCall);
	InstructionListType MovedInsts = BB.splitInstructions(&*InternalCall);
	if (!MovedInsts.empty()) {
	// Split this block at the call instruction.
	std::unique_ptr<BinaryBasicBlock> NewBB = Function.createBasicBlock();
	NewBB->addInstructions(MovedInsts.begin(), MovedInsts.end());
	BB.moveAllSuccessorsTo(NewBB.get());

	Work.emplace(NewBB.get());
	std::vector<std::unique_ptr<BinaryBasicBlock>> NewBBs;
	NewBBs.emplace_back(std::move(NewBB));
	Function.insertBasicBlocks(&BB, std::move(NewBBs));
	}
	// Update successors
	BB.removeAllSuccessors();
	BB.addSuccessor(Target, BB.getExecutionCount(), 0ULL);
	}
	}

	bool ValidateInternalCalls::fixCFGForIC(BinaryFunction &Function) const {
	const BinaryContext &BC = Function.getBinaryContext();
	// Track SP value
	StackPointerTrackingForInternalCalls SPTIC(Function);
	SPTIC.run();

	// Track instructions reaching a given point of the CFG to answer
	// "There is a path from entry to point A that contains instruction B"
	ReachingInsns<false> RI(Function);
	RI.run();

	// We use the InsnToBB map that DataflowInfoManager provides us
	DataflowInfoManager Info(Function, nullptr, nullptr);

	bool Updated = false;

	auto processReturns = [&](BinaryBasicBlock &BB, MCInst &Return) {
	// Check all reaching internal calls
	for (auto I = RI.expr_begin(Return), E = RI.expr_end(); I != E; ++I) {
	MCInst &ReachingInst = **I;
	if (!getInternalCallTarget(Function, ReachingInst) \|\|
	BC.MIB->hasAnnotation(ReachingInst, getProcessedICTag()))
	continue;

	// Stack pointer matching
	int SPAtCall = SPTIC.getStateAt(ReachingInst)->first;
	int SPAtRet = SPTIC.getStateAt(Return)->first;
	if (SPAtCall != StackPointerTracking::SUPERPOSITION &&
	SPAtRet != StackPointerTracking::SUPERPOSITION &&
	SPAtCall != SPAtRet - 8)
	continue;

	Updated = true;

	// Mark this call as processed, so we don't try to analyze it as a
	// PIC-computation internal call.
	BC.MIB->addAnnotation(ReachingInst, getProcessedICTag(), 0U);

	// Connect this block with the returning block of the caller
	BinaryBasicBlock *CallerBlock = Info.getInsnToBBMap()[&ReachingInst];
	BinaryBasicBlock *ReturnDestBlock =
	Function.getLayout().getBasicBlockAfter(CallerBlock);
	BB.addSuccessor(ReturnDestBlock, BB.getExecutionCount(), 0);
	}
	};

	// This will connect blocks terminated with RETs to their respective
	// internal caller return block. A note here: this is overly conservative
	// because in nested calls, or unrelated calls, it will create edges
	// connecting RETs to potentially unrelated internal calls. This is safe
	// and if this causes a problem to recover the stack offsets properly, we
	// will fail later.
	for (BinaryBasicBlock &BB : Function) {
	for (MCInst &Inst : BB) {
	if (!BC.MIB->isReturn(Inst))
	continue;

	processReturns(BB, Inst);
	}
	}
	return Updated;
	}

	bool ValidateInternalCalls::hasTailCallsInRange(
	BinaryFunction &Function) const {
	const BinaryContext &BC = Function.getBinaryContext();
	for (BinaryBasicBlock &BB : Function)
	for (MCInst &Inst : BB)
	if (BC.MIB->isTailCall(Inst))
	return true;
	return false;
	}

	bool ValidateInternalCalls::analyzeFunction(BinaryFunction &Function) const {
	fixCFGForPIC(Function);
	while (fixCFGForIC(Function)) {
	}

	BinaryContext &BC = Function.getBinaryContext();
	RegAnalysis RA = RegAnalysis(BC, nullptr, nullptr);
	RA.setConservativeStrategy(RegAnalysis::ConservativeStrategy::CLOBBERS_NONE);
	bool HasTailCalls = hasTailCallsInRange(Function);

	for (BinaryBasicBlock &BB : Function) {
	for (MCInst &Inst : BB) {
	BinaryBasicBlock *Target = getInternalCallTarget(Function, Inst);
	if (!Target \|\| BC.MIB->hasAnnotation(Inst, getProcessedICTag()))
	continue;

	if (HasTailCalls) {
	LLVM_DEBUG(dbgs() << Function
	<< " has tail calls and internal calls.\n");
	return false;
	}

	FrameIndexEntry FIE;
	int32_t SrcImm = 0;
	MCPhysReg Reg = 0;
	int64_t StackOffset = 0;
	bool IsIndexed = false;
	MCInst TargetInst = ProgramPoint::getFirstPointAt(Target).getInst();
	if (!BC.MIB->isStackAccess(*TargetInst, FIE.IsLoad, FIE.IsStore,
	FIE.IsStoreFromReg, Reg, SrcImm,
	FIE.StackPtrReg, StackOffset, FIE.Size,
	FIE.IsSimple, IsIndexed)) {
	LLVM_DEBUG({
	dbgs() << "Frame analysis failed - not simple: " << Function << "\n";
	Function.dump();
	});
	return false;
	}
	if (!FIE.IsLoad \|\| FIE.StackPtrReg != BC.MIB->getStackPointer() \|\|
	StackOffset != 0) {
	LLVM_DEBUG({
	dbgs() << "Target instruction does not fetch return address - not "
	"simple: "
	<< Function << "\n";
	Function.dump();
	});
	return false;
	}
	// Now track how the return address is used by tracking uses of Reg
	ReachingDefOrUse</Def=/false> RU =
	ReachingDefOrUse<false>(RA, Function, Reg);
	RU.run();

	int64_t Offset = static_cast<int64_t>(Target->getInputOffset());
	bool UseDetected = false;
	for (auto I = RU.expr_begin(RU.getStateBefore(TargetInst)),
	E = RU.expr_end();
	I != E; ++I) {
	MCInst &Use = **I;
	BitVector UsedRegs = BitVector(BC.MRI->getNumRegs(), false);
	BC.MIB->getTouchedRegs(Use, UsedRegs);
	if (!UsedRegs[Reg])
	continue;
	UseDetected = true;
	int64_t Output;
	std::pair<MCPhysReg, int64_t> Input1 = std::make_pair(Reg, 0);
	std::pair<MCPhysReg, int64_t> Input2 = std::make_pair(0, 0);
	if (!BC.MIB->evaluateStackOffsetExpr(Use, Output, Input1, Input2)) {
	LLVM_DEBUG(dbgs() << "Evaluate stack offset expr failed.\n");
	return false;
	}
	if (Offset + Output < 0 \|\|
	Offset + Output > static_cast<int64_t>(Function.getSize())) {
	LLVM_DEBUG({
	dbgs() << "Detected out-of-range PIC reference in " << Function
	<< "\nReturn address load: ";
	BC.dump(*TargetInst);
	dbgs() << "Use: ";
	BC.dump(Use);
	Function.dump();
	});
	return false;
	}
	LLVM_DEBUG({
	dbgs() << "Validated access: ";
	BC.dump(Use);
	});
	}
	if (!UseDetected) {
	LLVM_DEBUG(dbgs() << "No use detected.\n");
	return false;
	}
	}
	}
	return true;
	}

	Error ValidateInternalCalls::runOnFunctions(BinaryContext &BC) {
	// Look for functions that need validation. This should be pretty rare.
	std::set<BinaryFunction *> NeedsValidation;
	for (auto &BFI : BC.getBinaryFunctions()) {
	BinaryFunction &Function = BFI.second;
	for (BinaryBasicBlock &BB : Function) {
	for (MCInst &Inst : BB) {
	if (getInternalCallTarget(Function, Inst)) {
	BC.errs() << "BOLT-WARNING: internal call detected in function "
	<< Function << '\n';
	NeedsValidation.insert(&Function);
	Function.setSimple(false);
	Function.setPreserveNops(true);
	break;
	}
	}
	}
	}

	if (!BC.isX86())
	return Error::success();

	// Skip validation for non-relocation mode
	if (!BC.HasRelocations)
	return Error::success();

	// Since few functions need validation, we can work with our most expensive
	// algorithms here. Fix the CFG treating internal calls as unconditional
	// jumps. This optimistically assumes this call is a PIC trick to get the PC
	// value, so it is not really a call, but a jump. If we find that it's not the
	// case, we mark this function as non-simple and stop processing it.
	std::set<BinaryFunction *> Invalid;
	for (BinaryFunction *Function : NeedsValidation) {
	LLVM_DEBUG(dbgs() << "Validating " << *Function << "\n");
	if (!analyzeFunction(*Function))
	Invalid.insert(Function);
	clearAnnotations(*Function);
	}

	if (!Invalid.empty()) {
	BC.errs()
	<< "BOLT-WARNING: will skip the following function(s) as unsupported"
	" internal calls were detected:\n";
	for (BinaryFunction *Function : Invalid) {
	BC.errs() << " " << *Function << "\n";
	Function->setIgnored();
	}
	}
	return Error::success();
	}

	} // namespace bolt
	} // namespace llvm