| //! A SSA-building API that handles incomplete CFGs. |
| //! |
| //! The algorithm is based upon Braun M., Buchwald S., Hack S., Leißa R., Mallon C., |
| //! Zwinkau A. (2013) Simple and Efficient Construction of Static Single Assignment Form. |
| //! In: Jhala R., De Bosschere K. (eds) Compiler Construction. CC 2013. |
| //! Lecture Notes in Computer Science, vol 7791. Springer, Berlin, Heidelberg |
| //! |
| //! <https://link.springer.com/content/pdf/10.1007/978-3-642-37051-9_6.pdf> |
| |
| use crate::Variable; |
| use alloc::vec::Vec; |
| use core::mem; |
| use cranelift_codegen::cursor::{Cursor, FuncCursor}; |
| use cranelift_codegen::entity::{EntityList, EntitySet, ListPool, SecondaryMap}; |
| use cranelift_codegen::ir::immediates::{Ieee32, Ieee64}; |
| use cranelift_codegen::ir::types::{F32, F64, I128, I64}; |
| use cranelift_codegen::ir::{Block, Function, Inst, InstBuilder, Type, Value}; |
| use cranelift_codegen::packed_option::PackedOption; |
| |
| /// Structure containing the data relevant the construction of SSA for a given function. |
| /// |
| /// The parameter struct [`Variable`] corresponds to the way variables are represented in the |
| /// non-SSA language you're translating from. |
| /// |
| /// The SSA building relies on information about the variables used and defined. |
| /// |
| /// This SSA building module allows you to def and use variables on the fly while you are |
| /// constructing the CFG, no need for a separate SSA pass after the CFG is completed. |
| /// |
| /// A basic block is said _filled_ if all the instruction that it contains have been translated, |
| /// and it is said _sealed_ if all of its predecessors have been declared. Only filled predecessors |
| /// can be declared. |
| #[derive(Default)] |
| pub struct SSABuilder { |
| // TODO: Consider a sparse representation rather than SecondaryMap-of-SecondaryMap. |
| /// Records for every variable and for every relevant block, the last definition of |
| /// the variable in the block. |
| variables: SecondaryMap<Variable, SecondaryMap<Block, PackedOption<Value>>>, |
| |
| /// Records the position of the basic blocks and the list of values used but not defined in the |
| /// block. |
| ssa_blocks: SecondaryMap<Block, SSABlockData>, |
| |
| /// Call stack for use in the `use_var`/`predecessors_lookup` state machine. |
| calls: Vec<Call>, |
| /// Result stack for use in the `use_var`/`predecessors_lookup` state machine. |
| results: Vec<Value>, |
| |
| /// Side effects accumulated in the `use_var`/`predecessors_lookup` state machine. |
| side_effects: SideEffects, |
| |
| /// Reused storage for cycle-detection. |
| visited: EntitySet<Block>, |
| |
| /// Storage for pending variable definitions. |
| variable_pool: ListPool<Variable>, |
| |
| /// Storage for predecessor definitions. |
| inst_pool: ListPool<Inst>, |
| } |
| |
| /// Side effects of a `use_var` or a `seal_block` method call. |
| #[derive(Default)] |
| pub struct SideEffects { |
| /// When a variable is used but has never been defined before (this happens in the case of |
| /// unreachable code), a placeholder `iconst` or `fconst` value is added to the right `Block`. |
| /// This field signals if it is the case and return the `Block` to which the initialization has |
| /// been added. |
| pub instructions_added_to_blocks: Vec<Block>, |
| } |
| |
| impl SideEffects { |
| fn is_empty(&self) -> bool { |
| self.instructions_added_to_blocks.is_empty() |
| } |
| } |
| |
| #[derive(Clone)] |
| enum Sealed { |
| No { |
| // List of current Block arguments for which an earlier def has not been found yet. |
| undef_variables: EntityList<Variable>, |
| }, |
| Yes, |
| } |
| |
| impl Default for Sealed { |
| fn default() -> Self { |
| Sealed::No { |
| undef_variables: EntityList::new(), |
| } |
| } |
| } |
| |
| #[derive(Clone, Default)] |
| struct SSABlockData { |
| // The predecessors of the Block with the block and branch instruction. |
| predecessors: EntityList<Inst>, |
| // A block is sealed if all of its predecessors have been declared. |
| sealed: Sealed, |
| // If this block is sealed and it has exactly one predecessor, this is that predecessor. |
| single_predecessor: PackedOption<Block>, |
| } |
| |
| impl SSABuilder { |
| /// Clears a `SSABuilder` from all its data, letting it in a pristine state without |
| /// deallocating memory. |
| pub fn clear(&mut self) { |
| self.variables.clear(); |
| self.ssa_blocks.clear(); |
| self.variable_pool.clear(); |
| self.inst_pool.clear(); |
| debug_assert!(self.calls.is_empty()); |
| debug_assert!(self.results.is_empty()); |
| debug_assert!(self.side_effects.is_empty()); |
| } |
| |
| /// Tests whether an `SSABuilder` is in a cleared state. |
| pub fn is_empty(&self) -> bool { |
| self.variables.is_empty() |
| && self.ssa_blocks.is_empty() |
| && self.calls.is_empty() |
| && self.results.is_empty() |
| && self.side_effects.is_empty() |
| } |
| } |
| |
| /// States for the `use_var`/`predecessors_lookup` state machine. |
| enum Call { |
| UseVar(Inst), |
| FinishPredecessorsLookup(Value, Block), |
| } |
| |
| /// Emit instructions to produce a zero value in the given type. |
| fn emit_zero(ty: Type, mut cur: FuncCursor) -> Value { |
| if ty == I128 { |
| let zero = cur.ins().iconst(I64, 0); |
| cur.ins().uextend(I128, zero) |
| } else if ty.is_int() { |
| cur.ins().iconst(ty, 0) |
| } else if ty == F32 { |
| cur.ins().f32const(Ieee32::with_bits(0)) |
| } else if ty == F64 { |
| cur.ins().f64const(Ieee64::with_bits(0)) |
| } else if ty.is_ref() { |
| cur.ins().null(ty) |
| } else if ty.is_vector() { |
| let scalar_ty = ty.lane_type(); |
| if scalar_ty.is_int() { |
| let zero = cur.func.dfg.constants.insert( |
| core::iter::repeat(0) |
| .take(ty.bytes().try_into().unwrap()) |
| .collect(), |
| ); |
| cur.ins().vconst(ty, zero) |
| } else if scalar_ty == F32 { |
| let scalar = cur.ins().f32const(Ieee32::with_bits(0)); |
| cur.ins().splat(ty, scalar) |
| } else if scalar_ty == F64 { |
| let scalar = cur.ins().f64const(Ieee64::with_bits(0)); |
| cur.ins().splat(ty, scalar) |
| } else { |
| panic!("unimplemented scalar type: {:?}", ty) |
| } |
| } else { |
| panic!("unimplemented type: {:?}", ty) |
| } |
| } |
| |
| /// The following methods are the API of the SSA builder. Here is how it should be used when |
| /// translating to Cranelift IR: |
| /// |
| /// - for each basic block, create a corresponding data for SSA construction with `declare_block`; |
| /// |
| /// - while traversing a basic block and translating instruction, use `def_var` and `use_var` |
| /// to record definitions and uses of variables, these methods will give you the corresponding |
| /// SSA values; |
| /// |
| /// - when all the instructions in a basic block have translated, the block is said _filled_ and |
| /// only then you can add it as a predecessor to other blocks with `declare_block_predecessor`; |
| /// |
| /// - when you have constructed all the predecessor to a basic block, |
| /// call `seal_block` on it with the `Function` that you are building. |
| /// |
| /// This API will give you the correct SSA values to use as arguments of your instructions, |
| /// as well as modify the jump instruction and `Block` parameters to account for the SSA |
| /// Phi functions. |
| /// |
| impl SSABuilder { |
| /// Declares a new definition of a variable in a given basic block. |
| /// The SSA value is passed as an argument because it should be created with |
| /// `ir::DataFlowGraph::append_result`. |
| pub fn def_var(&mut self, var: Variable, val: Value, block: Block) { |
| self.variables[var][block] = PackedOption::from(val); |
| } |
| |
| /// Declares a use of a variable in a given basic block. Returns the SSA value corresponding |
| /// to the current SSA definition of this variable and a list of newly created Blocks that |
| /// are the results of critical edge splitting for `br_table` with arguments. |
| /// |
| /// If the variable has never been defined in this blocks or recursively in its predecessors, |
| /// this method will silently create an initializer with `iconst` or `fconst`. You are |
| /// responsible for making sure that you initialize your variables. |
| pub fn use_var( |
| &mut self, |
| func: &mut Function, |
| var: Variable, |
| ty: Type, |
| block: Block, |
| ) -> (Value, SideEffects) { |
| debug_assert!(self.calls.is_empty()); |
| debug_assert!(self.results.is_empty()); |
| debug_assert!(self.side_effects.is_empty()); |
| |
| // Prepare the 'calls' and 'results' stacks for the state machine. |
| self.use_var_nonlocal(func, var, ty, block); |
| let value = self.run_state_machine(func, var, ty); |
| |
| let side_effects = mem::take(&mut self.side_effects); |
| (value, side_effects) |
| } |
| |
| /// Resolve the minimal SSA Value of `var` in `block` by traversing predecessors. |
| /// |
| /// This function sets up state for `run_state_machine()` but does not execute it. |
| fn use_var_nonlocal(&mut self, func: &mut Function, var: Variable, ty: Type, mut block: Block) { |
| // First, try Local Value Numbering (Algorithm 1 in the paper). |
| // If the variable already has a known Value in this block, use that. |
| if let Some(val) = self.variables[var][block].expand() { |
| self.results.push(val); |
| return; |
| } |
| |
| // Otherwise, use Global Value Numbering (Algorithm 2 in the paper). |
| // This resolves the Value with respect to its predecessors. |
| // Find the most recent definition of `var`, and the block the definition comes from. |
| let (val, from) = self.find_var(func, var, ty, block); |
| |
| // The `from` block returned from `find_var` is guaranteed to be on the path we follow by |
| // traversing only single-predecessor edges. It might be equal to `block` if there is no |
| // such path, but in that case `find_var` ensures that the variable is defined in this block |
| // by a new block parameter. It also might be somewhere in a cycle, but even then this loop |
| // will terminate the first time it encounters that block, rather than continuing around the |
| // cycle forever. |
| // |
| // Why is it okay to copy the definition to all intervening blocks? For the initial block, |
| // this may not be the final definition of this variable within this block, but if we've |
| // gotten here then we know there is no earlier definition in the block already. |
| // |
| // For the remaining blocks: Recall that a block is only allowed to be set as a predecessor |
| // after all its instructions have already been filled in, so when we follow a predecessor |
| // edge to a block, we know there will never be any more local variable definitions added to |
| // that block. We also know that `find_var` didn't find a definition for this variable in |
| // any of the blocks before `from`. |
| // |
| // So in either case there is no definition in these blocks yet and we can blindly set one. |
| let var_defs = &mut self.variables[var]; |
| while block != from { |
| debug_assert!(var_defs[block].is_none()); |
| var_defs[block] = PackedOption::from(val); |
| block = self.ssa_blocks[block].single_predecessor.unwrap(); |
| } |
| } |
| |
| /// Find the most recent definition of this variable, returning both the definition and the |
| /// block in which it was found. If we can't find a definition that's provably the right one for |
| /// all paths to the current block, then append a block parameter to some block and use that as |
| /// the definition. Either way, also arrange that the definition will be on the `results` stack |
| /// when `run_state_machine` is done processing the current step. |
| /// |
| /// If a block has exactly one predecessor, and the block is sealed so we know its predecessors |
| /// will never change, then its definition for this variable is the same as the definition from |
| /// that one predecessor. In this case it's easy to see that no block parameter is necessary, |
| /// but we need to look at the predecessor to see if a block parameter might be needed there. |
| /// That holds transitively across any chain of sealed blocks with exactly one predecessor each. |
| /// |
| /// This runs into a problem, though, if such a chain has a cycle: Blindly following a cyclic |
| /// chain that never defines this variable would lead to an infinite loop in the compiler. It |
| /// doesn't really matter what code we generate in that case. Since each block in the cycle has |
| /// exactly one predecessor, there's no way to enter the cycle from the function's entry block; |
| /// and since all blocks in the cycle are sealed, the entire cycle is permanently dead code. But |
| /// we still have to prevent the possibility of an infinite loop. |
| /// |
| /// To break cycles, we can pick any block within the cycle as the one where we'll add a block |
| /// parameter. It's convenient to pick the block at which we entered the cycle, because that's |
| /// the first place where we can detect that we just followed a cycle. Adding a block parameter |
| /// gives us a definition we can reuse throughout the rest of the cycle. |
| fn find_var( |
| &mut self, |
| func: &mut Function, |
| var: Variable, |
| ty: Type, |
| mut block: Block, |
| ) -> (Value, Block) { |
| // Try to find an existing definition along single-predecessor edges first. |
| self.visited.clear(); |
| let var_defs = &mut self.variables[var]; |
| while let Some(pred) = self.ssa_blocks[block].single_predecessor.expand() { |
| if !self.visited.insert(block) { |
| break; |
| } |
| block = pred; |
| if let Some(val) = var_defs[block].expand() { |
| self.results.push(val); |
| return (val, block); |
| } |
| } |
| |
| // We've promised to return the most recent block where `var` was defined, but we didn't |
| // find a usable definition. So create one. |
| let val = func.dfg.append_block_param(block, ty); |
| var_defs[block] = PackedOption::from(val); |
| |
| // Now every predecessor needs to pass its definition of this variable to the newly added |
| // block parameter. To do that we have to "recursively" call `use_var`, but there are two |
| // problems with doing that. First, we need to keep a fixed bound on stack depth, so we |
| // can't actually recurse; instead we defer to `run_state_machine`. Second, if we don't |
| // know all our predecessors yet, we have to defer this work until the block gets sealed. |
| match &mut self.ssa_blocks[block].sealed { |
| // Once all the `calls` added here complete, this leaves either `val` or an equivalent |
| // definition on the `results` stack. |
| Sealed::Yes => self.begin_predecessors_lookup(val, block), |
| Sealed::No { undef_variables } => { |
| undef_variables.push(var, &mut self.variable_pool); |
| self.results.push(val); |
| } |
| } |
| (val, block) |
| } |
| |
| /// Declares a new basic block to construct corresponding data for SSA construction. |
| /// No predecessors are declared here and the block is not sealed. |
| /// Predecessors have to be added with `declare_block_predecessor`. |
| pub fn declare_block(&mut self, block: Block) { |
| // Ensure the block exists so seal_all_blocks will see it even if no predecessors or |
| // variables get declared for this block. But don't assign anything to it: |
| // SecondaryMap automatically sets all blocks to `default()`. |
| let _ = &mut self.ssa_blocks[block]; |
| } |
| |
| /// Declares a new predecessor for a `Block` and record the branch instruction |
| /// of the predecessor that leads to it. |
| /// |
| /// The precedent `Block` must be filled before added as predecessor. |
| /// Note that you must provide no jump arguments to the branch |
| /// instruction when you create it since `SSABuilder` will fill them for you. |
| /// |
| /// Callers are expected to avoid adding the same predecessor more than once in the case |
| /// of a jump table. |
| pub fn declare_block_predecessor(&mut self, block: Block, inst: Inst) { |
| debug_assert!(!self.is_sealed(block)); |
| self.ssa_blocks[block] |
| .predecessors |
| .push(inst, &mut self.inst_pool); |
| } |
| |
| /// Remove a previously declared Block predecessor by giving a reference to the jump |
| /// instruction. Returns the basic block containing the instruction. |
| /// |
| /// Note: use only when you know what you are doing, this might break the SSA building problem |
| pub fn remove_block_predecessor(&mut self, block: Block, inst: Inst) { |
| debug_assert!(!self.is_sealed(block)); |
| let data = &mut self.ssa_blocks[block]; |
| let pred = data |
| .predecessors |
| .as_slice(&self.inst_pool) |
| .iter() |
| .position(|&branch| branch == inst) |
| .expect("the predecessor you are trying to remove is not declared"); |
| data.predecessors.swap_remove(pred, &mut self.inst_pool); |
| } |
| |
| /// Completes the global value numbering for a `Block`, all of its predecessors having been |
| /// already sealed. |
| /// |
| /// This method modifies the function's `Layout` by adding arguments to the `Block`s to |
| /// take into account the Phi function placed by the SSA algorithm. |
| /// |
| /// Returns the list of newly created blocks for critical edge splitting. |
| pub fn seal_block(&mut self, block: Block, func: &mut Function) -> SideEffects { |
| debug_assert!( |
| !self.is_sealed(block), |
| "Attempting to seal {} which is already sealed.", |
| block |
| ); |
| self.seal_one_block(block, func); |
| mem::take(&mut self.side_effects) |
| } |
| |
| /// Completes the global value numbering for all unsealed `Block`s in `func`. |
| /// |
| /// It's more efficient to seal `Block`s as soon as possible, during |
| /// translation, but for frontends where this is impractical to do, this |
| /// function can be used at the end of translating all blocks to ensure |
| /// that everything is sealed. |
| pub fn seal_all_blocks(&mut self, func: &mut Function) -> SideEffects { |
| // Seal all `Block`s currently in the function. This can entail splitting |
| // and creation of new blocks, however such new blocks are sealed on |
| // the fly, so we don't need to account for them here. |
| for block in self.ssa_blocks.keys() { |
| self.seal_one_block(block, func); |
| } |
| mem::take(&mut self.side_effects) |
| } |
| |
| /// Helper function for `seal_block` and `seal_all_blocks`. |
| fn seal_one_block(&mut self, block: Block, func: &mut Function) { |
| // For each undef var we look up values in the predecessors and create a block parameter |
| // only if necessary. |
| let mut undef_variables = |
| match mem::replace(&mut self.ssa_blocks[block].sealed, Sealed::Yes) { |
| Sealed::No { undef_variables } => undef_variables, |
| Sealed::Yes => return, |
| }; |
| let ssa_params = undef_variables.len(&self.variable_pool); |
| |
| let predecessors = self.predecessors(block); |
| if predecessors.len() == 1 { |
| let pred = func.layout.inst_block(predecessors[0]).unwrap(); |
| self.ssa_blocks[block].single_predecessor = PackedOption::from(pred); |
| } |
| |
| // Note that begin_predecessors_lookup requires visiting these variables in the same order |
| // that they were defined by find_var, because it appends arguments to the jump instructions |
| // in all the predecessor blocks one variable at a time. |
| for idx in 0..ssa_params { |
| let var = undef_variables.get(idx, &self.variable_pool).unwrap(); |
| |
| // We need the temporary Value that was assigned to this Variable. If that Value shows |
| // up as a result from any of our predecessors, then it never got assigned on the loop |
| // through that block. We get the value from the next block param, where it was first |
| // allocated in find_var. |
| let block_params = func.dfg.block_params(block); |
| |
| // On each iteration through this loop, there are (ssa_params - idx) undefined variables |
| // left to process. Previous iterations through the loop may have removed earlier block |
| // parameters, but the last (ssa_params - idx) block parameters always correspond to the |
| // remaining undefined variables. So index from the end of the current block params. |
| let val = block_params[block_params.len() - (ssa_params - idx)]; |
| |
| debug_assert!(self.calls.is_empty()); |
| debug_assert!(self.results.is_empty()); |
| // self.side_effects may be non-empty here so that callers can |
| // accumulate side effects over multiple calls. |
| self.begin_predecessors_lookup(val, block); |
| self.run_state_machine(func, var, func.dfg.value_type(val)); |
| } |
| |
| undef_variables.clear(&mut self.variable_pool); |
| } |
| |
| /// Given the local SSA Value of a Variable in a Block, perform a recursive lookup on |
| /// predecessors to determine if it is redundant with another Value earlier in the CFG. |
| /// |
| /// If such a Value exists and is redundant, the local Value is replaced by the |
| /// corresponding non-local Value. If the original Value was a Block parameter, |
| /// the parameter may be removed if redundant. Parameters are placed eagerly by callers |
| /// to avoid infinite loops when looking up a Value for a Block that is in a CFG loop. |
| /// |
| /// Doing this lookup for each Value in each Block preserves SSA form during construction. |
| /// |
| /// ## Arguments |
| /// |
| /// `sentinel` is a dummy Block parameter inserted by `use_var_nonlocal()`. |
| /// Its purpose is to allow detection of CFG cycles while traversing predecessors. |
| fn begin_predecessors_lookup(&mut self, sentinel: Value, dest_block: Block) { |
| self.calls |
| .push(Call::FinishPredecessorsLookup(sentinel, dest_block)); |
| // Iterate over the predecessors. |
| self.calls.extend( |
| self.ssa_blocks[dest_block] |
| .predecessors |
| .as_slice(&self.inst_pool) |
| .iter() |
| .rev() |
| .copied() |
| .map(Call::UseVar), |
| ); |
| } |
| |
| /// Examine the values from the predecessors and compute a result value, creating |
| /// block parameters as needed. |
| fn finish_predecessors_lookup( |
| &mut self, |
| func: &mut Function, |
| sentinel: Value, |
| dest_block: Block, |
| ) -> Value { |
| // Determine how many predecessors are yielding unique, non-temporary Values. If a variable |
| // is live and unmodified across several control-flow join points, earlier blocks will |
| // introduce aliases for that variable's definition, so we resolve aliases eagerly here to |
| // ensure that we can tell when the same definition has reached this block via multiple |
| // paths. Doing so also detects cyclic references to the sentinel, which can occur in |
| // unreachable code. |
| let num_predecessors = self.predecessors(dest_block).len(); |
| // When this `Drain` is dropped, these elements will get truncated. |
| let results = self.results.drain(self.results.len() - num_predecessors..); |
| |
| let pred_val = { |
| let mut iter = results |
| .as_slice() |
| .iter() |
| .map(|&val| func.dfg.resolve_aliases(val)) |
| .filter(|&val| val != sentinel); |
| if let Some(val) = iter.next() { |
| // This variable has at least one non-temporary definition. If they're all the same |
| // value, we can remove the block parameter and reference that value instead. |
| if iter.all(|other| other == val) { |
| Some(val) |
| } else { |
| None |
| } |
| } else { |
| // The variable is used but never defined before. This is an irregularity in the |
| // code, but rather than throwing an error we silently initialize the variable to |
| // 0. This will have no effect since this situation happens in unreachable code. |
| if !func.layout.is_block_inserted(dest_block) { |
| func.layout.append_block(dest_block); |
| } |
| self.side_effects |
| .instructions_added_to_blocks |
| .push(dest_block); |
| let zero = emit_zero( |
| func.dfg.value_type(sentinel), |
| FuncCursor::new(func).at_first_insertion_point(dest_block), |
| ); |
| Some(zero) |
| } |
| }; |
| |
| if let Some(pred_val) = pred_val { |
| // Here all the predecessors use a single value to represent our variable |
| // so we don't need to have it as a block argument. |
| // We need to replace all the occurrences of val with pred_val but since |
| // we can't afford a re-writing pass right now we just declare an alias. |
| func.dfg.remove_block_param(sentinel); |
| func.dfg.change_to_alias(sentinel, pred_val); |
| pred_val |
| } else { |
| // There is disagreement in the predecessors on which value to use so we have |
| // to keep the block argument. |
| let mut preds = self.ssa_blocks[dest_block].predecessors; |
| let dfg = &mut func.stencil.dfg; |
| for (idx, &val) in results.as_slice().iter().enumerate() { |
| let pred = preds.get_mut(idx, &mut self.inst_pool).unwrap(); |
| let branch = *pred; |
| |
| let dests = dfg.insts[branch].branch_destination_mut(&mut dfg.jump_tables); |
| assert!( |
| !dests.is_empty(), |
| "you have declared a non-branch instruction as a predecessor to a block!" |
| ); |
| for block in dests { |
| if block.block(&dfg.value_lists) == dest_block { |
| block.append_argument(val, &mut dfg.value_lists); |
| } |
| } |
| } |
| sentinel |
| } |
| } |
| |
| /// Returns the list of `Block`s that have been declared as predecessors of the argument. |
| fn predecessors(&self, block: Block) -> &[Inst] { |
| self.ssa_blocks[block] |
| .predecessors |
| .as_slice(&self.inst_pool) |
| } |
| |
| /// Returns whether the given Block has any predecessor or not. |
| pub fn has_any_predecessors(&self, block: Block) -> bool { |
| !self.predecessors(block).is_empty() |
| } |
| |
| /// Returns `true` if and only if `seal_block` has been called on the argument. |
| pub fn is_sealed(&self, block: Block) -> bool { |
| matches!(self.ssa_blocks[block].sealed, Sealed::Yes) |
| } |
| |
| /// The main algorithm is naturally recursive: when there's a `use_var` in a |
| /// block with no corresponding local defs, it recurses and performs a |
| /// `use_var` in each predecessor. To avoid risking running out of callstack |
| /// space, we keep an explicit stack and use a small state machine rather |
| /// than literal recursion. |
| fn run_state_machine(&mut self, func: &mut Function, var: Variable, ty: Type) -> Value { |
| // Process the calls scheduled in `self.calls` until it is empty. |
| while let Some(call) = self.calls.pop() { |
| match call { |
| Call::UseVar(branch) => { |
| let block = func.layout.inst_block(branch).unwrap(); |
| self.use_var_nonlocal(func, var, ty, block); |
| } |
| Call::FinishPredecessorsLookup(sentinel, dest_block) => { |
| let val = self.finish_predecessors_lookup(func, sentinel, dest_block); |
| self.results.push(val); |
| } |
| } |
| } |
| debug_assert_eq!(self.results.len(), 1); |
| self.results.pop().unwrap() |
| } |
| } |
| |
| #[cfg(test)] |
| mod tests { |
| use crate::ssa::SSABuilder; |
| use crate::Variable; |
| use cranelift_codegen::cursor::{Cursor, FuncCursor}; |
| use cranelift_codegen::entity::EntityRef; |
| use cranelift_codegen::ir; |
| use cranelift_codegen::ir::types::*; |
| use cranelift_codegen::ir::{Function, Inst, InstBuilder, JumpTableData, Opcode}; |
| use cranelift_codegen::settings; |
| use cranelift_codegen::verify_function; |
| |
| #[test] |
| fn simple_block() { |
| let mut func = Function::new(); |
| let mut ssa = SSABuilder::default(); |
| let block0 = func.dfg.make_block(); |
| // Here is the pseudo-program we want to translate: |
| // block0: |
| // x = 1; |
| // y = 2; |
| // z = x + y; |
| // z = x + z; |
| |
| ssa.declare_block(block0); |
| let x_var = Variable::new(0); |
| let x_ssa = { |
| let mut cur = FuncCursor::new(&mut func); |
| cur.insert_block(block0); |
| cur.ins().iconst(I32, 1) |
| }; |
| ssa.def_var(x_var, x_ssa, block0); |
| let y_var = Variable::new(1); |
| let y_ssa = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| cur.ins().iconst(I32, 2) |
| }; |
| ssa.def_var(y_var, y_ssa, block0); |
| assert_eq!(ssa.use_var(&mut func, x_var, I32, block0).0, x_ssa); |
| assert_eq!(ssa.use_var(&mut func, y_var, I32, block0).0, y_ssa); |
| |
| let z_var = Variable::new(2); |
| let x_use1 = ssa.use_var(&mut func, x_var, I32, block0).0; |
| let y_use1 = ssa.use_var(&mut func, y_var, I32, block0).0; |
| let z1_ssa = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| cur.ins().iadd(x_use1, y_use1) |
| }; |
| ssa.def_var(z_var, z1_ssa, block0); |
| assert_eq!(ssa.use_var(&mut func, z_var, I32, block0).0, z1_ssa); |
| |
| let x_use2 = ssa.use_var(&mut func, x_var, I32, block0).0; |
| let z_use1 = ssa.use_var(&mut func, z_var, I32, block0).0; |
| let z2_ssa = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| cur.ins().iadd(x_use2, z_use1) |
| }; |
| ssa.def_var(z_var, z2_ssa, block0); |
| assert_eq!(ssa.use_var(&mut func, z_var, I32, block0).0, z2_ssa); |
| } |
| |
| #[test] |
| fn sequence_of_blocks() { |
| let mut func = Function::new(); |
| let mut ssa = SSABuilder::default(); |
| let block0 = func.dfg.make_block(); |
| let block1 = func.dfg.make_block(); |
| let block2 = func.dfg.make_block(); |
| // Here is the pseudo-program we want to translate: |
| // block0: |
| // x = 1; |
| // y = 2; |
| // z = x + y; |
| // brif y, block1, block1; |
| // block1: |
| // z = x + z; |
| // jump block2; |
| // block2: |
| // y = x + y; |
| { |
| let mut cur = FuncCursor::new(&mut func); |
| cur.insert_block(block0); |
| cur.insert_block(block1); |
| cur.insert_block(block2); |
| } |
| |
| // block0 |
| ssa.declare_block(block0); |
| ssa.seal_block(block0, &mut func); |
| let x_var = Variable::new(0); |
| let x_ssa = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| cur.ins().iconst(I32, 1) |
| }; |
| ssa.def_var(x_var, x_ssa, block0); |
| let y_var = Variable::new(1); |
| let y_ssa = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| cur.ins().iconst(I32, 2) |
| }; |
| ssa.def_var(y_var, y_ssa, block0); |
| let z_var = Variable::new(2); |
| let x_use1 = ssa.use_var(&mut func, x_var, I32, block0).0; |
| let y_use1 = ssa.use_var(&mut func, y_var, I32, block0).0; |
| let z1_ssa = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| cur.ins().iadd(x_use1, y_use1) |
| }; |
| ssa.def_var(z_var, z1_ssa, block0); |
| let y_use2 = ssa.use_var(&mut func, y_var, I32, block0).0; |
| let brif_block0_block2_block1: Inst = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| cur.ins().brif(y_use2, block2, &[], block1, &[]) |
| }; |
| |
| assert_eq!(ssa.use_var(&mut func, x_var, I32, block0).0, x_ssa); |
| assert_eq!(ssa.use_var(&mut func, y_var, I32, block0).0, y_ssa); |
| assert_eq!(ssa.use_var(&mut func, z_var, I32, block0).0, z1_ssa); |
| |
| // block1 |
| ssa.declare_block(block1); |
| ssa.declare_block_predecessor(block1, brif_block0_block2_block1); |
| ssa.seal_block(block1, &mut func); |
| |
| let x_use2 = ssa.use_var(&mut func, x_var, I32, block1).0; |
| let z_use1 = ssa.use_var(&mut func, z_var, I32, block1).0; |
| let z2_ssa = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block1); |
| cur.ins().iadd(x_use2, z_use1) |
| }; |
| ssa.def_var(z_var, z2_ssa, block1); |
| let jump_block1_block2: Inst = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block1); |
| cur.ins().jump(block2, &[]) |
| }; |
| |
| assert_eq!(x_use2, x_ssa); |
| assert_eq!(z_use1, z1_ssa); |
| assert_eq!(ssa.use_var(&mut func, z_var, I32, block1).0, z2_ssa); |
| |
| // block2 |
| ssa.declare_block(block2); |
| ssa.declare_block_predecessor(block2, brif_block0_block2_block1); |
| ssa.declare_block_predecessor(block2, jump_block1_block2); |
| ssa.seal_block(block2, &mut func); |
| let x_use3 = ssa.use_var(&mut func, x_var, I32, block2).0; |
| let y_use3 = ssa.use_var(&mut func, y_var, I32, block2).0; |
| let y2_ssa = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block2); |
| cur.ins().iadd(x_use3, y_use3) |
| }; |
| ssa.def_var(y_var, y2_ssa, block2); |
| |
| assert_eq!(x_ssa, x_use3); |
| assert_eq!(y_ssa, y_use3); |
| match func.dfg.insts[brif_block0_block2_block1] { |
| ir::InstructionData::Brif { |
| blocks: [block_then, block_else], |
| .. |
| } => { |
| assert_eq!(block_then.block(&func.dfg.value_lists), block2); |
| assert_eq!(block_then.args_slice(&func.dfg.value_lists).len(), 0); |
| assert_eq!(block_else.block(&func.dfg.value_lists), block1); |
| assert_eq!(block_else.args_slice(&func.dfg.value_lists).len(), 0); |
| } |
| _ => assert!(false), |
| }; |
| match func.dfg.insts[brif_block0_block2_block1] { |
| ir::InstructionData::Brif { |
| blocks: [block_then, block_else], |
| .. |
| } => { |
| assert_eq!(block_then.block(&func.dfg.value_lists), block2); |
| assert_eq!(block_then.args_slice(&func.dfg.value_lists).len(), 0); |
| assert_eq!(block_else.block(&func.dfg.value_lists), block1); |
| assert_eq!(block_else.args_slice(&func.dfg.value_lists).len(), 0); |
| } |
| _ => assert!(false), |
| }; |
| match func.dfg.insts[jump_block1_block2] { |
| ir::InstructionData::Jump { |
| destination: dest, .. |
| } => { |
| assert_eq!(dest.block(&func.dfg.value_lists), block2); |
| assert_eq!(dest.args_slice(&func.dfg.value_lists).len(), 0); |
| } |
| _ => assert!(false), |
| }; |
| } |
| |
| #[test] |
| fn program_with_loop() { |
| let mut func = Function::new(); |
| let mut ssa = SSABuilder::default(); |
| let block0 = func.dfg.make_block(); |
| let block1 = func.dfg.make_block(); |
| let block2 = func.dfg.make_block(); |
| let block3 = func.dfg.make_block(); |
| { |
| let mut cur = FuncCursor::new(&mut func); |
| cur.insert_block(block0); |
| cur.insert_block(block1); |
| cur.insert_block(block2); |
| cur.insert_block(block3); |
| } |
| // Here is the pseudo-program we want to translate: |
| // block0: |
| // x = 1; |
| // y = 2; |
| // z = x + y; |
| // jump block1 |
| // block1: |
| // z = z + y; |
| // brif y, block3, block2; |
| // block2: |
| // z = z - x; |
| // return y |
| // block3: |
| // y = y - x |
| // jump block1 |
| |
| // block0 |
| ssa.declare_block(block0); |
| ssa.seal_block(block0, &mut func); |
| let x_var = Variable::new(0); |
| let x1 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| cur.ins().iconst(I32, 1) |
| }; |
| ssa.def_var(x_var, x1, block0); |
| let y_var = Variable::new(1); |
| let y1 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| cur.ins().iconst(I32, 2) |
| }; |
| ssa.def_var(y_var, y1, block0); |
| let z_var = Variable::new(2); |
| let x2 = ssa.use_var(&mut func, x_var, I32, block0).0; |
| let y2 = ssa.use_var(&mut func, y_var, I32, block0).0; |
| let z1 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| cur.ins().iadd(x2, y2) |
| }; |
| ssa.def_var(z_var, z1, block0); |
| let jump_block0_block1 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| cur.ins().jump(block1, &[]) |
| }; |
| assert_eq!(ssa.use_var(&mut func, x_var, I32, block0).0, x1); |
| assert_eq!(ssa.use_var(&mut func, y_var, I32, block0).0, y1); |
| assert_eq!(x2, x1); |
| assert_eq!(y2, y1); |
| |
| // block1 |
| ssa.declare_block(block1); |
| ssa.declare_block_predecessor(block1, jump_block0_block1); |
| let z2 = ssa.use_var(&mut func, z_var, I32, block1).0; |
| let y3 = ssa.use_var(&mut func, y_var, I32, block1).0; |
| let z3 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block1); |
| cur.ins().iadd(z2, y3) |
| }; |
| ssa.def_var(z_var, z3, block1); |
| let y4 = ssa.use_var(&mut func, y_var, I32, block1).0; |
| assert_eq!(y4, y3); |
| let brif_block1_block3_block2 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block1); |
| cur.ins().brif(y4, block3, &[], block2, &[]) |
| }; |
| |
| // block2 |
| ssa.declare_block(block2); |
| ssa.declare_block_predecessor(block2, brif_block1_block3_block2); |
| ssa.seal_block(block2, &mut func); |
| let z4 = ssa.use_var(&mut func, z_var, I32, block2).0; |
| assert_eq!(z4, z3); |
| let x3 = ssa.use_var(&mut func, x_var, I32, block2).0; |
| let z5 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block2); |
| cur.ins().isub(z4, x3) |
| }; |
| ssa.def_var(z_var, z5, block2); |
| let y5 = ssa.use_var(&mut func, y_var, I32, block2).0; |
| assert_eq!(y5, y3); |
| { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block2); |
| cur.ins().return_(&[y5]) |
| }; |
| |
| // block3 |
| ssa.declare_block(block3); |
| ssa.declare_block_predecessor(block3, brif_block1_block3_block2); |
| ssa.seal_block(block3, &mut func); |
| let y6 = ssa.use_var(&mut func, y_var, I32, block3).0; |
| assert_eq!(y6, y3); |
| let x4 = ssa.use_var(&mut func, x_var, I32, block3).0; |
| assert_eq!(x4, x3); |
| let y7 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block3); |
| cur.ins().isub(y6, x4) |
| }; |
| ssa.def_var(y_var, y7, block3); |
| let jump_block3_block1 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block3); |
| cur.ins().jump(block1, &[]) |
| }; |
| |
| // block1 after all predecessors have been visited. |
| ssa.declare_block_predecessor(block1, jump_block3_block1); |
| ssa.seal_block(block1, &mut func); |
| assert_eq!(func.dfg.block_params(block1)[0], z2); |
| assert_eq!(func.dfg.block_params(block1)[1], y3); |
| assert_eq!(func.dfg.resolve_aliases(x3), x1); |
| } |
| |
| #[test] |
| fn br_table_with_args() { |
| // This tests the on-demand splitting of critical edges for br_table with jump arguments |
| // |
| // Here is the pseudo-program we want to translate: |
| // |
| // function %f { |
| // block0: |
| // x = 1; |
| // br_table x, block2, [block2, block1] |
| // block1: |
| // x = 2 |
| // jump block2 |
| // block2: |
| // x = x + 1 |
| // return |
| // } |
| |
| let mut func = Function::new(); |
| let mut ssa = SSABuilder::default(); |
| let block0 = func.dfg.make_block(); |
| let block1 = func.dfg.make_block(); |
| let block2 = func.dfg.make_block(); |
| { |
| let mut cur = FuncCursor::new(&mut func); |
| cur.insert_block(block0); |
| cur.insert_block(block1); |
| cur.insert_block(block2); |
| } |
| |
| // block0 |
| let x1 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| cur.ins().iconst(I32, 1) |
| }; |
| ssa.declare_block(block0); |
| ssa.seal_block(block0, &mut func); |
| let x_var = Variable::new(0); |
| ssa.def_var(x_var, x1, block0); |
| ssa.use_var(&mut func, x_var, I32, block0).0; |
| let br_table = { |
| let jump_table = JumpTableData::new( |
| func.dfg.block_call(block2, &[]), |
| &[ |
| func.dfg.block_call(block2, &[]), |
| func.dfg.block_call(block1, &[]), |
| ], |
| ); |
| let jt = func.create_jump_table(jump_table); |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| cur.ins().br_table(x1, jt) |
| }; |
| |
| // block1 |
| ssa.declare_block(block1); |
| ssa.declare_block_predecessor(block1, br_table); |
| ssa.seal_block(block1, &mut func); |
| let x2 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block1); |
| cur.ins().iconst(I32, 2) |
| }; |
| ssa.def_var(x_var, x2, block1); |
| let jump_block1_block2 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block1); |
| cur.ins().jump(block2, &[]) |
| }; |
| |
| // block2 |
| ssa.declare_block(block2); |
| ssa.declare_block_predecessor(block2, jump_block1_block2); |
| ssa.declare_block_predecessor(block2, br_table); |
| ssa.seal_block(block2, &mut func); |
| let x3 = ssa.use_var(&mut func, x_var, I32, block2).0; |
| let x4 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block2); |
| cur.ins().iadd_imm(x3, 1) |
| }; |
| ssa.def_var(x_var, x4, block2); |
| { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block2); |
| cur.ins().return_(&[]) |
| }; |
| |
| let flags = settings::Flags::new(settings::builder()); |
| match verify_function(&func, &flags) { |
| Ok(()) => {} |
| Err(_errors) => { |
| #[cfg(feature = "std")] |
| panic!("{}", _errors); |
| #[cfg(not(feature = "std"))] |
| panic!("function failed to verify"); |
| } |
| } |
| } |
| |
| #[test] |
| fn undef_values_reordering() { |
| // Here is the pseudo-program we want to translate: |
| // block0: |
| // x = 0; |
| // y = 1; |
| // z = 2; |
| // jump block1; |
| // block1: |
| // x = z + x; |
| // y = y - x; |
| // jump block1; |
| // |
| let mut func = Function::new(); |
| let mut ssa = SSABuilder::default(); |
| let block0 = func.dfg.make_block(); |
| let block1 = func.dfg.make_block(); |
| { |
| let mut cur = FuncCursor::new(&mut func); |
| cur.insert_block(block0); |
| cur.insert_block(block1); |
| } |
| |
| // block0 |
| ssa.declare_block(block0); |
| let x_var = Variable::new(0); |
| ssa.seal_block(block0, &mut func); |
| let x1 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| cur.ins().iconst(I32, 0) |
| }; |
| ssa.def_var(x_var, x1, block0); |
| let y_var = Variable::new(1); |
| let y1 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| cur.ins().iconst(I32, 1) |
| }; |
| ssa.def_var(y_var, y1, block0); |
| let z_var = Variable::new(2); |
| let z1 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| cur.ins().iconst(I32, 2) |
| }; |
| ssa.def_var(z_var, z1, block0); |
| let jump_block0_block1 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| cur.ins().jump(block1, &[]) |
| }; |
| |
| // block1 |
| ssa.declare_block(block1); |
| ssa.declare_block_predecessor(block1, jump_block0_block1); |
| let z2 = ssa.use_var(&mut func, z_var, I32, block1).0; |
| assert_eq!(func.dfg.block_params(block1)[0], z2); |
| let x2 = ssa.use_var(&mut func, x_var, I32, block1).0; |
| assert_eq!(func.dfg.block_params(block1)[1], x2); |
| let x3 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block1); |
| cur.ins().iadd(x2, z2) |
| }; |
| ssa.def_var(x_var, x3, block1); |
| let x4 = ssa.use_var(&mut func, x_var, I32, block1).0; |
| let y3 = ssa.use_var(&mut func, y_var, I32, block1).0; |
| assert_eq!(func.dfg.block_params(block1)[2], y3); |
| let y4 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block1); |
| cur.ins().isub(y3, x4) |
| }; |
| ssa.def_var(y_var, y4, block1); |
| let jump_block1_block1 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block1); |
| cur.ins().jump(block1, &[]) |
| }; |
| ssa.declare_block_predecessor(block1, jump_block1_block1); |
| ssa.seal_block(block1, &mut func); |
| // At sealing the "z" argument disappear but the remaining "x" and "y" args have to be |
| // in the right order. |
| assert_eq!(func.dfg.block_params(block1)[1], y3); |
| assert_eq!(func.dfg.block_params(block1)[0], x2); |
| } |
| |
| #[test] |
| fn undef() { |
| // Use vars of various types which have not been defined. |
| let mut func = Function::new(); |
| let mut ssa = SSABuilder::default(); |
| let block0 = func.dfg.make_block(); |
| ssa.declare_block(block0); |
| ssa.seal_block(block0, &mut func); |
| let i32_var = Variable::new(0); |
| let f32_var = Variable::new(1); |
| let f64_var = Variable::new(2); |
| let i8_var = Variable::new(3); |
| let f32x4_var = Variable::new(4); |
| ssa.use_var(&mut func, i32_var, I32, block0); |
| ssa.use_var(&mut func, f32_var, F32, block0); |
| ssa.use_var(&mut func, f64_var, F64, block0); |
| ssa.use_var(&mut func, i8_var, I8, block0); |
| ssa.use_var(&mut func, f32x4_var, F32X4, block0); |
| assert_eq!(func.dfg.num_block_params(block0), 0); |
| } |
| |
| #[test] |
| fn undef_in_entry() { |
| // Use a var which has not been defined. The search should hit the |
| // top of the entry block, and then fall back to inserting an iconst. |
| let mut func = Function::new(); |
| let mut ssa = SSABuilder::default(); |
| let block0 = func.dfg.make_block(); |
| ssa.declare_block(block0); |
| ssa.seal_block(block0, &mut func); |
| let x_var = Variable::new(0); |
| assert_eq!(func.dfg.num_block_params(block0), 0); |
| ssa.use_var(&mut func, x_var, I32, block0); |
| assert_eq!(func.dfg.num_block_params(block0), 0); |
| assert_eq!( |
| func.dfg.insts[func.layout.first_inst(block0).unwrap()].opcode(), |
| Opcode::Iconst |
| ); |
| } |
| |
| #[test] |
| fn undef_in_entry_sealed_after() { |
| // Use a var which has not been defined, but the block is not sealed |
| // until afterward. Before sealing, the SSA builder should insert an |
| // block param; after sealing, it should be removed. |
| let mut func = Function::new(); |
| let mut ssa = SSABuilder::default(); |
| let block0 = func.dfg.make_block(); |
| ssa.declare_block(block0); |
| let x_var = Variable::new(0); |
| assert_eq!(func.dfg.num_block_params(block0), 0); |
| ssa.use_var(&mut func, x_var, I32, block0); |
| assert_eq!(func.dfg.num_block_params(block0), 1); |
| ssa.seal_block(block0, &mut func); |
| assert_eq!(func.dfg.num_block_params(block0), 0); |
| assert_eq!( |
| func.dfg.insts[func.layout.first_inst(block0).unwrap()].opcode(), |
| Opcode::Iconst |
| ); |
| } |
| |
| #[test] |
| fn unreachable_use() { |
| // Here is the pseudo-program we want to translate: |
| // block0: |
| // return; |
| // block1: |
| // brif x, block1, block1; |
| let mut func = Function::new(); |
| let mut ssa = SSABuilder::default(); |
| let block0 = func.dfg.make_block(); |
| let block1 = func.dfg.make_block(); |
| { |
| let mut cur = FuncCursor::new(&mut func); |
| cur.insert_block(block0); |
| cur.insert_block(block1); |
| } |
| |
| // block0 |
| ssa.declare_block(block0); |
| ssa.seal_block(block0, &mut func); |
| { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| cur.ins().return_(&[]); |
| } |
| |
| // block1 |
| ssa.declare_block(block1); |
| { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block1); |
| let x_var = Variable::new(0); |
| let x_val = ssa.use_var(&mut cur.func, x_var, I32, block1).0; |
| let brif = cur.ins().brif(x_val, block1, &[], block1, &[]); |
| ssa.declare_block_predecessor(block1, brif); |
| } |
| ssa.seal_block(block1, &mut func); |
| |
| let flags = settings::Flags::new(settings::builder()); |
| match verify_function(&func, &flags) { |
| Ok(()) => {} |
| Err(_errors) => { |
| #[cfg(feature = "std")] |
| panic!("{}", _errors); |
| #[cfg(not(feature = "std"))] |
| panic!("function failed to verify"); |
| } |
| } |
| } |
| |
| #[test] |
| fn unreachable_use_with_multiple_preds() { |
| // Here is the pseudo-program we want to translate: |
| // block0: |
| // return; |
| // block1: |
| // brif x, block1, block2; |
| // block2: |
| // jump block1; |
| let mut func = Function::new(); |
| let mut ssa = SSABuilder::default(); |
| let block0 = func.dfg.make_block(); |
| let block1 = func.dfg.make_block(); |
| let block2 = func.dfg.make_block(); |
| { |
| let mut cur = FuncCursor::new(&mut func); |
| cur.insert_block(block0); |
| cur.insert_block(block1); |
| cur.insert_block(block2); |
| } |
| |
| // block0 |
| ssa.declare_block(block0); |
| ssa.seal_block(block0, &mut func); |
| { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| cur.ins().return_(&[]); |
| } |
| |
| // block1 |
| ssa.declare_block(block1); |
| let brif = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block1); |
| let x_var = Variable::new(0); |
| let x_val = ssa.use_var(&mut cur.func, x_var, I32, block1).0; |
| cur.ins().brif(x_val, block2, &[], block1, &[]) |
| }; |
| |
| // block2 |
| ssa.declare_block(block2); |
| ssa.declare_block_predecessor(block1, brif); |
| ssa.declare_block_predecessor(block2, brif); |
| ssa.seal_block(block2, &mut func); |
| let jump_block2_block1 = { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block2); |
| cur.ins().jump(block1, &[]) |
| }; |
| |
| // seal block1 |
| ssa.declare_block_predecessor(block1, jump_block2_block1); |
| ssa.seal_block(block1, &mut func); |
| let flags = settings::Flags::new(settings::builder()); |
| match verify_function(&func, &flags) { |
| Ok(()) => {} |
| Err(_errors) => { |
| #[cfg(feature = "std")] |
| panic!("{}", _errors); |
| #[cfg(not(feature = "std"))] |
| panic!("function failed to verify"); |
| } |
| } |
| } |
| |
| #[test] |
| fn reassign_with_predecessor_loop_hangs() { |
| // Here is the pseudo-program we want to translate: |
| // block0: |
| // var0 = iconst 0 |
| // return; |
| // block1: |
| // jump block2; |
| // block2: |
| // ; phantom use of var0 |
| // var0 = iconst 1 |
| // jump block1; |
| |
| let mut func = Function::new(); |
| let mut ssa = SSABuilder::default(); |
| let block0 = func.dfg.make_block(); |
| let block1 = func.dfg.make_block(); |
| let block2 = func.dfg.make_block(); |
| let var0 = Variable::new(0); |
| |
| { |
| let mut cur = FuncCursor::new(&mut func); |
| for block in [block0, block1, block2] { |
| cur.insert_block(block); |
| ssa.declare_block(block); |
| } |
| } |
| |
| // block0 |
| { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block0); |
| |
| let var0_iconst = cur.ins().iconst(I32, 0); |
| ssa.def_var(var0, var0_iconst, block0); |
| |
| cur.ins().return_(&[]); |
| } |
| |
| // block1 |
| { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block1); |
| |
| let jump = cur.ins().jump(block2, &[]); |
| ssa.declare_block_predecessor(block2, jump); |
| } |
| |
| // block2 |
| { |
| let mut cur = FuncCursor::new(&mut func).at_bottom(block2); |
| |
| let _ = ssa.use_var(&mut cur.func, var0, I32, block2).0; |
| let var0_iconst = cur.ins().iconst(I32, 1); |
| ssa.def_var(var0, var0_iconst, block2); |
| |
| let jump = cur.ins().jump(block1, &[]); |
| ssa.declare_block_predecessor(block1, jump); |
| } |
| |
| // The sealing algorithm would enter a infinite loop here |
| ssa.seal_all_blocks(&mut func); |
| } |
| } |
