| //===- SCCPSolver.cpp - SCCP Utility --------------------------- *- C++ -*-===// |
| // |
| // 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 |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // \file |
| // This file implements the Sparse Conditional Constant Propagation (SCCP) |
| // utility. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Transforms/Utils/SCCPSolver.h" |
| #include "llvm/Analysis/ConstantFolding.h" |
| #include "llvm/Analysis/InstructionSimplify.h" |
| #include "llvm/Analysis/ValueLattice.h" |
| #include "llvm/Analysis/ValueLatticeUtils.h" |
| #include "llvm/Analysis/ValueTracking.h" |
| #include "llvm/IR/InstVisitor.h" |
| #include "llvm/Support/Casting.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| #include <cassert> |
| #include <utility> |
| #include <vector> |
| |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "sccp" |
| |
| // The maximum number of range extensions allowed for operations requiring |
| // widening. |
| static const unsigned MaxNumRangeExtensions = 10; |
| |
| /// Returns MergeOptions with MaxWidenSteps set to MaxNumRangeExtensions. |
| static ValueLatticeElement::MergeOptions getMaxWidenStepsOpts() { |
| return ValueLatticeElement::MergeOptions().setMaxWidenSteps( |
| MaxNumRangeExtensions); |
| } |
| |
| static ConstantRange getConstantRange(const ValueLatticeElement &LV, Type *Ty, |
| bool UndefAllowed = true) { |
| assert(Ty->isIntOrIntVectorTy() && "Should be int or int vector"); |
| if (LV.isConstantRange(UndefAllowed)) |
| return LV.getConstantRange(); |
| return ConstantRange::getFull(Ty->getScalarSizeInBits()); |
| } |
| |
| namespace llvm { |
| |
| bool SCCPSolver::isConstant(const ValueLatticeElement &LV) { |
| return LV.isConstant() || |
| (LV.isConstantRange() && LV.getConstantRange().isSingleElement()); |
| } |
| |
| bool SCCPSolver::isOverdefined(const ValueLatticeElement &LV) { |
| return !LV.isUnknownOrUndef() && !SCCPSolver::isConstant(LV); |
| } |
| |
| static bool canRemoveInstruction(Instruction *I) { |
| if (wouldInstructionBeTriviallyDead(I)) |
| return true; |
| |
| // Some instructions can be handled but are rejected above. Catch |
| // those cases by falling through to here. |
| // TODO: Mark globals as being constant earlier, so |
| // TODO: wouldInstructionBeTriviallyDead() knows that atomic loads |
| // TODO: are safe to remove. |
| return isa<LoadInst>(I); |
| } |
| |
| bool SCCPSolver::tryToReplaceWithConstant(Value *V) { |
| Constant *Const = getConstantOrNull(V); |
| if (!Const) |
| return false; |
| // Replacing `musttail` instructions with constant breaks `musttail` invariant |
| // unless the call itself can be removed. |
| // Calls with "clang.arc.attachedcall" implicitly use the return value and |
| // those uses cannot be updated with a constant. |
| CallBase *CB = dyn_cast<CallBase>(V); |
| if (CB && ((CB->isMustTailCall() && |
| !canRemoveInstruction(CB)) || |
| CB->getOperandBundle(LLVMContext::OB_clang_arc_attachedcall))) { |
| Function *F = CB->getCalledFunction(); |
| |
| // Don't zap returns of the callee |
| if (F) |
| addToMustPreserveReturnsInFunctions(F); |
| |
| LLVM_DEBUG(dbgs() << " Can\'t treat the result of call " << *CB |
| << " as a constant\n"); |
| return false; |
| } |
| |
| LLVM_DEBUG(dbgs() << " Constant: " << *Const << " = " << *V << '\n'); |
| |
| // Replaces all of the uses of a variable with uses of the constant. |
| V->replaceAllUsesWith(Const); |
| return true; |
| } |
| |
| /// Try to use \p Inst's value range from \p Solver to infer the NUW flag. |
| static bool refineInstruction(SCCPSolver &Solver, |
| const SmallPtrSetImpl<Value *> &InsertedValues, |
| Instruction &Inst) { |
| bool Changed = false; |
| auto GetRange = [&Solver, &InsertedValues](Value *Op) { |
| if (auto *Const = dyn_cast<ConstantInt>(Op)) |
| return ConstantRange(Const->getValue()); |
| if (isa<Constant>(Op) || InsertedValues.contains(Op)) { |
| unsigned Bitwidth = Op->getType()->getScalarSizeInBits(); |
| return ConstantRange::getFull(Bitwidth); |
| } |
| return getConstantRange(Solver.getLatticeValueFor(Op), Op->getType(), |
| /*UndefAllowed=*/false); |
| }; |
| |
| if (isa<OverflowingBinaryOperator>(Inst)) { |
| auto RangeA = GetRange(Inst.getOperand(0)); |
| auto RangeB = GetRange(Inst.getOperand(1)); |
| if (!Inst.hasNoUnsignedWrap()) { |
| auto NUWRange = ConstantRange::makeGuaranteedNoWrapRegion( |
| Instruction::BinaryOps(Inst.getOpcode()), RangeB, |
| OverflowingBinaryOperator::NoUnsignedWrap); |
| if (NUWRange.contains(RangeA)) { |
| Inst.setHasNoUnsignedWrap(); |
| Changed = true; |
| } |
| } |
| if (!Inst.hasNoSignedWrap()) { |
| auto NSWRange = ConstantRange::makeGuaranteedNoWrapRegion( |
| Instruction::BinaryOps(Inst.getOpcode()), RangeB, |
| OverflowingBinaryOperator::NoSignedWrap); |
| if (NSWRange.contains(RangeA)) { |
| Inst.setHasNoSignedWrap(); |
| Changed = true; |
| } |
| } |
| } else if (isa<ZExtInst>(Inst) && !Inst.hasNonNeg()) { |
| auto Range = GetRange(Inst.getOperand(0)); |
| if (Range.isAllNonNegative()) { |
| Inst.setNonNeg(); |
| Changed = true; |
| } |
| } |
| |
| return Changed; |
| } |
| |
| /// Try to replace signed instructions with their unsigned equivalent. |
| static bool replaceSignedInst(SCCPSolver &Solver, |
| SmallPtrSetImpl<Value *> &InsertedValues, |
| Instruction &Inst) { |
| // Determine if a signed value is known to be >= 0. |
| auto isNonNegative = [&Solver](Value *V) { |
| // If this value was constant-folded, it may not have a solver entry. |
| // Handle integers. Otherwise, return false. |
| if (auto *C = dyn_cast<Constant>(V)) { |
| auto *CInt = dyn_cast<ConstantInt>(C); |
| return CInt && !CInt->isNegative(); |
| } |
| const ValueLatticeElement &IV = Solver.getLatticeValueFor(V); |
| return IV.isConstantRange(/*UndefAllowed=*/false) && |
| IV.getConstantRange().isAllNonNegative(); |
| }; |
| |
| Instruction *NewInst = nullptr; |
| switch (Inst.getOpcode()) { |
| // Note: We do not fold sitofp -> uitofp here because that could be more |
| // expensive in codegen and may not be reversible in the backend. |
| case Instruction::SExt: { |
| // If the source value is not negative, this is a zext. |
| Value *Op0 = Inst.getOperand(0); |
| if (InsertedValues.count(Op0) || !isNonNegative(Op0)) |
| return false; |
| NewInst = new ZExtInst(Op0, Inst.getType(), "", &Inst); |
| NewInst->setNonNeg(); |
| break; |
| } |
| case Instruction::AShr: { |
| // If the shifted value is not negative, this is a logical shift right. |
| Value *Op0 = Inst.getOperand(0); |
| if (InsertedValues.count(Op0) || !isNonNegative(Op0)) |
| return false; |
| NewInst = BinaryOperator::CreateLShr(Op0, Inst.getOperand(1), "", &Inst); |
| NewInst->setIsExact(Inst.isExact()); |
| break; |
| } |
| case Instruction::SDiv: |
| case Instruction::SRem: { |
| // If both operands are not negative, this is the same as udiv/urem. |
| Value *Op0 = Inst.getOperand(0), *Op1 = Inst.getOperand(1); |
| if (InsertedValues.count(Op0) || InsertedValues.count(Op1) || |
| !isNonNegative(Op0) || !isNonNegative(Op1)) |
| return false; |
| auto NewOpcode = Inst.getOpcode() == Instruction::SDiv ? Instruction::UDiv |
| : Instruction::URem; |
| NewInst = BinaryOperator::Create(NewOpcode, Op0, Op1, "", &Inst); |
| if (Inst.getOpcode() == Instruction::SDiv) |
| NewInst->setIsExact(Inst.isExact()); |
| break; |
| } |
| default: |
| return false; |
| } |
| |
| // Wire up the new instruction and update state. |
| assert(NewInst && "Expected replacement instruction"); |
| NewInst->takeName(&Inst); |
| InsertedValues.insert(NewInst); |
| Inst.replaceAllUsesWith(NewInst); |
| Solver.removeLatticeValueFor(&Inst); |
| Inst.eraseFromParent(); |
| return true; |
| } |
| |
| bool SCCPSolver::simplifyInstsInBlock(BasicBlock &BB, |
| SmallPtrSetImpl<Value *> &InsertedValues, |
| Statistic &InstRemovedStat, |
| Statistic &InstReplacedStat) { |
| bool MadeChanges = false; |
| for (Instruction &Inst : make_early_inc_range(BB)) { |
| if (Inst.getType()->isVoidTy()) |
| continue; |
| if (tryToReplaceWithConstant(&Inst)) { |
| if (canRemoveInstruction(&Inst)) |
| Inst.eraseFromParent(); |
| |
| MadeChanges = true; |
| ++InstRemovedStat; |
| } else if (replaceSignedInst(*this, InsertedValues, Inst)) { |
| MadeChanges = true; |
| ++InstReplacedStat; |
| } else if (refineInstruction(*this, InsertedValues, Inst)) { |
| MadeChanges = true; |
| } |
| } |
| return MadeChanges; |
| } |
| |
| bool SCCPSolver::removeNonFeasibleEdges(BasicBlock *BB, DomTreeUpdater &DTU, |
| BasicBlock *&NewUnreachableBB) const { |
| SmallPtrSet<BasicBlock *, 8> FeasibleSuccessors; |
| bool HasNonFeasibleEdges = false; |
| for (BasicBlock *Succ : successors(BB)) { |
| if (isEdgeFeasible(BB, Succ)) |
| FeasibleSuccessors.insert(Succ); |
| else |
| HasNonFeasibleEdges = true; |
| } |
| |
| // All edges feasible, nothing to do. |
| if (!HasNonFeasibleEdges) |
| return false; |
| |
| // SCCP can only determine non-feasible edges for br, switch and indirectbr. |
| Instruction *TI = BB->getTerminator(); |
| assert((isa<BranchInst>(TI) || isa<SwitchInst>(TI) || |
| isa<IndirectBrInst>(TI)) && |
| "Terminator must be a br, switch or indirectbr"); |
| |
| if (FeasibleSuccessors.size() == 0) { |
| // Branch on undef/poison, replace with unreachable. |
| SmallPtrSet<BasicBlock *, 8> SeenSuccs; |
| SmallVector<DominatorTree::UpdateType, 8> Updates; |
| for (BasicBlock *Succ : successors(BB)) { |
| Succ->removePredecessor(BB); |
| if (SeenSuccs.insert(Succ).second) |
| Updates.push_back({DominatorTree::Delete, BB, Succ}); |
| } |
| TI->eraseFromParent(); |
| new UnreachableInst(BB->getContext(), BB); |
| DTU.applyUpdatesPermissive(Updates); |
| } else if (FeasibleSuccessors.size() == 1) { |
| // Replace with an unconditional branch to the only feasible successor. |
| BasicBlock *OnlyFeasibleSuccessor = *FeasibleSuccessors.begin(); |
| SmallVector<DominatorTree::UpdateType, 8> Updates; |
| bool HaveSeenOnlyFeasibleSuccessor = false; |
| for (BasicBlock *Succ : successors(BB)) { |
| if (Succ == OnlyFeasibleSuccessor && !HaveSeenOnlyFeasibleSuccessor) { |
| // Don't remove the edge to the only feasible successor the first time |
| // we see it. We still do need to remove any multi-edges to it though. |
| HaveSeenOnlyFeasibleSuccessor = true; |
| continue; |
| } |
| |
| Succ->removePredecessor(BB); |
| Updates.push_back({DominatorTree::Delete, BB, Succ}); |
| } |
| |
| BranchInst::Create(OnlyFeasibleSuccessor, BB); |
| TI->eraseFromParent(); |
| DTU.applyUpdatesPermissive(Updates); |
| } else if (FeasibleSuccessors.size() > 1) { |
| SwitchInstProfUpdateWrapper SI(*cast<SwitchInst>(TI)); |
| SmallVector<DominatorTree::UpdateType, 8> Updates; |
| |
| // If the default destination is unfeasible it will never be taken. Replace |
| // it with a new block with a single Unreachable instruction. |
| BasicBlock *DefaultDest = SI->getDefaultDest(); |
| if (!FeasibleSuccessors.contains(DefaultDest)) { |
| if (!NewUnreachableBB) { |
| NewUnreachableBB = |
| BasicBlock::Create(DefaultDest->getContext(), "default.unreachable", |
| DefaultDest->getParent(), DefaultDest); |
| new UnreachableInst(DefaultDest->getContext(), NewUnreachableBB); |
| } |
| |
| DefaultDest->removePredecessor(BB); |
| SI->setDefaultDest(NewUnreachableBB); |
| Updates.push_back({DominatorTree::Delete, BB, DefaultDest}); |
| Updates.push_back({DominatorTree::Insert, BB, NewUnreachableBB}); |
| } |
| |
| for (auto CI = SI->case_begin(); CI != SI->case_end();) { |
| if (FeasibleSuccessors.contains(CI->getCaseSuccessor())) { |
| ++CI; |
| continue; |
| } |
| |
| BasicBlock *Succ = CI->getCaseSuccessor(); |
| Succ->removePredecessor(BB); |
| Updates.push_back({DominatorTree::Delete, BB, Succ}); |
| SI.removeCase(CI); |
| // Don't increment CI, as we removed a case. |
| } |
| |
| DTU.applyUpdatesPermissive(Updates); |
| } else { |
| llvm_unreachable("Must have at least one feasible successor"); |
| } |
| return true; |
| } |
| |
| /// Helper class for SCCPSolver. This implements the instruction visitor and |
| /// holds all the state. |
| class SCCPInstVisitor : public InstVisitor<SCCPInstVisitor> { |
| const DataLayout &DL; |
| std::function<const TargetLibraryInfo &(Function &)> GetTLI; |
| SmallPtrSet<BasicBlock *, 8> BBExecutable; // The BBs that are executable. |
| DenseMap<Value *, ValueLatticeElement> |
| ValueState; // The state each value is in. |
| |
| /// StructValueState - This maintains ValueState for values that have |
| /// StructType, for example for formal arguments, calls, insertelement, etc. |
| DenseMap<std::pair<Value *, unsigned>, ValueLatticeElement> StructValueState; |
| |
| /// GlobalValue - If we are tracking any values for the contents of a global |
| /// variable, we keep a mapping from the constant accessor to the element of |
| /// the global, to the currently known value. If the value becomes |
| /// overdefined, it's entry is simply removed from this map. |
| DenseMap<GlobalVariable *, ValueLatticeElement> TrackedGlobals; |
| |
| /// TrackedRetVals - If we are tracking arguments into and the return |
| /// value out of a function, it will have an entry in this map, indicating |
| /// what the known return value for the function is. |
| MapVector<Function *, ValueLatticeElement> TrackedRetVals; |
| |
| /// TrackedMultipleRetVals - Same as TrackedRetVals, but used for functions |
| /// that return multiple values. |
| MapVector<std::pair<Function *, unsigned>, ValueLatticeElement> |
| TrackedMultipleRetVals; |
| |
| /// The set of values whose lattice has been invalidated. |
| /// Populated by resetLatticeValueFor(), cleared after resolving undefs. |
| DenseSet<Value *> Invalidated; |
| |
| /// MRVFunctionsTracked - Each function in TrackedMultipleRetVals is |
| /// represented here for efficient lookup. |
| SmallPtrSet<Function *, 16> MRVFunctionsTracked; |
| |
| /// A list of functions whose return cannot be modified. |
| SmallPtrSet<Function *, 16> MustPreserveReturnsInFunctions; |
| |
| /// TrackingIncomingArguments - This is the set of functions for whose |
| /// arguments we make optimistic assumptions about and try to prove as |
| /// constants. |
| SmallPtrSet<Function *, 16> TrackingIncomingArguments; |
| |
| /// The reason for two worklists is that overdefined is the lowest state |
| /// on the lattice, and moving things to overdefined as fast as possible |
| /// makes SCCP converge much faster. |
| /// |
| /// By having a separate worklist, we accomplish this because everything |
| /// possibly overdefined will become overdefined at the soonest possible |
| /// point. |
| SmallVector<Value *, 64> OverdefinedInstWorkList; |
| SmallVector<Value *, 64> InstWorkList; |
| |
| // The BasicBlock work list |
| SmallVector<BasicBlock *, 64> BBWorkList; |
| |
| /// KnownFeasibleEdges - Entries in this set are edges which have already had |
| /// PHI nodes retriggered. |
| using Edge = std::pair<BasicBlock *, BasicBlock *>; |
| DenseSet<Edge> KnownFeasibleEdges; |
| |
| DenseMap<Function *, std::unique_ptr<PredicateInfo>> FnPredicateInfo; |
| |
| DenseMap<Value *, SmallPtrSet<User *, 2>> AdditionalUsers; |
| |
| LLVMContext &Ctx; |
| |
| private: |
| ConstantInt *getConstantInt(const ValueLatticeElement &IV, Type *Ty) const { |
| return dyn_cast_or_null<ConstantInt>(getConstant(IV, Ty)); |
| } |
| |
| // pushToWorkList - Helper for markConstant/markOverdefined |
| void pushToWorkList(ValueLatticeElement &IV, Value *V); |
| |
| // Helper to push \p V to the worklist, after updating it to \p IV. Also |
| // prints a debug message with the updated value. |
| void pushToWorkListMsg(ValueLatticeElement &IV, Value *V); |
| |
| // markConstant - Make a value be marked as "constant". If the value |
| // is not already a constant, add it to the instruction work list so that |
| // the users of the instruction are updated later. |
| bool markConstant(ValueLatticeElement &IV, Value *V, Constant *C, |
| bool MayIncludeUndef = false); |
| |
| bool markConstant(Value *V, Constant *C) { |
| assert(!V->getType()->isStructTy() && "structs should use mergeInValue"); |
| return markConstant(ValueState[V], V, C); |
| } |
| |
| // markOverdefined - Make a value be marked as "overdefined". If the |
| // value is not already overdefined, add it to the overdefined instruction |
| // work list so that the users of the instruction are updated later. |
| bool markOverdefined(ValueLatticeElement &IV, Value *V); |
| |
| /// Merge \p MergeWithV into \p IV and push \p V to the worklist, if \p IV |
| /// changes. |
| bool mergeInValue(ValueLatticeElement &IV, Value *V, |
| ValueLatticeElement MergeWithV, |
| ValueLatticeElement::MergeOptions Opts = { |
| /*MayIncludeUndef=*/false, /*CheckWiden=*/false}); |
| |
| bool mergeInValue(Value *V, ValueLatticeElement MergeWithV, |
| ValueLatticeElement::MergeOptions Opts = { |
| /*MayIncludeUndef=*/false, /*CheckWiden=*/false}) { |
| assert(!V->getType()->isStructTy() && |
| "non-structs should use markConstant"); |
| return mergeInValue(ValueState[V], V, MergeWithV, Opts); |
| } |
| |
| /// getValueState - Return the ValueLatticeElement object that corresponds to |
| /// the value. This function handles the case when the value hasn't been seen |
| /// yet by properly seeding constants etc. |
| ValueLatticeElement &getValueState(Value *V) { |
| assert(!V->getType()->isStructTy() && "Should use getStructValueState"); |
| |
| auto I = ValueState.insert(std::make_pair(V, ValueLatticeElement())); |
| ValueLatticeElement &LV = I.first->second; |
| |
| if (!I.second) |
| return LV; // Common case, already in the map. |
| |
| if (auto *C = dyn_cast<Constant>(V)) |
| LV.markConstant(C); // Constants are constant |
| |
| // All others are unknown by default. |
| return LV; |
| } |
| |
| /// getStructValueState - Return the ValueLatticeElement object that |
| /// corresponds to the value/field pair. This function handles the case when |
| /// the value hasn't been seen yet by properly seeding constants etc. |
| ValueLatticeElement &getStructValueState(Value *V, unsigned i) { |
| assert(V->getType()->isStructTy() && "Should use getValueState"); |
| assert(i < cast<StructType>(V->getType())->getNumElements() && |
| "Invalid element #"); |
| |
| auto I = StructValueState.insert( |
| std::make_pair(std::make_pair(V, i), ValueLatticeElement())); |
| ValueLatticeElement &LV = I.first->second; |
| |
| if (!I.second) |
| return LV; // Common case, already in the map. |
| |
| if (auto *C = dyn_cast<Constant>(V)) { |
| Constant *Elt = C->getAggregateElement(i); |
| |
| if (!Elt) |
| LV.markOverdefined(); // Unknown sort of constant. |
| else |
| LV.markConstant(Elt); // Constants are constant. |
| } |
| |
| // All others are underdefined by default. |
| return LV; |
| } |
| |
| /// Traverse the use-def chain of \p Call, marking itself and its users as |
| /// "unknown" on the way. |
| void invalidate(CallBase *Call) { |
| SmallVector<Instruction *, 64> ToInvalidate; |
| ToInvalidate.push_back(Call); |
| |
| while (!ToInvalidate.empty()) { |
| Instruction *Inst = ToInvalidate.pop_back_val(); |
| |
| if (!Invalidated.insert(Inst).second) |
| continue; |
| |
| if (!BBExecutable.count(Inst->getParent())) |
| continue; |
| |
| Value *V = nullptr; |
| // For return instructions we need to invalidate the tracked returns map. |
| // Anything else has its lattice in the value map. |
| if (auto *RetInst = dyn_cast<ReturnInst>(Inst)) { |
| Function *F = RetInst->getParent()->getParent(); |
| if (auto It = TrackedRetVals.find(F); It != TrackedRetVals.end()) { |
| It->second = ValueLatticeElement(); |
| V = F; |
| } else if (MRVFunctionsTracked.count(F)) { |
| auto *STy = cast<StructType>(F->getReturnType()); |
| for (unsigned I = 0, E = STy->getNumElements(); I != E; ++I) |
| TrackedMultipleRetVals[{F, I}] = ValueLatticeElement(); |
| V = F; |
| } |
| } else if (auto *STy = dyn_cast<StructType>(Inst->getType())) { |
| for (unsigned I = 0, E = STy->getNumElements(); I != E; ++I) { |
| if (auto It = StructValueState.find({Inst, I}); |
| It != StructValueState.end()) { |
| It->second = ValueLatticeElement(); |
| V = Inst; |
| } |
| } |
| } else if (auto It = ValueState.find(Inst); It != ValueState.end()) { |
| It->second = ValueLatticeElement(); |
| V = Inst; |
| } |
| |
| if (V) { |
| LLVM_DEBUG(dbgs() << "Invalidated lattice for " << *V << "\n"); |
| |
| for (User *U : V->users()) |
| if (auto *UI = dyn_cast<Instruction>(U)) |
| ToInvalidate.push_back(UI); |
| |
| auto It = AdditionalUsers.find(V); |
| if (It != AdditionalUsers.end()) |
| for (User *U : It->second) |
| if (auto *UI = dyn_cast<Instruction>(U)) |
| ToInvalidate.push_back(UI); |
| } |
| } |
| } |
| |
| /// markEdgeExecutable - Mark a basic block as executable, adding it to the BB |
| /// work list if it is not already executable. |
| bool markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest); |
| |
| // getFeasibleSuccessors - Return a vector of booleans to indicate which |
| // successors are reachable from a given terminator instruction. |
| void getFeasibleSuccessors(Instruction &TI, SmallVectorImpl<bool> &Succs); |
| |
| // OperandChangedState - This method is invoked on all of the users of an |
| // instruction that was just changed state somehow. Based on this |
| // information, we need to update the specified user of this instruction. |
| void operandChangedState(Instruction *I) { |
| if (BBExecutable.count(I->getParent())) // Inst is executable? |
| visit(*I); |
| } |
| |
| // Add U as additional user of V. |
| void addAdditionalUser(Value *V, User *U) { |
| auto Iter = AdditionalUsers.insert({V, {}}); |
| Iter.first->second.insert(U); |
| } |
| |
| // Mark I's users as changed, including AdditionalUsers. |
| void markUsersAsChanged(Value *I) { |
| // Functions include their arguments in the use-list. Changed function |
| // values mean that the result of the function changed. We only need to |
| // update the call sites with the new function result and do not have to |
| // propagate the call arguments. |
| if (isa<Function>(I)) { |
| for (User *U : I->users()) { |
| if (auto *CB = dyn_cast<CallBase>(U)) |
| handleCallResult(*CB); |
| } |
| } else { |
| for (User *U : I->users()) |
| if (auto *UI = dyn_cast<Instruction>(U)) |
| operandChangedState(UI); |
| } |
| |
| auto Iter = AdditionalUsers.find(I); |
| if (Iter != AdditionalUsers.end()) { |
| // Copy additional users before notifying them of changes, because new |
| // users may be added, potentially invalidating the iterator. |
| SmallVector<Instruction *, 2> ToNotify; |
| for (User *U : Iter->second) |
| if (auto *UI = dyn_cast<Instruction>(U)) |
| ToNotify.push_back(UI); |
| for (Instruction *UI : ToNotify) |
| operandChangedState(UI); |
| } |
| } |
| void handleCallOverdefined(CallBase &CB); |
| void handleCallResult(CallBase &CB); |
| void handleCallArguments(CallBase &CB); |
| void handleExtractOfWithOverflow(ExtractValueInst &EVI, |
| const WithOverflowInst *WO, unsigned Idx); |
| |
| private: |
| friend class InstVisitor<SCCPInstVisitor>; |
| |
| // visit implementations - Something changed in this instruction. Either an |
| // operand made a transition, or the instruction is newly executable. Change |
| // the value type of I to reflect these changes if appropriate. |
| void visitPHINode(PHINode &I); |
| |
| // Terminators |
| |
| void visitReturnInst(ReturnInst &I); |
| void visitTerminator(Instruction &TI); |
| |
| void visitCastInst(CastInst &I); |
| void visitSelectInst(SelectInst &I); |
| void visitUnaryOperator(Instruction &I); |
| void visitFreezeInst(FreezeInst &I); |
| void visitBinaryOperator(Instruction &I); |
| void visitCmpInst(CmpInst &I); |
| void visitExtractValueInst(ExtractValueInst &EVI); |
| void visitInsertValueInst(InsertValueInst &IVI); |
| |
| void visitCatchSwitchInst(CatchSwitchInst &CPI) { |
| markOverdefined(&CPI); |
| visitTerminator(CPI); |
| } |
| |
| // Instructions that cannot be folded away. |
| |
| void visitStoreInst(StoreInst &I); |
| void visitLoadInst(LoadInst &I); |
| void visitGetElementPtrInst(GetElementPtrInst &I); |
| |
| void visitInvokeInst(InvokeInst &II) { |
| visitCallBase(II); |
| visitTerminator(II); |
| } |
| |
| void visitCallBrInst(CallBrInst &CBI) { |
| visitCallBase(CBI); |
| visitTerminator(CBI); |
| } |
| |
| void visitCallBase(CallBase &CB); |
| void visitResumeInst(ResumeInst &I) { /*returns void*/ |
| } |
| void visitUnreachableInst(UnreachableInst &I) { /*returns void*/ |
| } |
| void visitFenceInst(FenceInst &I) { /*returns void*/ |
| } |
| |
| void visitInstruction(Instruction &I); |
| |
| public: |
| void addPredicateInfo(Function &F, DominatorTree &DT, AssumptionCache &AC) { |
| FnPredicateInfo.insert({&F, std::make_unique<PredicateInfo>(F, DT, AC)}); |
| } |
| |
| void visitCallInst(CallInst &I) { visitCallBase(I); } |
| |
| bool markBlockExecutable(BasicBlock *BB); |
| |
| const PredicateBase *getPredicateInfoFor(Instruction *I) { |
| auto It = FnPredicateInfo.find(I->getParent()->getParent()); |
| if (It == FnPredicateInfo.end()) |
| return nullptr; |
| return It->second->getPredicateInfoFor(I); |
| } |
| |
| SCCPInstVisitor(const DataLayout &DL, |
| std::function<const TargetLibraryInfo &(Function &)> GetTLI, |
| LLVMContext &Ctx) |
| : DL(DL), GetTLI(GetTLI), Ctx(Ctx) {} |
| |
| void trackValueOfGlobalVariable(GlobalVariable *GV) { |
| // We only track the contents of scalar globals. |
| if (GV->getValueType()->isSingleValueType()) { |
| ValueLatticeElement &IV = TrackedGlobals[GV]; |
| IV.markConstant(GV->getInitializer()); |
| } |
| } |
| |
| void addTrackedFunction(Function *F) { |
| // Add an entry, F -> undef. |
| if (auto *STy = dyn_cast<StructType>(F->getReturnType())) { |
| MRVFunctionsTracked.insert(F); |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) |
| TrackedMultipleRetVals.insert( |
| std::make_pair(std::make_pair(F, i), ValueLatticeElement())); |
| } else if (!F->getReturnType()->isVoidTy()) |
| TrackedRetVals.insert(std::make_pair(F, ValueLatticeElement())); |
| } |
| |
| void addToMustPreserveReturnsInFunctions(Function *F) { |
| MustPreserveReturnsInFunctions.insert(F); |
| } |
| |
| bool mustPreserveReturn(Function *F) { |
| return MustPreserveReturnsInFunctions.count(F); |
| } |
| |
| void addArgumentTrackedFunction(Function *F) { |
| TrackingIncomingArguments.insert(F); |
| } |
| |
| bool isArgumentTrackedFunction(Function *F) { |
| return TrackingIncomingArguments.count(F); |
| } |
| |
| void solve(); |
| |
| bool resolvedUndef(Instruction &I); |
| |
| bool resolvedUndefsIn(Function &F); |
| |
| bool isBlockExecutable(BasicBlock *BB) const { |
| return BBExecutable.count(BB); |
| } |
| |
| bool isEdgeFeasible(BasicBlock *From, BasicBlock *To) const; |
| |
| std::vector<ValueLatticeElement> getStructLatticeValueFor(Value *V) const { |
| std::vector<ValueLatticeElement> StructValues; |
| auto *STy = dyn_cast<StructType>(V->getType()); |
| assert(STy && "getStructLatticeValueFor() can be called only on structs"); |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { |
| auto I = StructValueState.find(std::make_pair(V, i)); |
| assert(I != StructValueState.end() && "Value not in valuemap!"); |
| StructValues.push_back(I->second); |
| } |
| return StructValues; |
| } |
| |
| void removeLatticeValueFor(Value *V) { ValueState.erase(V); } |
| |
| /// Invalidate the Lattice Value of \p Call and its users after specializing |
| /// the call. Then recompute it. |
| void resetLatticeValueFor(CallBase *Call) { |
| // Calls to void returning functions do not need invalidation. |
| Function *F = Call->getCalledFunction(); |
| (void)F; |
| assert(!F->getReturnType()->isVoidTy() && |
| (TrackedRetVals.count(F) || MRVFunctionsTracked.count(F)) && |
| "All non void specializations should be tracked"); |
| invalidate(Call); |
| handleCallResult(*Call); |
| } |
| |
| const ValueLatticeElement &getLatticeValueFor(Value *V) const { |
| assert(!V->getType()->isStructTy() && |
| "Should use getStructLatticeValueFor"); |
| DenseMap<Value *, ValueLatticeElement>::const_iterator I = |
| ValueState.find(V); |
| assert(I != ValueState.end() && |
| "V not found in ValueState nor Paramstate map!"); |
| return I->second; |
| } |
| |
| const MapVector<Function *, ValueLatticeElement> &getTrackedRetVals() { |
| return TrackedRetVals; |
| } |
| |
| const DenseMap<GlobalVariable *, ValueLatticeElement> &getTrackedGlobals() { |
| return TrackedGlobals; |
| } |
| |
| const SmallPtrSet<Function *, 16> getMRVFunctionsTracked() { |
| return MRVFunctionsTracked; |
| } |
| |
| void markOverdefined(Value *V) { |
| if (auto *STy = dyn_cast<StructType>(V->getType())) |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) |
| markOverdefined(getStructValueState(V, i), V); |
| else |
| markOverdefined(ValueState[V], V); |
| } |
| |
| bool isStructLatticeConstant(Function *F, StructType *STy); |
| |
| Constant *getConstant(const ValueLatticeElement &LV, Type *Ty) const; |
| |
| Constant *getConstantOrNull(Value *V) const; |
| |
| SmallPtrSetImpl<Function *> &getArgumentTrackedFunctions() { |
| return TrackingIncomingArguments; |
| } |
| |
| void setLatticeValueForSpecializationArguments(Function *F, |
| const SmallVectorImpl<ArgInfo> &Args); |
| |
| void markFunctionUnreachable(Function *F) { |
| for (auto &BB : *F) |
| BBExecutable.erase(&BB); |
| } |
| |
| void solveWhileResolvedUndefsIn(Module &M) { |
| bool ResolvedUndefs = true; |
| while (ResolvedUndefs) { |
| solve(); |
| ResolvedUndefs = false; |
| for (Function &F : M) |
| ResolvedUndefs |= resolvedUndefsIn(F); |
| } |
| } |
| |
| void solveWhileResolvedUndefsIn(SmallVectorImpl<Function *> &WorkList) { |
| bool ResolvedUndefs = true; |
| while (ResolvedUndefs) { |
| solve(); |
| ResolvedUndefs = false; |
| for (Function *F : WorkList) |
| ResolvedUndefs |= resolvedUndefsIn(*F); |
| } |
| } |
| |
| void solveWhileResolvedUndefs() { |
| bool ResolvedUndefs = true; |
| while (ResolvedUndefs) { |
| solve(); |
| ResolvedUndefs = false; |
| for (Value *V : Invalidated) |
| if (auto *I = dyn_cast<Instruction>(V)) |
| ResolvedUndefs |= resolvedUndef(*I); |
| } |
| Invalidated.clear(); |
| } |
| }; |
| |
| } // namespace llvm |
| |
| bool SCCPInstVisitor::markBlockExecutable(BasicBlock *BB) { |
| if (!BBExecutable.insert(BB).second) |
| return false; |
| LLVM_DEBUG(dbgs() << "Marking Block Executable: " << BB->getName() << '\n'); |
| BBWorkList.push_back(BB); // Add the block to the work list! |
| return true; |
| } |
| |
| void SCCPInstVisitor::pushToWorkList(ValueLatticeElement &IV, Value *V) { |
| if (IV.isOverdefined()) { |
| if (OverdefinedInstWorkList.empty() || OverdefinedInstWorkList.back() != V) |
| OverdefinedInstWorkList.push_back(V); |
| return; |
| } |
| if (InstWorkList.empty() || InstWorkList.back() != V) |
| InstWorkList.push_back(V); |
| } |
| |
| void SCCPInstVisitor::pushToWorkListMsg(ValueLatticeElement &IV, Value *V) { |
| LLVM_DEBUG(dbgs() << "updated " << IV << ": " << *V << '\n'); |
| pushToWorkList(IV, V); |
| } |
| |
| bool SCCPInstVisitor::markConstant(ValueLatticeElement &IV, Value *V, |
| Constant *C, bool MayIncludeUndef) { |
| if (!IV.markConstant(C, MayIncludeUndef)) |
| return false; |
| LLVM_DEBUG(dbgs() << "markConstant: " << *C << ": " << *V << '\n'); |
| pushToWorkList(IV, V); |
| return true; |
| } |
| |
| bool SCCPInstVisitor::markOverdefined(ValueLatticeElement &IV, Value *V) { |
| if (!IV.markOverdefined()) |
| return false; |
| |
| LLVM_DEBUG(dbgs() << "markOverdefined: "; |
| if (auto *F = dyn_cast<Function>(V)) dbgs() |
| << "Function '" << F->getName() << "'\n"; |
| else dbgs() << *V << '\n'); |
| // Only instructions go on the work list |
| pushToWorkList(IV, V); |
| return true; |
| } |
| |
| bool SCCPInstVisitor::isStructLatticeConstant(Function *F, StructType *STy) { |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { |
| const auto &It = TrackedMultipleRetVals.find(std::make_pair(F, i)); |
| assert(It != TrackedMultipleRetVals.end()); |
| ValueLatticeElement LV = It->second; |
| if (!SCCPSolver::isConstant(LV)) |
| return false; |
| } |
| return true; |
| } |
| |
| Constant *SCCPInstVisitor::getConstant(const ValueLatticeElement &LV, |
| Type *Ty) const { |
| if (LV.isConstant()) { |
| Constant *C = LV.getConstant(); |
| assert(C->getType() == Ty && "Type mismatch"); |
| return C; |
| } |
| |
| if (LV.isConstantRange()) { |
| const auto &CR = LV.getConstantRange(); |
| if (CR.getSingleElement()) |
| return ConstantInt::get(Ty, *CR.getSingleElement()); |
| } |
| return nullptr; |
| } |
| |
| Constant *SCCPInstVisitor::getConstantOrNull(Value *V) const { |
| Constant *Const = nullptr; |
| if (V->getType()->isStructTy()) { |
| std::vector<ValueLatticeElement> LVs = getStructLatticeValueFor(V); |
| if (any_of(LVs, SCCPSolver::isOverdefined)) |
| return nullptr; |
| std::vector<Constant *> ConstVals; |
| auto *ST = cast<StructType>(V->getType()); |
| for (unsigned I = 0, E = ST->getNumElements(); I != E; ++I) { |
| ValueLatticeElement LV = LVs[I]; |
| ConstVals.push_back(SCCPSolver::isConstant(LV) |
| ? getConstant(LV, ST->getElementType(I)) |
| : UndefValue::get(ST->getElementType(I))); |
| } |
| Const = ConstantStruct::get(ST, ConstVals); |
| } else { |
| const ValueLatticeElement &LV = getLatticeValueFor(V); |
| if (SCCPSolver::isOverdefined(LV)) |
| return nullptr; |
| Const = SCCPSolver::isConstant(LV) ? getConstant(LV, V->getType()) |
| : UndefValue::get(V->getType()); |
| } |
| assert(Const && "Constant is nullptr here!"); |
| return Const; |
| } |
| |
| void SCCPInstVisitor::setLatticeValueForSpecializationArguments(Function *F, |
| const SmallVectorImpl<ArgInfo> &Args) { |
| assert(!Args.empty() && "Specialization without arguments"); |
| assert(F->arg_size() == Args[0].Formal->getParent()->arg_size() && |
| "Functions should have the same number of arguments"); |
| |
| auto Iter = Args.begin(); |
| Function::arg_iterator NewArg = F->arg_begin(); |
| Function::arg_iterator OldArg = Args[0].Formal->getParent()->arg_begin(); |
| for (auto End = F->arg_end(); NewArg != End; ++NewArg, ++OldArg) { |
| |
| LLVM_DEBUG(dbgs() << "SCCP: Marking argument " |
| << NewArg->getNameOrAsOperand() << "\n"); |
| |
| // Mark the argument constants in the new function |
| // or copy the lattice state over from the old function. |
| if (Iter != Args.end() && Iter->Formal == &*OldArg) { |
| if (auto *STy = dyn_cast<StructType>(NewArg->getType())) { |
| for (unsigned I = 0, E = STy->getNumElements(); I != E; ++I) { |
| ValueLatticeElement &NewValue = StructValueState[{&*NewArg, I}]; |
| NewValue.markConstant(Iter->Actual->getAggregateElement(I)); |
| } |
| } else { |
| ValueState[&*NewArg].markConstant(Iter->Actual); |
| } |
| ++Iter; |
| } else { |
| if (auto *STy = dyn_cast<StructType>(NewArg->getType())) { |
| for (unsigned I = 0, E = STy->getNumElements(); I != E; ++I) { |
| ValueLatticeElement &NewValue = StructValueState[{&*NewArg, I}]; |
| NewValue = StructValueState[{&*OldArg, I}]; |
| } |
| } else { |
| ValueLatticeElement &NewValue = ValueState[&*NewArg]; |
| NewValue = ValueState[&*OldArg]; |
| } |
| } |
| } |
| } |
| |
| void SCCPInstVisitor::visitInstruction(Instruction &I) { |
| // All the instructions we don't do any special handling for just |
| // go to overdefined. |
| LLVM_DEBUG(dbgs() << "SCCP: Don't know how to handle: " << I << '\n'); |
| markOverdefined(&I); |
| } |
| |
| bool SCCPInstVisitor::mergeInValue(ValueLatticeElement &IV, Value *V, |
| ValueLatticeElement MergeWithV, |
| ValueLatticeElement::MergeOptions Opts) { |
| if (IV.mergeIn(MergeWithV, Opts)) { |
| pushToWorkList(IV, V); |
| LLVM_DEBUG(dbgs() << "Merged " << MergeWithV << " into " << *V << " : " |
| << IV << "\n"); |
| return true; |
| } |
| return false; |
| } |
| |
| bool SCCPInstVisitor::markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest) { |
| if (!KnownFeasibleEdges.insert(Edge(Source, Dest)).second) |
| return false; // This edge is already known to be executable! |
| |
| if (!markBlockExecutable(Dest)) { |
| // If the destination is already executable, we just made an *edge* |
| // feasible that wasn't before. Revisit the PHI nodes in the block |
| // because they have potentially new operands. |
| LLVM_DEBUG(dbgs() << "Marking Edge Executable: " << Source->getName() |
| << " -> " << Dest->getName() << '\n'); |
| |
| for (PHINode &PN : Dest->phis()) |
| visitPHINode(PN); |
| } |
| return true; |
| } |
| |
| // getFeasibleSuccessors - Return a vector of booleans to indicate which |
| // successors are reachable from a given terminator instruction. |
| void SCCPInstVisitor::getFeasibleSuccessors(Instruction &TI, |
| SmallVectorImpl<bool> &Succs) { |
| Succs.resize(TI.getNumSuccessors()); |
| if (auto *BI = dyn_cast<BranchInst>(&TI)) { |
| if (BI->isUnconditional()) { |
| Succs[0] = true; |
| return; |
| } |
| |
| ValueLatticeElement BCValue = getValueState(BI->getCondition()); |
| ConstantInt *CI = getConstantInt(BCValue, BI->getCondition()->getType()); |
| if (!CI) { |
| // Overdefined condition variables, and branches on unfoldable constant |
| // conditions, mean the branch could go either way. |
| if (!BCValue.isUnknownOrUndef()) |
| Succs[0] = Succs[1] = true; |
| return; |
| } |
| |
| // Constant condition variables mean the branch can only go a single way. |
| Succs[CI->isZero()] = true; |
| return; |
| } |
| |
| // We cannot analyze special terminators, so consider all successors |
| // executable. |
| if (TI.isSpecialTerminator()) { |
| Succs.assign(TI.getNumSuccessors(), true); |
| return; |
| } |
| |
| if (auto *SI = dyn_cast<SwitchInst>(&TI)) { |
| if (!SI->getNumCases()) { |
| Succs[0] = true; |
| return; |
| } |
| const ValueLatticeElement &SCValue = getValueState(SI->getCondition()); |
| if (ConstantInt *CI = |
| getConstantInt(SCValue, SI->getCondition()->getType())) { |
| Succs[SI->findCaseValue(CI)->getSuccessorIndex()] = true; |
| return; |
| } |
| |
| // TODO: Switch on undef is UB. Stop passing false once the rest of LLVM |
| // is ready. |
| if (SCValue.isConstantRange(/*UndefAllowed=*/false)) { |
| const ConstantRange &Range = SCValue.getConstantRange(); |
| unsigned ReachableCaseCount = 0; |
| for (const auto &Case : SI->cases()) { |
| const APInt &CaseValue = Case.getCaseValue()->getValue(); |
| if (Range.contains(CaseValue)) { |
| Succs[Case.getSuccessorIndex()] = true; |
| ++ReachableCaseCount; |
| } |
| } |
| |
| Succs[SI->case_default()->getSuccessorIndex()] = |
| Range.isSizeLargerThan(ReachableCaseCount); |
| return; |
| } |
| |
| // Overdefined or unknown condition? All destinations are executable! |
| if (!SCValue.isUnknownOrUndef()) |
| Succs.assign(TI.getNumSuccessors(), true); |
| return; |
| } |
| |
| // In case of indirect branch and its address is a blockaddress, we mark |
| // the target as executable. |
| if (auto *IBR = dyn_cast<IndirectBrInst>(&TI)) { |
| // Casts are folded by visitCastInst. |
| ValueLatticeElement IBRValue = getValueState(IBR->getAddress()); |
| BlockAddress *Addr = dyn_cast_or_null<BlockAddress>( |
| getConstant(IBRValue, IBR->getAddress()->getType())); |
| if (!Addr) { // Overdefined or unknown condition? |
| // All destinations are executable! |
| if (!IBRValue.isUnknownOrUndef()) |
| Succs.assign(TI.getNumSuccessors(), true); |
| return; |
| } |
| |
| BasicBlock *T = Addr->getBasicBlock(); |
| assert(Addr->getFunction() == T->getParent() && |
| "Block address of a different function ?"); |
| for (unsigned i = 0; i < IBR->getNumSuccessors(); ++i) { |
| // This is the target. |
| if (IBR->getDestination(i) == T) { |
| Succs[i] = true; |
| return; |
| } |
| } |
| |
| // If we didn't find our destination in the IBR successor list, then we |
| // have undefined behavior. Its ok to assume no successor is executable. |
| return; |
| } |
| |
| LLVM_DEBUG(dbgs() << "Unknown terminator instruction: " << TI << '\n'); |
| llvm_unreachable("SCCP: Don't know how to handle this terminator!"); |
| } |
| |
| // isEdgeFeasible - Return true if the control flow edge from the 'From' basic |
| // block to the 'To' basic block is currently feasible. |
| bool SCCPInstVisitor::isEdgeFeasible(BasicBlock *From, BasicBlock *To) const { |
| // Check if we've called markEdgeExecutable on the edge yet. (We could |
| // be more aggressive and try to consider edges which haven't been marked |
| // yet, but there isn't any need.) |
| return KnownFeasibleEdges.count(Edge(From, To)); |
| } |
| |
| // visit Implementations - Something changed in this instruction, either an |
| // operand made a transition, or the instruction is newly executable. Change |
| // the value type of I to reflect these changes if appropriate. This method |
| // makes sure to do the following actions: |
| // |
| // 1. If a phi node merges two constants in, and has conflicting value coming |
| // from different branches, or if the PHI node merges in an overdefined |
| // value, then the PHI node becomes overdefined. |
| // 2. If a phi node merges only constants in, and they all agree on value, the |
| // PHI node becomes a constant value equal to that. |
| // 3. If V <- x (op) y && isConstant(x) && isConstant(y) V = Constant |
| // 4. If V <- x (op) y && (isOverdefined(x) || isOverdefined(y)) V = Overdefined |
| // 5. If V <- MEM or V <- CALL or V <- (unknown) then V = Overdefined |
| // 6. If a conditional branch has a value that is constant, make the selected |
| // destination executable |
| // 7. If a conditional branch has a value that is overdefined, make all |
| // successors executable. |
| void SCCPInstVisitor::visitPHINode(PHINode &PN) { |
| // If this PN returns a struct, just mark the result overdefined. |
| // TODO: We could do a lot better than this if code actually uses this. |
| if (PN.getType()->isStructTy()) |
| return (void)markOverdefined(&PN); |
| |
| if (getValueState(&PN).isOverdefined()) |
| return; // Quick exit |
| |
| // Super-extra-high-degree PHI nodes are unlikely to ever be marked constant, |
| // and slow us down a lot. Just mark them overdefined. |
| if (PN.getNumIncomingValues() > 64) |
| return (void)markOverdefined(&PN); |
| |
| unsigned NumActiveIncoming = 0; |
| |
| // Look at all of the executable operands of the PHI node. If any of them |
| // are overdefined, the PHI becomes overdefined as well. If they are all |
| // constant, and they agree with each other, the PHI becomes the identical |
| // constant. If they are constant and don't agree, the PHI is a constant |
| // range. If there are no executable operands, the PHI remains unknown. |
| ValueLatticeElement PhiState = getValueState(&PN); |
| for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) { |
| if (!isEdgeFeasible(PN.getIncomingBlock(i), PN.getParent())) |
| continue; |
| |
| ValueLatticeElement IV = getValueState(PN.getIncomingValue(i)); |
| PhiState.mergeIn(IV); |
| NumActiveIncoming++; |
| if (PhiState.isOverdefined()) |
| break; |
| } |
| |
| // We allow up to 1 range extension per active incoming value and one |
| // additional extension. Note that we manually adjust the number of range |
| // extensions to match the number of active incoming values. This helps to |
| // limit multiple extensions caused by the same incoming value, if other |
| // incoming values are equal. |
| mergeInValue(&PN, PhiState, |
| ValueLatticeElement::MergeOptions().setMaxWidenSteps( |
| NumActiveIncoming + 1)); |
| ValueLatticeElement &PhiStateRef = getValueState(&PN); |
| PhiStateRef.setNumRangeExtensions( |
| std::max(NumActiveIncoming, PhiStateRef.getNumRangeExtensions())); |
| } |
| |
| void SCCPInstVisitor::visitReturnInst(ReturnInst &I) { |
| if (I.getNumOperands() == 0) |
| return; // ret void |
| |
| Function *F = I.getParent()->getParent(); |
| Value *ResultOp = I.getOperand(0); |
| |
| // If we are tracking the return value of this function, merge it in. |
| if (!TrackedRetVals.empty() && !ResultOp->getType()->isStructTy()) { |
| auto TFRVI = TrackedRetVals.find(F); |
| if (TFRVI != TrackedRetVals.end()) { |
| mergeInValue(TFRVI->second, F, getValueState(ResultOp)); |
| return; |
| } |
| } |
| |
| // Handle functions that return multiple values. |
| if (!TrackedMultipleRetVals.empty()) { |
| if (auto *STy = dyn_cast<StructType>(ResultOp->getType())) |
| if (MRVFunctionsTracked.count(F)) |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) |
| mergeInValue(TrackedMultipleRetVals[std::make_pair(F, i)], F, |
| getStructValueState(ResultOp, i)); |
| } |
| } |
| |
| void SCCPInstVisitor::visitTerminator(Instruction &TI) { |
| SmallVector<bool, 16> SuccFeasible; |
| getFeasibleSuccessors(TI, SuccFeasible); |
| |
| BasicBlock *BB = TI.getParent(); |
| |
| // Mark all feasible successors executable. |
| for (unsigned i = 0, e = SuccFeasible.size(); i != e; ++i) |
| if (SuccFeasible[i]) |
| markEdgeExecutable(BB, TI.getSuccessor(i)); |
| } |
| |
| void SCCPInstVisitor::visitCastInst(CastInst &I) { |
| // ResolvedUndefsIn might mark I as overdefined. Bail out, even if we would |
| // discover a concrete value later. |
| if (ValueState[&I].isOverdefined()) |
| return; |
| |
| ValueLatticeElement OpSt = getValueState(I.getOperand(0)); |
| if (OpSt.isUnknownOrUndef()) |
| return; |
| |
| if (Constant *OpC = getConstant(OpSt, I.getOperand(0)->getType())) { |
| // Fold the constant as we build. |
| if (Constant *C = |
| ConstantFoldCastOperand(I.getOpcode(), OpC, I.getType(), DL)) |
| return (void)markConstant(&I, C); |
| } |
| |
| if (I.getDestTy()->isIntegerTy() && I.getSrcTy()->isIntOrIntVectorTy()) { |
| auto &LV = getValueState(&I); |
| ConstantRange OpRange = getConstantRange(OpSt, I.getSrcTy()); |
| |
| Type *DestTy = I.getDestTy(); |
| // Vectors where all elements have the same known constant range are treated |
| // as a single constant range in the lattice. When bitcasting such vectors, |
| // there is a mis-match between the width of the lattice value (single |
| // constant range) and the original operands (vector). Go to overdefined in |
| // that case. |
| if (I.getOpcode() == Instruction::BitCast && |
| I.getOperand(0)->getType()->isVectorTy() && |
| OpRange.getBitWidth() < DL.getTypeSizeInBits(DestTy)) |
| return (void)markOverdefined(&I); |
| |
| ConstantRange Res = |
| OpRange.castOp(I.getOpcode(), DL.getTypeSizeInBits(DestTy)); |
| mergeInValue(LV, &I, ValueLatticeElement::getRange(Res)); |
| } else |
| markOverdefined(&I); |
| } |
| |
| void SCCPInstVisitor::handleExtractOfWithOverflow(ExtractValueInst &EVI, |
| const WithOverflowInst *WO, |
| unsigned Idx) { |
| Value *LHS = WO->getLHS(), *RHS = WO->getRHS(); |
| ValueLatticeElement L = getValueState(LHS); |
| ValueLatticeElement R = getValueState(RHS); |
| addAdditionalUser(LHS, &EVI); |
| addAdditionalUser(RHS, &EVI); |
| if (L.isUnknownOrUndef() || R.isUnknownOrUndef()) |
| return; // Wait to resolve. |
| |
| Type *Ty = LHS->getType(); |
| ConstantRange LR = getConstantRange(L, Ty); |
| ConstantRange RR = getConstantRange(R, Ty); |
| if (Idx == 0) { |
| ConstantRange Res = LR.binaryOp(WO->getBinaryOp(), RR); |
| mergeInValue(&EVI, ValueLatticeElement::getRange(Res)); |
| } else { |
| assert(Idx == 1 && "Index can only be 0 or 1"); |
| ConstantRange NWRegion = ConstantRange::makeGuaranteedNoWrapRegion( |
| WO->getBinaryOp(), RR, WO->getNoWrapKind()); |
| if (NWRegion.contains(LR)) |
| return (void)markConstant(&EVI, ConstantInt::getFalse(EVI.getType())); |
| markOverdefined(&EVI); |
| } |
| } |
| |
| void SCCPInstVisitor::visitExtractValueInst(ExtractValueInst &EVI) { |
| // If this returns a struct, mark all elements over defined, we don't track |
| // structs in structs. |
| if (EVI.getType()->isStructTy()) |
| return (void)markOverdefined(&EVI); |
| |
| // resolvedUndefsIn might mark I as overdefined. Bail out, even if we would |
| // discover a concrete value later. |
| if (ValueState[&EVI].isOverdefined()) |
| return (void)markOverdefined(&EVI); |
| |
| // If this is extracting from more than one level of struct, we don't know. |
| if (EVI.getNumIndices() != 1) |
| return (void)markOverdefined(&EVI); |
| |
| Value *AggVal = EVI.getAggregateOperand(); |
| if (AggVal->getType()->isStructTy()) { |
| unsigned i = *EVI.idx_begin(); |
| if (auto *WO = dyn_cast<WithOverflowInst>(AggVal)) |
| return handleExtractOfWithOverflow(EVI, WO, i); |
| ValueLatticeElement EltVal = getStructValueState(AggVal, i); |
| mergeInValue(getValueState(&EVI), &EVI, EltVal); |
| } else { |
| // Otherwise, must be extracting from an array. |
| return (void)markOverdefined(&EVI); |
| } |
| } |
| |
| void SCCPInstVisitor::visitInsertValueInst(InsertValueInst &IVI) { |
| auto *STy = dyn_cast<StructType>(IVI.getType()); |
| if (!STy) |
| return (void)markOverdefined(&IVI); |
| |
| // resolvedUndefsIn might mark I as overdefined. Bail out, even if we would |
| // discover a concrete value later. |
| if (SCCPSolver::isOverdefined(ValueState[&IVI])) |
| return (void)markOverdefined(&IVI); |
| |
| // If this has more than one index, we can't handle it, drive all results to |
| // undef. |
| if (IVI.getNumIndices() != 1) |
| return (void)markOverdefined(&IVI); |
| |
| Value *Aggr = IVI.getAggregateOperand(); |
| unsigned Idx = *IVI.idx_begin(); |
| |
| // Compute the result based on what we're inserting. |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { |
| // This passes through all values that aren't the inserted element. |
| if (i != Idx) { |
| ValueLatticeElement EltVal = getStructValueState(Aggr, i); |
| mergeInValue(getStructValueState(&IVI, i), &IVI, EltVal); |
| continue; |
| } |
| |
| Value *Val = IVI.getInsertedValueOperand(); |
| if (Val->getType()->isStructTy()) |
| // We don't track structs in structs. |
| markOverdefined(getStructValueState(&IVI, i), &IVI); |
| else { |
| ValueLatticeElement InVal = getValueState(Val); |
| mergeInValue(getStructValueState(&IVI, i), &IVI, InVal); |
| } |
| } |
| } |
| |
| void SCCPInstVisitor::visitSelectInst(SelectInst &I) { |
| // If this select returns a struct, just mark the result overdefined. |
| // TODO: We could do a lot better than this if code actually uses this. |
| if (I.getType()->isStructTy()) |
| return (void)markOverdefined(&I); |
| |
| // resolvedUndefsIn might mark I as overdefined. Bail out, even if we would |
| // discover a concrete value later. |
| if (ValueState[&I].isOverdefined()) |
| return (void)markOverdefined(&I); |
| |
| ValueLatticeElement CondValue = getValueState(I.getCondition()); |
| if (CondValue.isUnknownOrUndef()) |
| return; |
| |
| if (ConstantInt *CondCB = |
| getConstantInt(CondValue, I.getCondition()->getType())) { |
| Value *OpVal = CondCB->isZero() ? I.getFalseValue() : I.getTrueValue(); |
| mergeInValue(&I, getValueState(OpVal)); |
| return; |
| } |
| |
| // Otherwise, the condition is overdefined or a constant we can't evaluate. |
| // See if we can produce something better than overdefined based on the T/F |
| // value. |
| ValueLatticeElement TVal = getValueState(I.getTrueValue()); |
| ValueLatticeElement FVal = getValueState(I.getFalseValue()); |
| |
| bool Changed = ValueState[&I].mergeIn(TVal); |
| Changed |= ValueState[&I].mergeIn(FVal); |
| if (Changed) |
| pushToWorkListMsg(ValueState[&I], &I); |
| } |
| |
| // Handle Unary Operators. |
| void SCCPInstVisitor::visitUnaryOperator(Instruction &I) { |
| ValueLatticeElement V0State = getValueState(I.getOperand(0)); |
| |
| ValueLatticeElement &IV = ValueState[&I]; |
| // resolvedUndefsIn might mark I as overdefined. Bail out, even if we would |
| // discover a concrete value later. |
| if (SCCPSolver::isOverdefined(IV)) |
| return (void)markOverdefined(&I); |
| |
| // If something is unknown/undef, wait for it to resolve. |
| if (V0State.isUnknownOrUndef()) |
| return; |
| |
| if (SCCPSolver::isConstant(V0State)) |
| if (Constant *C = ConstantFoldUnaryOpOperand( |
| I.getOpcode(), getConstant(V0State, I.getType()), DL)) |
| return (void)markConstant(IV, &I, C); |
| |
| markOverdefined(&I); |
| } |
| |
| void SCCPInstVisitor::visitFreezeInst(FreezeInst &I) { |
| // If this freeze returns a struct, just mark the result overdefined. |
| // TODO: We could do a lot better than this. |
| if (I.getType()->isStructTy()) |
| return (void)markOverdefined(&I); |
| |
| ValueLatticeElement V0State = getValueState(I.getOperand(0)); |
| ValueLatticeElement &IV = ValueState[&I]; |
| // resolvedUndefsIn might mark I as overdefined. Bail out, even if we would |
| // discover a concrete value later. |
| if (SCCPSolver::isOverdefined(IV)) |
| return (void)markOverdefined(&I); |
| |
| // If something is unknown/undef, wait for it to resolve. |
| if (V0State.isUnknownOrUndef()) |
| return; |
| |
| if (SCCPSolver::isConstant(V0State) && |
| isGuaranteedNotToBeUndefOrPoison(getConstant(V0State, I.getType()))) |
| return (void)markConstant(IV, &I, getConstant(V0State, I.getType())); |
| |
| markOverdefined(&I); |
| } |
| |
| // Handle Binary Operators. |
| void SCCPInstVisitor::visitBinaryOperator(Instruction &I) { |
| ValueLatticeElement V1State = getValueState(I.getOperand(0)); |
| ValueLatticeElement V2State = getValueState(I.getOperand(1)); |
| |
| ValueLatticeElement &IV = ValueState[&I]; |
| if (IV.isOverdefined()) |
| return; |
| |
| // If something is undef, wait for it to resolve. |
| if (V1State.isUnknownOrUndef() || V2State.isUnknownOrUndef()) |
| return; |
| |
| if (V1State.isOverdefined() && V2State.isOverdefined()) |
| return (void)markOverdefined(&I); |
| |
| // If either of the operands is a constant, try to fold it to a constant. |
| // TODO: Use information from notconstant better. |
| if ((V1State.isConstant() || V2State.isConstant())) { |
| Value *V1 = SCCPSolver::isConstant(V1State) |
| ? getConstant(V1State, I.getOperand(0)->getType()) |
| : I.getOperand(0); |
| Value *V2 = SCCPSolver::isConstant(V2State) |
| ? getConstant(V2State, I.getOperand(1)->getType()) |
| : I.getOperand(1); |
| Value *R = simplifyBinOp(I.getOpcode(), V1, V2, SimplifyQuery(DL)); |
| auto *C = dyn_cast_or_null<Constant>(R); |
| if (C) { |
| // Conservatively assume that the result may be based on operands that may |
| // be undef. Note that we use mergeInValue to combine the constant with |
| // the existing lattice value for I, as different constants might be found |
| // after one of the operands go to overdefined, e.g. due to one operand |
| // being a special floating value. |
| ValueLatticeElement NewV; |
| NewV.markConstant(C, /*MayIncludeUndef=*/true); |
| return (void)mergeInValue(&I, NewV); |
| } |
| } |
| |
| // Only use ranges for binary operators on integers. |
| if (!I.getType()->isIntegerTy()) |
| return markOverdefined(&I); |
| |
| // Try to simplify to a constant range. |
| ConstantRange A = getConstantRange(V1State, I.getType()); |
| ConstantRange B = getConstantRange(V2State, I.getType()); |
| ConstantRange R = A.binaryOp(cast<BinaryOperator>(&I)->getOpcode(), B); |
| mergeInValue(&I, ValueLatticeElement::getRange(R)); |
| |
| // TODO: Currently we do not exploit special values that produce something |
| // better than overdefined with an overdefined operand for vector or floating |
| // point types, like and <4 x i32> overdefined, zeroinitializer. |
| } |
| |
| // Handle ICmpInst instruction. |
| void SCCPInstVisitor::visitCmpInst(CmpInst &I) { |
| // Do not cache this lookup, getValueState calls later in the function might |
| // invalidate the reference. |
| if (SCCPSolver::isOverdefined(ValueState[&I])) |
| return (void)markOverdefined(&I); |
| |
| Value *Op1 = I.getOperand(0); |
| Value *Op2 = I.getOperand(1); |
| |
| // For parameters, use ParamState which includes constant range info if |
| // available. |
| auto V1State = getValueState(Op1); |
| auto V2State = getValueState(Op2); |
| |
| Constant *C = V1State.getCompare(I.getPredicate(), I.getType(), V2State, DL); |
| if (C) { |
| ValueLatticeElement CV; |
| CV.markConstant(C); |
| mergeInValue(&I, CV); |
| return; |
| } |
| |
| // If operands are still unknown, wait for it to resolve. |
| if ((V1State.isUnknownOrUndef() || V2State.isUnknownOrUndef()) && |
| !SCCPSolver::isConstant(ValueState[&I])) |
| return; |
| |
| markOverdefined(&I); |
| } |
| |
| // Handle getelementptr instructions. If all operands are constants then we |
| // can turn this into a getelementptr ConstantExpr. |
| void SCCPInstVisitor::visitGetElementPtrInst(GetElementPtrInst &I) { |
| if (SCCPSolver::isOverdefined(ValueState[&I])) |
| return (void)markOverdefined(&I); |
| |
| SmallVector<Constant *, 8> Operands; |
| Operands.reserve(I.getNumOperands()); |
| |
| for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) { |
| ValueLatticeElement State = getValueState(I.getOperand(i)); |
| if (State.isUnknownOrUndef()) |
| return; // Operands are not resolved yet. |
| |
| if (SCCPSolver::isOverdefined(State)) |
| return (void)markOverdefined(&I); |
| |
| if (Constant *C = getConstant(State, I.getOperand(i)->getType())) { |
| Operands.push_back(C); |
| continue; |
| } |
| |
| return (void)markOverdefined(&I); |
| } |
| |
| if (Constant *C = ConstantFoldInstOperands(&I, Operands, DL)) |
| markConstant(&I, C); |
| } |
| |
| void SCCPInstVisitor::visitStoreInst(StoreInst &SI) { |
| // If this store is of a struct, ignore it. |
| if (SI.getOperand(0)->getType()->isStructTy()) |
| return; |
| |
| if (TrackedGlobals.empty() || !isa<GlobalVariable>(SI.getOperand(1))) |
| return; |
| |
| GlobalVariable *GV = cast<GlobalVariable>(SI.getOperand(1)); |
| auto I = TrackedGlobals.find(GV); |
| if (I == TrackedGlobals.end()) |
| return; |
| |
| // Get the value we are storing into the global, then merge it. |
| mergeInValue(I->second, GV, getValueState(SI.getOperand(0)), |
| ValueLatticeElement::MergeOptions().setCheckWiden(false)); |
| if (I->second.isOverdefined()) |
| TrackedGlobals.erase(I); // No need to keep tracking this! |
| } |
| |
| static ValueLatticeElement getValueFromMetadata(const Instruction *I) { |
| if (MDNode *Ranges = I->getMetadata(LLVMContext::MD_range)) |
| if (I->getType()->isIntegerTy()) |
| return ValueLatticeElement::getRange( |
| getConstantRangeFromMetadata(*Ranges)); |
| if (I->hasMetadata(LLVMContext::MD_nonnull)) |
| return ValueLatticeElement::getNot( |
| ConstantPointerNull::get(cast<PointerType>(I->getType()))); |
| return ValueLatticeElement::getOverdefined(); |
| } |
| |
| // Handle load instructions. If the operand is a constant pointer to a constant |
| // global, we can replace the load with the loaded constant value! |
| void SCCPInstVisitor::visitLoadInst(LoadInst &I) { |
| // If this load is of a struct or the load is volatile, just mark the result |
| // as overdefined. |
| if (I.getType()->isStructTy() || I.isVolatile()) |
| return (void)markOverdefined(&I); |
| |
| // resolvedUndefsIn might mark I as overdefined. Bail out, even if we would |
| // discover a concrete value later. |
| if (ValueState[&I].isOverdefined()) |
| return (void)markOverdefined(&I); |
| |
| ValueLatticeElement PtrVal = getValueState(I.getOperand(0)); |
| if (PtrVal.isUnknownOrUndef()) |
| return; // The pointer is not resolved yet! |
| |
| ValueLatticeElement &IV = ValueState[&I]; |
| |
| if (SCCPSolver::isConstant(PtrVal)) { |
| Constant *Ptr = getConstant(PtrVal, I.getOperand(0)->getType()); |
| |
| // load null is undefined. |
| if (isa<ConstantPointerNull>(Ptr)) { |
| if (NullPointerIsDefined(I.getFunction(), I.getPointerAddressSpace())) |
| return (void)markOverdefined(IV, &I); |
| else |
| return; |
| } |
| |
| // Transform load (constant global) into the value loaded. |
| if (auto *GV = dyn_cast<GlobalVariable>(Ptr)) { |
| if (!TrackedGlobals.empty()) { |
| // If we are tracking this global, merge in the known value for it. |
| auto It = TrackedGlobals.find(GV); |
| if (It != TrackedGlobals.end()) { |
| mergeInValue(IV, &I, It->second, getMaxWidenStepsOpts()); |
| return; |
| } |
| } |
| } |
| |
| // Transform load from a constant into a constant if possible. |
| if (Constant *C = ConstantFoldLoadFromConstPtr(Ptr, I.getType(), DL)) |
| return (void)markConstant(IV, &I, C); |
| } |
| |
| // Fall back to metadata. |
| mergeInValue(&I, getValueFromMetadata(&I)); |
| } |
| |
| void SCCPInstVisitor::visitCallBase(CallBase &CB) { |
| handleCallResult(CB); |
| handleCallArguments(CB); |
| } |
| |
| void SCCPInstVisitor::handleCallOverdefined(CallBase &CB) { |
| Function *F = CB.getCalledFunction(); |
| |
| // Void return and not tracking callee, just bail. |
| if (CB.getType()->isVoidTy()) |
| return; |
| |
| // Always mark struct return as overdefined. |
| if (CB.getType()->isStructTy()) |
| return (void)markOverdefined(&CB); |
| |
| // Otherwise, if we have a single return value case, and if the function is |
| // a declaration, maybe we can constant fold it. |
| if (F && F->isDeclaration() && canConstantFoldCallTo(&CB, F)) { |
| SmallVector<Constant *, 8> Operands; |
| for (const Use &A : CB.args()) { |
| if (A.get()->getType()->isStructTy()) |
| return markOverdefined(&CB); // Can't handle struct args. |
| if (A.get()->getType()->isMetadataTy()) |
| continue; // Carried in CB, not allowed in Operands. |
| ValueLatticeElement State = getValueState(A); |
| |
| if (State.isUnknownOrUndef()) |
| return; // Operands are not resolved yet. |
| if (SCCPSolver::isOverdefined(State)) |
| return (void)markOverdefined(&CB); |
| assert(SCCPSolver::isConstant(State) && "Unknown state!"); |
| Operands.push_back(getConstant(State, A->getType())); |
| } |
| |
| if (SCCPSolver::isOverdefined(getValueState(&CB))) |
| return (void)markOverdefined(&CB); |
| |
| // If we can constant fold this, mark the result of the call as a |
| // constant. |
| if (Constant *C = ConstantFoldCall(&CB, F, Operands, &GetTLI(*F))) |
| return (void)markConstant(&CB, C); |
| } |
| |
| // Fall back to metadata. |
| mergeInValue(&CB, getValueFromMetadata(&CB)); |
| } |
| |
| void SCCPInstVisitor::handleCallArguments(CallBase &CB) { |
| Function *F = CB.getCalledFunction(); |
| // If this is a local function that doesn't have its address taken, mark its |
| // entry block executable and merge in the actual arguments to the call into |
| // the formal arguments of the function. |
| if (TrackingIncomingArguments.count(F)) { |
| markBlockExecutable(&F->front()); |
| |
| // Propagate information from this call site into the callee. |
| auto CAI = CB.arg_begin(); |
| for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E; |
| ++AI, ++CAI) { |
| // If this argument is byval, and if the function is not readonly, there |
| // will be an implicit copy formed of the input aggregate. |
| if (AI->hasByValAttr() && !F->onlyReadsMemory()) { |
| markOverdefined(&*AI); |
| continue; |
| } |
| |
| if (auto *STy = dyn_cast<StructType>(AI->getType())) { |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { |
| ValueLatticeElement CallArg = getStructValueState(*CAI, i); |
| mergeInValue(getStructValueState(&*AI, i), &*AI, CallArg, |
| getMaxWidenStepsOpts()); |
| } |
| } else |
| mergeInValue(&*AI, getValueState(*CAI), getMaxWidenStepsOpts()); |
| } |
| } |
| } |
| |
| void SCCPInstVisitor::handleCallResult(CallBase &CB) { |
| Function *F = CB.getCalledFunction(); |
| |
| if (auto *II = dyn_cast<IntrinsicInst>(&CB)) { |
| if (II->getIntrinsicID() == Intrinsic::ssa_copy) { |
| if (ValueState[&CB].isOverdefined()) |
| return; |
| |
| Value *CopyOf = CB.getOperand(0); |
| ValueLatticeElement CopyOfVal = getValueState(CopyOf); |
| const auto *PI = getPredicateInfoFor(&CB); |
| assert(PI && "Missing predicate info for ssa.copy"); |
| |
| const std::optional<PredicateConstraint> &Constraint = |
| PI->getConstraint(); |
| if (!Constraint) { |
| mergeInValue(ValueState[&CB], &CB, CopyOfVal); |
| return; |
| } |
| |
| CmpInst::Predicate Pred = Constraint->Predicate; |
| Value *OtherOp = Constraint->OtherOp; |
| |
| // Wait until OtherOp is resolved. |
| if (getValueState(OtherOp).isUnknown()) { |
| addAdditionalUser(OtherOp, &CB); |
| return; |
| } |
| |
| ValueLatticeElement CondVal = getValueState(OtherOp); |
| ValueLatticeElement &IV = ValueState[&CB]; |
| if (CondVal.isConstantRange() || CopyOfVal.isConstantRange()) { |
| auto ImposedCR = |
| ConstantRange::getFull(DL.getTypeSizeInBits(CopyOf->getType())); |
| |
| // Get the range imposed by the condition. |
| if (CondVal.isConstantRange()) |
| ImposedCR = ConstantRange::makeAllowedICmpRegion( |
| Pred, CondVal.getConstantRange()); |
| |
| // Combine range info for the original value with the new range from the |
| // condition. |
| auto CopyOfCR = getConstantRange(CopyOfVal, CopyOf->getType()); |
| auto NewCR = ImposedCR.intersectWith(CopyOfCR); |
| // If the existing information is != x, do not use the information from |
| // a chained predicate, as the != x information is more likely to be |
| // helpful in practice. |
| if (!CopyOfCR.contains(NewCR) && CopyOfCR.getSingleMissingElement()) |
| NewCR = CopyOfCR; |
| |
| // The new range is based on a branch condition. That guarantees that |
| // neither of the compare operands can be undef in the branch targets, |
| // unless we have conditions that are always true/false (e.g. icmp ule |
| // i32, %a, i32_max). For the latter overdefined/empty range will be |
| // inferred, but the branch will get folded accordingly anyways. |
| addAdditionalUser(OtherOp, &CB); |
| mergeInValue( |
| IV, &CB, |
| ValueLatticeElement::getRange(NewCR, /*MayIncludeUndef*/ false)); |
| return; |
| } else if (Pred == CmpInst::ICMP_EQ && |
| (CondVal.isConstant() || CondVal.isNotConstant())) { |
| // For non-integer values or integer constant expressions, only |
| // propagate equal constants or not-constants. |
| addAdditionalUser(OtherOp, &CB); |
| mergeInValue(IV, &CB, CondVal); |
| return; |
| } else if (Pred == CmpInst::ICMP_NE && CondVal.isConstant()) { |
| // Propagate inequalities. |
| addAdditionalUser(OtherOp, &CB); |
| mergeInValue(IV, &CB, |
| ValueLatticeElement::getNot(CondVal.getConstant())); |
| return; |
| } |
| |
| return (void)mergeInValue(IV, &CB, CopyOfVal); |
| } |
| |
| if (ConstantRange::isIntrinsicSupported(II->getIntrinsicID())) { |
| // Compute result range for intrinsics supported by ConstantRange. |
| // Do this even if we don't know a range for all operands, as we may |
| // still know something about the result range, e.g. of abs(x). |
| SmallVector<ConstantRange, 2> OpRanges; |
| for (Value *Op : II->args()) { |
| const ValueLatticeElement &State = getValueState(Op); |
| if (State.isUnknownOrUndef()) |
| return; |
| OpRanges.push_back(getConstantRange(State, Op->getType())); |
| } |
| |
| ConstantRange Result = |
| ConstantRange::intrinsic(II->getIntrinsicID(), OpRanges); |
| return (void)mergeInValue(II, ValueLatticeElement::getRange(Result)); |
| } |
| } |
| |
| // The common case is that we aren't tracking the callee, either because we |
| // are not doing interprocedural analysis or the callee is indirect, or is |
| // external. Handle these cases first. |
| if (!F || F->isDeclaration()) |
| return handleCallOverdefined(CB); |
| |
| // If this is a single/zero retval case, see if we're tracking the function. |
| if (auto *STy = dyn_cast<StructType>(F->getReturnType())) { |
| if (!MRVFunctionsTracked.count(F)) |
| return handleCallOverdefined(CB); // Not tracking this callee. |
| |
| // If we are tracking this callee, propagate the result of the function |
| // into this call site. |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) |
| mergeInValue(getStructValueState(&CB, i), &CB, |
| TrackedMultipleRetVals[std::make_pair(F, i)], |
| getMaxWidenStepsOpts()); |
| } else { |
| auto TFRVI = TrackedRetVals.find(F); |
| if (TFRVI == TrackedRetVals.end()) |
| return handleCallOverdefined(CB); // Not tracking this callee. |
| |
| // If so, propagate the return value of the callee into this call result. |
| mergeInValue(&CB, TFRVI->second, getMaxWidenStepsOpts()); |
| } |
| } |
| |
| void SCCPInstVisitor::solve() { |
| // Process the work lists until they are empty! |
| while (!BBWorkList.empty() || !InstWorkList.empty() || |
| !OverdefinedInstWorkList.empty()) { |
| // Process the overdefined instruction's work list first, which drives other |
| // things to overdefined more quickly. |
| while (!OverdefinedInstWorkList.empty()) { |
| Value *I = OverdefinedInstWorkList.pop_back_val(); |
| Invalidated.erase(I); |
| |
| LLVM_DEBUG(dbgs() << "\nPopped off OI-WL: " << *I << '\n'); |
| |
| // "I" got into the work list because it either made the transition from |
| // bottom to constant, or to overdefined. |
| // |
| // Anything on this worklist that is overdefined need not be visited |
| // since all of its users will have already been marked as overdefined |
| // Update all of the users of this instruction's value. |
| // |
| markUsersAsChanged(I); |
| } |
| |
| // Process the instruction work list. |
| while (!InstWorkList.empty()) { |
| Value *I = InstWorkList.pop_back_val(); |
| Invalidated.erase(I); |
| |
| LLVM_DEBUG(dbgs() << "\nPopped off I-WL: " << *I << '\n'); |
| |
| // "I" got into the work list because it made the transition from undef to |
| // constant. |
| // |
| // Anything on this worklist that is overdefined need not be visited |
| // since all of its users will have already been marked as overdefined. |
| // Update all of the users of this instruction's value. |
| // |
| if (I->getType()->isStructTy() || !getValueState(I).isOverdefined()) |
| markUsersAsChanged(I); |
| } |
| |
| // Process the basic block work list. |
| while (!BBWorkList.empty()) { |
| BasicBlock *BB = BBWorkList.pop_back_val(); |
| |
| LLVM_DEBUG(dbgs() << "\nPopped off BBWL: " << *BB << '\n'); |
| |
| // Notify all instructions in this basic block that they are newly |
| // executable. |
| visit(BB); |
| } |
| } |
| } |
| |
| bool SCCPInstVisitor::resolvedUndef(Instruction &I) { |
| // Look for instructions which produce undef values. |
| if (I.getType()->isVoidTy()) |
| return false; |
| |
| if (auto *STy = dyn_cast<StructType>(I.getType())) { |
| // Only a few things that can be structs matter for undef. |
| |
| // Tracked calls must never be marked overdefined in resolvedUndefsIn. |
| if (auto *CB = dyn_cast<CallBase>(&I)) |
| if (Function *F = CB->getCalledFunction()) |
| if (MRVFunctionsTracked.count(F)) |
| return false; |
| |
| // extractvalue and insertvalue don't need to be marked; they are |
| // tracked as precisely as their operands. |
| if (isa<ExtractValueInst>(I) || isa<InsertValueInst>(I)) |
| return false; |
| // Send the results of everything else to overdefined. We could be |
| // more precise than this but it isn't worth bothering. |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { |
| ValueLatticeElement &LV = getStructValueState(&I, i); |
| if (LV.isUnknown()) { |
| markOverdefined(LV, &I); |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| ValueLatticeElement &LV = getValueState(&I); |
| if (!LV.isUnknown()) |
| return false; |
| |
| // There are two reasons a call can have an undef result |
| // 1. It could be tracked. |
| // 2. It could be constant-foldable. |
| // Because of the way we solve return values, tracked calls must |
| // never be marked overdefined in resolvedUndefsIn. |
| if (auto *CB = dyn_cast<CallBase>(&I)) |
| if (Function *F = CB->getCalledFunction()) |
| if (TrackedRetVals.count(F)) |
| return false; |
| |
| if (isa<LoadInst>(I)) { |
| // A load here means one of two things: a load of undef from a global, |
| // a load from an unknown pointer. Either way, having it return undef |
| // is okay. |
| return false; |
| } |
| |
| markOverdefined(&I); |
| return true; |
| } |
| |
| /// While solving the dataflow for a function, we don't compute a result for |
| /// operations with an undef operand, to allow undef to be lowered to a |
| /// constant later. For example, constant folding of "zext i8 undef to i16" |
| /// would result in "i16 0", and if undef is later lowered to "i8 1", then the |
| /// zext result would become "i16 1" and would result into an overdefined |
| /// lattice value once merged with the previous result. Not computing the |
| /// result of the zext (treating undef the same as unknown) allows us to handle |
| /// a later undef->constant lowering more optimally. |
| /// |
| /// However, if the operand remains undef when the solver returns, we do need |
| /// to assign some result to the instruction (otherwise we would treat it as |
| /// unreachable). For simplicity, we mark any instructions that are still |
| /// unknown as overdefined. |
| bool SCCPInstVisitor::resolvedUndefsIn(Function &F) { |
| bool MadeChange = false; |
| for (BasicBlock &BB : F) { |
| if (!BBExecutable.count(&BB)) |
| continue; |
| |
| for (Instruction &I : BB) |
| MadeChange |= resolvedUndef(I); |
| } |
| |
| LLVM_DEBUG(if (MadeChange) dbgs() |
| << "\nResolved undefs in " << F.getName() << '\n'); |
| |
| return MadeChange; |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // |
| // SCCPSolver implementations |
| // |
| SCCPSolver::SCCPSolver( |
| const DataLayout &DL, |
| std::function<const TargetLibraryInfo &(Function &)> GetTLI, |
| LLVMContext &Ctx) |
| : Visitor(new SCCPInstVisitor(DL, std::move(GetTLI), Ctx)) {} |
| |
| SCCPSolver::~SCCPSolver() = default; |
| |
| void SCCPSolver::addPredicateInfo(Function &F, DominatorTree &DT, |
| AssumptionCache &AC) { |
| Visitor->addPredicateInfo(F, DT, AC); |
| } |
| |
| bool SCCPSolver::markBlockExecutable(BasicBlock *BB) { |
| return Visitor->markBlockExecutable(BB); |
| } |
| |
| const PredicateBase *SCCPSolver::getPredicateInfoFor(Instruction *I) { |
| return Visitor->getPredicateInfoFor(I); |
| } |
| |
| void SCCPSolver::trackValueOfGlobalVariable(GlobalVariable *GV) { |
| Visitor->trackValueOfGlobalVariable(GV); |
| } |
| |
| void SCCPSolver::addTrackedFunction(Function *F) { |
| Visitor->addTrackedFunction(F); |
| } |
| |
| void SCCPSolver::addToMustPreserveReturnsInFunctions(Function *F) { |
| Visitor->addToMustPreserveReturnsInFunctions(F); |
| } |
| |
| bool SCCPSolver::mustPreserveReturn(Function *F) { |
| return Visitor->mustPreserveReturn(F); |
| } |
| |
| void SCCPSolver::addArgumentTrackedFunction(Function *F) { |
| Visitor->addArgumentTrackedFunction(F); |
| } |
| |
| bool SCCPSolver::isArgumentTrackedFunction(Function *F) { |
| return Visitor->isArgumentTrackedFunction(F); |
| } |
| |
| void SCCPSolver::solve() { Visitor->solve(); } |
| |
| bool SCCPSolver::resolvedUndefsIn(Function &F) { |
| return Visitor->resolvedUndefsIn(F); |
| } |
| |
| void SCCPSolver::solveWhileResolvedUndefsIn(Module &M) { |
| Visitor->solveWhileResolvedUndefsIn(M); |
| } |
| |
| void |
| SCCPSolver::solveWhileResolvedUndefsIn(SmallVectorImpl<Function *> &WorkList) { |
| Visitor->solveWhileResolvedUndefsIn(WorkList); |
| } |
| |
| void SCCPSolver::solveWhileResolvedUndefs() { |
| Visitor->solveWhileResolvedUndefs(); |
| } |
| |
| bool SCCPSolver::isBlockExecutable(BasicBlock *BB) const { |
| return Visitor->isBlockExecutable(BB); |
| } |
| |
| bool SCCPSolver::isEdgeFeasible(BasicBlock *From, BasicBlock *To) const { |
| return Visitor->isEdgeFeasible(From, To); |
| } |
| |
| std::vector<ValueLatticeElement> |
| SCCPSolver::getStructLatticeValueFor(Value *V) const { |
| return Visitor->getStructLatticeValueFor(V); |
| } |
| |
| void SCCPSolver::removeLatticeValueFor(Value *V) { |
| return Visitor->removeLatticeValueFor(V); |
| } |
| |
| void SCCPSolver::resetLatticeValueFor(CallBase *Call) { |
| Visitor->resetLatticeValueFor(Call); |
| } |
| |
| const ValueLatticeElement &SCCPSolver::getLatticeValueFor(Value *V) const { |
| return Visitor->getLatticeValueFor(V); |
| } |
| |
| const MapVector<Function *, ValueLatticeElement> & |
| SCCPSolver::getTrackedRetVals() { |
| return Visitor->getTrackedRetVals(); |
| } |
| |
| const DenseMap<GlobalVariable *, ValueLatticeElement> & |
| SCCPSolver::getTrackedGlobals() { |
| return Visitor->getTrackedGlobals(); |
| } |
| |
| const SmallPtrSet<Function *, 16> SCCPSolver::getMRVFunctionsTracked() { |
| return Visitor->getMRVFunctionsTracked(); |
| } |
| |
| void SCCPSolver::markOverdefined(Value *V) { Visitor->markOverdefined(V); } |
| |
| bool SCCPSolver::isStructLatticeConstant(Function *F, StructType *STy) { |
| return Visitor->isStructLatticeConstant(F, STy); |
| } |
| |
| Constant *SCCPSolver::getConstant(const ValueLatticeElement &LV, |
| Type *Ty) const { |
| return Visitor->getConstant(LV, Ty); |
| } |
| |
| Constant *SCCPSolver::getConstantOrNull(Value *V) const { |
| return Visitor->getConstantOrNull(V); |
| } |
| |
| SmallPtrSetImpl<Function *> &SCCPSolver::getArgumentTrackedFunctions() { |
| return Visitor->getArgumentTrackedFunctions(); |
| } |
| |
| void SCCPSolver::setLatticeValueForSpecializationArguments(Function *F, |
| const SmallVectorImpl<ArgInfo> &Args) { |
| Visitor->setLatticeValueForSpecializationArguments(F, Args); |
| } |
| |
| void SCCPSolver::markFunctionUnreachable(Function *F) { |
| Visitor->markFunctionUnreachable(F); |
| } |
| |
| void SCCPSolver::visit(Instruction *I) { Visitor->visit(I); } |
| |
| void SCCPSolver::visitCall(CallInst &I) { Visitor->visitCall(I); } |