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Diffstat (limited to 'llvm/lib/Transforms/Utils/Local.cpp')
| -rw-r--r-- | llvm/lib/Transforms/Utils/Local.cpp | 2991 |
1 files changed, 2991 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp new file mode 100644 index 0000000000000..5bcd05757ec13 --- /dev/null +++ b/llvm/lib/Transforms/Utils/Local.cpp @@ -0,0 +1,2991 @@ +//===- Local.cpp - Functions to perform local transformations -------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// This family of functions perform various local transformations to the +// program. +// +//===----------------------------------------------------------------------===// + +#include "llvm/Transforms/Utils/Local.h" +#include "llvm/ADT/APInt.h" +#include "llvm/ADT/DenseMap.h" +#include "llvm/ADT/DenseMapInfo.h" +#include "llvm/ADT/DenseSet.h" +#include "llvm/ADT/Hashing.h" +#include "llvm/ADT/None.h" +#include "llvm/ADT/Optional.h" +#include "llvm/ADT/STLExtras.h" +#include "llvm/ADT/SetVector.h" +#include "llvm/ADT/SmallPtrSet.h" +#include "llvm/ADT/SmallVector.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/ADT/TinyPtrVector.h" +#include "llvm/Analysis/ConstantFolding.h" +#include "llvm/Analysis/DomTreeUpdater.h" +#include "llvm/Analysis/EHPersonalities.h" +#include "llvm/Analysis/InstructionSimplify.h" +#include "llvm/Analysis/LazyValueInfo.h" +#include "llvm/Analysis/MemoryBuiltins.h" +#include "llvm/Analysis/MemorySSAUpdater.h" +#include "llvm/Analysis/TargetLibraryInfo.h" +#include "llvm/Analysis/ValueTracking.h" +#include "llvm/Analysis/VectorUtils.h" +#include "llvm/BinaryFormat/Dwarf.h" +#include "llvm/IR/Argument.h" +#include "llvm/IR/Attributes.h" +#include "llvm/IR/BasicBlock.h" +#include "llvm/IR/CFG.h" +#include "llvm/IR/CallSite.h" +#include "llvm/IR/Constant.h" +#include "llvm/IR/ConstantRange.h" +#include "llvm/IR/Constants.h" +#include "llvm/IR/DIBuilder.h" +#include "llvm/IR/DataLayout.h" +#include "llvm/IR/DebugInfoMetadata.h" +#include "llvm/IR/DebugLoc.h" +#include "llvm/IR/DerivedTypes.h" +#include "llvm/IR/Dominators.h" +#include "llvm/IR/Function.h" +#include "llvm/IR/GetElementPtrTypeIterator.h" +#include "llvm/IR/GlobalObject.h" +#include "llvm/IR/IRBuilder.h" +#include "llvm/IR/InstrTypes.h" +#include "llvm/IR/Instruction.h" +#include "llvm/IR/Instructions.h" +#include "llvm/IR/IntrinsicInst.h" +#include "llvm/IR/Intrinsics.h" +#include "llvm/IR/LLVMContext.h" +#include "llvm/IR/MDBuilder.h" +#include "llvm/IR/Metadata.h" +#include "llvm/IR/Module.h" +#include "llvm/IR/Operator.h" +#include "llvm/IR/PatternMatch.h" +#include "llvm/IR/Type.h" +#include "llvm/IR/Use.h" +#include "llvm/IR/User.h" +#include "llvm/IR/Value.h" +#include "llvm/IR/ValueHandle.h" +#include "llvm/Support/Casting.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/ErrorHandling.h" +#include "llvm/Support/KnownBits.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/Transforms/Utils/ValueMapper.h" +#include <algorithm> +#include <cassert> +#include <climits> +#include <cstdint> +#include <iterator> +#include <map> +#include <utility> + +using namespace llvm; +using namespace llvm::PatternMatch; + +#define DEBUG_TYPE "local" + +STATISTIC(NumRemoved, "Number of unreachable basic blocks removed"); + +// Max recursion depth for collectBitParts used when detecting bswap and +// bitreverse idioms +static const unsigned BitPartRecursionMaxDepth = 64; + +//===----------------------------------------------------------------------===// +// Local constant propagation. +// + +/// ConstantFoldTerminator - If a terminator instruction is predicated on a +/// constant value, convert it into an unconditional branch to the constant +/// destination. This is a nontrivial operation because the successors of this +/// basic block must have their PHI nodes updated. +/// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch +/// conditions and indirectbr addresses this might make dead if +/// DeleteDeadConditions is true. +bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions, + const TargetLibraryInfo *TLI, + DomTreeUpdater *DTU) { + Instruction *T = BB->getTerminator(); + IRBuilder<> Builder(T); + + // Branch - See if we are conditional jumping on constant + if (auto *BI = dyn_cast<BranchInst>(T)) { + if (BI->isUnconditional()) return false; // Can't optimize uncond branch + BasicBlock *Dest1 = BI->getSuccessor(0); + BasicBlock *Dest2 = BI->getSuccessor(1); + + if (auto *Cond = dyn_cast<ConstantInt>(BI->getCondition())) { + // Are we branching on constant? + // YES. Change to unconditional branch... + BasicBlock *Destination = Cond->getZExtValue() ? Dest1 : Dest2; + BasicBlock *OldDest = Cond->getZExtValue() ? Dest2 : Dest1; + + // Let the basic block know that we are letting go of it. Based on this, + // it will adjust it's PHI nodes. + OldDest->removePredecessor(BB); + + // Replace the conditional branch with an unconditional one. + Builder.CreateBr(Destination); + BI->eraseFromParent(); + if (DTU) + DTU->applyUpdatesPermissive({{DominatorTree::Delete, BB, OldDest}}); + return true; + } + + if (Dest2 == Dest1) { // Conditional branch to same location? + // This branch matches something like this: + // br bool %cond, label %Dest, label %Dest + // and changes it into: br label %Dest + + // Let the basic block know that we are letting go of one copy of it. + assert(BI->getParent() && "Terminator not inserted in block!"); + Dest1->removePredecessor(BI->getParent()); + + // Replace the conditional branch with an unconditional one. + Builder.CreateBr(Dest1); + Value *Cond = BI->getCondition(); + BI->eraseFromParent(); + if (DeleteDeadConditions) + RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI); + return true; + } + return false; + } + + if (auto *SI = dyn_cast<SwitchInst>(T)) { + // If we are switching on a constant, we can convert the switch to an + // unconditional branch. + auto *CI = dyn_cast<ConstantInt>(SI->getCondition()); + BasicBlock *DefaultDest = SI->getDefaultDest(); + BasicBlock *TheOnlyDest = DefaultDest; + + // If the default is unreachable, ignore it when searching for TheOnlyDest. + if (isa<UnreachableInst>(DefaultDest->getFirstNonPHIOrDbg()) && + SI->getNumCases() > 0) { + TheOnlyDest = SI->case_begin()->getCaseSuccessor(); + } + + // Figure out which case it goes to. + for (auto i = SI->case_begin(), e = SI->case_end(); i != e;) { + // Found case matching a constant operand? + if (i->getCaseValue() == CI) { + TheOnlyDest = i->getCaseSuccessor(); + break; + } + + // Check to see if this branch is going to the same place as the default + // dest. If so, eliminate it as an explicit compare. + if (i->getCaseSuccessor() == DefaultDest) { + MDNode *MD = SI->getMetadata(LLVMContext::MD_prof); + unsigned NCases = SI->getNumCases(); + // Fold the case metadata into the default if there will be any branches + // left, unless the metadata doesn't match the switch. + if (NCases > 1 && MD && MD->getNumOperands() == 2 + NCases) { + // Collect branch weights into a vector. + SmallVector<uint32_t, 8> Weights; + for (unsigned MD_i = 1, MD_e = MD->getNumOperands(); MD_i < MD_e; + ++MD_i) { + auto *CI = mdconst::extract<ConstantInt>(MD->getOperand(MD_i)); + Weights.push_back(CI->getValue().getZExtValue()); + } + // Merge weight of this case to the default weight. + unsigned idx = i->getCaseIndex(); + Weights[0] += Weights[idx+1]; + // Remove weight for this case. + std::swap(Weights[idx+1], Weights.back()); + Weights.pop_back(); + SI->setMetadata(LLVMContext::MD_prof, + MDBuilder(BB->getContext()). + createBranchWeights(Weights)); + } + // Remove this entry. + BasicBlock *ParentBB = SI->getParent(); + DefaultDest->removePredecessor(ParentBB); + i = SI->removeCase(i); + e = SI->case_end(); + if (DTU) + DTU->applyUpdatesPermissive( + {{DominatorTree::Delete, ParentBB, DefaultDest}}); + continue; + } + + // Otherwise, check to see if the switch only branches to one destination. + // We do this by reseting "TheOnlyDest" to null when we find two non-equal + // destinations. + if (i->getCaseSuccessor() != TheOnlyDest) + TheOnlyDest = nullptr; + + // Increment this iterator as we haven't removed the case. + ++i; + } + + if (CI && !TheOnlyDest) { + // Branching on a constant, but not any of the cases, go to the default + // successor. + TheOnlyDest = SI->getDefaultDest(); + } + + // If we found a single destination that we can fold the switch into, do so + // now. + if (TheOnlyDest) { + // Insert the new branch. + Builder.CreateBr(TheOnlyDest); + BasicBlock *BB = SI->getParent(); + std::vector <DominatorTree::UpdateType> Updates; + if (DTU) + Updates.reserve(SI->getNumSuccessors() - 1); + + // Remove entries from PHI nodes which we no longer branch to... + for (BasicBlock *Succ : successors(SI)) { + // Found case matching a constant operand? + if (Succ == TheOnlyDest) { + TheOnlyDest = nullptr; // Don't modify the first branch to TheOnlyDest + } else { + Succ->removePredecessor(BB); + if (DTU) + Updates.push_back({DominatorTree::Delete, BB, Succ}); + } + } + + // Delete the old switch. + Value *Cond = SI->getCondition(); + SI->eraseFromParent(); + if (DeleteDeadConditions) + RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI); + if (DTU) + DTU->applyUpdatesPermissive(Updates); + return true; + } + + if (SI->getNumCases() == 1) { + // Otherwise, we can fold this switch into a conditional branch + // instruction if it has only one non-default destination. + auto FirstCase = *SI->case_begin(); + Value *Cond = Builder.CreateICmpEQ(SI->getCondition(), + FirstCase.getCaseValue(), "cond"); + + // Insert the new branch. + BranchInst *NewBr = Builder.CreateCondBr(Cond, + FirstCase.getCaseSuccessor(), + SI->getDefaultDest()); + MDNode *MD = SI->getMetadata(LLVMContext::MD_prof); + if (MD && MD->getNumOperands() == 3) { + ConstantInt *SICase = + mdconst::dyn_extract<ConstantInt>(MD->getOperand(2)); + ConstantInt *SIDef = + mdconst::dyn_extract<ConstantInt>(MD->getOperand(1)); + assert(SICase && SIDef); + // The TrueWeight should be the weight for the single case of SI. + NewBr->setMetadata(LLVMContext::MD_prof, + MDBuilder(BB->getContext()). + createBranchWeights(SICase->getValue().getZExtValue(), + SIDef->getValue().getZExtValue())); + } + + // Update make.implicit metadata to the newly-created conditional branch. + MDNode *MakeImplicitMD = SI->getMetadata(LLVMContext::MD_make_implicit); + if (MakeImplicitMD) + NewBr->setMetadata(LLVMContext::MD_make_implicit, MakeImplicitMD); + + // Delete the old switch. + SI->eraseFromParent(); + return true; + } + return false; + } + + if (auto *IBI = dyn_cast<IndirectBrInst>(T)) { + // indirectbr blockaddress(@F, @BB) -> br label @BB + if (auto *BA = + dyn_cast<BlockAddress>(IBI->getAddress()->stripPointerCasts())) { + BasicBlock *TheOnlyDest = BA->getBasicBlock(); + std::vector <DominatorTree::UpdateType> Updates; + if (DTU) + Updates.reserve(IBI->getNumDestinations() - 1); + + // Insert the new branch. + Builder.CreateBr(TheOnlyDest); + + for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) { + if (IBI->getDestination(i) == TheOnlyDest) { + TheOnlyDest = nullptr; + } else { + BasicBlock *ParentBB = IBI->getParent(); + BasicBlock *DestBB = IBI->getDestination(i); + DestBB->removePredecessor(ParentBB); + if (DTU) + Updates.push_back({DominatorTree::Delete, ParentBB, DestBB}); + } + } + Value *Address = IBI->getAddress(); + IBI->eraseFromParent(); + if (DeleteDeadConditions) + // Delete pointer cast instructions. + RecursivelyDeleteTriviallyDeadInstructions(Address, TLI); + + // Also zap the blockaddress constant if there are no users remaining, + // otherwise the destination is still marked as having its address taken. + if (BA->use_empty()) + BA->destroyConstant(); + + // If we didn't find our destination in the IBI successor list, then we + // have undefined behavior. Replace the unconditional branch with an + // 'unreachable' instruction. + if (TheOnlyDest) { + BB->getTerminator()->eraseFromParent(); + new UnreachableInst(BB->getContext(), BB); + } + + if (DTU) + DTU->applyUpdatesPermissive(Updates); + return true; + } + } + + return false; +} + +//===----------------------------------------------------------------------===// +// Local dead code elimination. +// + +/// isInstructionTriviallyDead - Return true if the result produced by the +/// instruction is not used, and the instruction has no side effects. +/// +bool llvm::isInstructionTriviallyDead(Instruction *I, + const TargetLibraryInfo *TLI) { + if (!I->use_empty()) + return false; + return wouldInstructionBeTriviallyDead(I, TLI); +} + +bool llvm::wouldInstructionBeTriviallyDead(Instruction *I, + const TargetLibraryInfo *TLI) { + if (I->isTerminator()) + return false; + + // We don't want the landingpad-like instructions removed by anything this + // general. + if (I->isEHPad()) + return false; + + // We don't want debug info removed by anything this general, unless + // debug info is empty. + if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(I)) { + if (DDI->getAddress()) + return false; + return true; + } + if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(I)) { + if (DVI->getValue()) + return false; + return true; + } + if (DbgLabelInst *DLI = dyn_cast<DbgLabelInst>(I)) { + if (DLI->getLabel()) + return false; + return true; + } + + if (!I->mayHaveSideEffects()) + return true; + + // Special case intrinsics that "may have side effects" but can be deleted + // when dead. + if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { + // Safe to delete llvm.stacksave and launder.invariant.group if dead. + if (II->getIntrinsicID() == Intrinsic::stacksave || + II->getIntrinsicID() == Intrinsic::launder_invariant_group) + return true; + + // Lifetime intrinsics are dead when their right-hand is undef. + if (II->isLifetimeStartOrEnd()) + return isa<UndefValue>(II->getArgOperand(1)); + + // Assumptions are dead if their condition is trivially true. Guards on + // true are operationally no-ops. In the future we can consider more + // sophisticated tradeoffs for guards considering potential for check + // widening, but for now we keep things simple. + if (II->getIntrinsicID() == Intrinsic::assume || + II->getIntrinsicID() == Intrinsic::experimental_guard) { + if (ConstantInt *Cond = dyn_cast<ConstantInt>(II->getArgOperand(0))) + return !Cond->isZero(); + + return false; + } + } + + if (isAllocLikeFn(I, TLI)) + return true; + + if (CallInst *CI = isFreeCall(I, TLI)) + if (Constant *C = dyn_cast<Constant>(CI->getArgOperand(0))) + return C->isNullValue() || isa<UndefValue>(C); + + if (auto *Call = dyn_cast<CallBase>(I)) + if (isMathLibCallNoop(Call, TLI)) + return true; + + return false; +} + +/// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a +/// trivially dead instruction, delete it. If that makes any of its operands +/// trivially dead, delete them too, recursively. Return true if any +/// instructions were deleted. +bool llvm::RecursivelyDeleteTriviallyDeadInstructions( + Value *V, const TargetLibraryInfo *TLI, MemorySSAUpdater *MSSAU) { + Instruction *I = dyn_cast<Instruction>(V); + if (!I || !isInstructionTriviallyDead(I, TLI)) + return false; + + SmallVector<Instruction*, 16> DeadInsts; + DeadInsts.push_back(I); + RecursivelyDeleteTriviallyDeadInstructions(DeadInsts, TLI, MSSAU); + + return true; +} + +void llvm::RecursivelyDeleteTriviallyDeadInstructions( + SmallVectorImpl<Instruction *> &DeadInsts, const TargetLibraryInfo *TLI, + MemorySSAUpdater *MSSAU) { + // Process the dead instruction list until empty. + while (!DeadInsts.empty()) { + Instruction &I = *DeadInsts.pop_back_val(); + assert(I.use_empty() && "Instructions with uses are not dead."); + assert(isInstructionTriviallyDead(&I, TLI) && + "Live instruction found in dead worklist!"); + + // Don't lose the debug info while deleting the instructions. + salvageDebugInfo(I); + + // Null out all of the instruction's operands to see if any operand becomes + // dead as we go. + for (Use &OpU : I.operands()) { + Value *OpV = OpU.get(); + OpU.set(nullptr); + + if (!OpV->use_empty()) + continue; + + // If the operand is an instruction that became dead as we nulled out the + // operand, and if it is 'trivially' dead, delete it in a future loop + // iteration. + if (Instruction *OpI = dyn_cast<Instruction>(OpV)) + if (isInstructionTriviallyDead(OpI, TLI)) + DeadInsts.push_back(OpI); + } + if (MSSAU) + MSSAU->removeMemoryAccess(&I); + + I.eraseFromParent(); + } +} + +bool llvm::replaceDbgUsesWithUndef(Instruction *I) { + SmallVector<DbgVariableIntrinsic *, 1> DbgUsers; + findDbgUsers(DbgUsers, I); + for (auto *DII : DbgUsers) { + Value *Undef = UndefValue::get(I->getType()); + DII->setOperand(0, MetadataAsValue::get(DII->getContext(), + ValueAsMetadata::get(Undef))); + } + return !DbgUsers.empty(); +} + +/// areAllUsesEqual - Check whether the uses of a value are all the same. +/// This is similar to Instruction::hasOneUse() except this will also return +/// true when there are no uses or multiple uses that all refer to the same +/// value. +static bool areAllUsesEqual(Instruction *I) { + Value::user_iterator UI = I->user_begin(); + Value::user_iterator UE = I->user_end(); + if (UI == UE) + return true; + + User *TheUse = *UI; + for (++UI; UI != UE; ++UI) { + if (*UI != TheUse) + return false; + } + return true; +} + +/// RecursivelyDeleteDeadPHINode - If the specified value is an effectively +/// dead PHI node, due to being a def-use chain of single-use nodes that +/// either forms a cycle or is terminated by a trivially dead instruction, +/// delete it. If that makes any of its operands trivially dead, delete them +/// too, recursively. Return true if a change was made. +bool llvm::RecursivelyDeleteDeadPHINode(PHINode *PN, + const TargetLibraryInfo *TLI) { + SmallPtrSet<Instruction*, 4> Visited; + for (Instruction *I = PN; areAllUsesEqual(I) && !I->mayHaveSideEffects(); + I = cast<Instruction>(*I->user_begin())) { + if (I->use_empty()) + return RecursivelyDeleteTriviallyDeadInstructions(I, TLI); + + // If we find an instruction more than once, we're on a cycle that + // won't prove fruitful. + if (!Visited.insert(I).second) { + // Break the cycle and delete the instruction and its operands. + I->replaceAllUsesWith(UndefValue::get(I->getType())); + (void)RecursivelyDeleteTriviallyDeadInstructions(I, TLI); + return true; + } + } + return false; +} + +static bool +simplifyAndDCEInstruction(Instruction *I, + SmallSetVector<Instruction *, 16> &WorkList, + const DataLayout &DL, + const TargetLibraryInfo *TLI) { + if (isInstructionTriviallyDead(I, TLI)) { + salvageDebugInfo(*I); + + // Null out all of the instruction's operands to see if any operand becomes + // dead as we go. + for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) { + Value *OpV = I->getOperand(i); + I->setOperand(i, nullptr); + + if (!OpV->use_empty() || I == OpV) + continue; + + // If the operand is an instruction that became dead as we nulled out the + // operand, and if it is 'trivially' dead, delete it in a future loop + // iteration. + if (Instruction *OpI = dyn_cast<Instruction>(OpV)) + if (isInstructionTriviallyDead(OpI, TLI)) + WorkList.insert(OpI); + } + + I->eraseFromParent(); + + return true; + } + + if (Value *SimpleV = SimplifyInstruction(I, DL)) { + // Add the users to the worklist. CAREFUL: an instruction can use itself, + // in the case of a phi node. + for (User *U : I->users()) { + if (U != I) { + WorkList.insert(cast<Instruction>(U)); + } + } + + // Replace the instruction with its simplified value. + bool Changed = false; + if (!I->use_empty()) { + I->replaceAllUsesWith(SimpleV); + Changed = true; + } + if (isInstructionTriviallyDead(I, TLI)) { + I->eraseFromParent(); + Changed = true; + } + return Changed; + } + return false; +} + +/// SimplifyInstructionsInBlock - Scan the specified basic block and try to +/// simplify any instructions in it and recursively delete dead instructions. +/// +/// This returns true if it changed the code, note that it can delete +/// instructions in other blocks as well in this block. +bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB, + const TargetLibraryInfo *TLI) { + bool MadeChange = false; + const DataLayout &DL = BB->getModule()->getDataLayout(); + +#ifndef NDEBUG + // In debug builds, ensure that the terminator of the block is never replaced + // or deleted by these simplifications. The idea of simplification is that it + // cannot introduce new instructions, and there is no way to replace the + // terminator of a block without introducing a new instruction. + AssertingVH<Instruction> TerminatorVH(&BB->back()); +#endif + + SmallSetVector<Instruction *, 16> WorkList; + // Iterate over the original function, only adding insts to the worklist + // if they actually need to be revisited. This avoids having to pre-init + // the worklist with the entire function's worth of instructions. + for (BasicBlock::iterator BI = BB->begin(), E = std::prev(BB->end()); + BI != E;) { + assert(!BI->isTerminator()); + Instruction *I = &*BI; + ++BI; + + // We're visiting this instruction now, so make sure it's not in the + // worklist from an earlier visit. + if (!WorkList.count(I)) + MadeChange |= simplifyAndDCEInstruction(I, WorkList, DL, TLI); + } + + while (!WorkList.empty()) { + Instruction *I = WorkList.pop_back_val(); + MadeChange |= simplifyAndDCEInstruction(I, WorkList, DL, TLI); + } + return MadeChange; +} + +//===----------------------------------------------------------------------===// +// Control Flow Graph Restructuring. +// + +void llvm::RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred, + DomTreeUpdater *DTU) { + // This only adjusts blocks with PHI nodes. + if (!isa<PHINode>(BB->begin())) + return; + + // Remove the entries for Pred from the PHI nodes in BB, but do not simplify + // them down. This will leave us with single entry phi nodes and other phis + // that can be removed. + BB->removePredecessor(Pred, true); + + WeakTrackingVH PhiIt = &BB->front(); + while (PHINode *PN = dyn_cast<PHINode>(PhiIt)) { + PhiIt = &*++BasicBlock::iterator(cast<Instruction>(PhiIt)); + Value *OldPhiIt = PhiIt; + + if (!recursivelySimplifyInstruction(PN)) + continue; + + // If recursive simplification ended up deleting the next PHI node we would + // iterate to, then our iterator is invalid, restart scanning from the top + // of the block. + if (PhiIt != OldPhiIt) PhiIt = &BB->front(); + } + if (DTU) + DTU->applyUpdatesPermissive({{DominatorTree::Delete, Pred, BB}}); +} + +void llvm::MergeBasicBlockIntoOnlyPred(BasicBlock *DestBB, + DomTreeUpdater *DTU) { + + // If BB has single-entry PHI nodes, fold them. + while (PHINode *PN = dyn_cast<PHINode>(DestBB->begin())) { + Value *NewVal = PN->getIncomingValue(0); + // Replace self referencing PHI with undef, it must be dead. + if (NewVal == PN) NewVal = UndefValue::get(PN->getType()); + PN->replaceAllUsesWith(NewVal); + PN->eraseFromParent(); + } + + BasicBlock *PredBB = DestBB->getSinglePredecessor(); + assert(PredBB && "Block doesn't have a single predecessor!"); + + bool ReplaceEntryBB = false; + if (PredBB == &DestBB->getParent()->getEntryBlock()) + ReplaceEntryBB = true; + + // DTU updates: Collect all the edges that enter + // PredBB. These dominator edges will be redirected to DestBB. + SmallVector<DominatorTree::UpdateType, 32> Updates; + + if (DTU) { + Updates.push_back({DominatorTree::Delete, PredBB, DestBB}); + for (auto I = pred_begin(PredBB), E = pred_end(PredBB); I != E; ++I) { + Updates.push_back({DominatorTree::Delete, *I, PredBB}); + // This predecessor of PredBB may already have DestBB as a successor. + if (llvm::find(successors(*I), DestBB) == succ_end(*I)) + Updates.push_back({DominatorTree::Insert, *I, DestBB}); + } + } + + // Zap anything that took the address of DestBB. Not doing this will give the + // address an invalid value. + if (DestBB->hasAddressTaken()) { + BlockAddress *BA = BlockAddress::get(DestBB); + Constant *Replacement = + ConstantInt::get(Type::getInt32Ty(BA->getContext()), 1); + BA->replaceAllUsesWith(ConstantExpr::getIntToPtr(Replacement, + BA->getType())); + BA->destroyConstant(); + } + + // Anything that branched to PredBB now branches to DestBB. + PredBB->replaceAllUsesWith(DestBB); + + // Splice all the instructions from PredBB to DestBB. + PredBB->getTerminator()->eraseFromParent(); + DestBB->getInstList().splice(DestBB->begin(), PredBB->getInstList()); + new UnreachableInst(PredBB->getContext(), PredBB); + + // If the PredBB is the entry block of the function, move DestBB up to + // become the entry block after we erase PredBB. + if (ReplaceEntryBB) + DestBB->moveAfter(PredBB); + + if (DTU) { + assert(PredBB->getInstList().size() == 1 && + isa<UnreachableInst>(PredBB->getTerminator()) && + "The successor list of PredBB isn't empty before " + "applying corresponding DTU updates."); + DTU->applyUpdatesPermissive(Updates); + DTU->deleteBB(PredBB); + // Recalculation of DomTree is needed when updating a forward DomTree and + // the Entry BB is replaced. + if (ReplaceEntryBB && DTU->hasDomTree()) { + // The entry block was removed and there is no external interface for + // the dominator tree to be notified of this change. In this corner-case + // we recalculate the entire tree. + DTU->recalculate(*(DestBB->getParent())); + } + } + + else { + PredBB->eraseFromParent(); // Nuke BB if DTU is nullptr. + } +} + +/// Return true if we can choose one of these values to use in place of the +/// other. Note that we will always choose the non-undef value to keep. +static bool CanMergeValues(Value *First, Value *Second) { + return First == Second || isa<UndefValue>(First) || isa<UndefValue>(Second); +} + +/// Return true if we can fold BB, an almost-empty BB ending in an unconditional +/// branch to Succ, into Succ. +/// +/// Assumption: Succ is the single successor for BB. +static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) { + assert(*succ_begin(BB) == Succ && "Succ is not successor of BB!"); + + LLVM_DEBUG(dbgs() << "Looking to fold " << BB->getName() << " into " + << Succ->getName() << "\n"); + // Shortcut, if there is only a single predecessor it must be BB and merging + // is always safe + if (Succ->getSinglePredecessor()) return true; + + // Make a list of the predecessors of BB + SmallPtrSet<BasicBlock*, 16> BBPreds(pred_begin(BB), pred_end(BB)); + + // Look at all the phi nodes in Succ, to see if they present a conflict when + // merging these blocks + for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) { + PHINode *PN = cast<PHINode>(I); + + // If the incoming value from BB is again a PHINode in + // BB which has the same incoming value for *PI as PN does, we can + // merge the phi nodes and then the blocks can still be merged + PHINode *BBPN = dyn_cast<PHINode>(PN->getIncomingValueForBlock(BB)); + if (BBPN && BBPN->getParent() == BB) { + for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) { + BasicBlock *IBB = PN->getIncomingBlock(PI); + if (BBPreds.count(IBB) && + !CanMergeValues(BBPN->getIncomingValueForBlock(IBB), + PN->getIncomingValue(PI))) { + LLVM_DEBUG(dbgs() + << "Can't fold, phi node " << PN->getName() << " in " + << Succ->getName() << " is conflicting with " + << BBPN->getName() << " with regard to common predecessor " + << IBB->getName() << "\n"); + return false; + } + } + } else { + Value* Val = PN->getIncomingValueForBlock(BB); + for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) { + // See if the incoming value for the common predecessor is equal to the + // one for BB, in which case this phi node will not prevent the merging + // of the block. + BasicBlock *IBB = PN->getIncomingBlock(PI); + if (BBPreds.count(IBB) && + !CanMergeValues(Val, PN->getIncomingValue(PI))) { + LLVM_DEBUG(dbgs() << "Can't fold, phi node " << PN->getName() + << " in " << Succ->getName() + << " is conflicting with regard to common " + << "predecessor " << IBB->getName() << "\n"); + return false; + } + } + } + } + + return true; +} + +using PredBlockVector = SmallVector<BasicBlock *, 16>; +using IncomingValueMap = DenseMap<BasicBlock *, Value *>; + +/// Determines the value to use as the phi node input for a block. +/// +/// Select between \p OldVal any value that we know flows from \p BB +/// to a particular phi on the basis of which one (if either) is not +/// undef. Update IncomingValues based on the selected value. +/// +/// \param OldVal The value we are considering selecting. +/// \param BB The block that the value flows in from. +/// \param IncomingValues A map from block-to-value for other phi inputs +/// that we have examined. +/// +/// \returns the selected value. +static Value *selectIncomingValueForBlock(Value *OldVal, BasicBlock *BB, + IncomingValueMap &IncomingValues) { + if (!isa<UndefValue>(OldVal)) { + assert((!IncomingValues.count(BB) || + IncomingValues.find(BB)->second == OldVal) && + "Expected OldVal to match incoming value from BB!"); + + IncomingValues.insert(std::make_pair(BB, OldVal)); + return OldVal; + } + + IncomingValueMap::const_iterator It = IncomingValues.find(BB); + if (It != IncomingValues.end()) return It->second; + + return OldVal; +} + +/// Create a map from block to value for the operands of a +/// given phi. +/// +/// Create a map from block to value for each non-undef value flowing +/// into \p PN. +/// +/// \param PN The phi we are collecting the map for. +/// \param IncomingValues [out] The map from block to value for this phi. +static void gatherIncomingValuesToPhi(PHINode *PN, + IncomingValueMap &IncomingValues) { + for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { + BasicBlock *BB = PN->getIncomingBlock(i); + Value *V = PN->getIncomingValue(i); + + if (!isa<UndefValue>(V)) + IncomingValues.insert(std::make_pair(BB, V)); + } +} + +/// Replace the incoming undef values to a phi with the values +/// from a block-to-value map. +/// +/// \param PN The phi we are replacing the undefs in. +/// \param IncomingValues A map from block to value. +static void replaceUndefValuesInPhi(PHINode *PN, + const IncomingValueMap &IncomingValues) { + for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { + Value *V = PN->getIncomingValue(i); + + if (!isa<UndefValue>(V)) continue; + + BasicBlock *BB = PN->getIncomingBlock(i); + IncomingValueMap::const_iterator It = IncomingValues.find(BB); + if (It == IncomingValues.end()) continue; + + PN->setIncomingValue(i, It->second); + } +} + +/// Replace a value flowing from a block to a phi with +/// potentially multiple instances of that value flowing from the +/// block's predecessors to the phi. +/// +/// \param BB The block with the value flowing into the phi. +/// \param BBPreds The predecessors of BB. +/// \param PN The phi that we are updating. +static void redirectValuesFromPredecessorsToPhi(BasicBlock *BB, + const PredBlockVector &BBPreds, + PHINode *PN) { + Value *OldVal = PN->removeIncomingValue(BB, false); + assert(OldVal && "No entry in PHI for Pred BB!"); + + IncomingValueMap IncomingValues; + + // We are merging two blocks - BB, and the block containing PN - and + // as a result we need to redirect edges from the predecessors of BB + // to go to the block containing PN, and update PN + // accordingly. Since we allow merging blocks in the case where the + // predecessor and successor blocks both share some predecessors, + // and where some of those common predecessors might have undef + // values flowing into PN, we want to rewrite those values to be + // consistent with the non-undef values. + + gatherIncomingValuesToPhi(PN, IncomingValues); + + // If this incoming value is one of the PHI nodes in BB, the new entries + // in the PHI node are the entries from the old PHI. + if (isa<PHINode>(OldVal) && cast<PHINode>(OldVal)->getParent() == BB) { + PHINode *OldValPN = cast<PHINode>(OldVal); + for (unsigned i = 0, e = OldValPN->getNumIncomingValues(); i != e; ++i) { + // Note that, since we are merging phi nodes and BB and Succ might + // have common predecessors, we could end up with a phi node with + // identical incoming branches. This will be cleaned up later (and + // will trigger asserts if we try to clean it up now, without also + // simplifying the corresponding conditional branch). + BasicBlock *PredBB = OldValPN->getIncomingBlock(i); + Value *PredVal = OldValPN->getIncomingValue(i); + Value *Selected = selectIncomingValueForBlock(PredVal, PredBB, + IncomingValues); + + // And add a new incoming value for this predecessor for the + // newly retargeted branch. + PN->addIncoming(Selected, PredBB); + } + } else { + for (unsigned i = 0, e = BBPreds.size(); i != e; ++i) { + // Update existing incoming values in PN for this + // predecessor of BB. + BasicBlock *PredBB = BBPreds[i]; + Value *Selected = selectIncomingValueForBlock(OldVal, PredBB, + IncomingValues); + + // And add a new incoming value for this predecessor for the + // newly retargeted branch. + PN->addIncoming(Selected, PredBB); + } + } + + replaceUndefValuesInPhi(PN, IncomingValues); +} + +bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB, + DomTreeUpdater *DTU) { + assert(BB != &BB->getParent()->getEntryBlock() && + "TryToSimplifyUncondBranchFromEmptyBlock called on entry block!"); + + // We can't eliminate infinite loops. + BasicBlock *Succ = cast<BranchInst>(BB->getTerminator())->getSuccessor(0); + if (BB == Succ) return false; + + // Check to see if merging these blocks would cause conflicts for any of the + // phi nodes in BB or Succ. If not, we can safely merge. + if (!CanPropagatePredecessorsForPHIs(BB, Succ)) return false; + + // Check for cases where Succ has multiple predecessors and a PHI node in BB + // has uses which will not disappear when the PHI nodes are merged. It is + // possible to handle such cases, but difficult: it requires checking whether + // BB dominates Succ, which is non-trivial to calculate in the case where + // Succ has multiple predecessors. Also, it requires checking whether + // constructing the necessary self-referential PHI node doesn't introduce any + // conflicts; this isn't too difficult, but the previous code for doing this + // was incorrect. + // + // Note that if this check finds a live use, BB dominates Succ, so BB is + // something like a loop pre-header (or rarely, a part of an irreducible CFG); + // folding the branch isn't profitable in that case anyway. + if (!Succ->getSinglePredecessor()) { + BasicBlock::iterator BBI = BB->begin(); + while (isa<PHINode>(*BBI)) { + for (Use &U : BBI->uses()) { + if (PHINode* PN = dyn_cast<PHINode>(U.getUser())) { + if (PN->getIncomingBlock(U) != BB) + return false; + } else { + return false; + } + } + ++BBI; + } + } + + // We cannot fold the block if it's a branch to an already present callbr + // successor because that creates duplicate successors. + for (auto I = pred_begin(BB), E = pred_end(BB); I != E; ++I) { + if (auto *CBI = dyn_cast<CallBrInst>((*I)->getTerminator())) { + if (Succ == CBI->getDefaultDest()) + return false; + for (unsigned i = 0, e = CBI->getNumIndirectDests(); i != e; ++i) + if (Succ == CBI->getIndirectDest(i)) + return false; + } + } + + LLVM_DEBUG(dbgs() << "Killing Trivial BB: \n" << *BB); + + SmallVector<DominatorTree::UpdateType, 32> Updates; + if (DTU) { + Updates.push_back({DominatorTree::Delete, BB, Succ}); + // All predecessors of BB will be moved to Succ. + for (auto I = pred_begin(BB), E = pred_end(BB); I != E; ++I) { + Updates.push_back({DominatorTree::Delete, *I, BB}); + // This predecessor of BB may already have Succ as a successor. + if (llvm::find(successors(*I), Succ) == succ_end(*I)) + Updates.push_back({DominatorTree::Insert, *I, Succ}); + } + } + + if (isa<PHINode>(Succ->begin())) { + // If there is more than one pred of succ, and there are PHI nodes in + // the successor, then we need to add incoming edges for the PHI nodes + // + const PredBlockVector BBPreds(pred_begin(BB), pred_end(BB)); + + // Loop over all of the PHI nodes in the successor of BB. + for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) { + PHINode *PN = cast<PHINode>(I); + + redirectValuesFromPredecessorsToPhi(BB, BBPreds, PN); + } + } + + if (Succ->getSinglePredecessor()) { + // BB is the only predecessor of Succ, so Succ will end up with exactly + // the same predecessors BB had. + + // Copy over any phi, debug or lifetime instruction. + BB->getTerminator()->eraseFromParent(); + Succ->getInstList().splice(Succ->getFirstNonPHI()->getIterator(), + BB->getInstList()); + } else { + while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) { + // We explicitly check for such uses in CanPropagatePredecessorsForPHIs. + assert(PN->use_empty() && "There shouldn't be any uses here!"); + PN->eraseFromParent(); + } + } + + // If the unconditional branch we replaced contains llvm.loop metadata, we + // add the metadata to the branch instructions in the predecessors. + unsigned LoopMDKind = BB->getContext().getMDKindID("llvm.loop"); + Instruction *TI = BB->getTerminator(); + if (TI) + if (MDNode *LoopMD = TI->getMetadata(LoopMDKind)) + for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) { + BasicBlock *Pred = *PI; + Pred->getTerminator()->setMetadata(LoopMDKind, LoopMD); + } + + // Everything that jumped to BB now goes to Succ. + BB->replaceAllUsesWith(Succ); + if (!Succ->hasName()) Succ->takeName(BB); + + // Clear the successor list of BB to match updates applying to DTU later. + if (BB->getTerminator()) + BB->getInstList().pop_back(); + new UnreachableInst(BB->getContext(), BB); + assert(succ_empty(BB) && "The successor list of BB isn't empty before " + "applying corresponding DTU updates."); + + if (DTU) { + DTU->applyUpdatesPermissive(Updates); + DTU->deleteBB(BB); + } else { + BB->eraseFromParent(); // Delete the old basic block. + } + return true; +} + +bool llvm::EliminateDuplicatePHINodes(BasicBlock *BB) { + // This implementation doesn't currently consider undef operands + // specially. Theoretically, two phis which are identical except for + // one having an undef where the other doesn't could be collapsed. + + struct PHIDenseMapInfo { + static PHINode *getEmptyKey() { + return DenseMapInfo<PHINode *>::getEmptyKey(); + } + + static PHINode *getTombstoneKey() { + return DenseMapInfo<PHINode *>::getTombstoneKey(); + } + + static unsigned getHashValue(PHINode *PN) { + // Compute a hash value on the operands. Instcombine will likely have + // sorted them, which helps expose duplicates, but we have to check all + // the operands to be safe in case instcombine hasn't run. + return static_cast<unsigned>(hash_combine( + hash_combine_range(PN->value_op_begin(), PN->value_op_end()), + hash_combine_range(PN->block_begin(), PN->block_end()))); + } + + static bool isEqual(PHINode *LHS, PHINode *RHS) { + if (LHS == getEmptyKey() || LHS == getTombstoneKey() || + RHS == getEmptyKey() || RHS == getTombstoneKey()) + return LHS == RHS; + return LHS->isIdenticalTo(RHS); + } + }; + + // Set of unique PHINodes. + DenseSet<PHINode *, PHIDenseMapInfo> PHISet; + + // Examine each PHI. + bool Changed = false; + for (auto I = BB->begin(); PHINode *PN = dyn_cast<PHINode>(I++);) { + auto Inserted = PHISet.insert(PN); + if (!Inserted.second) { + // A duplicate. Replace this PHI with its duplicate. + PN->replaceAllUsesWith(*Inserted.first); + PN->eraseFromParent(); + Changed = true; + + // The RAUW can change PHIs that we already visited. Start over from the + // beginning. + PHISet.clear(); + I = BB->begin(); + } + } + + return Changed; +} + +/// enforceKnownAlignment - If the specified pointer points to an object that +/// we control, modify the object's alignment to PrefAlign. This isn't +/// often possible though. If alignment is important, a more reliable approach +/// is to simply align all global variables and allocation instructions to +/// their preferred alignment from the beginning. +static unsigned enforceKnownAlignment(Value *V, unsigned Alignment, + unsigned PrefAlign, + const DataLayout &DL) { + assert(PrefAlign > Alignment); + + V = V->stripPointerCasts(); + + if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) { + // TODO: ideally, computeKnownBits ought to have used + // AllocaInst::getAlignment() in its computation already, making + // the below max redundant. But, as it turns out, + // stripPointerCasts recurses through infinite layers of bitcasts, + // while computeKnownBits is not allowed to traverse more than 6 + // levels. + Alignment = std::max(AI->getAlignment(), Alignment); + if (PrefAlign <= Alignment) + return Alignment; + + // If the preferred alignment is greater than the natural stack alignment + // then don't round up. This avoids dynamic stack realignment. + if (DL.exceedsNaturalStackAlignment(Align(PrefAlign))) + return Alignment; + AI->setAlignment(MaybeAlign(PrefAlign)); + return PrefAlign; + } + + if (auto *GO = dyn_cast<GlobalObject>(V)) { + // TODO: as above, this shouldn't be necessary. + Alignment = std::max(GO->getAlignment(), Alignment); + if (PrefAlign <= Alignment) + return Alignment; + + // If there is a large requested alignment and we can, bump up the alignment + // of the global. If the memory we set aside for the global may not be the + // memory used by the final program then it is impossible for us to reliably + // enforce the preferred alignment. + if (!GO->canIncreaseAlignment()) + return Alignment; + + GO->setAlignment(MaybeAlign(PrefAlign)); + return PrefAlign; + } + + return Alignment; +} + +unsigned llvm::getOrEnforceKnownAlignment(Value *V, unsigned PrefAlign, + const DataLayout &DL, + const Instruction *CxtI, + AssumptionCache *AC, + const DominatorTree *DT) { + assert(V->getType()->isPointerTy() && + "getOrEnforceKnownAlignment expects a pointer!"); + + KnownBits Known = computeKnownBits(V, DL, 0, AC, CxtI, DT); + unsigned TrailZ = Known.countMinTrailingZeros(); + + // Avoid trouble with ridiculously large TrailZ values, such as + // those computed from a null pointer. + TrailZ = std::min(TrailZ, unsigned(sizeof(unsigned) * CHAR_BIT - 1)); + + unsigned Align = 1u << std::min(Known.getBitWidth() - 1, TrailZ); + + // LLVM doesn't support alignments larger than this currently. + Align = std::min(Align, +Value::MaximumAlignment); + + if (PrefAlign > Align) + Align = enforceKnownAlignment(V, Align, PrefAlign, DL); + + // We don't need to make any adjustment. + return Align; +} + +///===---------------------------------------------------------------------===// +/// Dbg Intrinsic utilities +/// + +/// See if there is a dbg.value intrinsic for DIVar before I. +static bool LdStHasDebugValue(DILocalVariable *DIVar, DIExpression *DIExpr, + Instruction *I) { + // Since we can't guarantee that the original dbg.declare instrinsic + // is removed by LowerDbgDeclare(), we need to make sure that we are + // not inserting the same dbg.value intrinsic over and over. + BasicBlock::InstListType::iterator PrevI(I); + if (PrevI != I->getParent()->getInstList().begin()) { + --PrevI; + if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(PrevI)) + if (DVI->getValue() == I->getOperand(0) && + DVI->getVariable() == DIVar && + DVI->getExpression() == DIExpr) + return true; + } + return false; +} + +/// See if there is a dbg.value intrinsic for DIVar for the PHI node. +static bool PhiHasDebugValue(DILocalVariable *DIVar, + DIExpression *DIExpr, + PHINode *APN) { + // Since we can't guarantee that the original dbg.declare instrinsic + // is removed by LowerDbgDeclare(), we need to make sure that we are + // not inserting the same dbg.value intrinsic over and over. + SmallVector<DbgValueInst *, 1> DbgValues; + findDbgValues(DbgValues, APN); + for (auto *DVI : DbgValues) { + assert(DVI->getValue() == APN); + if ((DVI->getVariable() == DIVar) && (DVI->getExpression() == DIExpr)) + return true; + } + return false; +} + +/// Check if the alloc size of \p ValTy is large enough to cover the variable +/// (or fragment of the variable) described by \p DII. +/// +/// This is primarily intended as a helper for the different +/// ConvertDebugDeclareToDebugValue functions. The dbg.declare/dbg.addr that is +/// converted describes an alloca'd variable, so we need to use the +/// alloc size of the value when doing the comparison. E.g. an i1 value will be +/// identified as covering an n-bit fragment, if the store size of i1 is at +/// least n bits. +static bool valueCoversEntireFragment(Type *ValTy, DbgVariableIntrinsic *DII) { + const DataLayout &DL = DII->getModule()->getDataLayout(); + uint64_t ValueSize = DL.getTypeAllocSizeInBits(ValTy); + if (auto FragmentSize = DII->getFragmentSizeInBits()) + return ValueSize >= *FragmentSize; + // We can't always calculate the size of the DI variable (e.g. if it is a + // VLA). Try to use the size of the alloca that the dbg intrinsic describes + // intead. + if (DII->isAddressOfVariable()) + if (auto *AI = dyn_cast_or_null<AllocaInst>(DII->getVariableLocation())) + if (auto FragmentSize = AI->getAllocationSizeInBits(DL)) + return ValueSize >= *FragmentSize; + // Could not determine size of variable. Conservatively return false. + return false; +} + +/// Produce a DebugLoc to use for each dbg.declare/inst pair that are promoted +/// to a dbg.value. Because no machine insts can come from debug intrinsics, +/// only the scope and inlinedAt is significant. Zero line numbers are used in +/// case this DebugLoc leaks into any adjacent instructions. +static DebugLoc getDebugValueLoc(DbgVariableIntrinsic *DII, Instruction *Src) { + // Original dbg.declare must have a location. + DebugLoc DeclareLoc = DII->getDebugLoc(); + MDNode *Scope = DeclareLoc.getScope(); + DILocation *InlinedAt = DeclareLoc.getInlinedAt(); + // Produce an unknown location with the correct scope / inlinedAt fields. + return DebugLoc::get(0, 0, Scope, InlinedAt); +} + +/// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value +/// that has an associated llvm.dbg.declare or llvm.dbg.addr intrinsic. +void llvm::ConvertDebugDeclareToDebugValue(DbgVariableIntrinsic *DII, + StoreInst *SI, DIBuilder &Builder) { + assert(DII->isAddressOfVariable()); + auto *DIVar = DII->getVariable(); + assert(DIVar && "Missing variable"); + auto *DIExpr = DII->getExpression(); + Value *DV = SI->getValueOperand(); + + DebugLoc NewLoc = getDebugValueLoc(DII, SI); + + if (!valueCoversEntireFragment(DV->getType(), DII)) { + // FIXME: If storing to a part of the variable described by the dbg.declare, + // then we want to insert a dbg.value for the corresponding fragment. + LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to dbg.value: " + << *DII << '\n'); + // For now, when there is a store to parts of the variable (but we do not + // know which part) we insert an dbg.value instrinsic to indicate that we + // know nothing about the variable's content. + DV = UndefValue::get(DV->getType()); + if (!LdStHasDebugValue(DIVar, DIExpr, SI)) + Builder.insertDbgValueIntrinsic(DV, DIVar, DIExpr, NewLoc, SI); + return; + } + + if (!LdStHasDebugValue(DIVar, DIExpr, SI)) + Builder.insertDbgValueIntrinsic(DV, DIVar, DIExpr, NewLoc, SI); +} + +/// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value +/// that has an associated llvm.dbg.declare or llvm.dbg.addr intrinsic. +void llvm::ConvertDebugDeclareToDebugValue(DbgVariableIntrinsic *DII, + LoadInst *LI, DIBuilder &Builder) { + auto *DIVar = DII->getVariable(); + auto *DIExpr = DII->getExpression(); + assert(DIVar && "Missing variable"); + + if (LdStHasDebugValue(DIVar, DIExpr, LI)) + return; + + if (!valueCoversEntireFragment(LI->getType(), DII)) { + // FIXME: If only referring to a part of the variable described by the + // dbg.declare, then we want to insert a dbg.value for the corresponding + // fragment. + LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to dbg.value: " + << *DII << '\n'); + return; + } + + DebugLoc NewLoc = getDebugValueLoc(DII, nullptr); + + // We are now tracking the loaded value instead of the address. In the + // future if multi-location support is added to the IR, it might be + // preferable to keep tracking both the loaded value and the original + // address in case the alloca can not be elided. + Instruction *DbgValue = Builder.insertDbgValueIntrinsic( + LI, DIVar, DIExpr, NewLoc, (Instruction *)nullptr); + DbgValue->insertAfter(LI); +} + +/// Inserts a llvm.dbg.value intrinsic after a phi that has an associated +/// llvm.dbg.declare or llvm.dbg.addr intrinsic. +void llvm::ConvertDebugDeclareToDebugValue(DbgVariableIntrinsic *DII, + PHINode *APN, DIBuilder &Builder) { + auto *DIVar = DII->getVariable(); + auto *DIExpr = DII->getExpression(); + assert(DIVar && "Missing variable"); + + if (PhiHasDebugValue(DIVar, DIExpr, APN)) + return; + + if (!valueCoversEntireFragment(APN->getType(), DII)) { + // FIXME: If only referring to a part of the variable described by the + // dbg.declare, then we want to insert a dbg.value for the corresponding + // fragment. + LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to dbg.value: " + << *DII << '\n'); + return; + } + + BasicBlock *BB = APN->getParent(); + auto InsertionPt = BB->getFirstInsertionPt(); + + DebugLoc NewLoc = getDebugValueLoc(DII, nullptr); + + // The block may be a catchswitch block, which does not have a valid + // insertion point. + // FIXME: Insert dbg.value markers in the successors when appropriate. + if (InsertionPt != BB->end()) + Builder.insertDbgValueIntrinsic(APN, DIVar, DIExpr, NewLoc, &*InsertionPt); +} + +/// Determine whether this alloca is either a VLA or an array. +static bool isArray(AllocaInst *AI) { + return AI->isArrayAllocation() || + (AI->getAllocatedType() && AI->getAllocatedType()->isArrayTy()); +} + +/// Determine whether this alloca is a structure. +static bool isStructure(AllocaInst *AI) { + return AI->getAllocatedType() && AI->getAllocatedType()->isStructTy(); +} + +/// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set +/// of llvm.dbg.value intrinsics. +bool llvm::LowerDbgDeclare(Function &F) { + DIBuilder DIB(*F.getParent(), /*AllowUnresolved*/ false); + SmallVector<DbgDeclareInst *, 4> Dbgs; + for (auto &FI : F) + for (Instruction &BI : FI) + if (auto DDI = dyn_cast<DbgDeclareInst>(&BI)) + Dbgs.push_back(DDI); + + if (Dbgs.empty()) + return false; + + for (auto &I : Dbgs) { + DbgDeclareInst *DDI = I; + AllocaInst *AI = dyn_cast_or_null<AllocaInst>(DDI->getAddress()); + // If this is an alloca for a scalar variable, insert a dbg.value + // at each load and store to the alloca and erase the dbg.declare. + // The dbg.values allow tracking a variable even if it is not + // stored on the stack, while the dbg.declare can only describe + // the stack slot (and at a lexical-scope granularity). Later + // passes will attempt to elide the stack slot. + if (!AI || isArray(AI) || isStructure(AI)) + continue; + + // A volatile load/store means that the alloca can't be elided anyway. + if (llvm::any_of(AI->users(), [](User *U) -> bool { + if (LoadInst *LI = dyn_cast<LoadInst>(U)) + return LI->isVolatile(); + if (StoreInst *SI = dyn_cast<StoreInst>(U)) + return SI->isVolatile(); + return false; + })) + continue; + + for (auto &AIUse : AI->uses()) { + User *U = AIUse.getUser(); + if (StoreInst *SI = dyn_cast<StoreInst>(U)) { + if (AIUse.getOperandNo() == 1) + ConvertDebugDeclareToDebugValue(DDI, SI, DIB); + } else if (LoadInst *LI = dyn_cast<LoadInst>(U)) { + ConvertDebugDeclareToDebugValue(DDI, LI, DIB); + } else if (CallInst *CI = dyn_cast<CallInst>(U)) { + // This is a call by-value or some other instruction that takes a + // pointer to the variable. Insert a *value* intrinsic that describes + // the variable by dereferencing the alloca. + DebugLoc NewLoc = getDebugValueLoc(DDI, nullptr); + auto *DerefExpr = + DIExpression::append(DDI->getExpression(), dwarf::DW_OP_deref); + DIB.insertDbgValueIntrinsic(AI, DDI->getVariable(), DerefExpr, NewLoc, + CI); + } + } + DDI->eraseFromParent(); + } + return true; +} + +/// Propagate dbg.value intrinsics through the newly inserted PHIs. +void llvm::insertDebugValuesForPHIs(BasicBlock *BB, + SmallVectorImpl<PHINode *> &InsertedPHIs) { + assert(BB && "No BasicBlock to clone dbg.value(s) from."); + if (InsertedPHIs.size() == 0) + return; + + // Map existing PHI nodes to their dbg.values. + ValueToValueMapTy DbgValueMap; + for (auto &I : *BB) { + if (auto DbgII = dyn_cast<DbgVariableIntrinsic>(&I)) { + if (auto *Loc = dyn_cast_or_null<PHINode>(DbgII->getVariableLocation())) + DbgValueMap.insert({Loc, DbgII}); + } + } + if (DbgValueMap.size() == 0) + return; + + // Then iterate through the new PHIs and look to see if they use one of the + // previously mapped PHIs. If so, insert a new dbg.value intrinsic that will + // propagate the info through the new PHI. + LLVMContext &C = BB->getContext(); + for (auto PHI : InsertedPHIs) { + BasicBlock *Parent = PHI->getParent(); + // Avoid inserting an intrinsic into an EH block. + if (Parent->getFirstNonPHI()->isEHPad()) + continue; + auto PhiMAV = MetadataAsValue::get(C, ValueAsMetadata::get(PHI)); + for (auto VI : PHI->operand_values()) { + auto V = DbgValueMap.find(VI); + if (V != DbgValueMap.end()) { + auto *DbgII = cast<DbgVariableIntrinsic>(V->second); + Instruction *NewDbgII = DbgII->clone(); + NewDbgII->setOperand(0, PhiMAV); + auto InsertionPt = Parent->getFirstInsertionPt(); + assert(InsertionPt != Parent->end() && "Ill-formed basic block"); + NewDbgII->insertBefore(&*InsertionPt); + } + } + } +} + +/// Finds all intrinsics declaring local variables as living in the memory that +/// 'V' points to. This may include a mix of dbg.declare and +/// dbg.addr intrinsics. +TinyPtrVector<DbgVariableIntrinsic *> llvm::FindDbgAddrUses(Value *V) { + // This function is hot. Check whether the value has any metadata to avoid a + // DenseMap lookup. + if (!V->isUsedByMetadata()) + return {}; + auto *L = LocalAsMetadata::getIfExists(V); + if (!L) + return {}; + auto *MDV = MetadataAsValue::getIfExists(V->getContext(), L); + if (!MDV) + return {}; + + TinyPtrVector<DbgVariableIntrinsic *> Declares; + for (User *U : MDV->users()) { + if (auto *DII = dyn_cast<DbgVariableIntrinsic>(U)) + if (DII->isAddressOfVariable()) + Declares.push_back(DII); + } + + return Declares; +} + +void llvm::findDbgValues(SmallVectorImpl<DbgValueInst *> &DbgValues, Value *V) { + // This function is hot. Check whether the value has any metadata to avoid a + // DenseMap lookup. + if (!V->isUsedByMetadata()) + return; + if (auto *L = LocalAsMetadata::getIfExists(V)) + if (auto *MDV = MetadataAsValue::getIfExists(V->getContext(), L)) + for (User *U : MDV->users()) + if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(U)) + DbgValues.push_back(DVI); +} + +void llvm::findDbgUsers(SmallVectorImpl<DbgVariableIntrinsic *> &DbgUsers, + Value *V) { + // This function is hot. Check whether the value has any metadata to avoid a + // DenseMap lookup. + if (!V->isUsedByMetadata()) + return; + if (auto *L = LocalAsMetadata::getIfExists(V)) + if (auto *MDV = MetadataAsValue::getIfExists(V->getContext(), L)) + for (User *U : MDV->users()) + if (DbgVariableIntrinsic *DII = dyn_cast<DbgVariableIntrinsic>(U)) + DbgUsers.push_back(DII); +} + +bool llvm::replaceDbgDeclare(Value *Address, Value *NewAddress, + Instruction *InsertBefore, DIBuilder &Builder, + uint8_t DIExprFlags, int Offset) { + auto DbgAddrs = FindDbgAddrUses(Address); + for (DbgVariableIntrinsic *DII : DbgAddrs) { + DebugLoc Loc = DII->getDebugLoc(); + auto *DIVar = DII->getVariable(); + auto *DIExpr = DII->getExpression(); + assert(DIVar && "Missing variable"); + DIExpr = DIExpression::prepend(DIExpr, DIExprFlags, Offset); + // Insert llvm.dbg.declare immediately before InsertBefore, and remove old + // llvm.dbg.declare. + Builder.insertDeclare(NewAddress, DIVar, DIExpr, Loc, InsertBefore); + if (DII == InsertBefore) + InsertBefore = InsertBefore->getNextNode(); + DII->eraseFromParent(); + } + return !DbgAddrs.empty(); +} + +bool llvm::replaceDbgDeclareForAlloca(AllocaInst *AI, Value *NewAllocaAddress, + DIBuilder &Builder, uint8_t DIExprFlags, + int Offset) { + return replaceDbgDeclare(AI, NewAllocaAddress, AI->getNextNode(), Builder, + DIExprFlags, Offset); +} + +static void replaceOneDbgValueForAlloca(DbgValueInst *DVI, Value *NewAddress, + DIBuilder &Builder, int Offset) { + DebugLoc Loc = DVI->getDebugLoc(); + auto *DIVar = DVI->getVariable(); + auto *DIExpr = DVI->getExpression(); + assert(DIVar && "Missing variable"); + + // This is an alloca-based llvm.dbg.value. The first thing it should do with + // the alloca pointer is dereference it. Otherwise we don't know how to handle + // it and give up. + if (!DIExpr || DIExpr->getNumElements() < 1 || + DIExpr->getElement(0) != dwarf::DW_OP_deref) + return; + + // Insert the offset before the first deref. + // We could just change the offset argument of dbg.value, but it's unsigned... + if (Offset) + DIExpr = DIExpression::prepend(DIExpr, 0, Offset); + + Builder.insertDbgValueIntrinsic(NewAddress, DIVar, DIExpr, Loc, DVI); + DVI->eraseFromParent(); +} + +void llvm::replaceDbgValueForAlloca(AllocaInst *AI, Value *NewAllocaAddress, + DIBuilder &Builder, int Offset) { + if (auto *L = LocalAsMetadata::getIfExists(AI)) + if (auto *MDV = MetadataAsValue::getIfExists(AI->getContext(), L)) + for (auto UI = MDV->use_begin(), UE = MDV->use_end(); UI != UE;) { + Use &U = *UI++; + if (auto *DVI = dyn_cast<DbgValueInst>(U.getUser())) + replaceOneDbgValueForAlloca(DVI, NewAllocaAddress, Builder, Offset); + } +} + +/// Wrap \p V in a ValueAsMetadata instance. +static MetadataAsValue *wrapValueInMetadata(LLVMContext &C, Value *V) { + return MetadataAsValue::get(C, ValueAsMetadata::get(V)); +} + +bool llvm::salvageDebugInfo(Instruction &I) { + SmallVector<DbgVariableIntrinsic *, 1> DbgUsers; + findDbgUsers(DbgUsers, &I); + if (DbgUsers.empty()) + return false; + + return salvageDebugInfoForDbgValues(I, DbgUsers); +} + +bool llvm::salvageDebugInfoForDbgValues( + Instruction &I, ArrayRef<DbgVariableIntrinsic *> DbgUsers) { + auto &Ctx = I.getContext(); + auto wrapMD = [&](Value *V) { return wrapValueInMetadata(Ctx, V); }; + + for (auto *DII : DbgUsers) { + // Do not add DW_OP_stack_value for DbgDeclare and DbgAddr, because they + // are implicitly pointing out the value as a DWARF memory location + // description. + bool StackValue = isa<DbgValueInst>(DII); + + DIExpression *DIExpr = + salvageDebugInfoImpl(I, DII->getExpression(), StackValue); + + // salvageDebugInfoImpl should fail on examining the first element of + // DbgUsers, or none of them. + if (!DIExpr) + return false; + + DII->setOperand(0, wrapMD(I.getOperand(0))); + DII->setOperand(2, MetadataAsValue::get(Ctx, DIExpr)); + LLVM_DEBUG(dbgs() << "SALVAGE: " << *DII << '\n'); + } + + return true; +} + +DIExpression *llvm::salvageDebugInfoImpl(Instruction &I, + DIExpression *SrcDIExpr, + bool WithStackValue) { + auto &M = *I.getModule(); + auto &DL = M.getDataLayout(); + + // Apply a vector of opcodes to the source DIExpression. + auto doSalvage = [&](SmallVectorImpl<uint64_t> &Ops) -> DIExpression * { + DIExpression *DIExpr = SrcDIExpr; + if (!Ops.empty()) { + DIExpr = DIExpression::prependOpcodes(DIExpr, Ops, WithStackValue); + } + return DIExpr; + }; + + // Apply the given offset to the source DIExpression. + auto applyOffset = [&](uint64_t Offset) -> DIExpression * { + SmallVector<uint64_t, 8> Ops; + DIExpression::appendOffset(Ops, Offset); + return doSalvage(Ops); + }; + + // initializer-list helper for applying operators to the source DIExpression. + auto applyOps = + [&](std::initializer_list<uint64_t> Opcodes) -> DIExpression * { + SmallVector<uint64_t, 8> Ops(Opcodes); + return doSalvage(Ops); + }; + + if (auto *CI = dyn_cast<CastInst>(&I)) { + // No-op casts and zexts are irrelevant for debug info. + if (CI->isNoopCast(DL) || isa<ZExtInst>(&I)) + return SrcDIExpr; + return nullptr; + } else if (auto *GEP = dyn_cast<GetElementPtrInst>(&I)) { + unsigned BitWidth = + M.getDataLayout().getIndexSizeInBits(GEP->getPointerAddressSpace()); + // Rewrite a constant GEP into a DIExpression. + APInt Offset(BitWidth, 0); + if (GEP->accumulateConstantOffset(M.getDataLayout(), Offset)) { + return applyOffset(Offset.getSExtValue()); + } else { + return nullptr; + } + } else if (auto *BI = dyn_cast<BinaryOperator>(&I)) { + // Rewrite binary operations with constant integer operands. + auto *ConstInt = dyn_cast<ConstantInt>(I.getOperand(1)); + if (!ConstInt || ConstInt->getBitWidth() > 64) + return nullptr; + + uint64_t Val = ConstInt->getSExtValue(); + switch (BI->getOpcode()) { + case Instruction::Add: + return applyOffset(Val); + case Instruction::Sub: + return applyOffset(-int64_t(Val)); + case Instruction::Mul: + return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_mul}); + case Instruction::SDiv: + return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_div}); + case Instruction::SRem: + return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_mod}); + case Instruction::Or: + return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_or}); + case Instruction::And: + return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_and}); + case Instruction::Xor: + return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_xor}); + case Instruction::Shl: + return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_shl}); + case Instruction::LShr: + return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_shr}); + case Instruction::AShr: + return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_shra}); + default: + // TODO: Salvage constants from each kind of binop we know about. + return nullptr; + } + // *Not* to do: we should not attempt to salvage load instructions, + // because the validity and lifetime of a dbg.value containing + // DW_OP_deref becomes difficult to analyze. See PR40628 for examples. + } + return nullptr; +} + +/// A replacement for a dbg.value expression. +using DbgValReplacement = Optional<DIExpression *>; + +/// Point debug users of \p From to \p To using exprs given by \p RewriteExpr, +/// possibly moving/deleting users to prevent use-before-def. Returns true if +/// changes are made. +static bool rewriteDebugUsers( + Instruction &From, Value &To, Instruction &DomPoint, DominatorTree &DT, + function_ref<DbgValReplacement(DbgVariableIntrinsic &DII)> RewriteExpr) { + // Find debug users of From. + SmallVector<DbgVariableIntrinsic *, 1> Users; + findDbgUsers(Users, &From); + if (Users.empty()) + return false; + + // Prevent use-before-def of To. + bool Changed = false; + SmallPtrSet<DbgVariableIntrinsic *, 1> DeleteOrSalvage; + if (isa<Instruction>(&To)) { + bool DomPointAfterFrom = From.getNextNonDebugInstruction() == &DomPoint; + + for (auto *DII : Users) { + // It's common to see a debug user between From and DomPoint. Move it + // after DomPoint to preserve the variable update without any reordering. + if (DomPointAfterFrom && DII->getNextNonDebugInstruction() == &DomPoint) { + LLVM_DEBUG(dbgs() << "MOVE: " << *DII << '\n'); + DII->moveAfter(&DomPoint); + Changed = true; + + // Users which otherwise aren't dominated by the replacement value must + // be salvaged or deleted. + } else if (!DT.dominates(&DomPoint, DII)) { + DeleteOrSalvage.insert(DII); + } + } + } + + // Update debug users without use-before-def risk. + for (auto *DII : Users) { + if (DeleteOrSalvage.count(DII)) + continue; + + LLVMContext &Ctx = DII->getContext(); + DbgValReplacement DVR = RewriteExpr(*DII); + if (!DVR) + continue; + + DII->setOperand(0, wrapValueInMetadata(Ctx, &To)); + DII->setOperand(2, MetadataAsValue::get(Ctx, *DVR)); + LLVM_DEBUG(dbgs() << "REWRITE: " << *DII << '\n'); + Changed = true; + } + + if (!DeleteOrSalvage.empty()) { + // Try to salvage the remaining debug users. + Changed |= salvageDebugInfo(From); + + // Delete the debug users which weren't salvaged. + for (auto *DII : DeleteOrSalvage) { + if (DII->getVariableLocation() == &From) { + LLVM_DEBUG(dbgs() << "Erased UseBeforeDef: " << *DII << '\n'); + DII->eraseFromParent(); + Changed = true; + } + } + } + + return Changed; +} + +/// Check if a bitcast between a value of type \p FromTy to type \p ToTy would +/// losslessly preserve the bits and semantics of the value. This predicate is +/// symmetric, i.e swapping \p FromTy and \p ToTy should give the same result. +/// +/// Note that Type::canLosslesslyBitCastTo is not suitable here because it +/// allows semantically unequivalent bitcasts, such as <2 x i64> -> <4 x i32>, +/// and also does not allow lossless pointer <-> integer conversions. +static bool isBitCastSemanticsPreserving(const DataLayout &DL, Type *FromTy, + Type *ToTy) { + // Trivially compatible types. + if (FromTy == ToTy) + return true; + + // Handle compatible pointer <-> integer conversions. + if (FromTy->isIntOrPtrTy() && ToTy->isIntOrPtrTy()) { + bool SameSize = DL.getTypeSizeInBits(FromTy) == DL.getTypeSizeInBits(ToTy); + bool LosslessConversion = !DL.isNonIntegralPointerType(FromTy) && + !DL.isNonIntegralPointerType(ToTy); + return SameSize && LosslessConversion; + } + + // TODO: This is not exhaustive. + return false; +} + +bool llvm::replaceAllDbgUsesWith(Instruction &From, Value &To, + Instruction &DomPoint, DominatorTree &DT) { + // Exit early if From has no debug users. + if (!From.isUsedByMetadata()) + return false; + + assert(&From != &To && "Can't replace something with itself"); + + Type *FromTy = From.getType(); + Type *ToTy = To.getType(); + + auto Identity = [&](DbgVariableIntrinsic &DII) -> DbgValReplacement { + return DII.getExpression(); + }; + + // Handle no-op conversions. + Module &M = *From.getModule(); + const DataLayout &DL = M.getDataLayout(); + if (isBitCastSemanticsPreserving(DL, FromTy, ToTy)) + return rewriteDebugUsers(From, To, DomPoint, DT, Identity); + + // Handle integer-to-integer widening and narrowing. + // FIXME: Use DW_OP_convert when it's available everywhere. + if (FromTy->isIntegerTy() && ToTy->isIntegerTy()) { + uint64_t FromBits = FromTy->getPrimitiveSizeInBits(); + uint64_t ToBits = ToTy->getPrimitiveSizeInBits(); + assert(FromBits != ToBits && "Unexpected no-op conversion"); + + // When the width of the result grows, assume that a debugger will only + // access the low `FromBits` bits when inspecting the source variable. + if (FromBits < ToBits) + return rewriteDebugUsers(From, To, DomPoint, DT, Identity); + + // The width of the result has shrunk. Use sign/zero extension to describe + // the source variable's high bits. + auto SignOrZeroExt = [&](DbgVariableIntrinsic &DII) -> DbgValReplacement { + DILocalVariable *Var = DII.getVariable(); + + // Without knowing signedness, sign/zero extension isn't possible. + auto Signedness = Var->getSignedness(); + if (!Signedness) + return None; + + bool Signed = *Signedness == DIBasicType::Signedness::Signed; + dwarf::TypeKind TK = Signed ? dwarf::DW_ATE_signed : dwarf::DW_ATE_unsigned; + SmallVector<uint64_t, 8> Ops({dwarf::DW_OP_LLVM_convert, ToBits, TK, + dwarf::DW_OP_LLVM_convert, FromBits, TK}); + return DIExpression::appendToStack(DII.getExpression(), Ops); + }; + return rewriteDebugUsers(From, To, DomPoint, DT, SignOrZeroExt); + } + + // TODO: Floating-point conversions, vectors. + return false; +} + +unsigned llvm::removeAllNonTerminatorAndEHPadInstructions(BasicBlock *BB) { + unsigned NumDeadInst = 0; + // Delete the instructions backwards, as it has a reduced likelihood of + // having to update as many def-use and use-def chains. + Instruction *EndInst = BB->getTerminator(); // Last not to be deleted. + while (EndInst != &BB->front()) { + // Delete the next to last instruction. + Instruction *Inst = &*--EndInst->getIterator(); + if (!Inst->use_empty() && !Inst->getType()->isTokenTy()) + Inst->replaceAllUsesWith(UndefValue::get(Inst->getType())); + if (Inst->isEHPad() || Inst->getType()->isTokenTy()) { + EndInst = Inst; + continue; + } + if (!isa<DbgInfoIntrinsic>(Inst)) + ++NumDeadInst; + Inst->eraseFromParent(); + } + return NumDeadInst; +} + +unsigned llvm::changeToUnreachable(Instruction *I, bool UseLLVMTrap, + bool PreserveLCSSA, DomTreeUpdater *DTU, + MemorySSAUpdater *MSSAU) { + BasicBlock *BB = I->getParent(); + std::vector <DominatorTree::UpdateType> Updates; + + if (MSSAU) + MSSAU->changeToUnreachable(I); + + // Loop over all of the successors, removing BB's entry from any PHI + // nodes. + if (DTU) + Updates.reserve(BB->getTerminator()->getNumSuccessors()); + for (BasicBlock *Successor : successors(BB)) { + Successor->removePredecessor(BB, PreserveLCSSA); + if (DTU) + Updates.push_back({DominatorTree::Delete, BB, Successor}); + } + // Insert a call to llvm.trap right before this. This turns the undefined + // behavior into a hard fail instead of falling through into random code. + if (UseLLVMTrap) { + Function *TrapFn = + Intrinsic::getDeclaration(BB->getParent()->getParent(), Intrinsic::trap); + CallInst *CallTrap = CallInst::Create(TrapFn, "", I); + CallTrap->setDebugLoc(I->getDebugLoc()); + } + auto *UI = new UnreachableInst(I->getContext(), I); + UI->setDebugLoc(I->getDebugLoc()); + + // All instructions after this are dead. + unsigned NumInstrsRemoved = 0; + BasicBlock::iterator BBI = I->getIterator(), BBE = BB->end(); + while (BBI != BBE) { + if (!BBI->use_empty()) + BBI->replaceAllUsesWith(UndefValue::get(BBI->getType())); + BB->getInstList().erase(BBI++); + ++NumInstrsRemoved; + } + if (DTU) + DTU->applyUpdatesPermissive(Updates); + return NumInstrsRemoved; +} + +CallInst *llvm::createCallMatchingInvoke(InvokeInst *II) { + SmallVector<Value *, 8> Args(II->arg_begin(), II->arg_end()); + SmallVector<OperandBundleDef, 1> OpBundles; + II->getOperandBundlesAsDefs(OpBundles); + CallInst *NewCall = CallInst::Create(II->getFunctionType(), + II->getCalledValue(), Args, OpBundles); + NewCall->setCallingConv(II->getCallingConv()); + NewCall->setAttributes(II->getAttributes()); + NewCall->setDebugLoc(II->getDebugLoc()); + NewCall->copyMetadata(*II); + return NewCall; +} + +/// changeToCall - Convert the specified invoke into a normal call. +void llvm::changeToCall(InvokeInst *II, DomTreeUpdater *DTU) { + CallInst *NewCall = createCallMatchingInvoke(II); + NewCall->takeName(II); + NewCall->insertBefore(II); + II->replaceAllUsesWith(NewCall); + + // Follow the call by a branch to the normal destination. + BasicBlock *NormalDestBB = II->getNormalDest(); + BranchInst::Create(NormalDestBB, II); + + // Update PHI nodes in the unwind destination + BasicBlock *BB = II->getParent(); + BasicBlock *UnwindDestBB = II->getUnwindDest(); + UnwindDestBB->removePredecessor(BB); + II->eraseFromParent(); + if (DTU) + DTU->applyUpdatesPermissive({{DominatorTree::Delete, BB, UnwindDestBB}}); +} + +BasicBlock *llvm::changeToInvokeAndSplitBasicBlock(CallInst *CI, + BasicBlock *UnwindEdge) { + BasicBlock *BB = CI->getParent(); + + // Convert this function call into an invoke instruction. First, split the + // basic block. + BasicBlock *Split = + BB->splitBasicBlock(CI->getIterator(), CI->getName() + ".noexc"); + + // Delete the unconditional branch inserted by splitBasicBlock + BB->getInstList().pop_back(); + + // Create the new invoke instruction. + SmallVector<Value *, 8> InvokeArgs(CI->arg_begin(), CI->arg_end()); + SmallVector<OperandBundleDef, 1> OpBundles; + + CI->getOperandBundlesAsDefs(OpBundles); + + // Note: we're round tripping operand bundles through memory here, and that + // can potentially be avoided with a cleverer API design that we do not have + // as of this time. + + InvokeInst *II = + InvokeInst::Create(CI->getFunctionType(), CI->getCalledValue(), Split, + UnwindEdge, InvokeArgs, OpBundles, CI->getName(), BB); + II->setDebugLoc(CI->getDebugLoc()); + II->setCallingConv(CI->getCallingConv()); + II->setAttributes(CI->getAttributes()); + + // Make sure that anything using the call now uses the invoke! This also + // updates the CallGraph if present, because it uses a WeakTrackingVH. + CI->replaceAllUsesWith(II); + + // Delete the original call + Split->getInstList().pop_front(); + return Split; +} + +static bool markAliveBlocks(Function &F, + SmallPtrSetImpl<BasicBlock *> &Reachable, + DomTreeUpdater *DTU = nullptr) { + SmallVector<BasicBlock*, 128> Worklist; + BasicBlock *BB = &F.front(); + Worklist.push_back(BB); + Reachable.insert(BB); + bool Changed = false; + do { + BB = Worklist.pop_back_val(); + + // Do a quick scan of the basic block, turning any obviously unreachable + // instructions into LLVM unreachable insts. The instruction combining pass + // canonicalizes unreachable insts into stores to null or undef. + for (Instruction &I : *BB) { + if (auto *CI = dyn_cast<CallInst>(&I)) { + Value *Callee = CI->getCalledValue(); + // Handle intrinsic calls. + if (Function *F = dyn_cast<Function>(Callee)) { + auto IntrinsicID = F->getIntrinsicID(); + // Assumptions that are known to be false are equivalent to + // unreachable. Also, if the condition is undefined, then we make the + // choice most beneficial to the optimizer, and choose that to also be + // unreachable. + if (IntrinsicID == Intrinsic::assume) { + if (match(CI->getArgOperand(0), m_CombineOr(m_Zero(), m_Undef()))) { + // Don't insert a call to llvm.trap right before the unreachable. + changeToUnreachable(CI, false, false, DTU); + Changed = true; + break; + } + } else if (IntrinsicID == Intrinsic::experimental_guard) { + // A call to the guard intrinsic bails out of the current + // compilation unit if the predicate passed to it is false. If the + // predicate is a constant false, then we know the guard will bail + // out of the current compile unconditionally, so all code following + // it is dead. + // + // Note: unlike in llvm.assume, it is not "obviously profitable" for + // guards to treat `undef` as `false` since a guard on `undef` can + // still be useful for widening. + if (match(CI->getArgOperand(0), m_Zero())) + if (!isa<UnreachableInst>(CI->getNextNode())) { + changeToUnreachable(CI->getNextNode(), /*UseLLVMTrap=*/false, + false, DTU); + Changed = true; + break; + } + } + } else if ((isa<ConstantPointerNull>(Callee) && + !NullPointerIsDefined(CI->getFunction())) || + isa<UndefValue>(Callee)) { + changeToUnreachable(CI, /*UseLLVMTrap=*/false, false, DTU); + Changed = true; + break; + } + if (CI->doesNotReturn() && !CI->isMustTailCall()) { + // If we found a call to a no-return function, insert an unreachable + // instruction after it. Make sure there isn't *already* one there + // though. + if (!isa<UnreachableInst>(CI->getNextNode())) { + // Don't insert a call to llvm.trap right before the unreachable. + changeToUnreachable(CI->getNextNode(), false, false, DTU); + Changed = true; + } + break; + } + } else if (auto *SI = dyn_cast<StoreInst>(&I)) { + // Store to undef and store to null are undefined and used to signal + // that they should be changed to unreachable by passes that can't + // modify the CFG. + + // Don't touch volatile stores. + if (SI->isVolatile()) continue; + + Value *Ptr = SI->getOperand(1); + + if (isa<UndefValue>(Ptr) || + (isa<ConstantPointerNull>(Ptr) && + !NullPointerIsDefined(SI->getFunction(), + SI->getPointerAddressSpace()))) { + changeToUnreachable(SI, true, false, DTU); + Changed = true; + break; + } + } + } + + Instruction *Terminator = BB->getTerminator(); + if (auto *II = dyn_cast<InvokeInst>(Terminator)) { + // Turn invokes that call 'nounwind' functions into ordinary calls. + Value *Callee = II->getCalledValue(); + if ((isa<ConstantPointerNull>(Callee) && + !NullPointerIsDefined(BB->getParent())) || + isa<UndefValue>(Callee)) { + changeToUnreachable(II, true, false, DTU); + Changed = true; + } else if (II->doesNotThrow() && canSimplifyInvokeNoUnwind(&F)) { + if (II->use_empty() && II->onlyReadsMemory()) { + // jump to the normal destination branch. + BasicBlock *NormalDestBB = II->getNormalDest(); + BasicBlock *UnwindDestBB = II->getUnwindDest(); + BranchInst::Create(NormalDestBB, II); + UnwindDestBB->removePredecessor(II->getParent()); + II->eraseFromParent(); + if (DTU) + DTU->applyUpdatesPermissive( + {{DominatorTree::Delete, BB, UnwindDestBB}}); + } else + changeToCall(II, DTU); + Changed = true; + } + } else if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(Terminator)) { + // Remove catchpads which cannot be reached. + struct CatchPadDenseMapInfo { + static CatchPadInst *getEmptyKey() { + return DenseMapInfo<CatchPadInst *>::getEmptyKey(); + } + + static CatchPadInst *getTombstoneKey() { + return DenseMapInfo<CatchPadInst *>::getTombstoneKey(); + } + + static unsigned getHashValue(CatchPadInst *CatchPad) { + return static_cast<unsigned>(hash_combine_range( + CatchPad->value_op_begin(), CatchPad->value_op_end())); + } + + static bool isEqual(CatchPadInst *LHS, CatchPadInst *RHS) { + if (LHS == getEmptyKey() || LHS == getTombstoneKey() || + RHS == getEmptyKey() || RHS == getTombstoneKey()) + return LHS == RHS; + return LHS->isIdenticalTo(RHS); + } + }; + + // Set of unique CatchPads. + SmallDenseMap<CatchPadInst *, detail::DenseSetEmpty, 4, + CatchPadDenseMapInfo, detail::DenseSetPair<CatchPadInst *>> + HandlerSet; + detail::DenseSetEmpty Empty; + for (CatchSwitchInst::handler_iterator I = CatchSwitch->handler_begin(), + E = CatchSwitch->handler_end(); + I != E; ++I) { + BasicBlock *HandlerBB = *I; + auto *CatchPad = cast<CatchPadInst>(HandlerBB->getFirstNonPHI()); + if (!HandlerSet.insert({CatchPad, Empty}).second) { + CatchSwitch->removeHandler(I); + --I; + --E; + Changed = true; + } + } + } + + Changed |= ConstantFoldTerminator(BB, true, nullptr, DTU); + for (BasicBlock *Successor : successors(BB)) + if (Reachable.insert(Successor).second) + Worklist.push_back(Successor); + } while (!Worklist.empty()); + return Changed; +} + +void llvm::removeUnwindEdge(BasicBlock *BB, DomTreeUpdater *DTU) { + Instruction *TI = BB->getTerminator(); + + if (auto *II = dyn_cast<InvokeInst>(TI)) { + changeToCall(II, DTU); + return; + } + + Instruction *NewTI; + BasicBlock *UnwindDest; + + if (auto *CRI = dyn_cast<CleanupReturnInst>(TI)) { + NewTI = CleanupReturnInst::Create(CRI->getCleanupPad(), nullptr, CRI); + UnwindDest = CRI->getUnwindDest(); + } else if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(TI)) { + auto *NewCatchSwitch = CatchSwitchInst::Create( + CatchSwitch->getParentPad(), nullptr, CatchSwitch->getNumHandlers(), + CatchSwitch->getName(), CatchSwitch); + for (BasicBlock *PadBB : CatchSwitch->handlers()) + NewCatchSwitch->addHandler(PadBB); + + NewTI = NewCatchSwitch; + UnwindDest = CatchSwitch->getUnwindDest(); + } else { + llvm_unreachable("Could not find unwind successor"); + } + + NewTI->takeName(TI); + NewTI->setDebugLoc(TI->getDebugLoc()); + UnwindDest->removePredecessor(BB); + TI->replaceAllUsesWith(NewTI); + TI->eraseFromParent(); + if (DTU) + DTU->applyUpdatesPermissive({{DominatorTree::Delete, BB, UnwindDest}}); +} + +/// removeUnreachableBlocks - Remove blocks that are not reachable, even +/// if they are in a dead cycle. Return true if a change was made, false +/// otherwise. +bool llvm::removeUnreachableBlocks(Function &F, DomTreeUpdater *DTU, + MemorySSAUpdater *MSSAU) { + SmallPtrSet<BasicBlock *, 16> Reachable; + bool Changed = markAliveBlocks(F, Reachable, DTU); + + // If there are unreachable blocks in the CFG... + if (Reachable.size() == F.size()) + return Changed; + + assert(Reachable.size() < F.size()); + NumRemoved += F.size() - Reachable.size(); + + SmallSetVector<BasicBlock *, 8> DeadBlockSet; + for (BasicBlock &BB : F) { + // Skip reachable basic blocks + if (Reachable.find(&BB) != Reachable.end()) + continue; + DeadBlockSet.insert(&BB); + } + + if (MSSAU) + MSSAU->removeBlocks(DeadBlockSet); + + // Loop over all of the basic blocks that are not reachable, dropping all of + // their internal references. Update DTU if available. + std::vector<DominatorTree::UpdateType> Updates; + for (auto *BB : DeadBlockSet) { + for (BasicBlock *Successor : successors(BB)) { + if (!DeadBlockSet.count(Successor)) + Successor->removePredecessor(BB); + if (DTU) + Updates.push_back({DominatorTree::Delete, BB, Successor}); + } + BB->dropAllReferences(); + if (DTU) { + Instruction *TI = BB->getTerminator(); + assert(TI && "Basic block should have a terminator"); + // Terminators like invoke can have users. We have to replace their users, + // before removing them. + if (!TI->use_empty()) + TI->replaceAllUsesWith(UndefValue::get(TI->getType())); + TI->eraseFromParent(); + new UnreachableInst(BB->getContext(), BB); + assert(succ_empty(BB) && "The successor list of BB isn't empty before " + "applying corresponding DTU updates."); + } + } + + if (DTU) { + DTU->applyUpdatesPermissive(Updates); + bool Deleted = false; + for (auto *BB : DeadBlockSet) { + if (DTU->isBBPendingDeletion(BB)) + --NumRemoved; + else + Deleted = true; + DTU->deleteBB(BB); + } + if (!Deleted) + return false; + } else { + for (auto *BB : DeadBlockSet) + BB->eraseFromParent(); + } + + return true; +} + +void llvm::combineMetadata(Instruction *K, const Instruction *J, + ArrayRef<unsigned> KnownIDs, bool DoesKMove) { + SmallVector<std::pair<unsigned, MDNode *>, 4> Metadata; + K->dropUnknownNonDebugMetadata(KnownIDs); + K->getAllMetadataOtherThanDebugLoc(Metadata); + for (const auto &MD : Metadata) { + unsigned Kind = MD.first; + MDNode *JMD = J->getMetadata(Kind); + MDNode *KMD = MD.second; + + switch (Kind) { + default: + K->setMetadata(Kind, nullptr); // Remove unknown metadata + break; + case LLVMContext::MD_dbg: + llvm_unreachable("getAllMetadataOtherThanDebugLoc returned a MD_dbg"); + case LLVMContext::MD_tbaa: + K->setMetadata(Kind, MDNode::getMostGenericTBAA(JMD, KMD)); + break; + case LLVMContext::MD_alias_scope: + K->setMetadata(Kind, MDNode::getMostGenericAliasScope(JMD, KMD)); + break; + case LLVMContext::MD_noalias: + case LLVMContext::MD_mem_parallel_loop_access: + K->setMetadata(Kind, MDNode::intersect(JMD, KMD)); + break; + case LLVMContext::MD_access_group: + K->setMetadata(LLVMContext::MD_access_group, + intersectAccessGroups(K, J)); + break; + case LLVMContext::MD_range: + + // If K does move, use most generic range. Otherwise keep the range of + // K. + if (DoesKMove) + // FIXME: If K does move, we should drop the range info and nonnull. + // Currently this function is used with DoesKMove in passes + // doing hoisting/sinking and the current behavior of using the + // most generic range is correct in those cases. + K->setMetadata(Kind, MDNode::getMostGenericRange(JMD, KMD)); + break; + case LLVMContext::MD_fpmath: + K->setMetadata(Kind, MDNode::getMostGenericFPMath(JMD, KMD)); + break; + case LLVMContext::MD_invariant_load: + // Only set the !invariant.load if it is present in both instructions. + K->setMetadata(Kind, JMD); + break; + case LLVMContext::MD_nonnull: + // If K does move, keep nonull if it is present in both instructions. + if (DoesKMove) + K->setMetadata(Kind, JMD); + break; + case LLVMContext::MD_invariant_group: + // Preserve !invariant.group in K. + break; + case LLVMContext::MD_align: + K->setMetadata(Kind, + MDNode::getMostGenericAlignmentOrDereferenceable(JMD, KMD)); + break; + case LLVMContext::MD_dereferenceable: + case LLVMContext::MD_dereferenceable_or_null: + K->setMetadata(Kind, + MDNode::getMostGenericAlignmentOrDereferenceable(JMD, KMD)); + break; + case LLVMContext::MD_preserve_access_index: + // Preserve !preserve.access.index in K. + break; + } + } + // Set !invariant.group from J if J has it. If both instructions have it + // then we will just pick it from J - even when they are different. + // Also make sure that K is load or store - f.e. combining bitcast with load + // could produce bitcast with invariant.group metadata, which is invalid. + // FIXME: we should try to preserve both invariant.group md if they are + // different, but right now instruction can only have one invariant.group. + if (auto *JMD = J->getMetadata(LLVMContext::MD_invariant_group)) + if (isa<LoadInst>(K) || isa<StoreInst>(K)) + K->setMetadata(LLVMContext::MD_invariant_group, JMD); +} + +void llvm::combineMetadataForCSE(Instruction *K, const Instruction *J, + bool KDominatesJ) { + unsigned KnownIDs[] = { + LLVMContext::MD_tbaa, LLVMContext::MD_alias_scope, + LLVMContext::MD_noalias, LLVMContext::MD_range, + LLVMContext::MD_invariant_load, LLVMContext::MD_nonnull, + LLVMContext::MD_invariant_group, LLVMContext::MD_align, + LLVMContext::MD_dereferenceable, + LLVMContext::MD_dereferenceable_or_null, + LLVMContext::MD_access_group, LLVMContext::MD_preserve_access_index}; + combineMetadata(K, J, KnownIDs, KDominatesJ); +} + +void llvm::copyMetadataForLoad(LoadInst &Dest, const LoadInst &Source) { + SmallVector<std::pair<unsigned, MDNode *>, 8> MD; + Source.getAllMetadata(MD); + MDBuilder MDB(Dest.getContext()); + Type *NewType = Dest.getType(); + const DataLayout &DL = Source.getModule()->getDataLayout(); + for (const auto &MDPair : MD) { + unsigned ID = MDPair.first; + MDNode *N = MDPair.second; + // Note, essentially every kind of metadata should be preserved here! This + // routine is supposed to clone a load instruction changing *only its type*. + // The only metadata it makes sense to drop is metadata which is invalidated + // when the pointer type changes. This should essentially never be the case + // in LLVM, but we explicitly switch over only known metadata to be + // conservatively correct. If you are adding metadata to LLVM which pertains + // to loads, you almost certainly want to add it here. + switch (ID) { + case LLVMContext::MD_dbg: + case LLVMContext::MD_tbaa: + case LLVMContext::MD_prof: + case LLVMContext::MD_fpmath: + case LLVMContext::MD_tbaa_struct: + case LLVMContext::MD_invariant_load: + case LLVMContext::MD_alias_scope: + case LLVMContext::MD_noalias: + case LLVMContext::MD_nontemporal: + case LLVMContext::MD_mem_parallel_loop_access: + case LLVMContext::MD_access_group: + // All of these directly apply. + Dest.setMetadata(ID, N); + break; + + case LLVMContext::MD_nonnull: + copyNonnullMetadata(Source, N, Dest); + break; + + case LLVMContext::MD_align: + case LLVMContext::MD_dereferenceable: + case LLVMContext::MD_dereferenceable_or_null: + // These only directly apply if the new type is also a pointer. + if (NewType->isPointerTy()) + Dest.setMetadata(ID, N); + break; + + case LLVMContext::MD_range: + copyRangeMetadata(DL, Source, N, Dest); + break; + } + } +} + +void llvm::patchReplacementInstruction(Instruction *I, Value *Repl) { + auto *ReplInst = dyn_cast<Instruction>(Repl); + if (!ReplInst) + return; + + // Patch the replacement so that it is not more restrictive than the value + // being replaced. + // Note that if 'I' is a load being replaced by some operation, + // for example, by an arithmetic operation, then andIRFlags() + // would just erase all math flags from the original arithmetic + // operation, which is clearly not wanted and not needed. + if (!isa<LoadInst>(I)) + ReplInst->andIRFlags(I); + + // FIXME: If both the original and replacement value are part of the + // same control-flow region (meaning that the execution of one + // guarantees the execution of the other), then we can combine the + // noalias scopes here and do better than the general conservative + // answer used in combineMetadata(). + + // In general, GVN unifies expressions over different control-flow + // regions, and so we need a conservative combination of the noalias + // scopes. + static const unsigned KnownIDs[] = { + LLVMContext::MD_tbaa, LLVMContext::MD_alias_scope, + LLVMContext::MD_noalias, LLVMContext::MD_range, + LLVMContext::MD_fpmath, LLVMContext::MD_invariant_load, + LLVMContext::MD_invariant_group, LLVMContext::MD_nonnull, + LLVMContext::MD_access_group, LLVMContext::MD_preserve_access_index}; + combineMetadata(ReplInst, I, KnownIDs, false); +} + +template <typename RootType, typename DominatesFn> +static unsigned replaceDominatedUsesWith(Value *From, Value *To, + const RootType &Root, + const DominatesFn &Dominates) { + assert(From->getType() == To->getType()); + + unsigned Count = 0; + for (Value::use_iterator UI = From->use_begin(), UE = From->use_end(); + UI != UE;) { + Use &U = *UI++; + if (!Dominates(Root, U)) + continue; + U.set(To); + LLVM_DEBUG(dbgs() << "Replace dominated use of '" << From->getName() + << "' as " << *To << " in " << *U << "\n"); + ++Count; + } + return Count; +} + +unsigned llvm::replaceNonLocalUsesWith(Instruction *From, Value *To) { + assert(From->getType() == To->getType()); + auto *BB = From->getParent(); + unsigned Count = 0; + + for (Value::use_iterator UI = From->use_begin(), UE = From->use_end(); + UI != UE;) { + Use &U = *UI++; + auto *I = cast<Instruction>(U.getUser()); + if (I->getParent() == BB) + continue; + U.set(To); + ++Count; + } + return Count; +} + +unsigned llvm::replaceDominatedUsesWith(Value *From, Value *To, + DominatorTree &DT, + const BasicBlockEdge &Root) { + auto Dominates = [&DT](const BasicBlockEdge &Root, const Use &U) { + return DT.dominates(Root, U); + }; + return ::replaceDominatedUsesWith(From, To, Root, Dominates); +} + +unsigned llvm::replaceDominatedUsesWith(Value *From, Value *To, + DominatorTree &DT, + const BasicBlock *BB) { + auto ProperlyDominates = [&DT](const BasicBlock *BB, const Use &U) { + auto *I = cast<Instruction>(U.getUser())->getParent(); + return DT.properlyDominates(BB, I); + }; + return ::replaceDominatedUsesWith(From, To, BB, ProperlyDominates); +} + +bool llvm::callsGCLeafFunction(const CallBase *Call, + const TargetLibraryInfo &TLI) { + // Check if the function is specifically marked as a gc leaf function. + if (Call->hasFnAttr("gc-leaf-function")) + return true; + if (const Function *F = Call->getCalledFunction()) { + if (F->hasFnAttribute("gc-leaf-function")) + return true; + + if (auto IID = F->getIntrinsicID()) + // Most LLVM intrinsics do not take safepoints. + return IID != Intrinsic::experimental_gc_statepoint && + IID != Intrinsic::experimental_deoptimize; + } + + // Lib calls can be materialized by some passes, and won't be + // marked as 'gc-leaf-function.' All available Libcalls are + // GC-leaf. + LibFunc LF; + if (TLI.getLibFunc(ImmutableCallSite(Call), LF)) { + return TLI.has(LF); + } + + return false; +} + +void llvm::copyNonnullMetadata(const LoadInst &OldLI, MDNode *N, + LoadInst &NewLI) { + auto *NewTy = NewLI.getType(); + + // This only directly applies if the new type is also a pointer. + if (NewTy->isPointerTy()) { + NewLI.setMetadata(LLVMContext::MD_nonnull, N); + return; + } + + // The only other translation we can do is to integral loads with !range + // metadata. + if (!NewTy->isIntegerTy()) + return; + + MDBuilder MDB(NewLI.getContext()); + const Value *Ptr = OldLI.getPointerOperand(); + auto *ITy = cast<IntegerType>(NewTy); + auto *NullInt = ConstantExpr::getPtrToInt( + ConstantPointerNull::get(cast<PointerType>(Ptr->getType())), ITy); + auto *NonNullInt = ConstantExpr::getAdd(NullInt, ConstantInt::get(ITy, 1)); + NewLI.setMetadata(LLVMContext::MD_range, + MDB.createRange(NonNullInt, NullInt)); +} + +void llvm::copyRangeMetadata(const DataLayout &DL, const LoadInst &OldLI, + MDNode *N, LoadInst &NewLI) { + auto *NewTy = NewLI.getType(); + + // Give up unless it is converted to a pointer where there is a single very + // valuable mapping we can do reliably. + // FIXME: It would be nice to propagate this in more ways, but the type + // conversions make it hard. + if (!NewTy->isPointerTy()) + return; + + unsigned BitWidth = DL.getIndexTypeSizeInBits(NewTy); + if (!getConstantRangeFromMetadata(*N).contains(APInt(BitWidth, 0))) { + MDNode *NN = MDNode::get(OldLI.getContext(), None); + NewLI.setMetadata(LLVMContext::MD_nonnull, NN); + } +} + +void llvm::dropDebugUsers(Instruction &I) { + SmallVector<DbgVariableIntrinsic *, 1> DbgUsers; + findDbgUsers(DbgUsers, &I); + for (auto *DII : DbgUsers) + DII->eraseFromParent(); +} + +void llvm::hoistAllInstructionsInto(BasicBlock *DomBlock, Instruction *InsertPt, + BasicBlock *BB) { + // Since we are moving the instructions out of its basic block, we do not + // retain their original debug locations (DILocations) and debug intrinsic + // instructions. + // + // Doing so would degrade the debugging experience and adversely affect the + // accuracy of profiling information. + // + // Currently, when hoisting the instructions, we take the following actions: + // - Remove their debug intrinsic instructions. + // - Set their debug locations to the values from the insertion point. + // + // As per PR39141 (comment #8), the more fundamental reason why the dbg.values + // need to be deleted, is because there will not be any instructions with a + // DILocation in either branch left after performing the transformation. We + // can only insert a dbg.value after the two branches are joined again. + // + // See PR38762, PR39243 for more details. + // + // TODO: Extend llvm.dbg.value to take more than one SSA Value (PR39141) to + // encode predicated DIExpressions that yield different results on different + // code paths. + for (BasicBlock::iterator II = BB->begin(), IE = BB->end(); II != IE;) { + Instruction *I = &*II; + I->dropUnknownNonDebugMetadata(); + if (I->isUsedByMetadata()) + dropDebugUsers(*I); + if (isa<DbgInfoIntrinsic>(I)) { + // Remove DbgInfo Intrinsics. + II = I->eraseFromParent(); + continue; + } + I->setDebugLoc(InsertPt->getDebugLoc()); + ++II; + } + DomBlock->getInstList().splice(InsertPt->getIterator(), BB->getInstList(), + BB->begin(), + BB->getTerminator()->getIterator()); +} + +namespace { + +/// A potential constituent of a bitreverse or bswap expression. See +/// collectBitParts for a fuller explanation. +struct BitPart { + BitPart(Value *P, unsigned BW) : Provider(P) { + Provenance.resize(BW); + } + + /// The Value that this is a bitreverse/bswap of. + Value *Provider; + + /// The "provenance" of each bit. Provenance[A] = B means that bit A + /// in Provider becomes bit B in the result of this expression. + SmallVector<int8_t, 32> Provenance; // int8_t means max size is i128. + + enum { Unset = -1 }; +}; + +} // end anonymous namespace + +/// Analyze the specified subexpression and see if it is capable of providing +/// pieces of a bswap or bitreverse. The subexpression provides a potential +/// piece of a bswap or bitreverse if it can be proven that each non-zero bit in +/// the output of the expression came from a corresponding bit in some other +/// value. This function is recursive, and the end result is a mapping of +/// bitnumber to bitnumber. It is the caller's responsibility to validate that +/// the bitnumber to bitnumber mapping is correct for a bswap or bitreverse. +/// +/// For example, if the current subexpression if "(shl i32 %X, 24)" then we know +/// that the expression deposits the low byte of %X into the high byte of the +/// result and that all other bits are zero. This expression is accepted and a +/// BitPart is returned with Provider set to %X and Provenance[24-31] set to +/// [0-7]. +/// +/// To avoid revisiting values, the BitPart results are memoized into the +/// provided map. To avoid unnecessary copying of BitParts, BitParts are +/// constructed in-place in the \c BPS map. Because of this \c BPS needs to +/// store BitParts objects, not pointers. As we need the concept of a nullptr +/// BitParts (Value has been analyzed and the analysis failed), we an Optional +/// type instead to provide the same functionality. +/// +/// Because we pass around references into \c BPS, we must use a container that +/// does not invalidate internal references (std::map instead of DenseMap). +static const Optional<BitPart> & +collectBitParts(Value *V, bool MatchBSwaps, bool MatchBitReversals, + std::map<Value *, Optional<BitPart>> &BPS, int Depth) { + auto I = BPS.find(V); + if (I != BPS.end()) + return I->second; + + auto &Result = BPS[V] = None; + auto BitWidth = cast<IntegerType>(V->getType())->getBitWidth(); + + // Prevent stack overflow by limiting the recursion depth + if (Depth == BitPartRecursionMaxDepth) { + LLVM_DEBUG(dbgs() << "collectBitParts max recursion depth reached.\n"); + return Result; + } + + if (Instruction *I = dyn_cast<Instruction>(V)) { + // If this is an or instruction, it may be an inner node of the bswap. + if (I->getOpcode() == Instruction::Or) { + auto &A = collectBitParts(I->getOperand(0), MatchBSwaps, + MatchBitReversals, BPS, Depth + 1); + auto &B = collectBitParts(I->getOperand(1), MatchBSwaps, + MatchBitReversals, BPS, Depth + 1); + if (!A || !B) + return Result; + + // Try and merge the two together. + if (!A->Provider || A->Provider != B->Provider) + return Result; + + Result = BitPart(A->Provider, BitWidth); + for (unsigned i = 0; i < A->Provenance.size(); ++i) { + if (A->Provenance[i] != BitPart::Unset && + B->Provenance[i] != BitPart::Unset && + A->Provenance[i] != B->Provenance[i]) + return Result = None; + + if (A->Provenance[i] == BitPart::Unset) + Result->Provenance[i] = B->Provenance[i]; + else + Result->Provenance[i] = A->Provenance[i]; + } + + return Result; + } + + // If this is a logical shift by a constant, recurse then shift the result. + if (I->isLogicalShift() && isa<ConstantInt>(I->getOperand(1))) { + unsigned BitShift = + cast<ConstantInt>(I->getOperand(1))->getLimitedValue(~0U); + // Ensure the shift amount is defined. + if (BitShift > BitWidth) + return Result; + + auto &Res = collectBitParts(I->getOperand(0), MatchBSwaps, + MatchBitReversals, BPS, Depth + 1); + if (!Res) + return Result; + Result = Res; + + // Perform the "shift" on BitProvenance. + auto &P = Result->Provenance; + if (I->getOpcode() == Instruction::Shl) { + P.erase(std::prev(P.end(), BitShift), P.end()); + P.insert(P.begin(), BitShift, BitPart::Unset); + } else { + P.erase(P.begin(), std::next(P.begin(), BitShift)); + P.insert(P.end(), BitShift, BitPart::Unset); + } + + return Result; + } + + // If this is a logical 'and' with a mask that clears bits, recurse then + // unset the appropriate bits. + if (I->getOpcode() == Instruction::And && + isa<ConstantInt>(I->getOperand(1))) { + APInt Bit(I->getType()->getPrimitiveSizeInBits(), 1); + const APInt &AndMask = cast<ConstantInt>(I->getOperand(1))->getValue(); + + // Check that the mask allows a multiple of 8 bits for a bswap, for an + // early exit. + unsigned NumMaskedBits = AndMask.countPopulation(); + if (!MatchBitReversals && NumMaskedBits % 8 != 0) + return Result; + + auto &Res = collectBitParts(I->getOperand(0), MatchBSwaps, + MatchBitReversals, BPS, Depth + 1); + if (!Res) + return Result; + Result = Res; + + for (unsigned i = 0; i < BitWidth; ++i, Bit <<= 1) + // If the AndMask is zero for this bit, clear the bit. + if ((AndMask & Bit) == 0) + Result->Provenance[i] = BitPart::Unset; + return Result; + } + + // If this is a zext instruction zero extend the result. + if (I->getOpcode() == Instruction::ZExt) { + auto &Res = collectBitParts(I->getOperand(0), MatchBSwaps, + MatchBitReversals, BPS, Depth + 1); + if (!Res) + return Result; + + Result = BitPart(Res->Provider, BitWidth); + auto NarrowBitWidth = + cast<IntegerType>(cast<ZExtInst>(I)->getSrcTy())->getBitWidth(); + for (unsigned i = 0; i < NarrowBitWidth; ++i) + Result->Provenance[i] = Res->Provenance[i]; + for (unsigned i = NarrowBitWidth; i < BitWidth; ++i) + Result->Provenance[i] = BitPart::Unset; + return Result; + } + } + + // Okay, we got to something that isn't a shift, 'or' or 'and'. This must be + // the input value to the bswap/bitreverse. + Result = BitPart(V, BitWidth); + for (unsigned i = 0; i < BitWidth; ++i) + Result->Provenance[i] = i; + return Result; +} + +static bool bitTransformIsCorrectForBSwap(unsigned From, unsigned To, + unsigned BitWidth) { + if (From % 8 != To % 8) + return false; + // Convert from bit indices to byte indices and check for a byte reversal. + From >>= 3; + To >>= 3; + BitWidth >>= 3; + return From == BitWidth - To - 1; +} + +static bool bitTransformIsCorrectForBitReverse(unsigned From, unsigned To, + unsigned BitWidth) { + return From == BitWidth - To - 1; +} + +bool llvm::recognizeBSwapOrBitReverseIdiom( + Instruction *I, bool MatchBSwaps, bool MatchBitReversals, + SmallVectorImpl<Instruction *> &InsertedInsts) { + if (Operator::getOpcode(I) != Instruction::Or) + return false; + if (!MatchBSwaps && !MatchBitReversals) + return false; + IntegerType *ITy = dyn_cast<IntegerType>(I->getType()); + if (!ITy || ITy->getBitWidth() > 128) + return false; // Can't do vectors or integers > 128 bits. + unsigned BW = ITy->getBitWidth(); + + unsigned DemandedBW = BW; + IntegerType *DemandedTy = ITy; + if (I->hasOneUse()) { + if (TruncInst *Trunc = dyn_cast<TruncInst>(I->user_back())) { + DemandedTy = cast<IntegerType>(Trunc->getType()); + DemandedBW = DemandedTy->getBitWidth(); + } + } + + // Try to find all the pieces corresponding to the bswap. + std::map<Value *, Optional<BitPart>> BPS; + auto Res = collectBitParts(I, MatchBSwaps, MatchBitReversals, BPS, 0); + if (!Res) + return false; + auto &BitProvenance = Res->Provenance; + + // Now, is the bit permutation correct for a bswap or a bitreverse? We can + // only byteswap values with an even number of bytes. + bool OKForBSwap = DemandedBW % 16 == 0, OKForBitReverse = true; + for (unsigned i = 0; i < DemandedBW; ++i) { + OKForBSwap &= + bitTransformIsCorrectForBSwap(BitProvenance[i], i, DemandedBW); + OKForBitReverse &= + bitTransformIsCorrectForBitReverse(BitProvenance[i], i, DemandedBW); + } + + Intrinsic::ID Intrin; + if (OKForBSwap && MatchBSwaps) + Intrin = Intrinsic::bswap; + else if (OKForBitReverse && MatchBitReversals) + Intrin = Intrinsic::bitreverse; + else + return false; + + if (ITy != DemandedTy) { + Function *F = Intrinsic::getDeclaration(I->getModule(), Intrin, DemandedTy); + Value *Provider = Res->Provider; + IntegerType *ProviderTy = cast<IntegerType>(Provider->getType()); + // We may need to truncate the provider. + if (DemandedTy != ProviderTy) { + auto *Trunc = CastInst::Create(Instruction::Trunc, Provider, DemandedTy, + "trunc", I); + InsertedInsts.push_back(Trunc); + Provider = Trunc; + } + auto *CI = CallInst::Create(F, Provider, "rev", I); + InsertedInsts.push_back(CI); + auto *ExtInst = CastInst::Create(Instruction::ZExt, CI, ITy, "zext", I); + InsertedInsts.push_back(ExtInst); + return true; + } + + Function *F = Intrinsic::getDeclaration(I->getModule(), Intrin, ITy); + InsertedInsts.push_back(CallInst::Create(F, Res->Provider, "rev", I)); + return true; +} + +// CodeGen has special handling for some string functions that may replace +// them with target-specific intrinsics. Since that'd skip our interceptors +// in ASan/MSan/TSan/DFSan, and thus make us miss some memory accesses, +// we mark affected calls as NoBuiltin, which will disable optimization +// in CodeGen. +void llvm::maybeMarkSanitizerLibraryCallNoBuiltin( + CallInst *CI, const TargetLibraryInfo *TLI) { + Function *F = CI->getCalledFunction(); + LibFunc Func; + if (F && !F->hasLocalLinkage() && F->hasName() && + TLI->getLibFunc(F->getName(), Func) && TLI->hasOptimizedCodeGen(Func) && + !F->doesNotAccessMemory()) + CI->addAttribute(AttributeList::FunctionIndex, Attribute::NoBuiltin); +} + +bool llvm::canReplaceOperandWithVariable(const Instruction *I, unsigned OpIdx) { + // We can't have a PHI with a metadata type. + if (I->getOperand(OpIdx)->getType()->isMetadataTy()) + return false; + + // Early exit. + if (!isa<Constant>(I->getOperand(OpIdx))) + return true; + + switch (I->getOpcode()) { + default: + return true; + case Instruction::Call: + case Instruction::Invoke: + // Can't handle inline asm. Skip it. + if (isa<InlineAsm>(ImmutableCallSite(I).getCalledValue())) + return false; + // Many arithmetic intrinsics have no issue taking a + // variable, however it's hard to distingish these from + // specials such as @llvm.frameaddress that require a constant. + if (isa<IntrinsicInst>(I)) + return false; + + // Constant bundle operands may need to retain their constant-ness for + // correctness. + if (ImmutableCallSite(I).isBundleOperand(OpIdx)) + return false; + return true; + case Instruction::ShuffleVector: + // Shufflevector masks are constant. + return OpIdx != 2; + case Instruction::Switch: + case Instruction::ExtractValue: + // All operands apart from the first are constant. + return OpIdx == 0; + case Instruction::InsertValue: + // All operands apart from the first and the second are constant. + return OpIdx < 2; + case Instruction::Alloca: + // Static allocas (constant size in the entry block) are handled by + // prologue/epilogue insertion so they're free anyway. We definitely don't + // want to make them non-constant. + return !cast<AllocaInst>(I)->isStaticAlloca(); + case Instruction::GetElementPtr: + if (OpIdx == 0) + return true; + gep_type_iterator It = gep_type_begin(I); + for (auto E = std::next(It, OpIdx); It != E; ++It) + if (It.isStruct()) + return false; + return true; + } +} + +using AllocaForValueMapTy = DenseMap<Value *, AllocaInst *>; +AllocaInst *llvm::findAllocaForValue(Value *V, + AllocaForValueMapTy &AllocaForValue) { + if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) + return AI; + // See if we've already calculated (or started to calculate) alloca for a + // given value. + AllocaForValueMapTy::iterator I = AllocaForValue.find(V); + if (I != AllocaForValue.end()) + return I->second; + // Store 0 while we're calculating alloca for value V to avoid + // infinite recursion if the value references itself. + AllocaForValue[V] = nullptr; + AllocaInst *Res = nullptr; + if (CastInst *CI = dyn_cast<CastInst>(V)) + Res = findAllocaForValue(CI->getOperand(0), AllocaForValue); + else if (PHINode *PN = dyn_cast<PHINode>(V)) { + for (Value *IncValue : PN->incoming_values()) { + // Allow self-referencing phi-nodes. + if (IncValue == PN) + continue; + AllocaInst *IncValueAI = findAllocaForValue(IncValue, AllocaForValue); + // AI for incoming values should exist and should all be equal. + if (IncValueAI == nullptr || (Res != nullptr && IncValueAI != Res)) + return nullptr; + Res = IncValueAI; + } + } else if (GetElementPtrInst *EP = dyn_cast<GetElementPtrInst>(V)) { + Res = findAllocaForValue(EP->getPointerOperand(), AllocaForValue); + } else { + LLVM_DEBUG(dbgs() << "Alloca search cancelled on unknown instruction: " + << *V << "\n"); + } + if (Res) + AllocaForValue[V] = Res; + return Res; +} |