| //===- InstCombinePHI.cpp -------------------------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements the visitPHINode function. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "InstCombineInternal.h" |
| #include "llvm/ADT/STLExtras.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/Analysis/InstructionSimplify.h" |
| #include "llvm/Analysis/ValueTracking.h" |
| #include "llvm/IR/PatternMatch.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Transforms/InstCombine/InstCombiner.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| |
| using namespace llvm; |
| using namespace llvm::PatternMatch; |
| |
| #define DEBUG_TYPE "instcombine" |
| |
| static cl::opt<unsigned> |
| MaxNumPhis("instcombine-max-num-phis", cl::init(512), |
| cl::desc("Maximum number phis to handle in intptr/ptrint folding")); |
| |
| STATISTIC(NumPHIsOfInsertValues, |
| "Number of phi-of-insertvalue turned into insertvalue-of-phis"); |
| STATISTIC(NumPHIsOfExtractValues, |
| "Number of phi-of-extractvalue turned into extractvalue-of-phi"); |
| STATISTIC(NumPHICSEs, "Number of PHI's that got CSE'd"); |
| |
| /// The PHI arguments will be folded into a single operation with a PHI node |
| /// as input. The debug location of the single operation will be the merged |
| /// locations of the original PHI node arguments. |
| void InstCombinerImpl::PHIArgMergedDebugLoc(Instruction *Inst, PHINode &PN) { |
| auto *FirstInst = cast<Instruction>(PN.getIncomingValue(0)); |
| Inst->setDebugLoc(FirstInst->getDebugLoc()); |
| // We do not expect a CallInst here, otherwise, N-way merging of DebugLoc |
| // will be inefficient. |
| assert(!isa<CallInst>(Inst)); |
| |
| for (unsigned i = 1; i != PN.getNumIncomingValues(); ++i) { |
| auto *I = cast<Instruction>(PN.getIncomingValue(i)); |
| Inst->applyMergedLocation(Inst->getDebugLoc(), I->getDebugLoc()); |
| } |
| } |
| |
| // Replace Integer typed PHI PN if the PHI's value is used as a pointer value. |
| // If there is an existing pointer typed PHI that produces the same value as PN, |
| // replace PN and the IntToPtr operation with it. Otherwise, synthesize a new |
| // PHI node: |
| // |
| // Case-1: |
| // bb1: |
| // int_init = PtrToInt(ptr_init) |
| // br label %bb2 |
| // bb2: |
| // int_val = PHI([int_init, %bb1], [int_val_inc, %bb2] |
| // ptr_val = PHI([ptr_init, %bb1], [ptr_val_inc, %bb2] |
| // ptr_val2 = IntToPtr(int_val) |
| // ... |
| // use(ptr_val2) |
| // ptr_val_inc = ... |
| // inc_val_inc = PtrToInt(ptr_val_inc) |
| // |
| // ==> |
| // bb1: |
| // br label %bb2 |
| // bb2: |
| // ptr_val = PHI([ptr_init, %bb1], [ptr_val_inc, %bb2] |
| // ... |
| // use(ptr_val) |
| // ptr_val_inc = ... |
| // |
| // Case-2: |
| // bb1: |
| // int_ptr = BitCast(ptr_ptr) |
| // int_init = Load(int_ptr) |
| // br label %bb2 |
| // bb2: |
| // int_val = PHI([int_init, %bb1], [int_val_inc, %bb2] |
| // ptr_val2 = IntToPtr(int_val) |
| // ... |
| // use(ptr_val2) |
| // ptr_val_inc = ... |
| // inc_val_inc = PtrToInt(ptr_val_inc) |
| // ==> |
| // bb1: |
| // ptr_init = Load(ptr_ptr) |
| // br label %bb2 |
| // bb2: |
| // ptr_val = PHI([ptr_init, %bb1], [ptr_val_inc, %bb2] |
| // ... |
| // use(ptr_val) |
| // ptr_val_inc = ... |
| // ... |
| // |
| Instruction *InstCombinerImpl::foldIntegerTypedPHI(PHINode &PN) { |
| if (!PN.getType()->isIntegerTy()) |
| return nullptr; |
| if (!PN.hasOneUse()) |
| return nullptr; |
| |
| auto *IntToPtr = dyn_cast<IntToPtrInst>(PN.user_back()); |
| if (!IntToPtr) |
| return nullptr; |
| |
| // Check if the pointer is actually used as pointer: |
| auto HasPointerUse = [](Instruction *IIP) { |
| for (User *U : IIP->users()) { |
| Value *Ptr = nullptr; |
| if (LoadInst *LoadI = dyn_cast<LoadInst>(U)) { |
| Ptr = LoadI->getPointerOperand(); |
| } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) { |
| Ptr = SI->getPointerOperand(); |
| } else if (GetElementPtrInst *GI = dyn_cast<GetElementPtrInst>(U)) { |
| Ptr = GI->getPointerOperand(); |
| } |
| |
| if (Ptr && Ptr == IIP) |
| return true; |
| } |
| return false; |
| }; |
| |
| if (!HasPointerUse(IntToPtr)) |
| return nullptr; |
| |
| if (DL.getPointerSizeInBits(IntToPtr->getAddressSpace()) != |
| DL.getTypeSizeInBits(IntToPtr->getOperand(0)->getType())) |
| return nullptr; |
| |
| SmallVector<Value *, 4> AvailablePtrVals; |
| for (unsigned i = 0; i != PN.getNumIncomingValues(); ++i) { |
| Value *Arg = PN.getIncomingValue(i); |
| |
| // First look backward: |
| if (auto *PI = dyn_cast<PtrToIntInst>(Arg)) { |
| AvailablePtrVals.emplace_back(PI->getOperand(0)); |
| continue; |
| } |
| |
| // Next look forward: |
| Value *ArgIntToPtr = nullptr; |
| for (User *U : Arg->users()) { |
| if (isa<IntToPtrInst>(U) && U->getType() == IntToPtr->getType() && |
| (DT.dominates(cast<Instruction>(U), PN.getIncomingBlock(i)) || |
| cast<Instruction>(U)->getParent() == PN.getIncomingBlock(i))) { |
| ArgIntToPtr = U; |
| break; |
| } |
| } |
| |
| if (ArgIntToPtr) { |
| AvailablePtrVals.emplace_back(ArgIntToPtr); |
| continue; |
| } |
| |
| // If Arg is defined by a PHI, allow it. This will also create |
| // more opportunities iteratively. |
| if (isa<PHINode>(Arg)) { |
| AvailablePtrVals.emplace_back(Arg); |
| continue; |
| } |
| |
| // For a single use integer load: |
| auto *LoadI = dyn_cast<LoadInst>(Arg); |
| if (!LoadI) |
| return nullptr; |
| |
| if (!LoadI->hasOneUse()) |
| return nullptr; |
| |
| // Push the integer typed Load instruction into the available |
| // value set, and fix it up later when the pointer typed PHI |
| // is synthesized. |
| AvailablePtrVals.emplace_back(LoadI); |
| } |
| |
| // Now search for a matching PHI |
| auto *BB = PN.getParent(); |
| assert(AvailablePtrVals.size() == PN.getNumIncomingValues() && |
| "Not enough available ptr typed incoming values"); |
| PHINode *MatchingPtrPHI = nullptr; |
| unsigned NumPhis = 0; |
| for (auto II = BB->begin(); II != BB->end(); II++, NumPhis++) { |
| // FIXME: consider handling this in AggressiveInstCombine |
| PHINode *PtrPHI = dyn_cast<PHINode>(II); |
| if (!PtrPHI) |
| break; |
| if (NumPhis > MaxNumPhis) |
| return nullptr; |
| if (PtrPHI == &PN || PtrPHI->getType() != IntToPtr->getType()) |
| continue; |
| MatchingPtrPHI = PtrPHI; |
| for (unsigned i = 0; i != PtrPHI->getNumIncomingValues(); ++i) { |
| if (AvailablePtrVals[i] != |
| PtrPHI->getIncomingValueForBlock(PN.getIncomingBlock(i))) { |
| MatchingPtrPHI = nullptr; |
| break; |
| } |
| } |
| |
| if (MatchingPtrPHI) |
| break; |
| } |
| |
| if (MatchingPtrPHI) { |
| assert(MatchingPtrPHI->getType() == IntToPtr->getType() && |
| "Phi's Type does not match with IntToPtr"); |
| // The PtrToCast + IntToPtr will be simplified later |
| return CastInst::CreateBitOrPointerCast(MatchingPtrPHI, |
| IntToPtr->getOperand(0)->getType()); |
| } |
| |
| // If it requires a conversion for every PHI operand, do not do it. |
| if (all_of(AvailablePtrVals, [&](Value *V) { |
| return (V->getType() != IntToPtr->getType()) || isa<IntToPtrInst>(V); |
| })) |
| return nullptr; |
| |
| // If any of the operand that requires casting is a terminator |
| // instruction, do not do it. Similarly, do not do the transform if the value |
| // is PHI in a block with no insertion point, for example, a catchswitch |
| // block, since we will not be able to insert a cast after the PHI. |
| if (any_of(AvailablePtrVals, [&](Value *V) { |
| if (V->getType() == IntToPtr->getType()) |
| return false; |
| auto *Inst = dyn_cast<Instruction>(V); |
| if (!Inst) |
| return false; |
| if (Inst->isTerminator()) |
| return true; |
| auto *BB = Inst->getParent(); |
| if (isa<PHINode>(Inst) && BB->getFirstInsertionPt() == BB->end()) |
| return true; |
| return false; |
| })) |
| return nullptr; |
| |
| PHINode *NewPtrPHI = PHINode::Create( |
| IntToPtr->getType(), PN.getNumIncomingValues(), PN.getName() + ".ptr"); |
| |
| InsertNewInstBefore(NewPtrPHI, PN); |
| SmallDenseMap<Value *, Instruction *> Casts; |
| for (unsigned i = 0; i != PN.getNumIncomingValues(); ++i) { |
| auto *IncomingBB = PN.getIncomingBlock(i); |
| auto *IncomingVal = AvailablePtrVals[i]; |
| |
| if (IncomingVal->getType() == IntToPtr->getType()) { |
| NewPtrPHI->addIncoming(IncomingVal, IncomingBB); |
| continue; |
| } |
| |
| #ifndef NDEBUG |
| LoadInst *LoadI = dyn_cast<LoadInst>(IncomingVal); |
| assert((isa<PHINode>(IncomingVal) || |
| IncomingVal->getType()->isPointerTy() || |
| (LoadI && LoadI->hasOneUse())) && |
| "Can not replace LoadInst with multiple uses"); |
| #endif |
| // Need to insert a BitCast. |
| // For an integer Load instruction with a single use, the load + IntToPtr |
| // cast will be simplified into a pointer load: |
| // %v = load i64, i64* %a.ip, align 8 |
| // %v.cast = inttoptr i64 %v to float ** |
| // ==> |
| // %v.ptrp = bitcast i64 * %a.ip to float ** |
| // %v.cast = load float *, float ** %v.ptrp, align 8 |
| Instruction *&CI = Casts[IncomingVal]; |
| if (!CI) { |
| CI = CastInst::CreateBitOrPointerCast(IncomingVal, IntToPtr->getType(), |
| IncomingVal->getName() + ".ptr"); |
| if (auto *IncomingI = dyn_cast<Instruction>(IncomingVal)) { |
| BasicBlock::iterator InsertPos(IncomingI); |
| InsertPos++; |
| BasicBlock *BB = IncomingI->getParent(); |
| if (isa<PHINode>(IncomingI)) |
| InsertPos = BB->getFirstInsertionPt(); |
| assert(InsertPos != BB->end() && "should have checked above"); |
| InsertNewInstBefore(CI, *InsertPos); |
| } else { |
| auto *InsertBB = &IncomingBB->getParent()->getEntryBlock(); |
| InsertNewInstBefore(CI, *InsertBB->getFirstInsertionPt()); |
| } |
| } |
| NewPtrPHI->addIncoming(CI, IncomingBB); |
| } |
| |
| // The PtrToCast + IntToPtr will be simplified later |
| return CastInst::CreateBitOrPointerCast(NewPtrPHI, |
| IntToPtr->getOperand(0)->getType()); |
| } |
| |
| /// If we have something like phi [insertvalue(a,b,0), insertvalue(c,d,0)], |
| /// turn this into a phi[a,c] and phi[b,d] and a single insertvalue. |
| Instruction * |
| InstCombinerImpl::foldPHIArgInsertValueInstructionIntoPHI(PHINode &PN) { |
| auto *FirstIVI = cast<InsertValueInst>(PN.getIncomingValue(0)); |
| |
| // Scan to see if all operands are `insertvalue`'s with the same indicies, |
| // and all have a single use. |
| for (unsigned i = 1; i != PN.getNumIncomingValues(); ++i) { |
| auto *I = dyn_cast<InsertValueInst>(PN.getIncomingValue(i)); |
| if (!I || !I->hasOneUser() || I->getIndices() != FirstIVI->getIndices()) |
| return nullptr; |
| } |
| |
| // For each operand of an `insertvalue` |
| std::array<PHINode *, 2> NewOperands; |
| for (int OpIdx : {0, 1}) { |
| auto *&NewOperand = NewOperands[OpIdx]; |
| // Create a new PHI node to receive the values the operand has in each |
| // incoming basic block. |
| NewOperand = PHINode::Create( |
| FirstIVI->getOperand(OpIdx)->getType(), PN.getNumIncomingValues(), |
| FirstIVI->getOperand(OpIdx)->getName() + ".pn"); |
| // And populate each operand's PHI with said values. |
| for (auto Incoming : zip(PN.blocks(), PN.incoming_values())) |
| NewOperand->addIncoming( |
| cast<InsertValueInst>(std::get<1>(Incoming))->getOperand(OpIdx), |
| std::get<0>(Incoming)); |
| InsertNewInstBefore(NewOperand, PN); |
| } |
| |
| // And finally, create `insertvalue` over the newly-formed PHI nodes. |
| auto *NewIVI = InsertValueInst::Create(NewOperands[0], NewOperands[1], |
| FirstIVI->getIndices(), PN.getName()); |
| |
| PHIArgMergedDebugLoc(NewIVI, PN); |
| ++NumPHIsOfInsertValues; |
| return NewIVI; |
| } |
| |
| /// If we have something like phi [extractvalue(a,0), extractvalue(b,0)], |
| /// turn this into a phi[a,b] and a single extractvalue. |
| Instruction * |
| InstCombinerImpl::foldPHIArgExtractValueInstructionIntoPHI(PHINode &PN) { |
| auto *FirstEVI = cast<ExtractValueInst>(PN.getIncomingValue(0)); |
| |
| // Scan to see if all operands are `extractvalue`'s with the same indicies, |
| // and all have a single use. |
| for (unsigned i = 1; i != PN.getNumIncomingValues(); ++i) { |
| auto *I = dyn_cast<ExtractValueInst>(PN.getIncomingValue(i)); |
| if (!I || !I->hasOneUser() || I->getIndices() != FirstEVI->getIndices() || |
| I->getAggregateOperand()->getType() != |
| FirstEVI->getAggregateOperand()->getType()) |
| return nullptr; |
| } |
| |
| // Create a new PHI node to receive the values the aggregate operand has |
| // in each incoming basic block. |
| auto *NewAggregateOperand = PHINode::Create( |
| FirstEVI->getAggregateOperand()->getType(), PN.getNumIncomingValues(), |
| FirstEVI->getAggregateOperand()->getName() + ".pn"); |
| // And populate the PHI with said values. |
| for (auto Incoming : zip(PN.blocks(), PN.incoming_values())) |
| NewAggregateOperand->addIncoming( |
| cast<ExtractValueInst>(std::get<1>(Incoming))->getAggregateOperand(), |
| std::get<0>(Incoming)); |
| InsertNewInstBefore(NewAggregateOperand, PN); |
| |
| // And finally, create `extractvalue` over the newly-formed PHI nodes. |
| auto *NewEVI = ExtractValueInst::Create(NewAggregateOperand, |
| FirstEVI->getIndices(), PN.getName()); |
| |
| PHIArgMergedDebugLoc(NewEVI, PN); |
| ++NumPHIsOfExtractValues; |
| return NewEVI; |
| } |
| |
| /// If we have something like phi [add (a,b), add(a,c)] and if a/b/c and the |
| /// adds all have a single user, turn this into a phi and a single binop. |
| Instruction *InstCombinerImpl::foldPHIArgBinOpIntoPHI(PHINode &PN) { |
| Instruction *FirstInst = cast<Instruction>(PN.getIncomingValue(0)); |
| assert(isa<BinaryOperator>(FirstInst) || isa<CmpInst>(FirstInst)); |
| unsigned Opc = FirstInst->getOpcode(); |
| Value *LHSVal = FirstInst->getOperand(0); |
| Value *RHSVal = FirstInst->getOperand(1); |
| |
| Type *LHSType = LHSVal->getType(); |
| Type *RHSType = RHSVal->getType(); |
| |
| // Scan to see if all operands are the same opcode, and all have one user. |
| for (unsigned i = 1; i != PN.getNumIncomingValues(); ++i) { |
| Instruction *I = dyn_cast<Instruction>(PN.getIncomingValue(i)); |
| if (!I || I->getOpcode() != Opc || !I->hasOneUser() || |
| // Verify type of the LHS matches so we don't fold cmp's of different |
| // types. |
| I->getOperand(0)->getType() != LHSType || |
| I->getOperand(1)->getType() != RHSType) |
| return nullptr; |
| |
| // If they are CmpInst instructions, check their predicates |
| if (CmpInst *CI = dyn_cast<CmpInst>(I)) |
| if (CI->getPredicate() != cast<CmpInst>(FirstInst)->getPredicate()) |
| return nullptr; |
| |
| // Keep track of which operand needs a phi node. |
| if (I->getOperand(0) != LHSVal) LHSVal = nullptr; |
| if (I->getOperand(1) != RHSVal) RHSVal = nullptr; |
| } |
| |
| // If both LHS and RHS would need a PHI, don't do this transformation, |
| // because it would increase the number of PHIs entering the block, |
| // which leads to higher register pressure. This is especially |
| // bad when the PHIs are in the header of a loop. |
| if (!LHSVal && !RHSVal) |
| return nullptr; |
| |
| // Otherwise, this is safe to transform! |
| |
| Value *InLHS = FirstInst->getOperand(0); |
| Value *InRHS = FirstInst->getOperand(1); |
| PHINode *NewLHS = nullptr, *NewRHS = nullptr; |
| if (!LHSVal) { |
| NewLHS = PHINode::Create(LHSType, PN.getNumIncomingValues(), |
| FirstInst->getOperand(0)->getName() + ".pn"); |
| NewLHS->addIncoming(InLHS, PN.getIncomingBlock(0)); |
| InsertNewInstBefore(NewLHS, PN); |
| LHSVal = NewLHS; |
| } |
| |
| if (!RHSVal) { |
| NewRHS = PHINode::Create(RHSType, PN.getNumIncomingValues(), |
| FirstInst->getOperand(1)->getName() + ".pn"); |
| NewRHS->addIncoming(InRHS, PN.getIncomingBlock(0)); |
| InsertNewInstBefore(NewRHS, PN); |
| RHSVal = NewRHS; |
| } |
| |
| // Add all operands to the new PHIs. |
| if (NewLHS || NewRHS) { |
| for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) { |
| Instruction *InInst = cast<Instruction>(PN.getIncomingValue(i)); |
| if (NewLHS) { |
| Value *NewInLHS = InInst->getOperand(0); |
| NewLHS->addIncoming(NewInLHS, PN.getIncomingBlock(i)); |
| } |
| if (NewRHS) { |
| Value *NewInRHS = InInst->getOperand(1); |
| NewRHS->addIncoming(NewInRHS, PN.getIncomingBlock(i)); |
| } |
| } |
| } |
| |
| if (CmpInst *CIOp = dyn_cast<CmpInst>(FirstInst)) { |
| CmpInst *NewCI = CmpInst::Create(CIOp->getOpcode(), CIOp->getPredicate(), |
| LHSVal, RHSVal); |
| PHIArgMergedDebugLoc(NewCI, PN); |
| return NewCI; |
| } |
| |
| BinaryOperator *BinOp = cast<BinaryOperator>(FirstInst); |
| BinaryOperator *NewBinOp = |
| BinaryOperator::Create(BinOp->getOpcode(), LHSVal, RHSVal); |
| |
| NewBinOp->copyIRFlags(PN.getIncomingValue(0)); |
| |
| for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) |
| NewBinOp->andIRFlags(PN.getIncomingValue(i)); |
| |
| PHIArgMergedDebugLoc(NewBinOp, PN); |
| return NewBinOp; |
| } |
| |
| Instruction *InstCombinerImpl::foldPHIArgGEPIntoPHI(PHINode &PN) { |
| GetElementPtrInst *FirstInst =cast<GetElementPtrInst>(PN.getIncomingValue(0)); |
| |
| SmallVector<Value*, 16> FixedOperands(FirstInst->op_begin(), |
| FirstInst->op_end()); |
| // This is true if all GEP bases are allocas and if all indices into them are |
| // constants. |
| bool AllBasePointersAreAllocas = true; |
| |
| // We don't want to replace this phi if the replacement would require |
| // more than one phi, which leads to higher register pressure. This is |
| // especially bad when the PHIs are in the header of a loop. |
| bool NeededPhi = false; |
| |
| bool AllInBounds = true; |
| |
| // Scan to see if all operands are the same opcode, and all have one user. |
| for (unsigned i = 1; i != PN.getNumIncomingValues(); ++i) { |
| GetElementPtrInst *GEP = |
| dyn_cast<GetElementPtrInst>(PN.getIncomingValue(i)); |
| if (!GEP || !GEP->hasOneUser() || GEP->getType() != FirstInst->getType() || |
| GEP->getNumOperands() != FirstInst->getNumOperands()) |
| return nullptr; |
| |
| AllInBounds &= GEP->isInBounds(); |
| |
| // Keep track of whether or not all GEPs are of alloca pointers. |
| if (AllBasePointersAreAllocas && |
| (!isa<AllocaInst>(GEP->getOperand(0)) || |
| !GEP->hasAllConstantIndices())) |
| AllBasePointersAreAllocas = false; |
| |
| // Compare the operand lists. |
| for (unsigned op = 0, e = FirstInst->getNumOperands(); op != e; ++op) { |
| if (FirstInst->getOperand(op) == GEP->getOperand(op)) |
| continue; |
| |
| // Don't merge two GEPs when two operands differ (introducing phi nodes) |
| // if one of the PHIs has a constant for the index. The index may be |
| // substantially cheaper to compute for the constants, so making it a |
| // variable index could pessimize the path. This also handles the case |
| // for struct indices, which must always be constant. |
| if (isa<ConstantInt>(FirstInst->getOperand(op)) || |
| isa<ConstantInt>(GEP->getOperand(op))) |
| return nullptr; |
| |
| if (FirstInst->getOperand(op)->getType() !=GEP->getOperand(op)->getType()) |
| return nullptr; |
| |
| // If we already needed a PHI for an earlier operand, and another operand |
| // also requires a PHI, we'd be introducing more PHIs than we're |
| // eliminating, which increases register pressure on entry to the PHI's |
| // block. |
| if (NeededPhi) |
| return nullptr; |
| |
| FixedOperands[op] = nullptr; // Needs a PHI. |
| NeededPhi = true; |
| } |
| } |
| |
| // If all of the base pointers of the PHI'd GEPs are from allocas, don't |
| // bother doing this transformation. At best, this will just save a bit of |
| // offset calculation, but all the predecessors will have to materialize the |
| // stack address into a register anyway. We'd actually rather *clone* the |
| // load up into the predecessors so that we have a load of a gep of an alloca, |
| // which can usually all be folded into the load. |
| if (AllBasePointersAreAllocas) |
| return nullptr; |
| |
| // Otherwise, this is safe to transform. Insert PHI nodes for each operand |
| // that is variable. |
| SmallVector<PHINode*, 16> OperandPhis(FixedOperands.size()); |
| |
| bool HasAnyPHIs = false; |
| for (unsigned i = 0, e = FixedOperands.size(); i != e; ++i) { |
| if (FixedOperands[i]) continue; // operand doesn't need a phi. |
| Value *FirstOp = FirstInst->getOperand(i); |
| PHINode *NewPN = PHINode::Create(FirstOp->getType(), e, |
| FirstOp->getName()+".pn"); |
| InsertNewInstBefore(NewPN, PN); |
| |
| NewPN->addIncoming(FirstOp, PN.getIncomingBlock(0)); |
| OperandPhis[i] = NewPN; |
| FixedOperands[i] = NewPN; |
| HasAnyPHIs = true; |
| } |
| |
| |
| // Add all operands to the new PHIs. |
| if (HasAnyPHIs) { |
| for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) { |
| GetElementPtrInst *InGEP =cast<GetElementPtrInst>(PN.getIncomingValue(i)); |
| BasicBlock *InBB = PN.getIncomingBlock(i); |
| |
| for (unsigned op = 0, e = OperandPhis.size(); op != e; ++op) |
| if (PHINode *OpPhi = OperandPhis[op]) |
| OpPhi->addIncoming(InGEP->getOperand(op), InBB); |
| } |
| } |
| |
| Value *Base = FixedOperands[0]; |
| GetElementPtrInst *NewGEP = |
| GetElementPtrInst::Create(FirstInst->getSourceElementType(), Base, |
| makeArrayRef(FixedOperands).slice(1)); |
| if (AllInBounds) NewGEP->setIsInBounds(); |
| PHIArgMergedDebugLoc(NewGEP, PN); |
| return NewGEP; |
| } |
| |
| /// Return true if we know that it is safe to sink the load out of the block |
| /// that defines it. This means that it must be obvious the value of the load is |
| /// not changed from the point of the load to the end of the block it is in. |
| /// |
| /// Finally, it is safe, but not profitable, to sink a load targeting a |
| /// non-address-taken alloca. Doing so will cause us to not promote the alloca |
| /// to a register. |
| static bool isSafeAndProfitableToSinkLoad(LoadInst *L) { |
| BasicBlock::iterator BBI = L->getIterator(), E = L->getParent()->end(); |
| |
| for (++BBI; BBI != E; ++BBI) |
| if (BBI->mayWriteToMemory()) { |
| // Calls that only access inaccessible memory do not block sinking the |
| // load. |
| if (auto *CB = dyn_cast<CallBase>(BBI)) |
| if (CB->onlyAccessesInaccessibleMemory()) |
| continue; |
| return false; |
| } |
| |
| // Check for non-address taken alloca. If not address-taken already, it isn't |
| // profitable to do this xform. |
| if (AllocaInst *AI = dyn_cast<AllocaInst>(L->getOperand(0))) { |
| bool isAddressTaken = false; |
| for (User *U : AI->users()) { |
| if (isa<LoadInst>(U)) continue; |
| if (StoreInst *SI = dyn_cast<StoreInst>(U)) { |
| // If storing TO the alloca, then the address isn't taken. |
| if (SI->getOperand(1) == AI) continue; |
| } |
| isAddressTaken = true; |
| break; |
| } |
| |
| if (!isAddressTaken && AI->isStaticAlloca()) |
| return false; |
| } |
| |
| // If this load is a load from a GEP with a constant offset from an alloca, |
| // then we don't want to sink it. In its present form, it will be |
| // load [constant stack offset]. Sinking it will cause us to have to |
| // materialize the stack addresses in each predecessor in a register only to |
| // do a shared load from register in the successor. |
| if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(L->getOperand(0))) |
| if (AllocaInst *AI = dyn_cast<AllocaInst>(GEP->getOperand(0))) |
| if (AI->isStaticAlloca() && GEP->hasAllConstantIndices()) |
| return false; |
| |
| return true; |
| } |
| |
| Instruction *InstCombinerImpl::foldPHIArgLoadIntoPHI(PHINode &PN) { |
| LoadInst *FirstLI = cast<LoadInst>(PN.getIncomingValue(0)); |
| |
| // FIXME: This is overconservative; this transform is allowed in some cases |
| // for atomic operations. |
| if (FirstLI->isAtomic()) |
| return nullptr; |
| |
| // When processing loads, we need to propagate two bits of information to the |
| // sunk load: whether it is volatile, and what its alignment is. We currently |
| // don't sink loads when some have their alignment specified and some don't. |
| // visitLoadInst will propagate an alignment onto the load when TD is around, |
| // and if TD isn't around, we can't handle the mixed case. |
| bool isVolatile = FirstLI->isVolatile(); |
| Align LoadAlignment = FirstLI->getAlign(); |
| unsigned LoadAddrSpace = FirstLI->getPointerAddressSpace(); |
| |
| // We can't sink the load if the loaded value could be modified between the |
| // load and the PHI. |
| if (FirstLI->getParent() != PN.getIncomingBlock(0) || |
| !isSafeAndProfitableToSinkLoad(FirstLI)) |
| return nullptr; |
| |
| // If the PHI is of volatile loads and the load block has multiple |
| // successors, sinking it would remove a load of the volatile value from |
| // the path through the other successor. |
| if (isVolatile && |
| FirstLI->getParent()->getTerminator()->getNumSuccessors() != 1) |
| return nullptr; |
| |
| // Check to see if all arguments are the same operation. |
| for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) { |
| LoadInst *LI = dyn_cast<LoadInst>(PN.getIncomingValue(i)); |
| if (!LI || !LI->hasOneUser()) |
| return nullptr; |
| |
| // We can't sink the load if the loaded value could be modified between |
| // the load and the PHI. |
| if (LI->isVolatile() != isVolatile || |
| LI->getParent() != PN.getIncomingBlock(i) || |
| LI->getPointerAddressSpace() != LoadAddrSpace || |
| !isSafeAndProfitableToSinkLoad(LI)) |
| return nullptr; |
| |
| LoadAlignment = std::min(LoadAlignment, Align(LI->getAlign())); |
| |
| // If the PHI is of volatile loads and the load block has multiple |
| // successors, sinking it would remove a load of the volatile value from |
| // the path through the other successor. |
| if (isVolatile && |
| LI->getParent()->getTerminator()->getNumSuccessors() != 1) |
| return nullptr; |
| } |
| |
| // Okay, they are all the same operation. Create a new PHI node of the |
| // correct type, and PHI together all of the LHS's of the instructions. |
| PHINode *NewPN = PHINode::Create(FirstLI->getOperand(0)->getType(), |
| PN.getNumIncomingValues(), |
| PN.getName()+".in"); |
| |
| Value *InVal = FirstLI->getOperand(0); |
| NewPN->addIncoming(InVal, PN.getIncomingBlock(0)); |
| LoadInst *NewLI = |
| new LoadInst(FirstLI->getType(), NewPN, "", isVolatile, LoadAlignment); |
| |
| unsigned KnownIDs[] = { |
| LLVMContext::MD_tbaa, |
| LLVMContext::MD_range, |
| LLVMContext::MD_invariant_load, |
| LLVMContext::MD_alias_scope, |
| LLVMContext::MD_noalias, |
| LLVMContext::MD_nonnull, |
| LLVMContext::MD_align, |
| LLVMContext::MD_dereferenceable, |
| LLVMContext::MD_dereferenceable_or_null, |
| LLVMContext::MD_access_group, |
| }; |
| |
| for (unsigned ID : KnownIDs) |
| NewLI->setMetadata(ID, FirstLI->getMetadata(ID)); |
| |
| // Add all operands to the new PHI and combine TBAA metadata. |
| for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) { |
| LoadInst *LI = cast<LoadInst>(PN.getIncomingValue(i)); |
| combineMetadata(NewLI, LI, KnownIDs, true); |
| Value *NewInVal = LI->getOperand(0); |
| if (NewInVal != InVal) |
| InVal = nullptr; |
| NewPN->addIncoming(NewInVal, PN.getIncomingBlock(i)); |
| } |
| |
| if (InVal) { |
| // The new PHI unions all of the same values together. This is really |
| // common, so we handle it intelligently here for compile-time speed. |
| NewLI->setOperand(0, InVal); |
| delete NewPN; |
| } else { |
| InsertNewInstBefore(NewPN, PN); |
| } |
| |
| // If this was a volatile load that we are merging, make sure to loop through |
| // and mark all the input loads as non-volatile. If we don't do this, we will |
| // insert a new volatile load and the old ones will not be deletable. |
| if (isVolatile) |
| for (Value *IncValue : PN.incoming_values()) |
| cast<LoadInst>(IncValue)->setVolatile(false); |
| |
| PHIArgMergedDebugLoc(NewLI, PN); |
| return NewLI; |
| } |
| |
| /// TODO: This function could handle other cast types, but then it might |
| /// require special-casing a cast from the 'i1' type. See the comment in |
| /// FoldPHIArgOpIntoPHI() about pessimizing illegal integer types. |
| Instruction *InstCombinerImpl::foldPHIArgZextsIntoPHI(PHINode &Phi) { |
| // We cannot create a new instruction after the PHI if the terminator is an |
| // EHPad because there is no valid insertion point. |
| if (Instruction *TI = Phi.getParent()->getTerminator()) |
| if (TI->isEHPad()) |
| return nullptr; |
| |
| // Early exit for the common case of a phi with two operands. These are |
| // handled elsewhere. See the comment below where we check the count of zexts |
| // and constants for more details. |
| unsigned NumIncomingValues = Phi.getNumIncomingValues(); |
| if (NumIncomingValues < 3) |
| return nullptr; |
| |
| // Find the narrower type specified by the first zext. |
| Type *NarrowType = nullptr; |
| for (Value *V : Phi.incoming_values()) { |
| if (auto *Zext = dyn_cast<ZExtInst>(V)) { |
| NarrowType = Zext->getSrcTy(); |
| break; |
| } |
| } |
| if (!NarrowType) |
| return nullptr; |
| |
| // Walk the phi operands checking that we only have zexts or constants that |
| // we can shrink for free. Store the new operands for the new phi. |
| SmallVector<Value *, 4> NewIncoming; |
| unsigned NumZexts = 0; |
| unsigned NumConsts = 0; |
| for (Value *V : Phi.incoming_values()) { |
| if (auto *Zext = dyn_cast<ZExtInst>(V)) { |
| // All zexts must be identical and have one user. |
| if (Zext->getSrcTy() != NarrowType || !Zext->hasOneUser()) |
| return nullptr; |
| NewIncoming.push_back(Zext->getOperand(0)); |
| NumZexts++; |
| } else if (auto *C = dyn_cast<Constant>(V)) { |
| // Make sure that constants can fit in the new type. |
| Constant *Trunc = ConstantExpr::getTrunc(C, NarrowType); |
| if (ConstantExpr::getZExt(Trunc, C->getType()) != C) |
| return nullptr; |
| NewIncoming.push_back(Trunc); |
| NumConsts++; |
| } else { |
| // If it's not a cast or a constant, bail out. |
| return nullptr; |
| } |
| } |
| |
| // The more common cases of a phi with no constant operands or just one |
| // variable operand are handled by FoldPHIArgOpIntoPHI() and foldOpIntoPhi() |
| // respectively. foldOpIntoPhi() wants to do the opposite transform that is |
| // performed here. It tries to replicate a cast in the phi operand's basic |
| // block to expose other folding opportunities. Thus, InstCombine will |
| // infinite loop without this check. |
| if (NumConsts == 0 || NumZexts < 2) |
| return nullptr; |
| |
| // All incoming values are zexts or constants that are safe to truncate. |
| // Create a new phi node of the narrow type, phi together all of the new |
| // operands, and zext the result back to the original type. |
| PHINode *NewPhi = PHINode::Create(NarrowType, NumIncomingValues, |
| Phi.getName() + ".shrunk"); |
| for (unsigned i = 0; i != NumIncomingValues; ++i) |
| NewPhi->addIncoming(NewIncoming[i], Phi.getIncomingBlock(i)); |
| |
| InsertNewInstBefore(NewPhi, Phi); |
| return CastInst::CreateZExtOrBitCast(NewPhi, Phi.getType()); |
| } |
| |
| /// If all operands to a PHI node are the same "unary" operator and they all are |
| /// only used by the PHI, PHI together their inputs, and do the operation once, |
| /// to the result of the PHI. |
| Instruction *InstCombinerImpl::foldPHIArgOpIntoPHI(PHINode &PN) { |
| // We cannot create a new instruction after the PHI if the terminator is an |
| // EHPad because there is no valid insertion point. |
| if (Instruction *TI = PN.getParent()->getTerminator()) |
| if (TI->isEHPad()) |
| return nullptr; |
| |
| Instruction *FirstInst = cast<Instruction>(PN.getIncomingValue(0)); |
| |
| if (isa<GetElementPtrInst>(FirstInst)) |
| return foldPHIArgGEPIntoPHI(PN); |
| if (isa<LoadInst>(FirstInst)) |
| return foldPHIArgLoadIntoPHI(PN); |
| if (isa<InsertValueInst>(FirstInst)) |
| return foldPHIArgInsertValueInstructionIntoPHI(PN); |
| if (isa<ExtractValueInst>(FirstInst)) |
| return foldPHIArgExtractValueInstructionIntoPHI(PN); |
| |
| // Scan the instruction, looking for input operations that can be folded away. |
| // If all input operands to the phi are the same instruction (e.g. a cast from |
| // the same type or "+42") we can pull the operation through the PHI, reducing |
| // code size and simplifying code. |
| Constant *ConstantOp = nullptr; |
| Type *CastSrcTy = nullptr; |
| |
| if (isa<CastInst>(FirstInst)) { |
| CastSrcTy = FirstInst->getOperand(0)->getType(); |
| |
| // Be careful about transforming integer PHIs. We don't want to pessimize |
| // the code by turning an i32 into an i1293. |
| if (PN.getType()->isIntegerTy() && CastSrcTy->isIntegerTy()) { |
| if (!shouldChangeType(PN.getType(), CastSrcTy)) |
| return nullptr; |
| } |
| } else if (isa<BinaryOperator>(FirstInst) || isa<CmpInst>(FirstInst)) { |
| // Can fold binop, compare or shift here if the RHS is a constant, |
| // otherwise call FoldPHIArgBinOpIntoPHI. |
| ConstantOp = dyn_cast<Constant>(FirstInst->getOperand(1)); |
| if (!ConstantOp) |
| return foldPHIArgBinOpIntoPHI(PN); |
| } else { |
| return nullptr; // Cannot fold this operation. |
| } |
| |
| // Check to see if all arguments are the same operation. |
| for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) { |
| Instruction *I = dyn_cast<Instruction>(PN.getIncomingValue(i)); |
| if (!I || !I->hasOneUser() || !I->isSameOperationAs(FirstInst)) |
| return nullptr; |
| if (CastSrcTy) { |
| if (I->getOperand(0)->getType() != CastSrcTy) |
| return nullptr; // Cast operation must match. |
| } else if (I->getOperand(1) != ConstantOp) { |
| return nullptr; |
| } |
| } |
| |
| // Okay, they are all the same operation. Create a new PHI node of the |
| // correct type, and PHI together all of the LHS's of the instructions. |
| PHINode *NewPN = PHINode::Create(FirstInst->getOperand(0)->getType(), |
| PN.getNumIncomingValues(), |
| PN.getName()+".in"); |
| |
| Value *InVal = FirstInst->getOperand(0); |
| NewPN->addIncoming(InVal, PN.getIncomingBlock(0)); |
| |
| // Add all operands to the new PHI. |
| for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) { |
| Value *NewInVal = cast<Instruction>(PN.getIncomingValue(i))->getOperand(0); |
| if (NewInVal != InVal) |
| InVal = nullptr; |
| NewPN->addIncoming(NewInVal, PN.getIncomingBlock(i)); |
| } |
| |
| Value *PhiVal; |
| if (InVal) { |
| // The new PHI unions all of the same values together. This is really |
| // common, so we handle it intelligently here for compile-time speed. |
| PhiVal = InVal; |
| delete NewPN; |
| } else { |
| InsertNewInstBefore(NewPN, PN); |
| PhiVal = NewPN; |
| } |
| |
| // Insert and return the new operation. |
| if (CastInst *FirstCI = dyn_cast<CastInst>(FirstInst)) { |
| CastInst *NewCI = CastInst::Create(FirstCI->getOpcode(), PhiVal, |
| PN.getType()); |
| PHIArgMergedDebugLoc(NewCI, PN); |
| return NewCI; |
| } |
| |
| if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst)) { |
| BinOp = BinaryOperator::Create(BinOp->getOpcode(), PhiVal, ConstantOp); |
| BinOp->copyIRFlags(PN.getIncomingValue(0)); |
| |
| for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) |
| BinOp->andIRFlags(PN.getIncomingValue(i)); |
| |
| PHIArgMergedDebugLoc(BinOp, PN); |
| return BinOp; |
| } |
| |
| CmpInst *CIOp = cast<CmpInst>(FirstInst); |
| CmpInst *NewCI = CmpInst::Create(CIOp->getOpcode(), CIOp->getPredicate(), |
| PhiVal, ConstantOp); |
| PHIArgMergedDebugLoc(NewCI, PN); |
| return NewCI; |
| } |
| |
| /// Return true if this PHI node is only used by a PHI node cycle that is dead. |
| static bool DeadPHICycle(PHINode *PN, |
| SmallPtrSetImpl<PHINode*> &PotentiallyDeadPHIs) { |
| if (PN->use_empty()) return true; |
| if (!PN->hasOneUse()) return false; |
| |
| // Remember this node, and if we find the cycle, return. |
| if (!PotentiallyDeadPHIs.insert(PN).second) |
| return true; |
| |
| // Don't scan crazily complex things. |
| if (PotentiallyDeadPHIs.size() == 16) |
| return false; |
| |
| if (PHINode *PU = dyn_cast<PHINode>(PN->user_back())) |
| return DeadPHICycle(PU, PotentiallyDeadPHIs); |
| |
| return false; |
| } |
| |
| /// Return true if this phi node is always equal to NonPhiInVal. |
| /// This happens with mutually cyclic phi nodes like: |
| /// z = some value; x = phi (y, z); y = phi (x, z) |
| static bool PHIsEqualValue(PHINode *PN, Value *NonPhiInVal, |
| SmallPtrSetImpl<PHINode*> &ValueEqualPHIs) { |
| // See if we already saw this PHI node. |
| if (!ValueEqualPHIs.insert(PN).second) |
| return true; |
| |
| // Don't scan crazily complex things. |
| if (ValueEqualPHIs.size() == 16) |
| return false; |
| |
| // Scan the operands to see if they are either phi nodes or are equal to |
| // the value. |
| for (Value *Op : PN->incoming_values()) { |
| if (PHINode *OpPN = dyn_cast<PHINode>(Op)) { |
| if (!PHIsEqualValue(OpPN, NonPhiInVal, ValueEqualPHIs)) |
| return false; |
| } else if (Op != NonPhiInVal) |
| return false; |
| } |
| |
| return true; |
| } |
| |
| /// Return an existing non-zero constant if this phi node has one, otherwise |
| /// return constant 1. |
| static ConstantInt *GetAnyNonZeroConstInt(PHINode &PN) { |
| assert(isa<IntegerType>(PN.getType()) && "Expect only integer type phi"); |
| for (Value *V : PN.operands()) |
| if (auto *ConstVA = dyn_cast<ConstantInt>(V)) |
| if (!ConstVA->isZero()) |
| return ConstVA; |
| return ConstantInt::get(cast<IntegerType>(PN.getType()), 1); |
| } |
| |
| namespace { |
| struct PHIUsageRecord { |
| unsigned PHIId; // The ID # of the PHI (something determinstic to sort on) |
| unsigned Shift; // The amount shifted. |
| Instruction *Inst; // The trunc instruction. |
| |
| PHIUsageRecord(unsigned pn, unsigned Sh, Instruction *User) |
| : PHIId(pn), Shift(Sh), Inst(User) {} |
| |
| bool operator<(const PHIUsageRecord &RHS) const { |
| if (PHIId < RHS.PHIId) return true; |
| if (PHIId > RHS.PHIId) return false; |
| if (Shift < RHS.Shift) return true; |
| if (Shift > RHS.Shift) return false; |
| return Inst->getType()->getPrimitiveSizeInBits() < |
| RHS.Inst->getType()->getPrimitiveSizeInBits(); |
| } |
| }; |
| |
| struct LoweredPHIRecord { |
| PHINode *PN; // The PHI that was lowered. |
| unsigned Shift; // The amount shifted. |
| unsigned Width; // The width extracted. |
| |
| LoweredPHIRecord(PHINode *pn, unsigned Sh, Type *Ty) |
| : PN(pn), Shift(Sh), Width(Ty->getPrimitiveSizeInBits()) {} |
| |
| // Ctor form used by DenseMap. |
| LoweredPHIRecord(PHINode *pn, unsigned Sh) |
| : PN(pn), Shift(Sh), Width(0) {} |
| }; |
| } // namespace |
| |
| namespace llvm { |
| template<> |
| struct DenseMapInfo<LoweredPHIRecord> { |
| static inline LoweredPHIRecord getEmptyKey() { |
| return LoweredPHIRecord(nullptr, 0); |
| } |
| static inline LoweredPHIRecord getTombstoneKey() { |
| return LoweredPHIRecord(nullptr, 1); |
| } |
| static unsigned getHashValue(const LoweredPHIRecord &Val) { |
| return DenseMapInfo<PHINode*>::getHashValue(Val.PN) ^ (Val.Shift>>3) ^ |
| (Val.Width>>3); |
| } |
| static bool isEqual(const LoweredPHIRecord &LHS, |
| const LoweredPHIRecord &RHS) { |
| return LHS.PN == RHS.PN && LHS.Shift == RHS.Shift && |
| LHS.Width == RHS.Width; |
| } |
| }; |
| } // namespace llvm |
| |
| |
| /// This is an integer PHI and we know that it has an illegal type: see if it is |
| /// only used by trunc or trunc(lshr) operations. If so, we split the PHI into |
| /// the various pieces being extracted. This sort of thing is introduced when |
| /// SROA promotes an aggregate to large integer values. |
| /// |
| /// TODO: The user of the trunc may be an bitcast to float/double/vector or an |
| /// inttoptr. We should produce new PHIs in the right type. |
| /// |
| Instruction *InstCombinerImpl::SliceUpIllegalIntegerPHI(PHINode &FirstPhi) { |
| // PHIUsers - Keep track of all of the truncated values extracted from a set |
| // of PHIs, along with their offset. These are the things we want to rewrite. |
| SmallVector<PHIUsageRecord, 16> PHIUsers; |
| |
| // PHIs are often mutually cyclic, so we keep track of a whole set of PHI |
| // nodes which are extracted from. PHIsToSlice is a set we use to avoid |
| // revisiting PHIs, PHIsInspected is a ordered list of PHIs that we need to |
| // check the uses of (to ensure they are all extracts). |
| SmallVector<PHINode*, 8> PHIsToSlice; |
| SmallPtrSet<PHINode*, 8> PHIsInspected; |
| |
| PHIsToSlice.push_back(&FirstPhi); |
| PHIsInspected.insert(&FirstPhi); |
| |
| for (unsigned PHIId = 0; PHIId != PHIsToSlice.size(); ++PHIId) { |
| PHINode *PN = PHIsToSlice[PHIId]; |
| |
| // Scan the input list of the PHI. If any input is an invoke, and if the |
| // input is defined in the predecessor, then we won't be split the critical |
| // edge which is required to insert a truncate. Because of this, we have to |
| // bail out. |
| for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { |
| InvokeInst *II = dyn_cast<InvokeInst>(PN->getIncomingValue(i)); |
| if (!II) continue; |
| if (II->getParent() != PN->getIncomingBlock(i)) |
| continue; |
| |
| // If we have a phi, and if it's directly in the predecessor, then we have |
| // a critical edge where we need to put the truncate. Since we can't |
| // split the edge in instcombine, we have to bail out. |
| return nullptr; |
| } |
| |
| for (User *U : PN->users()) { |
| Instruction *UserI = cast<Instruction>(U); |
| |
| // If the user is a PHI, inspect its uses recursively. |
| if (PHINode *UserPN = dyn_cast<PHINode>(UserI)) { |
| if (PHIsInspected.insert(UserPN).second) |
| PHIsToSlice.push_back(UserPN); |
| continue; |
| } |
| |
| // Truncates are always ok. |
| if (isa<TruncInst>(UserI)) { |
| PHIUsers.push_back(PHIUsageRecord(PHIId, 0, UserI)); |
| continue; |
| } |
| |
| // Otherwise it must be a lshr which can only be used by one trunc. |
| if (UserI->getOpcode() != Instruction::LShr || |
| !UserI->hasOneUse() || !isa<TruncInst>(UserI->user_back()) || |
| !isa<ConstantInt>(UserI->getOperand(1))) |
| return nullptr; |
| |
| // Bail on out of range shifts. |
| unsigned SizeInBits = UserI->getType()->getScalarSizeInBits(); |
| if (cast<ConstantInt>(UserI->getOperand(1))->getValue().uge(SizeInBits)) |
| return nullptr; |
| |
| unsigned Shift = cast<ConstantInt>(UserI->getOperand(1))->getZExtValue(); |
| PHIUsers.push_back(PHIUsageRecord(PHIId, Shift, UserI->user_back())); |
| } |
| } |
| |
| // If we have no users, they must be all self uses, just nuke the PHI. |
| if (PHIUsers.empty()) |
| return replaceInstUsesWith(FirstPhi, UndefValue::get(FirstPhi.getType())); |
| |
| // If this phi node is transformable, create new PHIs for all the pieces |
| // extracted out of it. First, sort the users by their offset and size. |
| array_pod_sort(PHIUsers.begin(), PHIUsers.end()); |
| |
| LLVM_DEBUG(dbgs() << "SLICING UP PHI: " << FirstPhi << '\n'; |
| for (unsigned i = 1, e = PHIsToSlice.size(); i != e; ++i) dbgs() |
| << "AND USER PHI #" << i << ": " << *PHIsToSlice[i] << '\n';); |
| |
| // PredValues - This is a temporary used when rewriting PHI nodes. It is |
| // hoisted out here to avoid construction/destruction thrashing. |
| DenseMap<BasicBlock*, Value*> PredValues; |
| |
| // ExtractedVals - Each new PHI we introduce is saved here so we don't |
| // introduce redundant PHIs. |
| DenseMap<LoweredPHIRecord, PHINode*> ExtractedVals; |
| |
| for (unsigned UserI = 0, UserE = PHIUsers.size(); UserI != UserE; ++UserI) { |
| unsigned PHIId = PHIUsers[UserI].PHIId; |
| PHINode *PN = PHIsToSlice[PHIId]; |
| unsigned Offset = PHIUsers[UserI].Shift; |
| Type *Ty = PHIUsers[UserI].Inst->getType(); |
| |
| PHINode *EltPHI; |
| |
| // If we've already lowered a user like this, reuse the previously lowered |
| // value. |
| if ((EltPHI = ExtractedVals[LoweredPHIRecord(PN, Offset, Ty)]) == nullptr) { |
| |
| // Otherwise, Create the new PHI node for this user. |
| EltPHI = PHINode::Create(Ty, PN->getNumIncomingValues(), |
| PN->getName()+".off"+Twine(Offset), PN); |
| assert(EltPHI->getType() != PN->getType() && |
| "Truncate didn't shrink phi?"); |
| |
| for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { |
| BasicBlock *Pred = PN->getIncomingBlock(i); |
| Value *&PredVal = PredValues[Pred]; |
| |
| // If we already have a value for this predecessor, reuse it. |
| if (PredVal) { |
| EltPHI->addIncoming(PredVal, Pred); |
| continue; |
| } |
| |
| // Handle the PHI self-reuse case. |
| Value *InVal = PN->getIncomingValue(i); |
| if (InVal == PN) { |
| PredVal = EltPHI; |
| EltPHI->addIncoming(PredVal, Pred); |
| continue; |
| } |
| |
| if (PHINode *InPHI = dyn_cast<PHINode>(PN)) { |
| // If the incoming value was a PHI, and if it was one of the PHIs we |
| // already rewrote it, just use the lowered value. |
| if (Value *Res = ExtractedVals[LoweredPHIRecord(InPHI, Offset, Ty)]) { |
| PredVal = Res; |
| EltPHI->addIncoming(PredVal, Pred); |
| continue; |
| } |
| } |
| |
| // Otherwise, do an extract in the predecessor. |
| Builder.SetInsertPoint(Pred->getTerminator()); |
| Value *Res = InVal; |
| if (Offset) |
| Res = Builder.CreateLShr(Res, ConstantInt::get(InVal->getType(), |
| Offset), "extract"); |
| Res = Builder.CreateTrunc(Res, Ty, "extract.t"); |
| PredVal = Res; |
| EltPHI->addIncoming(Res, Pred); |
| |
| // If the incoming value was a PHI, and if it was one of the PHIs we are |
| // rewriting, we will ultimately delete the code we inserted. This |
| // means we need to revisit that PHI to make sure we extract out the |
| // needed piece. |
| if (PHINode *OldInVal = dyn_cast<PHINode>(PN->getIncomingValue(i))) |
| if (PHIsInspected.count(OldInVal)) { |
| unsigned RefPHIId = |
| find(PHIsToSlice, OldInVal) - PHIsToSlice.begin(); |
| PHIUsers.push_back(PHIUsageRecord(RefPHIId, Offset, |
| cast<Instruction>(Res))); |
| ++UserE; |
| } |
| } |
| PredValues.clear(); |
| |
| LLVM_DEBUG(dbgs() << " Made element PHI for offset " << Offset << ": " |
| << *EltPHI << '\n'); |
| ExtractedVals[LoweredPHIRecord(PN, Offset, Ty)] = EltPHI; |
| } |
| |
| // Replace the use of this piece with the PHI node. |
| replaceInstUsesWith(*PHIUsers[UserI].Inst, EltPHI); |
| } |
| |
| // Replace all the remaining uses of the PHI nodes (self uses and the lshrs) |
| // with undefs. |
| Value *Undef = UndefValue::get(FirstPhi.getType()); |
| for (unsigned i = 1, e = PHIsToSlice.size(); i != e; ++i) |
| replaceInstUsesWith(*PHIsToSlice[i], Undef); |
| return replaceInstUsesWith(FirstPhi, Undef); |
| } |
| |
| static Value *SimplifyUsingControlFlow(InstCombiner &Self, PHINode &PN, |
| const DominatorTree &DT) { |
| // Simplify the following patterns: |
| // if (cond) |
| // / \ |
| // ... ... |
| // \ / |
| // phi [true] [false] |
| if (!PN.getType()->isIntegerTy(1)) |
| return nullptr; |
| |
| if (PN.getNumOperands() != 2) |
| return nullptr; |
| |
| // Make sure all inputs are constants. |
| if (!all_of(PN.operands(), [](Value *V) { return isa<ConstantInt>(V); })) |
| return nullptr; |
| |
| BasicBlock *BB = PN.getParent(); |
| // Do not bother with unreachable instructions. |
| if (!DT.isReachableFromEntry(BB)) |
| return nullptr; |
| |
| // Same inputs. |
| if (PN.getOperand(0) == PN.getOperand(1)) |
| return PN.getOperand(0); |
| |
| BasicBlock *TruePred = nullptr, *FalsePred = nullptr; |
| for (auto *Pred : predecessors(BB)) { |
| auto *Input = cast<ConstantInt>(PN.getIncomingValueForBlock(Pred)); |
| if (Input->isAllOnesValue()) |
| TruePred = Pred; |
| else |
| FalsePred = Pred; |
| } |
| assert(TruePred && FalsePred && "Must be!"); |
| |
| // Check which edge of the dominator dominates the true input. If it is the |
| // false edge, we should invert the condition. |
| auto *IDom = DT.getNode(BB)->getIDom()->getBlock(); |
| auto *BI = dyn_cast<BranchInst>(IDom->getTerminator()); |
| if (!BI || BI->isUnconditional()) |
| return nullptr; |
| |
| // Check that edges outgoing from the idom's terminators dominate respective |
| // inputs of the Phi. |
| BasicBlockEdge TrueOutEdge(IDom, BI->getSuccessor(0)); |
| BasicBlockEdge FalseOutEdge(IDom, BI->getSuccessor(1)); |
| |
| BasicBlockEdge TrueIncEdge(TruePred, BB); |
| BasicBlockEdge FalseIncEdge(FalsePred, BB); |
| |
| auto *Cond = BI->getCondition(); |
| if (DT.dominates(TrueOutEdge, TrueIncEdge) && |
| DT.dominates(FalseOutEdge, FalseIncEdge)) |
| // This Phi is actually equivalent to branching condition of IDom. |
| return Cond; |
| else if (DT.dominates(TrueOutEdge, FalseIncEdge) && |
| DT.dominates(FalseOutEdge, TrueIncEdge)) { |
| // This Phi is actually opposite to branching condition of IDom. We invert |
| // the condition that will potentially open up some opportunities for |
| // sinking. |
| auto InsertPt = BB->getFirstInsertionPt(); |
| if (InsertPt != BB->end()) { |
| Self.Builder.SetInsertPoint(&*InsertPt); |
| return Self.Builder.CreateNot(Cond); |
| } |
| } |
| |
| return nullptr; |
| } |
| |
| // PHINode simplification |
| // |
| Instruction *InstCombinerImpl::visitPHINode(PHINode &PN) { |
| if (Value *V = SimplifyInstruction(&PN, SQ.getWithInstruction(&PN))) |
| return replaceInstUsesWith(PN, V); |
| |
| if (Instruction *Result = foldPHIArgZextsIntoPHI(PN)) |
| return Result; |
| |
| // If all PHI operands are the same operation, pull them through the PHI, |
| // reducing code size. |
| if (isa<Instruction>(PN.getIncomingValue(0)) && |
| isa<Instruction>(PN.getIncomingValue(1)) && |
| cast<Instruction>(PN.getIncomingValue(0))->getOpcode() == |
| cast<Instruction>(PN.getIncomingValue(1))->getOpcode() && |
| PN.getIncomingValue(0)->hasOneUser()) |
| if (Instruction *Result = foldPHIArgOpIntoPHI(PN)) |
| return Result; |
| |
| // If the incoming values are pointer casts of the same original value, |
| // replace the phi with a single cast. |
| if (PN.getType()->isPointerTy()) { |
| Value *IV0 = PN.getIncomingValue(0); |
| Value *IV0Stripped = IV0->stripPointerCasts(); |
| // Set to keep track of values known to be equal to IV0Stripped after |
| // stripping pointer casts. |
| SmallPtrSet<Value *, 4> CheckedIVs; |
| CheckedIVs.insert(IV0); |
| if (IV0 != IV0Stripped && |
| all_of(PN.incoming_values(), [&CheckedIVs, IV0Stripped](Value *IV) { |
| return !CheckedIVs.insert(IV).second || |
| IV0Stripped == IV->stripPointerCasts(); |
| })) { |
| return CastInst::CreatePointerCast(IV0Stripped, PN.getType()); |
| } |
| } |
| |
| // If this is a trivial cycle in the PHI node graph, remove it. Basically, if |
| // this PHI only has a single use (a PHI), and if that PHI only has one use (a |
| // PHI)... break the cycle. |
| if (PN.hasOneUse()) { |
| if (Instruction *Result = foldIntegerTypedPHI(PN)) |
| return Result; |
| |
| Instruction *PHIUser = cast<Instruction>(PN.user_back()); |
| if (PHINode *PU = dyn_cast<PHINode>(PHIUser)) { |
| SmallPtrSet<PHINode*, 16> PotentiallyDeadPHIs; |
| PotentiallyDeadPHIs.insert(&PN); |
| if (DeadPHICycle(PU, PotentiallyDeadPHIs)) |
| return replaceInstUsesWith(PN, UndefValue::get(PN.getType())); |
| } |
| |
| // If this phi has a single use, and if that use just computes a value for |
| // the next iteration of a loop, delete the phi. This occurs with unused |
| // induction variables, e.g. "for (int j = 0; ; ++j);". Detecting this |
| // common case here is good because the only other things that catch this |
| // are induction variable analysis (sometimes) and ADCE, which is only run |
| // late. |
| if (PHIUser->hasOneUse() && |
| (isa<BinaryOperator>(PHIUser) || isa<GetElementPtrInst>(PHIUser)) && |
| PHIUser->user_back() == &PN) { |
| return replaceInstUsesWith(PN, UndefValue::get(PN.getType())); |
| } |
| // When a PHI is used only to be compared with zero, it is safe to replace |
| // an incoming value proved as known nonzero with any non-zero constant. |
| // For example, in the code below, the incoming value %v can be replaced |
| // with any non-zero constant based on the fact that the PHI is only used to |
| // be compared with zero and %v is a known non-zero value: |
| // %v = select %cond, 1, 2 |
| // %p = phi [%v, BB] ... |
| // icmp eq, %p, 0 |
| auto *CmpInst = dyn_cast<ICmpInst>(PHIUser); |
| // FIXME: To be simple, handle only integer type for now. |
| if (CmpInst && isa<IntegerType>(PN.getType()) && CmpInst->isEquality() && |
| match(CmpInst->getOperand(1), m_Zero())) { |
| ConstantInt *NonZeroConst = nullptr; |
| bool MadeChange = false; |
| for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) { |
| Instruction *CtxI = PN.getIncomingBlock(i)->getTerminator(); |
| Value *VA = PN.getIncomingValue(i); |
| if (isKnownNonZero(VA, DL, 0, &AC, CtxI, &DT)) { |
| if (!NonZeroConst) |
| NonZeroConst = GetAnyNonZeroConstInt(PN); |
| |
| if (NonZeroConst != VA) { |
| replaceOperand(PN, i, NonZeroConst); |
| MadeChange = true; |
| } |
| } |
| } |
| if (MadeChange) |
| return &PN; |
| } |
| } |
| |
| // We sometimes end up with phi cycles that non-obviously end up being the |
| // same value, for example: |
| // z = some value; x = phi (y, z); y = phi (x, z) |
| // where the phi nodes don't necessarily need to be in the same block. Do a |
| // quick check to see if the PHI node only contains a single non-phi value, if |
| // so, scan to see if the phi cycle is actually equal to that value. |
| { |
| unsigned InValNo = 0, NumIncomingVals = PN.getNumIncomingValues(); |
| // Scan for the first non-phi operand. |
| while (InValNo != NumIncomingVals && |
| isa<PHINode>(PN.getIncomingValue(InValNo))) |
| ++InValNo; |
| |
| if (InValNo != NumIncomingVals) { |
| Value *NonPhiInVal = PN.getIncomingValue(InValNo); |
| |
| // Scan the rest of the operands to see if there are any conflicts, if so |
| // there is no need to recursively scan other phis. |
| for (++InValNo; InValNo != NumIncomingVals; ++InValNo) { |
| Value *OpVal = PN.getIncomingValue(InValNo); |
| if (OpVal != NonPhiInVal && !isa<PHINode>(OpVal)) |
| break; |
| } |
| |
| // If we scanned over all operands, then we have one unique value plus |
| // phi values. Scan PHI nodes to see if they all merge in each other or |
| // the value. |
| if (InValNo == NumIncomingVals) { |
| SmallPtrSet<PHINode*, 16> ValueEqualPHIs; |
| if (PHIsEqualValue(&PN, NonPhiInVal, ValueEqualPHIs)) |
| return replaceInstUsesWith(PN, NonPhiInVal); |
| } |
| } |
| } |
| |
| // If there are multiple PHIs, sort their operands so that they all list |
| // the blocks in the same order. This will help identical PHIs be eliminated |
| // by other passes. Other passes shouldn't depend on this for correctness |
| // however. |
| PHINode *FirstPN = cast<PHINode>(PN.getParent()->begin()); |
| if (&PN != FirstPN) |
| for (unsigned i = 0, e = FirstPN->getNumIncomingValues(); i != e; ++i) { |
| BasicBlock *BBA = PN.getIncomingBlock(i); |
| BasicBlock *BBB = FirstPN->getIncomingBlock(i); |
| if (BBA != BBB) { |
| Value *VA = PN.getIncomingValue(i); |
| unsigned j = PN.getBasicBlockIndex(BBB); |
| Value *VB = PN.getIncomingValue(j); |
| PN.setIncomingBlock(i, BBB); |
| PN.setIncomingValue(i, VB); |
| PN.setIncomingBlock(j, BBA); |
| PN.setIncomingValue(j, VA); |
| // NOTE: Instcombine normally would want us to "return &PN" if we |
| // modified any of the operands of an instruction. However, since we |
| // aren't adding or removing uses (just rearranging them) we don't do |
| // this in this case. |
| } |
| } |
| |
| // Is there an identical PHI node in this basic block? |
| for (PHINode &IdenticalPN : PN.getParent()->phis()) { |
| // Ignore the PHI node itself. |
| if (&IdenticalPN == &PN) |
| continue; |
| // Note that even though we've just canonicalized this PHI, due to the |
| // worklist visitation order, there are no guarantess that *every* PHI |
| // has been canonicalized, so we can't just compare operands ranges. |
| if (!PN.isIdenticalToWhenDefined(&IdenticalPN)) |
| continue; |
| // Just use that PHI instead then. |
| ++NumPHICSEs; |
| return replaceInstUsesWith(PN, &IdenticalPN); |
| } |
| |
| // If this is an integer PHI and we know that it has an illegal type, see if |
| // it is only used by trunc or trunc(lshr) operations. If so, we split the |
| // PHI into the various pieces being extracted. This sort of thing is |
| // introduced when SROA promotes an aggregate to a single large integer type. |
| if (PN.getType()->isIntegerTy() && |
| !DL.isLegalInteger(PN.getType()->getPrimitiveSizeInBits())) |
| if (Instruction *Res = SliceUpIllegalIntegerPHI(PN)) |
| return Res; |
| |
| // Ultimately, try to replace this Phi with a dominating condition. |
| if (auto *V = SimplifyUsingControlFlow(*this, PN, DT)) |
| return replaceInstUsesWith(PN, V); |
| |
| return nullptr; |
| } |