diff options
Diffstat (limited to 'gnu/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp')
| -rw-r--r-- | gnu/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp | 1261 |
1 files changed, 0 insertions, 1261 deletions
diff --git a/gnu/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp b/gnu/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp deleted file mode 100644 index 7603cf4d795..00000000000 --- a/gnu/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp +++ /dev/null @@ -1,1261 +0,0 @@ -//===- InstCombinePHI.cpp -------------------------------------------------===// -// -// The LLVM Compiler Infrastructure -// -// This file is distributed under the University of Illinois Open Source -// License. See LICENSE.TXT for details. -// -//===----------------------------------------------------------------------===// -// -// This file implements the visitPHINode function. -// -//===----------------------------------------------------------------------===// - -#include "InstCombineInternal.h" -#include "llvm/ADT/STLExtras.h" -#include "llvm/ADT/SmallPtrSet.h" -#include "llvm/Analysis/InstructionSimplify.h" -#include "llvm/Transforms/Utils/Local.h" -#include "llvm/Analysis/ValueTracking.h" -#include "llvm/IR/PatternMatch.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")); - -/// 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 InstCombiner::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 *InstCombiner::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(), EI = BasicBlock::iterator(BB->getFirstNonPHI()); - II != EI; II++, NumPhis++) { - // FIXME: consider handling this in AggressiveInstCombine - if (NumPhis > MaxNumPhis) - return nullptr; - PHINode *PtrPHI = dyn_cast<PHINode>(II); - if (!PtrPHI || 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. - if (any_of(AvailablePtrVals, [&](Value *V) { - if (V->getType() == IntToPtr->getType()) - return false; - - auto *Inst = dyn_cast<Instruction>(V); - return Inst && Inst->isTerminator(); - })) - 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++; - if (isa<PHINode>(IncomingI)) - InsertPos = IncomingI->getParent()->getFirstInsertionPt(); - 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 [add (a,b), add(a,c)] and if a/b/c and the -/// adds all have a single use, turn this into a phi and a single binop. -Instruction *InstCombiner::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 use. - for (unsigned i = 1; i != PN.getNumIncomingValues(); ++i) { - Instruction *I = dyn_cast<Instruction>(PN.getIncomingValue(i)); - if (!I || I->getOpcode() != Opc || !I->hasOneUse() || - // 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 *InstCombiner::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 use. - for (unsigned i = 1; i != PN.getNumIncomingValues(); ++i) { - GetElementPtrInst *GEP= dyn_cast<GetElementPtrInst>(PN.getIncomingValue(i)); - if (!GEP || !GEP->hasOneUse() || 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()) - 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 *InstCombiner::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(); - unsigned LoadAlignment = FirstLI->getAlignment(); - 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->hasOneUse()) - 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; - - // If some of the loads have an alignment specified but not all of them, - // we can't do the transformation. - if ((LoadAlignment != 0) != (LI->getAlignment() != 0)) - return nullptr; - - LoadAlignment = std::min(LoadAlignment, LI->getAlignment()); - - // 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(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 *InstCombiner::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 use. - if (Zext->getSrcTy() != NarrowType || !Zext->hasOneUse()) - 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 *InstCombiner::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); - - // 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->hasOneUse() || !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 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; - } - }; -} - - -/// 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 *InstCombiner::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; - - 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); -} - -// PHINode simplification -// -Instruction *InstCombiner::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() && - // FIXME: The hasOneUse check will fail for PHIs that use the value more - // than themselves more than once. - PN.getIncomingValue(0)->hasOneUse()) - if (Instruction *Result = FoldPHIArgOpIntoPHI(PN)) - return Result; - - // 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; - 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); - PN.setIncomingValue(i, NonZeroConst); - } - } - } - } - - // 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. - } - } - - // 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; - - return nullptr; -} |