[llvm-commits] [llvm] r92682 - in /llvm/trunk/lib/Transforms/InstCombine: CMakeLists.txt InstCombinePHI.cpp InstructionCombining.cpp
Chris Lattner
sabre at nondot.org
Mon Jan 4 21:32:00 PST 2010
Author: lattner
Date: Mon Jan 4 23:31:55 2010
New Revision: 92682
URL: http://llvm.org/viewvc/llvm-project?rev=92682&view=rev
Log:
split PHI node stuff out to InstCombinePHI.cpp
Added:
llvm/trunk/lib/Transforms/InstCombine/InstCombinePHI.cpp
Modified:
llvm/trunk/lib/Transforms/InstCombine/CMakeLists.txt
llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
Modified: llvm/trunk/lib/Transforms/InstCombine/CMakeLists.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/CMakeLists.txt?rev=92682&r1=92681&r2=92682&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/CMakeLists.txt (original)
+++ llvm/trunk/lib/Transforms/InstCombine/CMakeLists.txt Mon Jan 4 23:31:55 2010
@@ -2,6 +2,7 @@
InstructionCombining.cpp
InstCombineCasts.cpp
InstCombineCompares.cpp
+ InstCombinePHI.cpp
InstCombineSimplifyDemanded.cpp
)
Added: llvm/trunk/lib/Transforms/InstCombine/InstCombinePHI.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombinePHI.cpp?rev=92682&view=auto
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombinePHI.cpp (added)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombinePHI.cpp Mon Jan 4 23:31:55 2010
@@ -0,0 +1,841 @@
+//===- 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 "InstCombine.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/STLExtras.h"
+using namespace llvm;
+
+/// FoldPHIArgBinOpIntoPHI - If we have something like phi [add (a,b), add(a,c)]
+/// and if a/b/c and the add's 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);
+
+ const Type *LHSType = LHSVal->getType();
+ const 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 or GEP's with different index types.
+ I->getOperand(0)->getType() != LHSType ||
+ I->getOperand(1)->getType() != RHSType)
+ return 0;
+
+ // If they are CmpInst instructions, check their predicates
+ if (Opc == Instruction::ICmp || Opc == Instruction::FCmp)
+ if (cast<CmpInst>(I)->getPredicate() !=
+ cast<CmpInst>(FirstInst)->getPredicate())
+ return 0;
+
+ // Keep track of which operand needs a phi node.
+ if (I->getOperand(0) != LHSVal) LHSVal = 0;
+ if (I->getOperand(1) != RHSVal) RHSVal = 0;
+ }
+
+ // 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 0;
+
+ // Otherwise, this is safe to transform!
+
+ Value *InLHS = FirstInst->getOperand(0);
+ Value *InRHS = FirstInst->getOperand(1);
+ PHINode *NewLHS = 0, *NewRHS = 0;
+ if (LHSVal == 0) {
+ NewLHS = PHINode::Create(LHSType,
+ FirstInst->getOperand(0)->getName() + ".pn");
+ NewLHS->reserveOperandSpace(PN.getNumOperands()/2);
+ NewLHS->addIncoming(InLHS, PN.getIncomingBlock(0));
+ InsertNewInstBefore(NewLHS, PN);
+ LHSVal = NewLHS;
+ }
+
+ if (RHSVal == 0) {
+ NewRHS = PHINode::Create(RHSType,
+ FirstInst->getOperand(1)->getName() + ".pn");
+ NewRHS->reserveOperandSpace(PN.getNumOperands()/2);
+ 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 (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
+ return BinaryOperator::Create(BinOp->getOpcode(), LHSVal, RHSVal);
+ CmpInst *CIOp = cast<CmpInst>(FirstInst);
+ return CmpInst::Create(CIOp->getOpcode(), CIOp->getPredicate(),
+ LHSVal, RHSVal);
+}
+
+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;
+
+ // 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 0;
+
+ // 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 0;
+
+ if (FirstInst->getOperand(op)->getType() !=GEP->getOperand(op)->getType())
+ return 0;
+
+ // 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 0;
+
+ FixedOperands[op] = 0; // 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 0;
+
+ // 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(),
+ FirstOp->getName()+".pn");
+ InsertNewInstBefore(NewPN, PN);
+
+ NewPN->reserveOperandSpace(e);
+ 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];
+ return cast<GEPOperator>(FirstInst)->isInBounds() ?
+ GetElementPtrInst::CreateInBounds(Base, FixedOperands.begin()+1,
+ FixedOperands.end()) :
+ GetElementPtrInst::Create(Base, FixedOperands.begin()+1,
+ FixedOperands.end());
+}
+
+
+/// isSafeAndProfitableToSinkLoad - 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 targetting 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, 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 (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
+ UI != E; ++UI) {
+ if (isa<LoadInst>(UI)) continue;
+ if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
+ // 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));
+
+ // 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();
+
+ // 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 0;
+
+ // 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 0;
+
+ // 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 0;
+
+ // 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) ||
+ !isSafeAndProfitableToSinkLoad(LI))
+ return 0;
+
+ // 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 0;
+
+ 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 0;
+ }
+
+ // 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.getName()+".in");
+ NewPN->reserveOperandSpace(PN.getNumOperands()/2);
+
+ Value *InVal = FirstLI->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<LoadInst>(PN.getIncomingValue(i))->getOperand(0);
+ if (NewInVal != InVal)
+ InVal = 0;
+ 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;
+ }
+
+ // 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 (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
+ cast<LoadInst>(PN.getIncomingValue(i))->setVolatile(false);
+
+ return new LoadInst(PhiVal, "", isVolatile, LoadAlignment);
+}
+
+
+
+/// FoldPHIArgOpIntoPHI - 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) {
+ 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 = 0;
+ const Type *CastSrcTy = 0;
+
+ 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 (isa<IntegerType>(PN.getType()) && isa<IntegerType>(CastSrcTy)) {
+ if (!ShouldChangeType(PN.getType(), CastSrcTy))
+ return 0;
+ }
+ } 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 == 0)
+ return FoldPHIArgBinOpIntoPHI(PN);
+ } else {
+ return 0; // 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 == 0 || !I->hasOneUse() || !I->isSameOperationAs(FirstInst))
+ return 0;
+ if (CastSrcTy) {
+ if (I->getOperand(0)->getType() != CastSrcTy)
+ return 0; // Cast operation must match.
+ } else if (I->getOperand(1) != ConstantOp) {
+ return 0;
+ }
+ }
+
+ // 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.getName()+".in");
+ NewPN->reserveOperandSpace(PN.getNumOperands()/2);
+
+ 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 = 0;
+ 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))
+ return CastInst::Create(FirstCI->getOpcode(), PhiVal, PN.getType());
+
+ if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
+ return BinaryOperator::Create(BinOp->getOpcode(), PhiVal, ConstantOp);
+
+ CmpInst *CIOp = cast<CmpInst>(FirstInst);
+ return CmpInst::Create(CIOp->getOpcode(), CIOp->getPredicate(),
+ PhiVal, ConstantOp);
+}
+
+/// DeadPHICycle - Return true if this PHI node is only used by a PHI node cycle
+/// that is dead.
+static bool DeadPHICycle(PHINode *PN,
+ SmallPtrSet<PHINode*, 16> &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))
+ return true;
+
+ // Don't scan crazily complex things.
+ if (PotentiallyDeadPHIs.size() == 16)
+ return false;
+
+ if (PHINode *PU = dyn_cast<PHINode>(PN->use_back()))
+ return DeadPHICycle(PU, PotentiallyDeadPHIs);
+
+ return false;
+}
+
+/// PHIsEqualValue - 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,
+ SmallPtrSet<PHINode*, 16> &ValueEqualPHIs) {
+ // See if we already saw this PHI node.
+ if (!ValueEqualPHIs.insert(PN))
+ 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 (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+ Value *Op = PN->getIncomingValue(i);
+ if (PHINode *OpPN = dyn_cast<PHINode>(Op)) {
+ if (!PHIsEqualValue(OpPN, NonPhiInVal, ValueEqualPHIs))
+ return false;
+ } else if (Op != NonPhiInVal)
+ return false;
+ }
+
+ return true;
+}
+
+
+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, const 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(0, 0);
+ }
+ static inline LoweredPHIRecord getTombstoneKey() {
+ return LoweredPHIRecord(0, 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;
+ }
+ };
+ template <>
+ struct isPodLike<LoweredPHIRecord> { static const bool value = true; };
+}
+
+
+/// SliceUpIllegalIntegerPHI - 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 == 0) 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 0;
+ }
+
+
+ for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end();
+ UI != E; ++UI) {
+ Instruction *User = cast<Instruction>(*UI);
+
+ // If the user is a PHI, inspect its uses recursively.
+ if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
+ if (PHIsInspected.insert(UserPN))
+ PHIsToSlice.push_back(UserPN);
+ continue;
+ }
+
+ // Truncates are always ok.
+ if (isa<TruncInst>(User)) {
+ PHIUsers.push_back(PHIUsageRecord(PHIId, 0, User));
+ continue;
+ }
+
+ // Otherwise it must be a lshr which can only be used by one trunc.
+ if (User->getOpcode() != Instruction::LShr ||
+ !User->hasOneUse() || !isa<TruncInst>(User->use_back()) ||
+ !isa<ConstantInt>(User->getOperand(1)))
+ return 0;
+
+ unsigned Shift = cast<ConstantInt>(User->getOperand(1))->getZExtValue();
+ PHIUsers.push_back(PHIUsageRecord(PHIId, Shift, User->use_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());
+
+ DEBUG(errs() << "SLICING UP PHI: " << FirstPhi << '\n';
+ for (unsigned i = 1, e = PHIsToSlice.size(); i != e; ++i)
+ errs() << "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;
+ const 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)]) == 0) {
+
+ // Otherwise, Create the new PHI node for this user.
+ EltPHI = PHINode::Create(Ty, 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, 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 = std::find(PHIsToSlice.begin(),PHIsToSlice.end(),
+ OldInVal)-PHIsToSlice.begin();
+ PHIUsers.push_back(PHIUsageRecord(RefPHIId, Offset,
+ cast<Instruction>(Res)));
+ ++UserE;
+ }
+ }
+ PredValues.clear();
+
+ DEBUG(errs() << " 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 LCSSA is around, don't mess with Phi nodes
+ if (MustPreserveLCSSA) return 0;
+
+ if (Value *V = PN.hasConstantValue())
+ return ReplaceInstUsesWith(PN, V);
+
+ // 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()) {
+ Instruction *PHIUser = cast<Instruction>(PN.use_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->use_back() == &PN) {
+ return ReplaceInstUsesWith(PN, UndefValue::get(PN.getType()));
+ }
+ }
+
+ // 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, NumOperandVals = PN.getNumIncomingValues();
+ // Scan for the first non-phi operand.
+ while (InValNo != NumOperandVals &&
+ isa<PHINode>(PN.getIncomingValue(InValNo)))
+ ++InValNo;
+
+ if (InValNo != NumOperandVals) {
+ Value *NonPhiInVal = PN.getOperand(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 != NumOperandVals; ++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 == NumOperandVals) {
+ 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 (isa<IntegerType>(PN.getType()) && TD &&
+ !TD->isLegalInteger(PN.getType()->getPrimitiveSizeInBits()))
+ if (Instruction *Res = SliceUpIllegalIntegerPHI(PN))
+ return Res;
+
+ return 0;
+}
\ No newline at end of file
Modified: llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp?rev=92682&r1=92681&r2=92682&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp Mon Jan 4 23:31:55 2010
@@ -6119,829 +6119,8 @@
return CS.getInstruction();
}
-/// FoldPHIArgBinOpIntoPHI - If we have something like phi [add (a,b), add(a,c)]
-/// and if a/b/c and the add's 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);
-
- const Type *LHSType = LHSVal->getType();
- const 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 or GEP's with different index types.
- I->getOperand(0)->getType() != LHSType ||
- I->getOperand(1)->getType() != RHSType)
- return 0;
-
- // If they are CmpInst instructions, check their predicates
- if (Opc == Instruction::ICmp || Opc == Instruction::FCmp)
- if (cast<CmpInst>(I)->getPredicate() !=
- cast<CmpInst>(FirstInst)->getPredicate())
- return 0;
-
- // Keep track of which operand needs a phi node.
- if (I->getOperand(0) != LHSVal) LHSVal = 0;
- if (I->getOperand(1) != RHSVal) RHSVal = 0;
- }
-
- // 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 0;
-
- // Otherwise, this is safe to transform!
-
- Value *InLHS = FirstInst->getOperand(0);
- Value *InRHS = FirstInst->getOperand(1);
- PHINode *NewLHS = 0, *NewRHS = 0;
- if (LHSVal == 0) {
- NewLHS = PHINode::Create(LHSType,
- FirstInst->getOperand(0)->getName() + ".pn");
- NewLHS->reserveOperandSpace(PN.getNumOperands()/2);
- NewLHS->addIncoming(InLHS, PN.getIncomingBlock(0));
- InsertNewInstBefore(NewLHS, PN);
- LHSVal = NewLHS;
- }
-
- if (RHSVal == 0) {
- NewRHS = PHINode::Create(RHSType,
- FirstInst->getOperand(1)->getName() + ".pn");
- NewRHS->reserveOperandSpace(PN.getNumOperands()/2);
- 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 (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
- return BinaryOperator::Create(BinOp->getOpcode(), LHSVal, RHSVal);
- CmpInst *CIOp = cast<CmpInst>(FirstInst);
- return CmpInst::Create(CIOp->getOpcode(), CIOp->getPredicate(),
- LHSVal, RHSVal);
-}
-
-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;
-
- // 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 0;
-
- // 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 0;
-
- if (FirstInst->getOperand(op)->getType() !=GEP->getOperand(op)->getType())
- return 0;
-
- // 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 0;
-
- FixedOperands[op] = 0; // 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 0;
-
- // 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(),
- FirstOp->getName()+".pn");
- InsertNewInstBefore(NewPN, PN);
-
- NewPN->reserveOperandSpace(e);
- 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];
- return cast<GEPOperator>(FirstInst)->isInBounds() ?
- GetElementPtrInst::CreateInBounds(Base, FixedOperands.begin()+1,
- FixedOperands.end()) :
- GetElementPtrInst::Create(Base, FixedOperands.begin()+1,
- FixedOperands.end());
-}
-/// isSafeAndProfitableToSinkLoad - 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 targetting 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, 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 (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
- UI != E; ++UI) {
- if (isa<LoadInst>(UI)) continue;
- if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
- // 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));
-
- // 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();
-
- // 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 0;
-
- // 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 0;
-
- // 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 0;
-
- // 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) ||
- !isSafeAndProfitableToSinkLoad(LI))
- return 0;
-
- // 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 0;
-
- 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 0;
- }
-
- // 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.getName()+".in");
- NewPN->reserveOperandSpace(PN.getNumOperands()/2);
-
- Value *InVal = FirstLI->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<LoadInst>(PN.getIncomingValue(i))->getOperand(0);
- if (NewInVal != InVal)
- InVal = 0;
- 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;
- }
-
- // 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 (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
- cast<LoadInst>(PN.getIncomingValue(i))->setVolatile(false);
-
- return new LoadInst(PhiVal, "", isVolatile, LoadAlignment);
-}
-
-
-
-/// FoldPHIArgOpIntoPHI - 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) {
- 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 = 0;
- const Type *CastSrcTy = 0;
-
- 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 (isa<IntegerType>(PN.getType()) && isa<IntegerType>(CastSrcTy)) {
- if (!ShouldChangeType(PN.getType(), CastSrcTy))
- return 0;
- }
- } 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 == 0)
- return FoldPHIArgBinOpIntoPHI(PN);
- } else {
- return 0; // 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 == 0 || !I->hasOneUse() || !I->isSameOperationAs(FirstInst))
- return 0;
- if (CastSrcTy) {
- if (I->getOperand(0)->getType() != CastSrcTy)
- return 0; // Cast operation must match.
- } else if (I->getOperand(1) != ConstantOp) {
- return 0;
- }
- }
-
- // 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.getName()+".in");
- NewPN->reserveOperandSpace(PN.getNumOperands()/2);
-
- 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 = 0;
- 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))
- return CastInst::Create(FirstCI->getOpcode(), PhiVal, PN.getType());
-
- if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
- return BinaryOperator::Create(BinOp->getOpcode(), PhiVal, ConstantOp);
-
- CmpInst *CIOp = cast<CmpInst>(FirstInst);
- return CmpInst::Create(CIOp->getOpcode(), CIOp->getPredicate(),
- PhiVal, ConstantOp);
-}
-
-/// DeadPHICycle - Return true if this PHI node is only used by a PHI node cycle
-/// that is dead.
-static bool DeadPHICycle(PHINode *PN,
- SmallPtrSet<PHINode*, 16> &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))
- return true;
-
- // Don't scan crazily complex things.
- if (PotentiallyDeadPHIs.size() == 16)
- return false;
-
- if (PHINode *PU = dyn_cast<PHINode>(PN->use_back()))
- return DeadPHICycle(PU, PotentiallyDeadPHIs);
-
- return false;
-}
-
-/// PHIsEqualValue - 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,
- SmallPtrSet<PHINode*, 16> &ValueEqualPHIs) {
- // See if we already saw this PHI node.
- if (!ValueEqualPHIs.insert(PN))
- 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 (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
- Value *Op = PN->getIncomingValue(i);
- if (PHINode *OpPN = dyn_cast<PHINode>(Op)) {
- if (!PHIsEqualValue(OpPN, NonPhiInVal, ValueEqualPHIs))
- return false;
- } else if (Op != NonPhiInVal)
- return false;
- }
-
- return true;
-}
-
-
-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, const 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(0, 0);
- }
- static inline LoweredPHIRecord getTombstoneKey() {
- return LoweredPHIRecord(0, 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;
- }
- };
- template <>
- struct isPodLike<LoweredPHIRecord> { static const bool value = true; };
-}
-
-
-/// SliceUpIllegalIntegerPHI - 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 == 0) 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 0;
- }
-
-
- for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end();
- UI != E; ++UI) {
- Instruction *User = cast<Instruction>(*UI);
-
- // If the user is a PHI, inspect its uses recursively.
- if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
- if (PHIsInspected.insert(UserPN))
- PHIsToSlice.push_back(UserPN);
- continue;
- }
-
- // Truncates are always ok.
- if (isa<TruncInst>(User)) {
- PHIUsers.push_back(PHIUsageRecord(PHIId, 0, User));
- continue;
- }
-
- // Otherwise it must be a lshr which can only be used by one trunc.
- if (User->getOpcode() != Instruction::LShr ||
- !User->hasOneUse() || !isa<TruncInst>(User->use_back()) ||
- !isa<ConstantInt>(User->getOperand(1)))
- return 0;
-
- unsigned Shift = cast<ConstantInt>(User->getOperand(1))->getZExtValue();
- PHIUsers.push_back(PHIUsageRecord(PHIId, Shift, User->use_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());
-
- DEBUG(errs() << "SLICING UP PHI: " << FirstPhi << '\n';
- for (unsigned i = 1, e = PHIsToSlice.size(); i != e; ++i)
- errs() << "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;
- const 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)]) == 0) {
-
- // Otherwise, Create the new PHI node for this user.
- EltPHI = PHINode::Create(Ty, 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, 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 = std::find(PHIsToSlice.begin(),PHIsToSlice.end(),
- OldInVal)-PHIsToSlice.begin();
- PHIUsers.push_back(PHIUsageRecord(RefPHIId, Offset,
- cast<Instruction>(Res)));
- ++UserE;
- }
- }
- PredValues.clear();
-
- DEBUG(errs() << " 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 LCSSA is around, don't mess with Phi nodes
- if (MustPreserveLCSSA) return 0;
-
- if (Value *V = PN.hasConstantValue())
- return ReplaceInstUsesWith(PN, V);
-
- // 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()) {
- Instruction *PHIUser = cast<Instruction>(PN.use_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->use_back() == &PN) {
- return ReplaceInstUsesWith(PN, UndefValue::get(PN.getType()));
- }
- }
-
- // 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, NumOperandVals = PN.getNumIncomingValues();
- // Scan for the first non-phi operand.
- while (InValNo != NumOperandVals &&
- isa<PHINode>(PN.getIncomingValue(InValNo)))
- ++InValNo;
-
- if (InValNo != NumOperandVals) {
- Value *NonPhiInVal = PN.getOperand(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 != NumOperandVals; ++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 == NumOperandVals) {
- 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 (isa<IntegerType>(PN.getType()) && TD &&
- !TD->isLegalInteger(PN.getType()->getPrimitiveSizeInBits()))
- if (Instruction *Res = SliceUpIllegalIntegerPHI(PN))
- return Res;
-
- return 0;
-}
-
Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
SmallVector<Value*, 8> Ops(GEP.op_begin(), GEP.op_end());
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