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author | Chris Lattner <sabre@nondot.org> | 2010-01-05 05:31:55 +0000 |
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committer | Chris Lattner <sabre@nondot.org> | 2010-01-05 05:31:55 +0000 |
commit | f54e72962991005a3c0cc7dce0c550a14af90792 (patch) | |
tree | 1d4f92e6a2a8400c6302d387c7c2cd55e1cb153f /lib/Transforms/InstCombine/InstructionCombining.cpp | |
parent | 43fd9017a69a6314fb780f87083b1e57a0981287 (diff) | |
download | external_llvm-f54e72962991005a3c0cc7dce0c550a14af90792.tar.gz external_llvm-f54e72962991005a3c0cc7dce0c550a14af90792.tar.bz2 external_llvm-f54e72962991005a3c0cc7dce0c550a14af90792.zip |
split PHI node stuff out to InstCombinePHI.cpp
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92682 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Transforms/InstCombine/InstructionCombining.cpp')
-rw-r--r-- | lib/Transforms/InstCombine/InstructionCombining.cpp | 821 |
1 files changed, 0 insertions, 821 deletions
diff --git a/lib/Transforms/InstCombine/InstructionCombining.cpp b/lib/Transforms/InstCombine/InstructionCombining.cpp index 2785fa8286..f9baffcf46 100644 --- a/lib/Transforms/InstCombine/InstructionCombining.cpp +++ b/lib/Transforms/InstCombine/InstructionCombining.cpp @@ -6119,828 +6119,7 @@ Instruction *InstCombiner::transformCallThroughTrampoline(CallSite CS) { 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()); |