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enhance PHI slicing to handle the case when a slicable PHI is begin
used by a chain of other PHIs. llvm-svn: 86503
This commit is contained in:
Chris Lattner
parent
bbbb62a090
commit
5a3a41a757
@ -11031,18 +11031,57 @@ static bool PHIsEqualValue(PHINode *PN, Value *NonPhiInVal,
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namespace {
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struct PHIUsageRecord {
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unsigned PHIId; // The ID # of the PHI (something determinstic to sort on)
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unsigned Shift; // The amount shifted.
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Instruction *Inst; // The trunc instruction.
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PHIUsageRecord(unsigned Sh, Instruction *User) : Shift(Sh), Inst(User) {}
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PHIUsageRecord(unsigned pn, unsigned Sh, Instruction *User)
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: PHIId(pn), Shift(Sh), Inst(User) {}
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bool operator<(const PHIUsageRecord &RHS) const {
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if (PHIId < RHS.PHIId) return true;
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if (PHIId > RHS.PHIId) return false;
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if (Shift < RHS.Shift) return true;
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return Shift == RHS.Shift &&
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Inst->getType()->getPrimitiveSizeInBits() <
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if (Shift > RHS.Shift) return false;
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return Inst->getType()->getPrimitiveSizeInBits() <
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RHS.Inst->getType()->getPrimitiveSizeInBits();
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}
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};
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struct LoweredPHIRecord {
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PHINode *PN; // The PHI that was lowered.
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unsigned Shift; // The amount shifted.
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unsigned Width; // The width extracted.
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LoweredPHIRecord(PHINode *pn, unsigned Sh, const Type *Ty)
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: PN(pn), Shift(Sh), Width(Ty->getPrimitiveSizeInBits()) {}
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// Ctor form used by DenseMap.
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LoweredPHIRecord(PHINode *pn, unsigned Sh)
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: PN(pn), Shift(Sh), Width(0) {}
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};
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}
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namespace llvm {
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template<>
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struct DenseMapInfo<LoweredPHIRecord> {
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static inline LoweredPHIRecord getEmptyKey() {
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return LoweredPHIRecord(0, 0);
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}
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static inline LoweredPHIRecord getTombstoneKey() {
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return LoweredPHIRecord(0, 1);
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}
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static unsigned getHashValue(const LoweredPHIRecord &Val) {
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return DenseMapInfo<PHINode*>::getHashValue(Val.PN) ^ (Val.Shift>>3) ^
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(Val.Width>>3);
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}
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static bool isEqual(const LoweredPHIRecord &LHS,
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const LoweredPHIRecord &RHS) {
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return LHS.PN == RHS.PN && LHS.Shift == RHS.Shift &&
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LHS.Width == RHS.Width;
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}
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static bool isPod() { return true; }
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};
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}
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@ -11054,102 +11093,156 @@ struct PHIUsageRecord {
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/// TODO: The user of the trunc may be an bitcast to float/double/vector or an
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/// inttoptr. We should produce new PHIs in the right type.
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///
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Instruction *InstCombiner::SliceUpIllegalIntegerPHI(PHINode &PN) {
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Instruction *InstCombiner::SliceUpIllegalIntegerPHI(PHINode &FirstPhi) {
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// PHIUsers - Keep track of all of the truncated values extracted from a set
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// of PHIs, along with their offset. These are the things we want to rewrite.
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SmallVector<PHIUsageRecord, 16> PHIUsers;
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for (Value::use_iterator UI = PN.use_begin(), E = PN.use_end();
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UI != E; ++UI) {
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Instruction *User = cast<Instruction>(*UI);
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// PHIs are often mutually cyclic, so we keep track of a whole set of PHI
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// nodes which are extracted from. PHIsToSlice is a set we use to avoid
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// revisiting PHIs, PHIsInspected is a ordered list of PHIs that we need to
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// check the uses of (to ensure they are all extracts).
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SmallVector<PHINode*, 8> PHIsToSlice;
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SmallPtrSet<PHINode*, 8> PHIsInspected;
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PHIsToSlice.push_back(&FirstPhi);
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PHIsInspected.insert(&FirstPhi);
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for (unsigned PHIId = 0; PHIId != PHIsToSlice.size(); ++PHIId) {
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PHINode *PN = PHIsToSlice[PHIId];
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// The PHI can use itself.
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if (User == &PN)
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continue;
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// Truncates are always ok.
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if (isa<TruncInst>(User)) {
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PHIUsers.push_back(PHIUsageRecord(0, User));
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continue;
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for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end();
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UI != E; ++UI) {
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Instruction *User = cast<Instruction>(*UI);
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// If the user is a PHI, inspect its uses recursively.
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if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
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if (PHIsInspected.insert(UserPN))
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PHIsToSlice.push_back(UserPN);
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continue;
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}
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// Truncates are always ok.
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if (isa<TruncInst>(User)) {
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PHIUsers.push_back(PHIUsageRecord(PHIId, 0, User));
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continue;
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}
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// Otherwise it must be a lshr which can only be used by one trunc.
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if (User->getOpcode() != Instruction::LShr ||
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!User->hasOneUse() || !isa<TruncInst>(User->use_back()) ||
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!isa<ConstantInt>(User->getOperand(1)))
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return 0;
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unsigned Shift = cast<ConstantInt>(User->getOperand(1))->getZExtValue();
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PHIUsers.push_back(PHIUsageRecord(PHIId, Shift, User->use_back()));
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}
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// Otherwise it must be a lshr which can only be used by one trunc.
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if (User->getOpcode() != Instruction::LShr ||
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!User->hasOneUse() || !isa<TruncInst>(User->use_back()) ||
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!isa<ConstantInt>(User->getOperand(1)))
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return 0;
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unsigned Shift = cast<ConstantInt>(User->getOperand(1))->getZExtValue();
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PHIUsers.push_back(PHIUsageRecord(Shift, User->use_back()));
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}
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// If we have no users, they must be all self uses, just nuke the PHI.
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if (PHIUsers.empty())
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return ReplaceInstUsesWith(PN, UndefValue::get(PN.getType()));
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return ReplaceInstUsesWith(FirstPhi, UndefValue::get(FirstPhi.getType()));
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// If this phi node is transformable, create new PHIs for all the pieces
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// extracted out of it. First, sort the users by their offset and size.
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array_pod_sort(PHIUsers.begin(), PHIUsers.end());
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DEBUG(errs() << "SLICING UP PHI: " << PN << '\n');
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DEBUG(errs() << "SLICING UP PHI: " << FirstPhi << '\n';
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for (unsigned i = 1, e = PHIsToSlice.size(); i != e; ++i)
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errs() << "AND USER PHI #" << i << ": " << *PHIsToSlice[i] <<'\n';
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);
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// PredValues - This is a temporary used when rewriting PHI nodes. It is
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// hoisted out here to avoid construction/destruction thrashing.
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DenseMap<BasicBlock*, Value*> PredValues;
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unsigned UserI = 0, UserE = PHIUsers.size();
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while (1) {
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assert(UserI != UserE && "Iteration fail, loop below should catch this");
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// ExtractedVals - Each new PHI we introduce is saved here so we don't
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// introduce redundant PHIs.
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DenseMap<LoweredPHIRecord, PHINode*> ExtractedVals;
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for (unsigned UserI = 0, UserE = PHIUsers.size(); UserI != UserE; ++UserI) {
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unsigned PHIId = PHIUsers[UserI].PHIId;
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PHINode *PN = PHIsToSlice[PHIId];
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unsigned Offset = PHIUsers[UserI].Shift;
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const Type *Ty = PHIUsers[UserI].Inst->getType();
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// Create the new PHI node for this user.
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PHINode *EltPHI =
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PHINode::Create(Ty, PN.getName()+".off"+Twine(Offset), &PN);
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assert(EltPHI->getType() != PN.getType() &&
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"Truncate didn't shrink phi?");
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for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
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BasicBlock *Pred = PN.getIncomingBlock(i);
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Value *&PredVal = PredValues[Pred];
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PHINode *EltPHI;
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// If we've already lowered a user like this, reuse the previously lowered
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// value.
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if ((EltPHI = ExtractedVals[LoweredPHIRecord(PN, Offset, Ty)]) == 0) {
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// If we already have a value for this predecessor, reuse it.
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if (PredVal) {
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EltPHI->addIncoming(PredVal, Pred);
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continue;
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}
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// Otherwise, Create the new PHI node for this user.
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EltPHI = PHINode::Create(Ty, PN->getName()+".off"+Twine(Offset), PN);
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assert(EltPHI->getType() != PN->getType() &&
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"Truncate didn't shrink phi?");
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for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
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BasicBlock *Pred = PN->getIncomingBlock(i);
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Value *&PredVal = PredValues[Pred];
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// If we already have a value for this predecessor, reuse it.
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if (PredVal) {
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EltPHI->addIncoming(PredVal, Pred);
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continue;
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}
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// Handle the PHI self-reuse case.
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Value *InVal = PN.getIncomingValue(i);
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if (InVal == &PN) {
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PredVal = EltPHI;
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EltPHI->addIncoming(PredVal, Pred);
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continue;
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// Handle the PHI self-reuse case.
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Value *InVal = PN->getIncomingValue(i);
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if (InVal == PN) {
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PredVal = EltPHI;
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EltPHI->addIncoming(PredVal, Pred);
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continue;
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} else if (PHINode *InPHI = dyn_cast<PHINode>(PN)) {
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// If the incoming value was a PHI, and if it was one of the PHIs we
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// already rewrote it, just use the lowered value.
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if (Value *Res = ExtractedVals[LoweredPHIRecord(InPHI, Offset, Ty)]) {
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PredVal = Res;
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EltPHI->addIncoming(PredVal, Pred);
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continue;
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}
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}
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// Otherwise, do an extract in the predecessor.
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Builder->SetInsertPoint(Pred, Pred->getTerminator());
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Value *Res = InVal;
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if (Offset)
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Res = Builder->CreateLShr(Res, ConstantInt::get(InVal->getType(),
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Offset), "extract");
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Res = Builder->CreateTrunc(Res, Ty, "extract.t");
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PredVal = Res;
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EltPHI->addIncoming(Res, Pred);
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// If the incoming value was a PHI, and if it was one of the PHIs we are
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// rewriting, we will ultimately delete the code we inserted. This
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// means we need to revisit that PHI to make sure we extract out the
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// needed piece.
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if (PHINode *OldInVal = dyn_cast<PHINode>(PN->getIncomingValue(i)))
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if (PHIsInspected.count(OldInVal)) {
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unsigned RefPHIId = std::find(PHIsToSlice.begin(),PHIsToSlice.end(),
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OldInVal)-PHIsToSlice.begin();
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PHIUsers.push_back(PHIUsageRecord(RefPHIId, Offset,
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cast<Instruction>(Res)));
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++UserE;
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}
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}
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PredValues.clear();
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// Otherwise, do an extract in the predecessor.
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Builder->SetInsertPoint(Pred, Pred->getTerminator());
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if (Offset)
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InVal = Builder->CreateLShr(InVal, ConstantInt::get(InVal->getType(),
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Offset), "extract");
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InVal = Builder->CreateTrunc(InVal, Ty, "extract.t");
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PredVal = InVal;
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EltPHI->addIncoming(PredVal, Pred);
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DEBUG(errs() << " Made element PHI for offset " << Offset << ": "
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<< *EltPHI << '\n');
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ExtractedVals[LoweredPHIRecord(PN, Offset, Ty)] = EltPHI;
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}
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PredValues.clear();
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DEBUG(errs() << " Made element PHI for offset " << Offset << ": "
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<< *EltPHI << '\n');
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// Now that we have a new PHI node, replace all uses of this piece of the
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// PHI with the one new PHI.
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while (PHIUsers[UserI].Shift == Offset &&
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PHIUsers[UserI].Inst->getType() == Ty) {
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ReplaceInstUsesWith(*PHIUsers[UserI].Inst, EltPHI);
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// If we replaced the last PHI user, we're done. Just replace all the
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// remaining uses of the PHI (self uses and the lshrs with undefs.
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if (++UserI == UserE)
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return ReplaceInstUsesWith(PN, UndefValue::get(PN.getType()));
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}
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// Replace the use of this piece with the PHI node.
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ReplaceInstUsesWith(*PHIUsers[UserI].Inst, EltPHI);
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}
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// Replace all the remaining uses of the PHI nodes (self uses and the lshrs)
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// with undefs.
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Value *Undef = UndefValue::get(FirstPhi.getType());
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for (unsigned i = 1, e = PHIsToSlice.size(); i != e; ++i)
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ReplaceInstUsesWith(*PHIsToSlice[i], Undef);
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return ReplaceInstUsesWith(FirstPhi, Undef);
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}
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// PHINode simplification
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@ -317,3 +317,48 @@ Exit: ; preds = %Loop
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; CHECK: Loop:
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; CHECK-NEXT: phi i160
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}
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declare i64 @test15a(i64)
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define i64 @test15b(i64 %A, i1 %b) {
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; CHECK: @test15b
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entry:
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%i0 = zext i64 %A to i128
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%i1 = shl i128 %i0, 64
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%i = or i128 %i1, %i0
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br i1 %b, label %one, label %two
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; CHECK: entry:
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; CHECK-NEXT: br i1 %b
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one:
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%x = phi i128 [%i, %entry], [%y, %two]
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%x1 = lshr i128 %x, 64
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%x2 = trunc i128 %x1 to i64
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%c = call i64 @test15a(i64 %x2)
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%c1 = zext i64 %c to i128
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br label %two
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; CHECK: one:
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; CHECK-NEXT: phi i64
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; CHECK-NEXT: %c = call i64 @test15a
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two:
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%y = phi i128 [%i, %entry], [%c1, %one]
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%y1 = lshr i128 %y, 64
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%y2 = trunc i128 %y1 to i64
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%d = call i64 @test15a(i64 %y2)
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%d1 = trunc i64 %d to i1
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br i1 %d1, label %one, label %end
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; CHECK: two:
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; CHECK-NEXT: phi i64
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; CHECK-NEXT: phi i64
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; CHECK-NEXT: %d = call i64 @test15a
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end:
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%g = trunc i128 %y to i64
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ret i64 %g
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; CHECK: end:
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; CHECK-NEXT: ret i64
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}
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