teach a couple of instcombine transformations involving PHIs to

not turn a PHI in a legal type into a PHI of an illegal type, and
add a new optimization that breaks up insane integer PHI nodes into
small pieces (PR3451).

llvm-svn: 86443
This commit is contained in:
Chris Lattner 2009-11-08 08:21:13 +00:00
parent 1909b23533
commit cddc8aa1b8
3 changed files with 155 additions and 8 deletions

View File

@ -283,6 +283,8 @@ namespace {
Instruction *visitSelectInstWithICmp(SelectInst &SI, ICmpInst *ICI);
Instruction *visitCallInst(CallInst &CI);
Instruction *visitInvokeInst(InvokeInst &II);
Instruction *SliceUpIllegalIntegerPHI(PHINode &PN);
Instruction *visitPHINode(PHINode &PN);
Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
Instruction *visitAllocaInst(AllocaInst &AI);
@ -8083,8 +8085,7 @@ bool InstCombiner::CanEvaluateInDifferentType(Value *V, const Type *Ty,
Value *InstCombiner::EvaluateInDifferentType(Value *V, const Type *Ty,
bool isSigned) {
if (Constant *C = dyn_cast<Constant>(V))
return ConstantExpr::getIntegerCast(C, Ty,
isSigned /*Sext or ZExt*/);
return ConstantExpr::getIntegerCast(C, Ty, isSigned /*Sext or ZExt*/);
// Otherwise, it must be an instruction.
Instruction *I = cast<Instruction>(V);
@ -8117,8 +8118,7 @@ Value *InstCombiner::EvaluateInDifferentType(Value *V, const Type *Ty,
return I->getOperand(0);
// Otherwise, must be the same type of cast, so just reinsert a new one.
Res = CastInst::Create(cast<CastInst>(I)->getOpcode(), I->getOperand(0),
Ty);
Res = CastInst::Create(cast<CastInst>(I)->getOpcode(), I->getOperand(0),Ty);
break;
case Instruction::Select: {
Value *True = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned);
@ -8167,10 +8167,18 @@ Instruction *InstCombiner::commonCastTransforms(CastInst &CI) {
return NV;
// If we are casting a PHI then fold the cast into the PHI
if (isa<PHINode>(Src))
if (isa<PHINode>(Src)) {
// We don't do this if this would create a PHI node with an illegal type if
// it is currently legal.
if (!isa<IntegerType>(Src->getType()) ||
!isa<IntegerType>(CI.getType()) ||
(TD && TD->isLegalInteger(CI.getType()->getPrimitiveSizeInBits())) ||
(TD && !TD->isLegalInteger(Src->getType()->getPrimitiveSizeInBits())))
if (Instruction *NV = FoldOpIntoPhi(CI))
return NV;
}
return 0;
}
@ -10886,6 +10894,15 @@ Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
if (isa<CastInst>(FirstInst)) {
CastSrcTy = FirstInst->getOperand(0)->getType();
// If this is a legal integer PHI node, and pulling the operation through
// would cause it to be an illegal integer PHI, don't do the transformation.
if (!TD ||
(isa<IntegerType>(PN.getType()) &&
isa<IntegerType>(CastSrcTy) &&
TD->isLegalInteger(PN.getType()->getPrimitiveSizeInBits()) &&
!TD->isLegalInteger(CastSrcTy->getPrimitiveSizeInBits())))
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.
@ -10998,6 +11015,123 @@ static bool PHIsEqualValue(PHINode *PN, Value *NonPhiInVal,
}
namespace {
struct PHIUsageRecord {
unsigned Shift; // The amount shifted.
Instruction *Inst; // The trunc instruction.
PHIUsageRecord(unsigned Sh, Instruction *User) : Shift(Sh), Inst(User) {}
bool operator<(const PHIUsageRecord &RHS) const {
if (Shift < RHS.Shift) return true;
return Shift == RHS.Shift &&
Inst->getType()->getPrimitiveSizeInBits() <
RHS.Inst->getType()->getPrimitiveSizeInBits();
}
};
}
/// 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 &PN) {
SmallVector<PHIUsageRecord, 16> PHIUsers;
for (Value::use_iterator UI = PN.use_begin(), E = PN.use_end();
UI != E; ++UI) {
Instruction *User = cast<Instruction>(*UI);
// The PHI can use itself.
if (User == &PN)
continue;
// Truncates are always ok.
if (isa<TruncInst>(User)) {
PHIUsers.push_back(PHIUsageRecord(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(Shift, User->use_back()));
}
// If we have no users, they must be all self uses, just nuke the PHI.
if (PHIUsers.empty())
return ReplaceInstUsesWith(PN, UndefValue::get(PN.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());
DenseMap<BasicBlock*, Value*> PredValues;
unsigned UserI = 0, UserE = PHIUsers.size();
while (1) {
assert(UserI != UserE && "Iteration fail, loop below should catch this");
unsigned Offset = PHIUsers[UserI].Shift;
const Type *Ty = PHIUsers[UserI].Inst->getType();
// Create the new PHI node for this user.
PHINode *EltPHI =
PHINode::Create(Ty, PN.getName()+".off"+Twine(Offset), &PN);
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;
}
// Otherwise, do an extract in the predecessor.
Builder->SetInsertPoint(Pred, Pred->getTerminator());
if (Offset)
InVal = Builder->CreateLShr(InVal, ConstantInt::get(InVal->getType(),
Offset), "extract");
InVal = Builder->CreateTrunc(InVal, Ty, "extract.t");
PredVal = InVal;
EltPHI->addIncoming(PredVal, Pred);
}
PredValues.clear();
// Now that we have a new PHI node, replace all uses of this piece of the
// PHI with the one new PHI.
while (PHIUsers[UserI].Shift == Offset &&
PHIUsers[UserI].Inst->getType() == Ty) {
ReplaceInstUsesWith(*PHIUsers[UserI].Inst, EltPHI);
// If we replaced the last PHI user, we're done. Just replace all the
// remaining uses of the PHI (self uses and the lshrs with undefs.
if (++UserI == UserE)
return ReplaceInstUsesWith(PN, UndefValue::get(PN.getType()));
}
}
}
// PHINode simplification
//
Instruction *InstCombiner::visitPHINode(PHINode &PN) {
@ -11103,6 +11237,15 @@ Instruction *InstCombiner::visitPHINode(PHINode &PN) {
}
}
// 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;
}

View File

@ -2,6 +2,8 @@
;
; RUN: opt < %s -instcombine -S | FileCheck %s
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
define i32 @test1(i32 %A, i1 %b) {
BB0:
br i1 %b, label %BB1, label %BB2

View File

@ -1,5 +1,7 @@
; RUN: opt < %s -instcombine -S | not grep sext
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
declare i32 @llvm.ctpop.i32(i32)
declare i32 @llvm.ctlz.i32(i32)
declare i32 @llvm.cttz.i32(i32)