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Allow tail call opportunity detection through nested and/or multiple iterations of extractelement/insertelement indirection

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179924 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Stephen Lin
2013-04-20 04:27:51 +00:00
parent d0ec6ddc14
commit 5c34e08b9f
2 changed files with 220 additions and 79 deletions
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lib/CodeGen/Analysis.cpp
+132 -79
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@@ -201,62 +201,135 @@ ISD::CondCode llvm::getICmpCondCode(ICmpInst::Predicate Pred) {
}
}
/// getNoopInput - If V is a noop (i.e., lowers to no machine code), look
/// through it (and any transitive noop operands to it) and return its input
/// value. This is used to determine if a tail call can be formed.
///
static const Value *getNoopInput(const Value *V, const TargetLowering &TLI) {
// If V is not an instruction, it can't be looked through.
const Instruction *I = dyn_cast<Instruction>(V);
if (I == 0 || !I->hasOneUse() || I->getNumOperands() == 0) return V;
Value *Op = I->getOperand(0);
// Look through truly no-op truncates.
if (isa<TruncInst>(I) &&
TLI.isTruncateFree(I->getOperand(0)->getType(), I->getType()))
return getNoopInput(I->getOperand(0), TLI);
// Look through truly no-op bitcasts.
if (isa<BitCastInst>(I)) {
// No type change at all.
if (Op->getType() == I->getType())
return getNoopInput(Op, TLI);
// Pointer to pointer cast.
if (Op->getType()->isPointerTy() && I->getType()->isPointerTy())
return getNoopInput(Op, TLI);
if (isa<VectorType>(Op->getType()) && isa<VectorType>(I->getType()) &&
TLI.isTypeLegal(EVT::getEVT(Op->getType())) &&
TLI.isTypeLegal(EVT::getEVT(I->getType())))
return getNoopInput(Op, TLI);
}
// Look through inttoptr.
if (isa<IntToPtrInst>(I) && !isa<VectorType>(I->getType())) {
// Make sure this isn't a truncating or extending cast. We could support
// this eventually, but don't bother for now.
if (TLI.getPointerTy().getSizeInBits() ==
cast<IntegerType>(Op->getType())->getBitWidth())
return getNoopInput(Op, TLI);
}
// Look through ptrtoint.
if (isa<PtrToIntInst>(I) && !isa<VectorType>(I->getType())) {
// Make sure this isn't a truncating or extending cast. We could support
// this eventually, but don't bother for now.
if (TLI.getPointerTy().getSizeInBits() ==
cast<IntegerType>(I->getType())->getBitWidth())
return getNoopInput(Op, TLI);
}
// Otherwise it's not something we can look through.
return V;
static bool isNoopBitcast(Type *T1, Type *T2,
const TargetLowering& TLI) {
return T1 == T2 || (T1->isPointerTy() && T2->isPointerTy()) ||
(isa<VectorType>(T1) && isa<VectorType>(T2) &&
TLI.isTypeLegal(EVT::getEVT(T1)) && TLI.isTypeLegal(EVT::getEVT(T2)));
}
/// sameNoopInput - Return true if V1 == V2, else if either V1 or V2 is a noop
/// (i.e., lowers to no machine code), look through it (and any transitive noop
/// operands to it) and check if it has the same noop input value. This is
/// used to determine if a tail call can be formed.
static bool sameNoopInput(const Value *V1, const Value *V2,
SmallVectorImpl<unsigned> &Els1,
SmallVectorImpl<unsigned> &Els2,
const TargetLowering &TLI) {
using std::swap;
bool swapParity = false;
bool equalEls = Els1 == Els2;
while (true) {
if ((equalEls && V1 == V2) || isa<UndefValue>(V1) || isa<UndefValue>(V2)) {
if (swapParity)
// Revert to original Els1 and Els2 to avoid confusing recursive calls
swap(Els1, Els2);
return true;
}
// Try to look through V1; if V1 is not an instruction, it can't be looked
// through.
const Instruction *I = dyn_cast<Instruction>(V1);
const Value *NoopInput = 0;
if (I != 0 && I->getNumOperands() > 0) {
Value *Op = I->getOperand(0);
if (isa<TruncInst>(I)) {
// Look through truly no-op truncates.
if (TLI.isTruncateFree(Op->getType(), I->getType()))
NoopInput = Op;
} else if (isa<BitCastInst>(I)) {
// Look through truly no-op bitcasts.
if (isNoopBitcast(Op->getType(), I->getType(), TLI))
NoopInput = Op;
} else if (isa<GetElementPtrInst>(I)) {
// Look through getelementptr
if (cast<GetElementPtrInst>(I)->hasAllZeroIndices())
NoopInput = Op;
} else if (isa<IntToPtrInst>(I)) {
// Look through inttoptr.
// Make sure this isn't a truncating or extending cast. We could
// support this eventually, but don't bother for now.
if (!isa<VectorType>(I->getType()) &&
TLI.getPointerTy().getSizeInBits() ==
cast<IntegerType>(Op->getType())->getBitWidth())
NoopInput = Op;
} else if (isa<PtrToIntInst>(I)) {
// Look through ptrtoint.
// Make sure this isn't a truncating or extending cast. We could
// support this eventually, but don't bother for now.
if (!isa<VectorType>(I->getType()) &&
TLI.getPointerTy().getSizeInBits() ==
cast<IntegerType>(I->getType())->getBitWidth())
NoopInput = Op;
}
}
if (NoopInput) {
V1 = NoopInput;
continue;
}
// If we already swapped, avoid infinite loop
if (swapParity)
break;
// Otherwise, swap V1<->V2, Els1<->Els2
swap(V1, V2);
swap(Els1, Els2);
swapParity = !swapParity;
}
for (unsigned n = 0; n < 2; ++n) {
if (isa<InsertValueInst>(V1)) {
if (isa<StructType>(V1->getType())) {
// Look through insertvalue
unsigned i, e;
for (i = 0, e = cast<StructType>(V1->getType())->getNumElements();
i != e; ++i) {
const Value *InScalar = FindInsertedValue(const_cast<Value*>(V1), i);
if (InScalar == 0)
break;
Els1.push_back(i);
if (!sameNoopInput(InScalar, V2, Els1, Els2, TLI)) {
Els1.pop_back();
break;
}
Els1.pop_back();
}
if (i == e) {
if (swapParity)
swap(Els1, Els2);
return true;
}
}
} else if (!Els1.empty() && isa<ExtractValueInst>(V1)) {
const ExtractValueInst *EVI = cast<ExtractValueInst>(V1);
unsigned i = Els1.back();
// If the scalar value being inserted is an extractvalue of the right
// index from the call, then everything is good.
if (isa<StructType>(EVI->getOperand(0)->getType()) &&
EVI->getNumIndices() == 1 && EVI->getIndices()[0] == i) {
// Look through extractvalue
Els1.pop_back();
if (sameNoopInput(EVI->getOperand(0), V2, Els1, Els2, TLI)) {
Els1.push_back(i);
if (swapParity)
swap(Els1, Els2);
return true;
}
Els1.push_back(i);
}
}
swap(V1, V2);
swap(Els1, Els2);
swapParity = !swapParity;
}
if (swapParity)
swap(Els1, Els2);
return false;
}
/// Test if the given instruction is in a position to be optimized
/// with a tail-call. This roughly means that it's in a block with
@@ -264,7 +337,8 @@ static const Value *getNoopInput(const Value *V, const TargetLowering &TLI) {
/// between it and the return.
///
/// This function only tests target-independent requirements.
bool llvm::isInTailCallPosition(ImmutableCallSite CS,const TargetLowering &TLI){
bool llvm::isInTailCallPosition(ImmutableCallSite CS,
const TargetLowering &TLI) {
const Instruction *I = CS.getInstruction();
const BasicBlock *ExitBB = I->getParent();
const TerminatorInst *Term = ExitBB->getTerminator();
@@ -322,28 +396,7 @@ bool llvm::isInTailCallPosition(ImmutableCallSite CS,const TargetLowering &TLI){
CallerAttrs.hasAttribute(AttributeSet::ReturnIndex, Attribute::SExt))
return false;
// Otherwise, make sure the unmodified return value of I is the return value.
// We handle two cases: multiple return values + scalars.
Value *RetVal = Ret->getOperand(0);
if (!isa<InsertValueInst>(RetVal) || !isa<StructType>(RetVal->getType()))
// Handle scalars first.
return getNoopInput(Ret->getOperand(0), TLI) == I;
// If this is an aggregate return, look through the insert/extract values and
// see if each is transparent.
for (unsigned i = 0, e =cast<StructType>(RetVal->getType())->getNumElements();
i != e; ++i) {
const Value *InScalar = FindInsertedValue(RetVal, i);
if (InScalar == 0) return false;
InScalar = getNoopInput(InScalar, TLI);
// If the scalar value being inserted is an extractvalue of the right index
// from the call, then everything is good.
const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(InScalar);
if (EVI == 0 || EVI->getOperand(0) != I || EVI->getNumIndices() != 1 ||
EVI->getIndices()[0] != i)
return false;
}
return true;
// Otherwise, make sure the return value and I have the same value
SmallVector<unsigned, 4> Els1, Els2;
return sameNoopInput(Ret->getOperand(0), I, Els1, Els2, TLI);
}