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[ConstantFolding] Fold masked loads

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We can constant fold a masked load if the operands are appropriately
constant.

Differential Revision: http://reviews.llvm.org/D22324

llvm-svn: 275352
This commit is contained in:
David Majnemer 2016-07-14 00:29:50 +00:00
parent 2ce62bc5b9
commit 774e517b3f
2 changed files with 47 additions and 1 deletions
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37
lib/Analysis/ConstantFolding.cpp
View File

@ -1299,6 +1299,7 @@ bool llvm::canConstantFoldCallTo(const Function *F) {
case Intrinsic::fmuladd:
case Intrinsic::copysign:
case Intrinsic::round:
case Intrinsic::masked_load:
case Intrinsic::sadd_with_overflow:
case Intrinsic::uadd_with_overflow:
case Intrinsic::ssub_with_overflow:
@ -1843,11 +1844,44 @@ Constant *ConstantFoldScalarCall(StringRef Name, unsigned IntrinsicID, Type *Ty,
Constant *ConstantFoldVectorCall(StringRef Name, unsigned IntrinsicID,
VectorType *VTy, ArrayRef<Constant *> Operands,
const DataLayout &DL,
const TargetLibraryInfo *TLI) {
SmallVector<Constant *, 4> Result(VTy->getNumElements());
SmallVector<Constant *, 4> Lane(Operands.size());
Type *Ty = VTy->getElementType();
if (IntrinsicID == Intrinsic::masked_load) {
auto *SrcPtr = Operands[0];
auto *Mask = Operands[2];
auto *Passthru = Operands[3];
Constant *VecData = ConstantFoldLoadFromConstPtr(SrcPtr, VTy, DL);
if (!VecData)
return nullptr;
SmallVector<Constant *, 32> NewElements;
for (unsigned I = 0, E = VTy->getNumElements(); I != E; ++I) {
auto *MaskElt =
dyn_cast_or_null<ConstantInt>(Mask->getAggregateElement(I));
if (!MaskElt)
break;
if (MaskElt->isZero()) {
auto *PassthruElt = Passthru->getAggregateElement(I);
if (!PassthruElt)
break;
NewElements.push_back(PassthruElt);
} else {
assert(MaskElt->isOne());
auto *VecElt = VecData->getAggregateElement(I);
if (!VecElt)
break;
NewElements.push_back(VecElt);
}
}
if (NewElements.size() == VTy->getNumElements())
return ConstantVector::get(NewElements);
return nullptr;
}
for (unsigned I = 0, E = VTy->getNumElements(); I != E; ++I) {
// Gather a column of constants.
for (unsigned J = 0, JE = Operands.size(); J != JE; ++J) {
@ -1880,7 +1914,8 @@ llvm::ConstantFoldCall(Function *F, ArrayRef<Constant *> Operands,
Type *Ty = F->getReturnType();
if (auto *VTy = dyn_cast<VectorType>(Ty))
return ConstantFoldVectorCall(Name, F->getIntrinsicID(), VTy, Operands, TLI);
return ConstantFoldVectorCall(Name, F->getIntrinsicID(), VTy, Operands,
F->getParent()->getDataLayout(), TLI);
return ConstantFoldScalarCall(Name, F->getIntrinsicID(), Ty, Operands, TLI);
}

11
test/Transforms/InstSimplify/call.ll
View File

@ -204,4 +204,15 @@ entry:
; CHECK-LABEL: define i32 @call_undef(
; CHECK: ret i32 undef
@GV = private constant [8 x i32] [i32 42, i32 43, i32 44, i32 45, i32 46, i32 47, i32 48, i32 49]
define <8 x i32> @partial_masked_load() {
; CHECK-LABEL: @partial_masked_load(
; CHECK: ret <8 x i32> <i32 undef, i32 undef, i32 42, i32 43, i32 44, i32 45, i32 46, i32 47>
%masked.load = call <8 x i32> @llvm.masked.load.v8i32.p0v8i32(<8 x i32>* bitcast (i32* getelementptr ([8 x i32], [8 x i32]* @GV, i64 0, i64 -2) to <8 x i32>*), i32 4, <8 x i1> <i1 false, i1 false, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true>, <8 x i32> undef)
ret <8 x i32> %masked.load
}
declare noalias i8* @malloc(i64)
declare <8 x i32> @llvm.masked.load.v8i32.p0v8i32(<8 x i32>*, i32, <8 x i1>, <8 x i32>)