[AArch64][GlobalISel] Fix a crash when selecting shufflevectors with an undef mask element.
If a shufflevector's mask vector has an element with "undef" then the generic
instruction defining that element register is a G_IMPLICT_DEF instead of G_CONSTANT.
This fixes the selector to handle this case, and for now assumes that undef just means
zero. In future we'll optimize this case properly.
llvm-svn: 358312
diff --git a/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp b/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
index a756d6b..2a7f218 100644
--- a/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
+++ b/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
@@ -93,7 +93,7 @@
bool selectUnmergeValues(MachineInstr &I, MachineRegisterInfo &MRI) const;
void collectShuffleMaskIndices(MachineInstr &I, MachineRegisterInfo &MRI,
- SmallVectorImpl<int> &Idxs) const;
+ SmallVectorImpl<Optional<int>> &Idxs) const;
bool selectShuffleVector(MachineInstr &I, MachineRegisterInfo &MRI) const;
bool selectExtractElt(MachineInstr &I, MachineRegisterInfo &MRI) const;
bool selectConcatVectors(MachineInstr &I, MachineRegisterInfo &MRI) const;
@@ -2430,7 +2430,7 @@
void AArch64InstructionSelector::collectShuffleMaskIndices(
MachineInstr &I, MachineRegisterInfo &MRI,
- SmallVectorImpl<int> &Idxs) const {
+ SmallVectorImpl<Optional<int>> &Idxs) const {
MachineInstr *MaskDef = MRI.getVRegDef(I.getOperand(3).getReg());
assert(
MaskDef->getOpcode() == TargetOpcode::G_BUILD_VECTOR &&
@@ -2444,8 +2444,13 @@
ScalarDef = MRI.getVRegDef(ScalarDef->getOperand(1).getReg());
assert(ScalarDef && "Could not find def of copy operand");
}
- assert(ScalarDef->getOpcode() == TargetOpcode::G_CONSTANT);
- Idxs.push_back(ScalarDef->getOperand(1).getCImm()->getSExtValue());
+ if (ScalarDef->getOpcode() != TargetOpcode::G_CONSTANT) {
+ // This be an undef if not a constant.
+ assert(ScalarDef->getOpcode() == TargetOpcode::G_IMPLICIT_DEF);
+ Idxs.push_back(None);
+ } else {
+ Idxs.push_back(ScalarDef->getOperand(1).getCImm()->getSExtValue());
+ }
}
}
@@ -2692,8 +2697,10 @@
// G_SHUFFLE_VECTOR doesn't really have a strictly enforced constant mask
// operand, it comes in as a normal vector value which we have to analyze to
- // find the mask indices.
- SmallVector<int, 8> Mask;
+ // find the mask indices. If the mask element is undef, then
+ // collectShuffleMaskIndices() will add a None entry for that index into
+ // the list.
+ SmallVector<Optional<int>, 8> Mask;
collectShuffleMaskIndices(I, MRI, Mask);
assert(!Mask.empty() && "Expected to find mask indices");
@@ -2708,7 +2715,10 @@
unsigned BytesPerElt = DstTy.getElementType().getSizeInBits() / 8;
SmallVector<Constant *, 64> CstIdxs;
- for (int Val : Mask) {
+ for (auto &MaybeVal : Mask) {
+ // For now, any undef indexes we'll just assume to be 0. This should be
+ // optimized in future, e.g. to select DUP etc.
+ int Val = MaybeVal.hasValue() ? *MaybeVal : 0;
for (unsigned Byte = 0; Byte < BytesPerElt; ++Byte) {
unsigned Offset = Byte + Val * BytesPerElt;
CstIdxs.emplace_back(ConstantInt::get(Type::getInt8Ty(Ctx), Offset));