// we are absolutely afraid of producing a shuffle mask not in the input
// program, because the code gen may not be smart enough to turn a merged
// shuffle into two specific shuffles: it may produce worse code. As such,
- // we only merge two shuffles if the result is one of the two input shuffle
- // masks. In this case, merging the shuffles just removes one instruction,
- // which we know is safe. This is good for things like turning:
- // (splat(splat)) -> splat.
+ // we only merge two shuffles if the result is either a splat or one of the
+ // two input shuffle masks. In this case, merging the shuffles just removes
+ // one instruction, which we know is safe. This is good for things like
+ // turning: (splat(splat)) -> splat.
if (ShuffleVectorInst *LHSSVI = dyn_cast<ShuffleVectorInst>(LHS)) {
if (isa<UndefValue>(RHS)) {
std::vector<unsigned> LHSMask = getShuffleMask(LHSSVI);
if (LHSMask.size() == Mask.size()) {
std::vector<unsigned> NewMask;
- for (unsigned i = 0, e = Mask.size(); i != e; ++i)
- if (Mask[i] >= e)
- NewMask.push_back(2*e);
- else
- NewMask.push_back(LHSMask[Mask[i]]);
+ bool isSplat = true;
+ unsigned SplatElt = 2 * Mask.size(); // undef
+ for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
+ unsigned MaskElt = 2 * e; // undef
+ if (Mask[i] < e)
+ MaskElt = LHSMask[Mask[i]];
+ // Check if this could still be a splat.
+ if (MaskElt < 2*e) {
+ if (SplatElt < 2*e && SplatElt != MaskElt)
+ isSplat = false;
+ SplatElt = MaskElt;
+ }
+ NewMask.push_back(MaskElt);
+ }
// If the result mask is equal to the src shuffle or this
// shuffle mask, do the replacement.
- if (NewMask == LHSMask || NewMask == Mask) {
+ if (isSplat || NewMask == LHSMask || NewMask == Mask) {
unsigned LHSInNElts =
cast<VectorType>(LHSSVI->getOperand(0)->getType())->
getNumElements();
std::vector<Constant*> Elts;
+ const Type *Int32Ty = Type::getInt32Ty(SVI.getContext());
for (unsigned i = 0, e = NewMask.size(); i != e; ++i) {
if (NewMask[i] >= LHSInNElts*2) {
- Elts.push_back(UndefValue::get(
- Type::getInt32Ty(SVI.getContext())));
+ Elts.push_back(UndefValue::get(Int32Ty));
} else {
- Elts.push_back(ConstantInt::get(
- Type::getInt32Ty(SVI.getContext()),
- NewMask[i]));
+ Elts.push_back(ConstantInt::get(Int32Ty, NewMask[i]));
}
}
return new ShuffleVectorInst(LHSSVI->getOperand(0),
%tmp9 = shufflevector <4 x i8> %tmp7, <4 x i8> undef, <4 x i32> < i32 3, i32 1, i32 2, i32 0 > ; <<4 x i8>> [#uses=1]
ret <4 x i8> %tmp9
}
+
+; Redundant vector splats should be removed. Radar 8597790.
+define <4 x i32> @test10(<4 x i32> %tmp5) nounwind {
+; CHECK: @test10
+; CHECK-NEXT: shufflevector
+; CHECK-NEXT: ret
+ %tmp6 = shufflevector <4 x i32> %tmp5, <4 x i32> undef, <4 x i32> <i32 1, i32 undef, i32 undef, i32 undef>
+ %tmp7 = shufflevector <4 x i32> %tmp6, <4 x i32> undef, <4 x i32> zeroinitializer
+ ret <4 x i32> %tmp7
+}