[InstCombine] remove unnecessary shuffle undef folding
Add a test for constant folding to show that (shuffle undef, undef, mask) should already be handled via instsimplify. llvm-svn: 340926
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@ -1379,13 +1379,6 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
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// Canonicalize shuffle(x ,x,mask) -> shuffle(x, undef,mask')
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// Canonicalize shuffle(x ,x,mask) -> shuffle(x, undef,mask')
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// Canonicalize shuffle(undef,x,mask) -> shuffle(x, undef,mask').
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// Canonicalize shuffle(undef,x,mask) -> shuffle(x, undef,mask').
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if (LHS == RHS || isa<UndefValue>(LHS)) {
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if (LHS == RHS || isa<UndefValue>(LHS)) {
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if (isa<UndefValue>(LHS) && LHS == RHS) {
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// shuffle(undef,undef,mask) -> undef.
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Value *Result = (VWidth == LHSWidth)
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? LHS : UndefValue::get(SVI.getType());
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return replaceInstUsesWith(SVI, Result);
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}
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// Remap any references to RHS to use LHS.
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// Remap any references to RHS to use LHS.
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SmallVector<Constant*, 16> Elts;
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SmallVector<Constant*, 16> Elts;
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for (unsigned i = 0, e = LHSWidth; i != VWidth; ++i) {
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for (unsigned i = 0, e = LHSWidth; i != VWidth; ++i) {
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@ -59,3 +59,11 @@ define <3 x float> @fadd_commute() {
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ret <3 x float> %c
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ret <3 x float> %c
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}
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}
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define <4 x i32> @shuffle_of_undefs(<4 x i32> %v1, <4 x i32> %v2) {
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; CHECK-LABEL: @shuffle_of_undefs(
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; CHECK-NEXT: ret <4 x i32> undef
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;
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%r = shufflevector <4 x i32> undef, <4 x i32> undef, <4 x i32> <i32 5, i32 1, i32 2, i32 3>
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ret <4 x i32> %r
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}
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