InstCombine: Fold shufflevector(select) and shufflevector(phi) #113746
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- Transform `shufflevector(select(c, x, y), C)` to `select(c, shufflevector(x, C), shufflevector(y, C))` by re-using the `FoldOpIntoSelect` helper. - Transform `shufflevector(phi(x, y), C)` to `phi(shufflevector(x, C), shufflevector(y, C))` by re-using the `foldOpInotPhi` helper.
MatzeB
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@llvm/pr-subscribers-llvm-transforms Author: Matthias Braun (MatzeB) Changes
Full diff: https://github.com/llvm/llvm-project/pull/113746.diff 2 Files Affected:
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
index d68ae64f08aa90..7989af5e0e2146 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -2900,6 +2900,17 @@ Instruction *InstCombinerImpl::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
if (Instruction *I = foldIdentityPaddedShuffles(SVI))
return I;
+ if (Constant *C = dyn_cast<Constant>(RHS)) {
+ if (SelectInst *SI = dyn_cast<SelectInst>(LHS)) {
+ if (Instruction *I = FoldOpIntoSelect(SVI, SI, /*FoldWIthMultiUse=*/false))
+ return I;
+ }
+ if (PHINode *PN = dyn_cast<PHINode>(LHS)) {
+ if (Instruction *I = foldOpIntoPhi(SVI, PN))
+ return I;
+ }
+ }
+
if (match(RHS, m_Poison()) && canEvaluateShuffled(LHS, Mask)) {
Value *V = evaluateInDifferentElementOrder(LHS, Mask, Builder);
return replaceInstUsesWith(SVI, V);
diff --git a/llvm/test/Transforms/InstCombine/vec_shuffle.ll b/llvm/test/Transforms/InstCombine/vec_shuffle.ll
index 75a84e51279b80..d050cf10849e3c 100644
--- a/llvm/test/Transforms/InstCombine/vec_shuffle.ll
+++ b/llvm/test/Transforms/InstCombine/vec_shuffle.ll
@@ -2377,3 +2377,47 @@ define <2 x i32> @not_splat_shuffle2(i32 %x) {
%shuf = shufflevector <2 x i32> %vec, <2 x i32> undef, <2 x i32> <i32 1, i32 3>
ret <2 x i32> %shuf
}
+define <2 x i32> @foldselect0(i1 %c) {
+; CHECK-LABEL: @foldselect0(
+; CHECK-NEXT: [[SHUF:%.*]] = select i1 [[C:%.*]], <2 x i32> <i32 7, i32 42>, <2 x i32> <i32 1, i32 0>
+; CHECK-NEXT: ret <2 x i32> [[SHUF]]
+;
+ %sel = select i1 %c, <2 x i32> <i32 42, i32 7>, <2 x i32> <i32 0, i32 1>
+ %shuf = shufflevector <2 x i32> %sel, <2 x i32> poison, <2 x i32> <i32 1, i32 0>
+ ret <2 x i32> %shuf
+}
+
+declare i1 @cond()
+declare <4 x i32> @value()
+
+define <4 x i32> @foldphi1() {
+; CHECK-LABEL: @foldphi1(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: br label [[LOOP:%.*]]
+; CHECK: loop:
+; CHECK-NEXT: [[V:%.*]] = phi <4 x i32> [ zeroinitializer, [[ENTRY:%.*]] ], [ [[XOR:%.*]], [[LOOP]] ]
+; CHECK-NEXT: [[VAL:%.*]] = call <4 x i32> @value()
+; CHECK-NEXT: [[XOR]] = xor <4 x i32> [[V]], [[VAL]]
+; CHECK-NEXT: [[C:%.*]] = call i1 @cond()
+; CHECK-NEXT: br i1 [[C]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK: exit:
+; CHECK-NEXT: [[SHUF1:%.*]] = shufflevector <4 x i32> [[XOR]], <4 x i32> poison, <4 x i32> <i32 3, i32 0, i32 1, i32 2>
+; CHECK-NEXT: ret <4 x i32> [[SHUF1]]
+;
+entry:
+ br label %loop
+
+loop:
+ %v = phi <4 x i32> [zeroinitializer, %entry], [%shuf1, %loop]
+
+ %shuf0 = shufflevector <4 x i32> %v, <4 x i32> poison, <4 x i32> <i32 1, i32 2, i32 3, i32 0>
+ %val = call <4 x i32> @value()
+ %xor = xor <4 x i32> %shuf0, %val
+ %shuf1 = shufflevector <4 x i32> %xor, <4 x i32> poison, <4 x i32> <i32 3, i32 0, i32 1, i32 2>
+
+ %c = call i1 @cond()
+ br i1 %c, label %loop, label %exit
+
+exit:
+ ret <4 x i32> %shuf1
+}
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✅ With the latest revision this PR passed the C/C++ code formatter. |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/153/builds/12978 Here is the relevant piece of the build log for the reference |
searlmc1
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Oct 30, 2024
revert: breaks oclBlender* 1831109 [InstCombine] Do not fold `shufflevector(select)` if the select condition is a vector (llvm#113993) 5903c6a InstCombine: Fold shufflevector(select) and shufflevector(phi) (llvm#113746) Change-Id: I516b3c6463cb32043ca22ef73d9c0d2bd000b947
searlmc1
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Nov 1, 2024
1831109 [InstCombine] Do not fold `shufflevector(select)` if the select condition is a vector (llvm#113993) 5903c6a InstCombine: Fold shufflevector(select) and shufflevector(phi) (llvm#113746) Change-Id: I35528e2f6682157bbe5a178a4108efc091457769
NoumanAmir657
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Nov 4, 2024
…113746) - Transform `shufflevector(select(c, x, y), C)` to `select(c, shufflevector(x, C), shufflevector(y, C))` by re-using the `FoldOpIntoSelect` helper. - Transform `shufflevector(phi(x, y), C)` to `phi(shufflevector(x, C), shufflevector(y, C))` by re-using the `foldOpInotPhi` helper.
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shufflevector(select(c, x, y), C)toselect(c, shufflevector(x, C), shufflevector(y, C))by re-usingthe
FoldOpIntoSelecthelper.shufflevector(phi(x, y), C)tophi(shufflevector(x, C), shufflevector(y, C))by re-using thefoldOpInotPhihelper.