[llvm] 519d787 - [VectorCombine] Avoid creating shuffle for extract-extract pattern on scalable vector.

[Sander de Smalen via llvm-commits]

Author: Sander de Smalen
Date: 2022-07-07T08:37:04Z
New Revision: 519d7876cbee5a5d3cd40d41525cd45e44fb07a8

URL: https://github.com/llvm/llvm-project/commit/519d7876cbee5a5d3cd40d41525cd45e44fb07a8
DIFF: https://github.com/llvm/llvm-project/commit/519d7876cbee5a5d3cd40d41525cd45e44fb07a8.diff

LOG: [VectorCombine] Avoid creating shuffle for extract-extract pattern on scalable vector.

This addresses https://github.com/llvm/llvm-project/issues/56377

Reviewed By: fhahn

Differential Revision: https://reviews.llvm.org/D129136

Added: 
    

Modified: 
    llvm/lib/Transforms/Vectorize/VectorCombine.cpp
    llvm/test/Transforms/VectorCombine/AArch64/extract-scalable.ll

Removed: 
    


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diff  --git a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
index 6a6efd03d49ad..d12624ffb824f 100644
--- a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
+++ b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
@@ -414,6 +414,10 @@ static Value *createShiftShuffle(Value *Vec, unsigned OldIndex,
 static ExtractElementInst *translateExtract(ExtractElementInst *ExtElt,
                                             unsigned NewIndex,
                                             IRBuilder<> &Builder) {
+  // Shufflevectors can only be created for fixed-width vectors.
+  if (!isa<FixedVectorType>(ExtElt->getOperand(0)->getType()))
+    return nullptr;
+
   // If the extract can be constant-folded, this code is unsimplified. Defer
   // to other passes to handle that.
   Value *X = ExtElt->getVectorOperand();

diff  --git a/llvm/test/Transforms/VectorCombine/AArch64/extract-scalable.ll b/llvm/test/Transforms/VectorCombine/AArch64/extract-scalable.ll
index 0b6ced730e7f2..fe32b2383592b 100644
--- a/llvm/test/Transforms/VectorCombine/AArch64/extract-scalable.ll
+++ b/llvm/test/Transforms/VectorCombine/AArch64/extract-scalable.ll
@@ -20,3 +20,20 @@ define i1 @extract_cmp_binop(<vscale x 4 x i32> %a) {
   %r = xor i1 %cmp1, %cmp2
   ret i1 %r
 }
+
+; Test that VectorCombine doesn't try to create a shufflevector for
+; an extract-extract pattern on a scalable vector type.
+define i32 @extract_extract(<vscale x 4 x i32> %vec) {
+; CHECK-LABEL: @extract_extract(
+; CHECK-NEXT:    [[ELT0:%.*]] = extractelement <vscale x 4 x i32> [[VEC:%.*]], i32 0
+; CHECK-NEXT:    [[ELT1:%.*]] = extractelement <vscale x 4 x i32> [[VEC]], i32 1
+; CHECK-NEXT:    [[IDX:%.*]] = add i32 [[ELT0]], [[ELT1]]
+; CHECK-NEXT:    [[ELTIDX:%.*]] = extractelement <vscale x 4 x i32> [[VEC]], i32 [[IDX]]
+; CHECK-NEXT:    ret i32 [[ELTIDX]]
+;
+  %elt0 = extractelement <vscale x 4 x i32> %vec, i32 0
+  %elt1 = extractelement <vscale x 4 x i32> %vec, i32 1
+  %idx = add i32 %elt0, %elt1
+  %eltidx = extractelement <vscale x 4 x i32> %vec, i32 %idx
+  ret i32 %eltidx;
+}