[VectorCombine] Fix the type used in foldShuffleOfIntrinsics Cost.

[davemgreen]

The shuffle needn't be twice the original number of vector elements, so the intermediate type used between the shuffle and the intrinsic should use the ShuffleDstTy number of elements.

I found this when looking at shuffle costs and do not have test where it alters the output, but have added some cases where the shuffle output is not twice the size of the input.

[llvmbot]

@llvm/pr-subscribers-vectorizers

@llvm/pr-subscribers-llvm-transforms

Author: David Green (davemgreen)

Changes

The shuffle needn't be twice the original number of vector elements, so the intermediate type used between the shuffle and the intrinsic should use the ShuffleDstTy number of elements.

I found this when looking at shuffle costs and do not have test where it alters the output, but have added some cases where the shuffle output is not twice the size of the input.

---

Full diff: https://github.com/llvm/llvm-project/pull/138419.diff

2 Files Affected:

• (modified) llvm/lib/Transforms/Vectorize/VectorCombine.cpp (+1-1)
• (modified) llvm/test/Transforms/VectorCombine/X86/shuffle-of-intrinsics.ll (+35)

diff --git a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
index 04c084ffdda97..352a816fe0af6 100644
--- a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
+++ b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
@@ -2377,7 +2377,7 @@ bool VectorCombine::foldShuffleOfIntrinsics(Instruction &I) {
     } else {
       auto *VecTy = cast<FixedVectorType>(II0->getArgOperand(I)->getType());
       NewArgsTy.push_back(FixedVectorType::get(VecTy->getElementType(),
-                                               VecTy->getNumElements() * 2));
+                                               ShuffleDstTy->getNumElements()));
       NewCost += TTI.getShuffleCost(TargetTransformInfo::SK_PermuteTwoSrc,
                                     VecTy, OldMask, CostKind);
     }
diff --git a/llvm/test/Transforms/VectorCombine/X86/shuffle-of-intrinsics.ll b/llvm/test/Transforms/VectorCombine/X86/shuffle-of-intrinsics.ll
index 2dc76cbfdda41..1e17e4db24ad4 100644
--- a/llvm/test/Transforms/VectorCombine/X86/shuffle-of-intrinsics.ll
+++ b/llvm/test/Transforms/VectorCombine/X86/shuffle-of-intrinsics.ll
@@ -69,6 +69,20 @@ entry:
   ret <8 x i1> %4
 }
 
+define <2 x i1> @test4b(<4 x float> %0, <4 x float> %1) {
+; CHECK-LABEL: @test4b(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP2:%.*]] = shufflevector <4 x float> [[TMP0:%.*]], <4 x float> [[TMP1:%.*]], <2 x i32> <i32 0, i32 4>
+; CHECK-NEXT:    [[TMP3:%.*]] = call <2 x i1> @llvm.is.fpclass.v2f32(<2 x float> [[TMP2]], i32 0)
+; CHECK-NEXT:    ret <2 x i1> [[TMP3]]
+;
+entry:
+  %2 = call <4 x i1> @llvm.is.fpclass.v4f32(<4 x float> %0, i32 0)
+  %3 = call <4 x i1> @llvm.is.fpclass.v4f32(<4 x float> %1, i32 0)
+  %4 = shufflevector <4 x i1> %2, <4 x i1> %3, <2 x i32> <i32 0, i32 4>
+  ret <2 x i1> %4
+}
+
 define <8 x float> @test5(<4 x float> %0, i32 %1, <4 x float> %2, <4 x i32> %3) {
 ; CHECK-LABEL: @test5(
 ; CHECK-NEXT:  entry:
@@ -84,6 +98,27 @@ entry:
   ret <8 x float> %6
 }
 
+define <2 x float> @test6(<4 x float> %a1, <4 x float> %b1, <4 x float> %c1, <4 x float> %a2, <4 x float> %b2, <4 x float> %c2) {
+; SSE-LABEL: @test6(
+; SSE-NEXT:    [[TMP1:%.*]] = shufflevector <4 x float> [[A1:%.*]], <4 x float> [[A2:%.*]], <2 x i32> <i32 0, i32 4>
+; SSE-NEXT:    [[TMP2:%.*]] = shufflevector <4 x float> [[B1:%.*]], <4 x float> [[B2:%.*]], <2 x i32> <i32 0, i32 4>
+; SSE-NEXT:    [[TMP3:%.*]] = shufflevector <4 x float> [[C1:%.*]], <4 x float> [[C2:%.*]], <2 x i32> <i32 0, i32 4>
+; SSE-NEXT:    [[S:%.*]] = call <2 x float> @llvm.fma.v2f32(<2 x float> [[TMP1]], <2 x float> [[TMP2]], <2 x float> [[TMP3]])
+; SSE-NEXT:    ret <2 x float> [[S]]
+;
+; AVX-LABEL: @test6(
+; AVX-NEXT:    [[F1:%.*]] = call <4 x float> @llvm.fma.v4f32(<4 x float> [[A1:%.*]], <4 x float> [[B1:%.*]], <4 x float> [[C1:%.*]])
+; AVX-NEXT:    [[F2:%.*]] = call <4 x float> @llvm.fma.v4f32(<4 x float> [[A2:%.*]], <4 x float> [[B2:%.*]], <4 x float> [[C2:%.*]])
+; AVX-NEXT:    [[S:%.*]] = shufflevector <4 x float> [[F1]], <4 x float> [[F2]], <2 x i32> <i32 0, i32 4>
+; AVX-NEXT:    ret <2 x float> [[S]]
+;
+  %f1 = call <4 x float> @llvm.fma.v4f32(<4 x float> %a1, <4 x float> %b1, <4 x float> %c1)
+  %f2 = call <4 x float> @llvm.fma.v4f32(<4 x float> %a2, <4 x float> %b2, <4 x float> %c2)
+  %s = shufflevector <4 x float> %f1, <4 x float> %f2, <2 x i32> <i32 0, i32 4>
+  ret <2 x float> %s
+}
+
+
 declare <4 x i32> @llvm.abs.v4i32(<4 x i32>, i1)
 declare <4 x i32> @llvm.smax.v4i32(<4 x i32>, <4 x i32>)
 declare <4 x i1> @llvm.is.fpclass.v4f32(<4 x float>, i32)

[RKSimon]

LGTM - cheers

[HanKuanChen]

remove 1 empty line