[llvm] 47d71b6 - [BasicTTI] Only split vectors with even element counts in getCastInstrCost (#166528)

[via llvm-commits]

Author: Shakil Ahmed
Date: 2025-11-06T12:45:42Z
New Revision: 47d71b69b49326f0305b9250184974b6b7397d6f

URL: https://github.com/llvm/llvm-project/commit/47d71b69b49326f0305b9250184974b6b7397d6f
DIFF: https://github.com/llvm/llvm-project/commit/47d71b69b49326f0305b9250184974b6b7397d6f.diff

LOG: [BasicTTI] Only split vectors with even element counts in getCastInstrCost (#166528)

Fixes #166320

Added: 
    llvm/test/Transforms/VectorCombine/AArch64/sve-interleave-splat.ll

Modified: 
    llvm/include/llvm/CodeGen/BasicTTIImpl.h

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/CodeGen/BasicTTIImpl.h b/llvm/include/llvm/CodeGen/BasicTTIImpl.h
index 221d8f1e2f673..f58525754d7a5 100644
--- a/llvm/include/llvm/CodeGen/BasicTTIImpl.h
+++ b/llvm/include/llvm/CodeGen/BasicTTIImpl.h
@@ -1331,8 +1331,8 @@ class BasicTTIImplBase : public TargetTransformInfoImplCRTPBase<T> {
       bool SplitDst =
           TLI->getTypeAction(Dst->getContext(), TLI->getValueType(DL, Dst)) ==
           TargetLowering::TypeSplitVector;
-      if ((SplitSrc || SplitDst) && SrcVTy->getElementCount().isVector() &&
-          DstVTy->getElementCount().isVector()) {
+      if ((SplitSrc || SplitDst) && SrcVTy->getElementCount().isKnownEven() &&
+          DstVTy->getElementCount().isKnownEven()) {
         Type *SplitDstTy = VectorType::getHalfElementsVectorType(DstVTy);
         Type *SplitSrcTy = VectorType::getHalfElementsVectorType(SrcVTy);
         const T *TTI = thisT();

diff  --git a/llvm/test/Transforms/VectorCombine/AArch64/sve-interleave-splat.ll b/llvm/test/Transforms/VectorCombine/AArch64/sve-interleave-splat.ll
new file mode 100644
index 0000000000000..921bcf086f2bf
--- /dev/null
+++ b/llvm/test/Transforms/VectorCombine/AArch64/sve-interleave-splat.ll
@@ -0,0 +1,11 @@
+; RUN: opt -passes=vector-combine %s -S -o - | FileCheck %s
+
+target triple = "aarch64-unknown-linux-gnu"
+
+define <vscale x 4 x i16> @interleave2_same_const_splat_nxv4i16() {
+;CHECK-LABEL: @interleave2_same_const_splat_nxv4i16(
+;CHECK: call <vscale x 4 x i16> @llvm.vector.interleave2
+;CHECK: ret <vscale x 4 x i16> %retval
+  %retval = call <vscale x 4 x i16> @llvm.vector.interleave2.nxv4i16(<vscale x 2 x i16> splat(i16 3), <vscale x 2 x i16> splat(i16 3))
+  ret <vscale x 4 x i16> %retval
+}