[llvm-branch-commits] [llvm] AMDGPU: Implement isExtractVecEltCheap (PR #122460)

[Joe Nash via llvm-branch-commits]

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@@ -1949,6 +1949,13 @@ bool SITargetLowering::isExtractSubvectorCheap(EVT ResVT, EVT SrcVT,
   return Index == 0;
 }
 
+bool SITargetLowering::isExtractVecEltCheap(EVT VT, unsigned Index) const {
+  // TODO: This should be more aggressive, particular for 16-bit element
+  // vectors. However there are some mixed improvements and regressions.
+  EVT EltTy = VT.getVectorElementType();
+  return EltTy.getSizeInBits() % 32 == 0;
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Sisyph wrote:

Yes I would think EltTy.getSizeInBits() * Index % 16 == 0 for True16 would be the way to go.

https://github.com/llvm/llvm-project/pull/122460