[llvm] [AMDGPU][TTI] Refine gfx9 packed FP32 SLP costs for pair formation and shuffles (PR #208572)

[Akash Dutta via llvm-commits]

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@@ -1344,6 +1355,15 @@ InstructionCost GCNTTIImpl::getShuffleCost(TTI::ShuffleKind Kind,
   Kind = improveShuffleKindFromMask(Kind, Mask, SrcTy, Index, SubTp);
 
   unsigned ScalarSize = DL.getTypeSizeInBits(SrcTy->getElementType());
+
+  // Gfx9 packed FP32 shuffles are free. InsertElement above already taxes
+  // assembling <2 x f32> pairs, and a per-lane shuffle cost stacks on top and
+  // over-penalizes SLP. f32-only on gfx9 targets with packed FP32 ops.
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akadutta wrote:

removed

https://github.com/llvm/llvm-project/pull/208572