[llvm] [AMDGPU][TTI] Add Target Hook for Instruction Uniformity (getInstructionUniformity) (PR #137639)

[Sameer Sahasrabuddhe via llvm-commits]

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@@ -290,6 +290,10 @@ class GCNTTIImpl final : public BasicTTIImplBase<GCNTTIImpl> {
   void collectKernelLaunchBounds(
       const Function &F,
       SmallVectorImpl<std::pair<StringRef, int64_t>> &LB) const override;
+  std::optional<InstructionUniformity>
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ssahasra wrote:

Why do we need the `std::optional`? If sufficient information is not available, we can just return `InstructionUniformity::Default`.

https://github.com/llvm/llvm-project/pull/137639