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

[Sameer Sahasrabuddhe via llvm-commits]

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@@ -23,7 +23,11 @@ enum class InstructionUniformity {
   AlwaysUniform,
 
   /// The result values can never be assumed to be uniform.
-  NeverUniform
+  NeverUniform,
+
+  /// The result value is uniform because one or more of its operand are
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ssahasra wrote:

This seems to be saying: "The result is uniform if any operand is uniform". That is unlikely to be true for all intrinsics. We need statements of the form "The result is uniform if operand N is uniform".

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