[llvm] AMDGPU: Ensure both wavesize features are not set (PR #159234)

[Jay Foad via llvm-commits]

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@@ -82,20 +82,36 @@ createAMDGPUMCSubtargetInfo(const Triple &TT, StringRef CPU, StringRef FS) {
   MCSubtargetInfo *STI =
       createAMDGPUMCSubtargetInfoImpl(TT, CPU, /*TuneCPU*/ CPU, FS);
 
+  bool IsWave64 = STI->hasFeature(AMDGPU::FeatureWavefrontSize64);
+  bool IsWave32 = STI->hasFeature(AMDGPU::FeatureWavefrontSize32);
+
   // FIXME: We should error for the default target.
   if (STI->getFeatureBits().none())
     STI->ToggleFeature(AMDGPU::FeatureSouthernIslands);
 
-  if (!STI->hasFeature(AMDGPU::FeatureWavefrontSize64) &&
-      !STI->hasFeature(AMDGPU::FeatureWavefrontSize32)) {
+  if (!IsWave64 && !IsWave32) {
     // If there is no default wave size it must be a generation before gfx10,
     // these have FeatureWavefrontSize64 in their definition already. For gfx10+
     // set wave32 as a default.
     STI->ToggleFeature(AMDGPU::isGFX10Plus(*STI)
                            ? AMDGPU::FeatureWavefrontSize32
                            : AMDGPU::FeatureWavefrontSize64);
+  } else if (IsWave64 && IsWave32) {
+    // The wave size is mutually exclusive. If both somehow end up set, wave64
+    // wins if supported.
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jayfoad wrote:

Comment is still wrong? Wave32 wins.

https://github.com/llvm/llvm-project/pull/159234