[llvm] [AMDGPU] Handle unset/max flat workgroup size in waves/EU (PR #139955)

[Shilei Tian via llvm-commits]

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@@ -1170,13 +1170,19 @@ struct AAAMDWavesPerEU : public AAAMDSizeRangeAttribute {
           !AssumedGroupSize->isValidState())
         return false;
 
+      unsigned MinFWGSize =
+          AssumedGroupSize->getAssumed().getLower().getZExtValue();
+      unsigned MaxFWGSize =
+          AssumedGroupSize->getAssumed().getUpper().getZExtValue();
+      if (MinFWGSize == 0 && MaxFWGSize == 0)
+        std::tie(MinFWGSize, MaxFWGSize) =
+            InfoCache.getDefaultFlatWorkGroupSize(*Func);
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shiltian wrote:

And it is also wrong to use default flat work group size here.

https://github.com/llvm/llvm-project/pull/139955