[Openmp-commits] [llvm] [openmp] Reapply "[OpenMP][OMPX] Add shfl_down_sync (#93311)" (PR #94139)

[Joseph Huber via Openmp-commits]

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@@ -9,6 +9,12 @@
 #ifndef __OMPX_H
 #define __OMPX_H
 
+#ifdef __AMDGCN_WAVEFRONT_SIZE
+#define __WARP_SIZE __AMDGCN_WAVEFRONT_SIZE
+#else
+#define __WARP_SIZE 32
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jhuber6 wrote:

Why is 32 the default? 64 is the fallback if nothing is set AFAIK. You could also make this go to `(__builtin_amdgcn_wavefrontsize())`. The builtin is not great because it confounds constant optimizations, but in the case where it's not set at all it can be useful.

https://github.com/llvm/llvm-project/pull/94139