[Openmp-commits] [PATCH] D102407: [libomptarget][amdgpu] Fix truncation error for partial wavefront

[Jon Chesterfield via Phabricator via Openmp-commits]

JonChesterfield created this revision.
JonChesterfield added reviewers: jdoerfert, dhruvachak, ronlieb.
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[libomptarget][amdgpu] Fix truncation error for partial wavefront

The partial barrier implementation involves one wavefront resetting and N-1
waiting. This change future proofs against launching with a number of threads
that is not a multiple of the wavefront size.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D102407

Files:
  openmp/libomptarget/deviceRTLs/amdgcn/src/target_impl.hip


Index: openmp/libomptarget/deviceRTLs/amdgcn/src/target_impl.hip
===================================================================
--- openmp/libomptarget/deviceRTLs/amdgcn/src/target_impl.hip
+++ openmp/libomptarget/deviceRTLs/amdgcn/src/target_impl.hip
@@ -56,7 +56,7 @@
 {
   __atomic_thread_fence(__ATOMIC_ACQUIRE);
 
-  uint32_t num_waves = num_threads / WARPSIZE;
+  uint32_t num_waves = (num_threads + WARPSIZE - 1) / WARPSIZE;
 
   // Partial barrier implementation for amdgcn.
   // Uses two 16 bit unsigned counters. One for the number of waves to have


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