[Openmp-commits] [openmp] [OpenMP][offload] Fix wave32 handling of xteam reductions (PR #233096)

[Robert Imschweiler via Openmp-commits]

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@@ -101,11 +101,14 @@ static uint32_t gpu_block_reduce(void *reduce_data, ShuffleReductFnTy shflFct,
   if constexpr (checkLiveness) {
     __kmpc_impl_lanemask_t Liveness = mapping::activemask();
     // Check for partial warp with non-contiguous lanes.
-    if (Liveness == lanes::All) {
+    // Consider that Liveness::ALL is a 64-bit value, so compare the actual
+    // number of set bits to handle 32bit waves correctly.
+    uint32_t NumLive = static_cast<uint32_t>(utils::popc(Liveness));
+    if (NumLive == mapping::getWarpSize()) {
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ro-i wrote:

the `Full` could also be a constexpr somewhere, but I guess that since it should be constant folded with __gpu_num_lanes anyway, it doesn't make a difference. And if it isn't constant-folded, the load from a location somewhere would probably be more expensive than computing, anyway...

https://github.com/llvm/llvm-project/pull/233096