[OpenMP] Add Environment Variable to disable Reuse of Blocks for High Loop Trip Counts (#89239)

Sometimes it might be beneficial to spawn more thread blocks instead of
reusing existing for multiple loop iterations.

**Alternatives considered:**

Make `DefaultNumBlocks` settable via an environment variable.

---------

Co-authored-by: Joseph Huber <huberjn@outlook.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/offload/plugins-nextgen/common/src/PluginInterface.cpp b/offload/plugins-nextgen/common/src/PluginInterface.cpp
index 94f9d4670b67..118265973f32 100644
--- a/offload/plugins-nextgen/common/src/PluginInterface.cpp
+++ b/offload/plugins-nextgen/common/src/PluginInterface.cpp
@@ -701,8 +701,11 @@ uint64_t GenericKernelTy::getNumBlocks(GenericDeviceTy &GenericDevice,
       TripCountNumBlocks = LoopTripCount;
     }
   }
+
+  uint32_t PreferredNumBlocks = TripCountNumBlocks;
   // If the loops are long running we rather reuse blocks than spawn too many.
-  uint32_t PreferredNumBlocks = std::min(TripCountNumBlocks, DefaultNumBlocks);
+  if (GenericDevice.getReuseBlocksForHighTripCount())
+    PreferredNumBlocks = std::min(TripCountNumBlocks, DefaultNumBlocks);
   return std::min(PreferredNumBlocks, GenericDevice.getBlockLimit());
 }