[PATCH] D154210: AMDGPU: Add some notes about amdgpu-flat-work-group-size
Matt Arsenault via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Fri Jul 7 12:44:55 PDT 2023
arsenm updated this revision to Diff 538233.
arsenm added a comment.
Reword again. I was trying to express you can't do what vulkan was doing and increasing the set of active lanes beyond the bounds
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D154210/new/
https://reviews.llvm.org/D154210
Files:
llvm/docs/AMDGPUUsage.rst
Index: llvm/docs/AMDGPUUsage.rst
===================================================================
--- llvm/docs/AMDGPUUsage.rst
+++ llvm/docs/AMDGPUUsage.rst
@@ -999,7 +999,12 @@
"amdgpu-flat-work-group-size"="min,max" Specify the minimum and maximum flat work group sizes that
will be specified when the kernel is dispatched. Generated
by the ``amdgpu_flat_work_group_size`` CLANG attribute [CLANG-ATTR]_.
- The implied default value is 1,1024.
+ The IR implied default value is 1,1024. Clang may emit this attribute
+ with more restrictive bounds depending on language defaults.
+ If the actual block or workgroup size exceeds the limit at any point during
+ the execution, the behavior is undefined. For example, even if there is
+ only one active thread but the thread local id exceeds the limit, the
+ behavior is undefined.
"amdgpu-implicitarg-num-bytes"="n" Number of kernel argument bytes to add to the kernel
argument block size for the implicit arguments. This
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