[libc-commits] [libc] 5a8fc41 - [libc] Disable atomic optimizations for `libc` AMDGPU builds

[Joseph Huber via libc-commits]

Author: Joseph Huber
Date: 2023-06-19T03:25:51-05:00
New Revision: 5a8fc419379faa517e614c55b0b27de59572019d

URL: https://github.com/llvm/llvm-project/commit/5a8fc419379faa517e614c55b0b27de59572019d
DIFF: https://github.com/llvm/llvm-project/commit/5a8fc419379faa517e614c55b0b27de59572019d.diff

LOG: [libc] Disable atomic optimizations for `libc` AMDGPU builds

Recently the AMDGPU backend automatically enables a pass to optimize
atomics. This results in the LTO build taking about 10x longer in all
cases. For now we disable this by default as was the case before the
patch in D152649.

Reviewed By: lntue

Differential Revision: https://reviews.llvm.org/D153232

Added: 
    

Modified: 
    libc/startup/gpu/amdgpu/CMakeLists.txt

Removed: 
    


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diff  --git a/libc/startup/gpu/amdgpu/CMakeLists.txt b/libc/startup/gpu/amdgpu/CMakeLists.txt
index e7c0aeafafd9a..b54dc377a629b 100644
--- a/libc/startup/gpu/amdgpu/CMakeLists.txt
+++ b/libc/startup/gpu/amdgpu/CMakeLists.txt
@@ -26,4 +26,7 @@ target_link_libraries(
   "--target=${LIBC_GPU_TARGET_TRIPLE}"
   "-flto"
   "-Wl,-mllvm,-amdgpu-lower-global-ctor-dtor=0"
+  # FIXME: This pass causes builds to take ~10x longer. Disable until the
+  # performance problems have been addressed.
+  "-Wl,-mllvm,-amdgpu-atomic-optimizations=0"
 )