[libclc] Fix memory fence scope mapping for OpenCL #170542
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The function `__opencl_get_memory_scope` incorrectly assumed that the Clang built-in `__MEMORY_SCOPE_*` macros defined as bitmasks, while they are actually defined as distinct integer values. This led to incorrect mapping of OpenCL memory fence flags to LLVM memory scopes, causing issues in generated code. The fix involves updating the `__opencl_get_memory_scope` function to return the correct `__MEMORY_SCOPE_*` values based on the provided `cl_mem_fence_flags`. Additionally, the `__opencl_get_memory_semantics` and the `__opencl_get_memory_scope` functions are marked as `static` to avoid potential multiple definition issues during linking.
wenju-he
reviewed
Dec 4, 2025
| memory_scope |= __MEMORY_SCOPE_WRKGRP; | ||
| return memory_scope; | ||
| return __MEMORY_SCOPE_WRKGRP; | ||
| return __MEMORY_SCOPE_SINGLE; |
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not sure if the default value is appropriate. Should we call __builtin_unreachable(); like in __opencl_get_memory_semantics?
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According to the OpenCL C spec, the synchronization functions allow the 0 to be passed as a valid argument value. When 0 is passed, the single-thread fence looks reasonable to me, because the implementation shouldn't issue any cross-thread memory synchronization in that case. The __builtin_unreachable() won't work correctly.
kcloudy0717
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Dec 4, 2025
The function `__opencl_get_memory_scope` incorrectly assumed that the Clang built-in `__MEMORY_SCOPE_*` macros defined as bitmasks, while they are actually defined as distinct integer values. This led to incorrect mapping of OpenCL memory fence flags to LLVM memory scopes, causing issues in generated code. The fix involves updating the `__opencl_get_memory_scope` function to return the correct `__MEMORY_SCOPE_*` values based on the provided `cl_mem_fence_flags`. Additionally, the `__opencl_get_memory_semantics` and the `__opencl_get_memory_scope` functions are marked as `static` to avoid potential multiple definition issues during linking.
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The function
__opencl_get_memory_scopeincorrectly assumed that theClang built-in
__MEMORY_SCOPE_*macros defined as bitmasks, while theyare actually defined as distinct integer values. This led to incorrect
mapping of OpenCL memory fence flags to LLVM memory scopes, causing
issues in generated code.
The fix involves updating the
__opencl_get_memory_scopefunction toreturn the correct
__MEMORY_SCOPE_*values based on the providedcl_mem_fence_flags. Additionally, the__opencl_get_memory_semanticsand the
__opencl_get_memory_scopefunctions are marked asstaticto avoid potential multiple definition issues during linking.