Remove compileMutex to enable parallel compilation on Windows #583
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The issue observed in 76bc7f9 seems fixed on llvm-14 branch based on new testing of a multi-threaded workload on Ice Lake server and Alder Lake desktop. The same workload still fails on llvm-9 branch on Alder Lake.
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Pull Request Overview
This PR removes the compileMutex synchronization mechanism that was previously serializing LLVM compilation operations on Windows. Based on testing with LLVM-14, the thread safety issues that necessitated this mutex appear to be resolved.
Key changes:
- Removal of the global
compileMutexdeclaration and initialization - Elimination of platform-specific mutex guards in the compilation path
- Deletion of explanatory comments about LLVM thread safety concerns
Reviewed Changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
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| common_clang.cpp | Removes the compileMutex definition and all scoped lock guards (both Windows-specific and non-Windows-specific) from the Compile function |
| options_compile.cpp | Removes the external compileMutex declaration and its usage in CheckCompileOptions function |
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| llvm::ManagedStatic<llvm::sys::SmartMutex<true>> compileMutex; | ||
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| void CommonClangTerminate() { llvm::llvm_shutdown(); } |
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With the removal of compileMutex, ensure that llvm::llvm_shutdown() is only called after all compilation threads have completed, as concurrent calls or compilation during shutdown could cause undefined behavior.
cdai2
approved these changes
Oct 31, 2025
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The issue observed in 76bc7f9 seems fixed on llvm-14 branch based on new testing of a multi-threaded workload on Ice Lake server and Alder Lake desktop.
The same workload still fails on llvm-9 branch on Alder Lake.