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32 lines
1.5 KiB
Diff
32 lines
1.5 KiB
Diff
Lock is_always_lock free test fails on i386 because std::atomic is aligned
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to 8 bytes while long long is aligned to 4 bytes. clang can't generate inline
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code for unaligned 8 byte atomics even tough instruction set and gcc support
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it.
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That makes it expected thaqt ATOMIC_LLONG_LOCK_FREE and
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std::atomic<long long>::is_always_lock_free don't match on i386. Correct test
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for std::atomic<long long> is to check if target cpu support cmpxchg8 instruction.
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To set instruction support one can check __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8 define.
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Bug: https://llvm.org/bugs/show_bug.cgi?id=19355
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Index: llvm-toolchain-19_19.1.2~++20241011093632+6c1fd539e43e/libcxx/test/std/atomics/atomics.lockfree/is_always_lock_free.pass.cpp
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===================================================================
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--- llvm-toolchain-19_19.1.2~++20241011093632+6c1fd539e43e.orig/libcxx/test/std/atomics/atomics.lockfree/is_always_lock_free.pass.cpp
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+++ llvm-toolchain-19_19.1.2~++20241011093632+6c1fd539e43e/libcxx/test/std/atomics/atomics.lockfree/is_always_lock_free.pass.cpp
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@@ -27,6 +27,14 @@
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#include "test_macros.h"
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#include "atomic_helpers.h"
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+#if defined(__i386__) && defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_8)
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+/* Fix for clang setting __GCC_ATOMIC_LLONG_LOCK_FREE incorrectly for x86
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+ * https://llvm.org/bugs/show_bug.cgi?id=19355
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+ */
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+#undef ATOMIC_LLONG_LOCK_FREE
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+#define ATOMIC_LLONG_LOCK_FREE 2
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+#endif
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+
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template <typename T>
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void check_always_lock_free(std::atomic<T> const& a) {
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using InfoT = LockFreeStatusInfo<T>;
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