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[libc] use LIBC_HAS_BUILTIN instead __has_builtin #82377

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Feb 20, 2024
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[libc] use LIBC_HAS_BUILTIN instead __has_builtin #82377

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2 changes: 1 addition & 1 deletion libc/src/__support/CPP/atomic.h
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Original file line number Diff line number Diff line change
Expand Up @@ -166,7 +166,7 @@ LIBC_INLINE void atomic_thread_fence([[maybe_unused]] MemoryOrder mem_ord) {
// except no instructions for memory ordering are issued. Only reordering of
// the instructions by the compiler is suppressed as order instructs.
LIBC_INLINE void atomic_signal_fence([[maybe_unused]] MemoryOrder mem_ord) {
#if __has_builtin(__atomic_signal_fence)
#if LIBC_HAS_BUILTIN(__atomic_signal_fence)
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constexpr if would be a good fit here as well.

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it seems that clang would not be happy with unknown function in constexpr if: https://godbolt.org/z/xeGevdqzW

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Ah, yeah. I remember running into that because constexpr is only evaluated after the AST is built.

__atomic_signal_fence(static_cast<int>(mem_ord));
#else
// if the builtin is not ready, use asm as a full compiler barrier.
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