[PATCH] D72579: Evaluate __{c11_,}atomic_is_lock_free to 0 (avoid libcall) if larger than MaxAtomicPromoteWidth

[Fangrui Song via Phabricator via cfe-commits]

MaskRay added a comment.

>From https://gcc.gnu.org/ml/gcc/2020-02/msg00116.html

> We discussed this on IRC in #gcc. There was no motivation to change GCC. The platform that wants to avoid the libatomic dependency doesn't use GCC anyway. Relying on not getting the libatomic dependency seems fragile (it only works for a specific codebase, and if some other is_lock_free check is added to the codebase, the libatomic dependency will return anyway).

So they will not extend the interface. Clang has `getMaxAtomicPromoteWidth()`. Do we need the extension? I'm happy with either way.


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