[PATCH] D98995: [CGAtomic] Lift stronger requirements on cmpxch and add support for acquire failure mode

[Bruno Cardoso Lopes via Phabricator via llvm-commits]

bruno created this revision.
bruno added reviewers: rjmccall, jfb, t.p.northover.
Herald added subscribers: hoy, modimo, wenlei, lxfind, jdoerfert, jkorous.
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- Fix `emitAtomicCmpXchgFailureSet` to support release/acquire (succ/fail) memory order.
- Remove stronger checks for cmpxch.

This is motivated by https://github.com/google/sanitizers/issues/970, based on discussions in https://groups.google.com/g/thread-sanitizer/c/bTOVyLAo8p4/m/Y-2yks6ZLAAJ

A follow patch should attempt to implement the TSAN side of failure mode support.


https://reviews.llvm.org/D98995

Files:
  clang/lib/CodeGen/CGAtomic.cpp
  clang/test/CodeGen/atomic-ops.c
  llvm/docs/LangRef.rst

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