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From: "hjl.tools at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/102566] [i386] GCC should emit LOCK BTS for simple
 bit-test-and-set operations with std::atomic
Date: Sun, 03 Oct 2021 12:56:42 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102566

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Version|unknown                     |12.0
   Last reconfirmed|                            |2021-10-03
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> ---
The C code:

#include <stdatomic.h>

_Atomic int v;

int
foo ()
{
  return atomic_fetch_or_explicit (&v, 1, memory_order_relaxed) & 1;
}=