[Bug target/55966] __atomic_fetch_* generate wrong code for HLE

[andi-gcc at firstfloor dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55966

--- Comment #8 from Andi Kleen <andi-gcc at firstfloor dot org> 2013-01-14 22:32:06 UTC ---
forbid = give warning and drop bit

It's a hint, but in a good implementation it should not be silently dropped or
code generated that has no chance to elide. It's a quality of implementation
issue.

IMHO there should be at least a warning for this case, like we do for other
cases where elision doesn't work.