[Bug target/70821] x86_64: __atomic_fetch_add/sub() uses XADD rather than DECL in some cases

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70821

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2016-04-28
                 CC|                            |jakub at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I don't see any xadd* insns if compiled with -O2, it doesn't indeed use lock;
decl, but lock; subl $1 or similar; but that is just the matter of generic
tuning which prefers not to use inc/dec; if you use e.g. -O2 -mtune=barcelona,
then you get even the lock; decl you are looking for.

So, are you testing with -Os instead?