[Bug target/54087] __atomic_fetch_add does not use xadd instruction

[amacleod at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54087

Andrew Macleod <amacleod at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #27927|0                           |1
        is obsolete|                            |
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-08-23
         AssignedTo|unassigned at gcc dot       |amacleod at redhat dot com
                   |gnu.org                     |
     Ever Confirmed|0                           |1

--- Comment #7 from Andrew Macleod <amacleod at redhat dot com> 2012-08-23 14:33:01 UTC ---
Created attachment 28074
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28074
Generic expansion patch proposal

This patch changes the tree-rtl expansion code to try using the complementary 
atomic add or sub operation with a negative operand if an instruction sequence
is not created.

This will enable the optimization automatically for all targets.

Check to see if it solves the problem as well.