2012-10-01  Andrew MacLeod  <amacleod@redhat.com>

	PR target/54087
	* optabs.c (expand_atomic_fetch_op_no_fallback): New.  Factored code
	from expand_atomic_fetch_op.
	(expand_atomic_fetch_op):  Try atomic_{add|sub} operations in terms of
	the other one if direct opcode fails.
	* testsuite/gcc.dg/pr54087.c:  New testcase for atomic_sub -> 
	atomic_add when atomic_sub fails.

From-SVN: r191929