PR rtl-optimization/57448
	PR target/67458
	PR target/81316
	* optabs.c (expand_atomic_load): Place compiler memory barriers if
	using atomic_load pattern.
	(expand_atomic_store): Likewise.
testsuite/
	* gcc.dg/atomic/pr80640-2.c: New testcase.
	* gcc.dg/atomic/pr81316.c: New testcase.

From-SVN: r251643