Attached patch implements TARGET_ATOMIC_ASSIGN_EXPAND_FENV for AARCH64.
With this, atomic test-case gcc.dg/atomic/c11-atomic-exec-5.c now PASS.

This implementation is based on SPARC and i386 implementations.

Regression tested on qemu-aarch64 for aarch64-none-linux-gnu with no new
regression. Is this OK for trunk?

Thanks,
Kugan

gcc/
+2014-04-27  Kugan Vivekanandarajah  <kuganv@linaro.org>
+
+	* config/aarch64/aarch64.c (TARGET_ATOMIC_ASSIGN_EXPAND_FENV): New
+	define.
+	* config/aarch64/aarch64-builtins.c (arm_builtins) : Add
+	AARCH64_BUILTIN_LDFPSCR and AARCH64_BUILTIN_STFPSCR.
+	(aarch64_init_builtins) : Initialize builtins
+	__builtins_aarch64_stfpscr and __builtins_aarch64_ldfpscr.
+	(aarch64_expand_builtin) : Expand builtins __builtins_aarch64_stfpscr
+	and __builtins_aarch64_ldfpscr.
+	(aarch64_atomic_assign_expand_fenv): New function.
+	* config/aarch64/aarch64.md (stfpscr): New pattern.
+	(ldfpscr) : Likewise.
+	(unspecv): Add UNSPECV_LDFPSCR and UNSPECV_STFPSCR.
+