i386: Improve memory copy from named address space [PR111657]

i386: Improve memory copy from named address space [PR111657]

The stringop strategy selection algorithm falls back to a libcall strategy
when it exhausts its pool of available strategies.  The memory area copy
function (memcpy) is not availabe from the system library for non-default
address spaces, so the compiler emits the most trivial byte-at-a-time
copy loop instead.

The compiler should instead emit an optimized copy loop as a fallback for
non-default address spaces.

	PR target/111657

gcc/ChangeLog:

	* config/i386/i386-expand.cc (alg_usable_p): Reject libcall
	strategy for non-default address spaces.
	(decide_alg): Use loop strategy as a fallback strategy for
	non-default address spaces.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/pr111657.c: New test.