Come up with hook libc_has_fast_function (PR middle-end/90263).

2019-05-20  Martin Liska  <mliska@suse.cz>

	PR middle-end/90263
	* builtins.c (expand_builtin_memory_copy_args): When having a
	target with fast mempcpy implementation do now use memcpy.
	* config/i386/i386.c (ix86_libc_has_fast_function): New.
	(TARGET_LIBC_HAS_FAST_FUNCTION): Likewise.
	* doc/tm.texi: Likewise.
	* doc/tm.texi.in: Likewise.
	* target.def:
	* expr.c (emit_block_move_hints): Add 2 new arguments.
	* expr.h (emit_block_move_hints): Bail out when libcall
	to memcpy would be used.
2019-05-20  Martin Liska  <mliska@suse.cz>

	PR middle-end/90263
	* gcc.c-torture/compile/pr90263.c: New test.
	* lib/target-supports.exp: Add check_effective_target_glibc.

From-SVN: r271400