* builtins.c (expand_builtin_memcpy): Remove endp argument and endp
	!= 0 handling.  Pass 0 to store_by_pieces.
	(expand_builtin_mempcpy): Add endp argument.  Don't call
	expand_builtin_memcpy, call store_by_pieces resp. move_by_pieces
	directly.  If ignoring result, only do expand_call.
	(expand_builtin_stpcpy): Likewise.  Call expand_builtin_mempcpy
	otherwise.
	(expand_builtin_strncpy, expand_builtin_memset): Adjust
	store_by_pices callers.
	(expand_builtin): Adjust expand_builtin_memcpy and
	expand_builtin_mempcpy callers.
	* expr.c (can_move_by_pieces): New function.
	(move_by_pieces): Add endp argument, return to resp. memory at end
	or one byte earlier depending on endp.
	(store_by_pieces): Likewise.
	(emit_block_move): Adjust call to move_by_pieces.
	(emit_push_insn): Adjust move_by_pieces caller.
	* expr.h (can_move_by_pieces): New prototype.
	(store_by_pieces): Adjust prototypes.
	* rtl.h (move_by_pieces): Adjust prototype.
	* config/mips/mips.c (expand_block_move): Adjust move_by_pieces
	caller.

	* gcc.c-torture/execute/builtins/string-4.c (main_test): Remove
	mempcpy test with post-increments.
	* gcc.c-torture/execute/string-opt-3.c: New test.
	* gcc.dg/string-opt-1.c: New test.

From-SVN: r67358