[31/77] Use scalar_int_mode for move2add

[31/77] Use scalar_int_mode for move2add

The postreload move2add optimisations are specific to scalar
integers.  This patch adds an explicit check to the main guarding
"if" and propagates the information through subroutines.

gcc/
2017-08-30  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

	* postreload.c (move2add_valid_value_p): Change the type of the
	mode parameter to scalar_int_mode.
	(move2add_use_add2_insn): Add a mode parameter and use it instead
	of GET_MODE (reg).
	(move2add_use_add3_insn): Likewise.
	(reload_cse_move2add): Update accordingly.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@251483 138bc75d-0d04-0410-961f-82ee72b054a4