[41/77] Split scalar integer handling out of force_to_mode

[41/77] Split scalar integer handling out of force_to_mode

force_to_mode exits partway through for modes that aren't scalar
integers.  This patch splits the remainder of the function out
into a subroutine, force_int_to_mode, so that the modes from that
point on can have type scalar_int_mode.

The patch also makes sure that xmode is kept up-to-date with x
and uses xmode instead of GET_MODE (x) throughout.

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

gcc/
	* combine.c (force_int_to_mode): New function, split out from...
	(force_to_mode): ...here.  Keep xmode up-to-date and use it
	instead of GET_MODE (x).

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>
From-SVN: r251493