[23/77] Replace != VOIDmode checks with is_a <scalar_int_mode>

[23/77] Replace != VOIDmode checks with is_a <scalar_int_mode>

This patch replaces some checks against VOIDmode with checks
of is_a <scalar_int_mode>, in cases where scalar integer modes
were the only useful alternatives left.

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

	* cfgexpand.c (expand_debug_expr): Use is_a <scalar_int_mode>
	instead of != VOIDmode.
	* combine.c (if_then_else_cond): Likewise.
	(change_zero_ext): Likewise.
	* dwarf2out.c (mem_loc_descriptor): Likewise.
	(loc_descriptor): Likewise.
	* rtlanal.c (canonicalize_condition): Likewise.
	* simplify-rtx.c (simplify_relational_operation_1): Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@251475 138bc75d-0d04-0410-961f-82ee72b054a4