gcc/
	* machmode.h (GET_MODE_UNIT_PRECISION): New macro.
	* simplify-rtx.c (simplify_truncation): New function,
	extracted from simplify_subreg and (in small part) from
	simplify_unary_operation_1.
	(simplify_unary_operation_1) <TRUNCATE>: Use it.  Remove sign bit
	test for !TRULY_NOOP_TRUNCATION_MODES_P.
	(simplify_subreg): Use simplify_truncate for lowpart subregs
	where both the inner and outer modes are scalar integers.
	* config/mips/mips.c (mips_truncated_op_cost): New function.
	(mips_rtx_costs): Adjust test for BADDU.
	* config/mips/mips.md (*baddu_di<mode>): Push truncates to operands.

From-SVN: r192186