[arm] Match subtraction from carry_operation

[arm] Match subtraction from carry_operation

On Arm we have both carry and borrow operations, but borrow is
essentially '~carry'.  Of course, with boolean logic ~carry is also
1-carry.

GCC transforms

	(1 - X - LTU (cc, 0))

into

	(GEU (cc, 0) - X)

Now the former matches a real insn in Arm state, using the RSC
instruction with #1 as the immediate, but we currently do not
recognize the canonicalized form.  Nevertheless, given the above
logic, this turns out to be quite straight forward as the original
expression matches arm_borrow_operation and the revised form can be
used with arm_carry_operation.  Since we match this new pattern we
also update rtx_costs to handle it.

	* config/arm/arm.md (rsbsi_carryin_reg): New pattern.
	* config/arm/arm.c (arm_rtx_costs_internal, case MINUS): Handle
	subtraction from a carry operation.

From-SVN: r277290