[arm] Early expansion of uaddvdi4.

[arm] Early expansion of uaddvdi4.

This code borrows strongly on the uaddvti4 expansion for aarch64 since
the principles are similar.  Firstly, if the one of the low words of
the expansion is 0, we can simply copy the other low word to the
destination and use uaddvsi4 for the upper word.  If that doesn't work
we have to handle three possible cases for the upper work (the lower
word is simply an add-with-carry operation as for adddi3): zero in the
upper word, some other constant and a register (each has a different
canonicalization).  We use CC_ADCmode (a new CC mode variant) to
describe the cases as the introduction of the carry means we can
no-longer use the normal overflow trick of comparing the sum against
one of the operands.

	* config/arm/arm-modes.def (CC_ADC): New CC mode.
	* config/arm/arm.c (arm_select_cc_mode): Detect selection of
	CC_ADCmode.
	(maybe_get_arm_condition_code): Handle CC_ADCmode.
	* config/arm/arm.md (uaddvdi4): Early expansion of unsigned addition
	with overflow.
	(addsi3_cin_cout_reg, addsi3_cin_cout_imm, addsi3_cin_cout_0): New
	expand patterns.
	(addsi3_cin_cout_reg_insn, addsi3_cin_cout_0_insn): New insn patterns
	(addsi3_cin_cout_imm_insn): Likewise.
	(adddi3_compareC): Delete insn.
	* config/arm/predicates.md (arm_carry_operation): Handle CC_ADCmode.

From-SVN: r277183