Back end question.

[Ian Lance Taylor]

"Dmitry" <mittie@ukr.net> writes:

> Ok but if people do not set each status bit individually, how do they set several not related bits in one CC mode and in one set rtx?

They represent the collection of bits as a mode, as you've been
discussing.

E.g., from config/i386/i386.md

(define_insn "*<plusminus_insn><mode>3_cc_overflow"
  [(set (reg:CCC FLAGS_REG)
	(compare:CCC
	    (plusminus:SWI
		(match_operand:SWI 1 "nonimmediate_operand" "<comm>0,0")
		(match_operand:SWI 2 "<general_operand>" "<r><i>,<r>m"))
	    (match_dup 1)))
   (set (match_operand:SWI 0 "nonimmediate_operand" "=<r>m,<r>")
	(plusminus:SWI (match_dup 1) (match_dup 2)))]
  "ix86_binary_operator_ok (<CODE>, <MODE>mode, operands)"
  "<plusminus_mnemonic>{<imodesuffix>}\t{%2, %0|%0, %2}"
  [(set_attr "type" "alu")
   (set_attr "mode" "<MODE>")])


Here the CCC mode (defined in i386-modes.def) means that the carry flag
is valid.

Ian