code hoisting with CCmode condition codes

[Alan Lehotsky]

I'm obvkously doing something stupid here; but I'm at a loss to figure it out.

Porting to a machine where most instructions set some condition codes and 
before hoisting, we have


(insn 1205 1204 1206 65 (set (reg:CC_ZN 24 *cc)
        (compare:CC_ZN (reg:SI 843)
            (reg:SI 844))) 
../../../../../uberbaum/newlib/libc/stdio/vfprintf.c:1046 83 {*cmpsi_zn}
     (expr_list:REG_EQUAL (compare:CC_ZN (reg:SI 843)
            (const_int 0 [0]))
        (expr_list:REG_DEAD (reg:SI 844)
            (nil))))

(jump_insn 1206 1205 1207 65 (set (pc)
        (if_then_else (eq (reg:CC_ZN 24 *cc)
                (const_int 0 [0]))
            (label_ref 1215)
            (pc))) ../../../../../uberbaum/newlib/libc/stdio/vfprintf.c:1046 86 
{branch_insn}
     (expr_list:REG_DEAD (reg:CC_ZN 24 *cc)
        (nil))
 -> 1215)


But after the hoist pass runs, we've  inserted a   (set (reg:1884) (plus (reg 
674) (const_int 4)))
between the CC set and use.


(insn 1203 1202 1205 62 (clobber (reg:CC 24 *cc)) 
../../../../../uberbaum/newlib/libc/stdio/vfprintf.c:1046 -1
     (expr_list:REG_UNUSED (reg:CC 24 *cc)
        (nil)))

(insn 1205 1203 6262 62 (set (reg:CC_ZN 24 *cc)
        (compare:CC_ZN (reg:SI 843)
            (const_int 0 [0]))) 
../../../../../uberbaum/newlib/libc/stdio/vfprintf.c:1046 83 {*cmpsi_zn}
     (expr_list:REG_EQUAL (compare:CC_ZN (reg:SI 843)
            (const_int 0 [0]))
        (expr_list:REG_DEAD (reg:SI 844)
            (nil))))

(insn 6262 1205 1206 62 (set (reg/f:SI 1884 [ ap ])
        (plus:SI (reg/v/f:SI 674 [ ap ])
            (const_int 4 [0x4]))) 10 {*addsi}
     (nil))

(jump_insn 1206 6262 1207 62 (set (pc)
        (if_then_else (eq (reg:CC_ZN 24 *cc)
                (const_int 0 [0]))
            (label_ref 1215)
            (pc))) ../../../../../uberbaum/newlib/libc/stdio/vfprintf.c:1046 86 
{branch_insn}
     (expr_list:REG_DEAD (reg:CC_ZN 24 *cc)
        (nil))
 -> 1215)


and this is a problem because that will codegen as a 

        move    $rtemp,src
        addi      $rtemp,4

and both of those instructions end up setting condition codes, breaking the 
dependency with the compare that actually sets the CCs..

I've looked at a number of the other CCmode ports, but can't see how they 
prevent this from occurring.

Do I need to do something like change my define_expand for addsi3 to be 
something like

 
    [ (parallel [ (clobber:CCmode (reg:CCmode CCREG))
                        (set:SI (match_operand:SI 0 "" "")
                                    (plus:SI (match_operand::SI 1 "" "" )
                                                   (match_operand:SI 2 "" 
"")))])]

So that there's an explicitly stated dependency that would prevent motioning 
before the use in the jump_insn?

But I don't see this construct used in other ports that have CCmode registers 
as opposed to cc0

I'm porting of 4.6.1 - is there any better documentation of CCmode ports or a 
reference port with