I haven't mentioned that I am using gcc 4.6 latest version.
To generalize the question. If I use an operand like lc_operand
(below) and leave the constraint open, is it guaranteed that the
register that would be chosen would be of class lc?
2010/8/3 roy rosen <roy.1ro...@gmail.com>:
> Hi All,
>
> If I don't use a constraint, is it possible that during ira I get a
> register which is not acceptable by the predicate?
> In my port I have the following to support HW loops:
>
> (define_predicate "lc_operand"
> (match_operand 0 "register_operand")
> {
> unsigned int regno;
> if (GET_CODE (op) == SUBREG)
> op = SUBREG_REG (op);
> regno = REGNO (op);
> return (regno >= FIRST_PSEUDO_REGISTER ||
> REGNO_REG_CLASS(regno) == LC_REGS);
> }
> )
>
> (define_expand "doloop_end"
> [(use (match_operand 0 "" "")) ; loop pseudo
> (use (match_operand 1 "" "")) ; iterations; zero if unknown
> (use (match_operand 2 "" "")) ; max iterations
> (use (match_operand 3 "" "")) ; loop level
> (use (match_operand 4 "" ""))] ; label
> ""
> {
> if (INTVAL (operands[3]) > 4
> )
> FAIL;
> emit_jump_insn (gen_doloop_end_internal (operands[4], operands[0]));
> DONE;
> }
> )
>
> (define_insn "doloop_end_internal"
> [(set (pc)
> (if_then_else (ne (match_operand:SI 1 "lc_operand" "")
> (const_int 0))
> (label_ref (match_operand 0 "" ""))
> (pc)))
> (set (match_dup 1) (plus:SI (match_dup 1) (const_int -1)))]
> ""
> "doloop_end%b1 %!"
> )
>
> I see that during ira operand 1 in doloop_end_internal is getting
> "best GENERAL_REGS" and eventually ends up as a register of a class
> other than LC_REGS.
> I thought that if I have predicate lc_operand then I don't need a
> constraint since all other register classes would be rejected in all
> stages for this operand.
> What might be the problem here?
>
> Thanks, Roy.
>
