Re: condition codes, haifa-sched and virtual-stack-vars

[Greg McGary <greg at mcgary dot org>]

Alexandre Oliva <aoliva@redhat.com> writes:

> How about having a pre-reload move pattern that clobbers CC, split
> after reload into one that does not, so that sched2 could put the move
> between compare and branch should it indeed not affect CC?

Alexandre,

I liked your idea best (less invasive than Jeff's idea of
reworking conditional branch patterns), and it works!

In the "movsi" expander, I added this bit:

        if (REG_P (src)
            && REGNO (src) >= FIRST_PSEUDO_REGISTER
            && REGNO (src) <= LAST_VIRTUAL_REGISTER)
          {
            emit_insn (gen_movsi_virtual_reg (dest, src));
            return 1;
          }

In the md file, *after* the normal movsi insn (so the normal takes
precedence), I added this pattern:

        (define_insn_and_split "movsi_virtual_reg"
          [(parallel [(set (match_operand:SI 0 "register_operand" "=r")
        		   (match_operand:SI 1 "register_operand"  "r"))
        	      (clobber (reg:CC CC_REGNUM))])]
          ""
          "#"
          "reload_completed"
          [(set (match_dup 0)
        	(match_dup 1))]
          "")

Thanks very much Alexandre & Jeff!

Greg