On Fri, Mar 28, 2025 at 12:20:18PM +0100, Jakub Jelinek wrote:
> Here is the incremental patch I was talking about.
> For noop sets, we don't need to test much, they can go to i2
> unless that would violate i3 JUMP condition.
>
> With this the try_combine on the pr119291.c testcase doesn't fail,
> but succeeds and we get
> (insn 22 21 23 4 (set (pc)
> (pc)) "pr119291.c":27:15 2147483647 {NOOP_MOVE}
> (nil))
> (insn 23 22 24 4 (set (reg/v:SI 117 [ e ])
> (reg/v:SI 116 [ e ])) 96 {*movsi_internal}
> (expr_list:REG_DEAD (reg/v:SI 116 [ e ])
> (nil)))
> (note 24 23 25 4 NOTE_INSN_DELETED)
> (insn 25 24 26 4 (set (reg/v:SI 116 [ e ])
> (const_int 0 [0])) "pr119291.c":28:13 96 {*movsi_internal}
> (nil))
> (note 26 25 27 4 NOTE_INSN_DELETED)
> (insn 27 26 28 4 (set (reg:DI 128 [ _9 ])
> (const_int 0 [0])) "pr119291.c":28:13 95 {*movdi_internal}
> (nil))
> after it.
I'd like to ping the
https://gcc.gnu.org/pipermail/gcc-patches/2025-March/679573.html
patch.
Ok for trunk?
> 2025-03-28 Jakub Jelinek <ja...@redhat.com>
>
> * combine.cc (try_combine): Sets which satisfy set_noop_p can go
> to i2 unless i3 is a jump and the other set is not.
>
> --- gcc/combine.cc.jj 2025-03-28 11:44:15.491458700 +0100
> +++ gcc/combine.cc 2025-03-28 12:11:49.505835983 +0100
> @@ -4017,13 +4017,14 @@ try_combine (rtx_insn *i3, rtx_insn *i2,
> in i3, so we need to make sure that we won't wrongly hoist a SET
> to i2 that would conflict with a death note present in there, or
> would have its dest modified or used between i2 and i3. */
> - if (!modified_between_p (SET_SRC (set1), i2, i3)
> - && !(REG_P (SET_DEST (set1))
> - && find_reg_note (i2, REG_DEAD, SET_DEST (set1)))
> - && !(GET_CODE (SET_DEST (set1)) == SUBREG
> - && find_reg_note (i2, REG_DEAD,
> - SUBREG_REG (SET_DEST (set1))))
> - && !reg_used_between_p (SET_DEST (set1), i2, i3)
> + if ((set_noop_p (set1)
> + || (!modified_between_p (SET_SRC (set1), i2, i3)
> + && !(REG_P (SET_DEST (set1))
> + && find_reg_note (i2, REG_DEAD, SET_DEST (set1)))
> + && !(GET_CODE (SET_DEST (set1)) == SUBREG
> + && find_reg_note (i2, REG_DEAD,
> + SUBREG_REG (SET_DEST (set1))))
> + && !reg_used_between_p (SET_DEST (set1), i2, i3)))
> /* If I3 is a jump, ensure that set0 is a jump so that
> we do not create invalid RTL. */
> && (!JUMP_P (i3) || SET_DEST (set0) == pc_rtx)
> @@ -4032,13 +4033,14 @@ try_combine (rtx_insn *i3, rtx_insn *i2,
> newi2pat = set1;
> newpat = set0;
> }
> - else if (!modified_between_p (SET_SRC (set0), i2, i3)
> - && !(REG_P (SET_DEST (set0))
> - && find_reg_note (i2, REG_DEAD, SET_DEST (set0)))
> - && !(GET_CODE (SET_DEST (set0)) == SUBREG
> - && find_reg_note (i2, REG_DEAD,
> - SUBREG_REG (SET_DEST (set0))))
> - && !reg_used_between_p (SET_DEST (set0), i2, i3)
> + else if ((set_noop_p (set0)
> + || (!modified_between_p (SET_SRC (set0), i2, i3)
> + && !(REG_P (SET_DEST (set0))
> + && find_reg_note (i2, REG_DEAD, SET_DEST (set0)))
> + && !(GET_CODE (SET_DEST (set0)) == SUBREG
> + && find_reg_note (i2, REG_DEAD,
> + SUBREG_REG (SET_DEST (set0))))
> + && !reg_used_between_p (SET_DEST (set0), i2, i3)))
> /* If I3 is a jump, ensure that set1 is a jump so that
> we do not create invalid RTL. */
> && (!JUMP_P (i3) || SET_DEST (set1) == pc_rtx)
Jakub
