Hi!
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.
Ok for trunk if this passes bootstrap/regtest?
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
