On Feb 23, 2022, Alexandre Oliva <ol...@adacore.com> wrote:
> On Feb 21, 2022, Richard Biener <richard.guent...@gmail.com> wrote:
>>> Ok to revert commit r12-5852-g50e8b0c9bca6cdc57804f860ec5311b641753fbb
>> OK. Please re-open the bug as appropriate.
> Thanks. I've reopened it. Here's what I'm installing. I'm not
> reverting the testcase, since it stopped failing even before the patch
> was put in.
And now here's a patch that fixes the underlying issue.
Undo multi-word optional reloads correctly
From: Alexandre Oliva <ol...@adacore.com>
Unlike e.g. remove_inheritance_pseudos, undo_optional_reloads didn't
deal with subregs, so instead of removing multi-word moves, it
replaced the reload pseudo with the original pseudo. Besides the
redundant move, that retained the clobber of the dest, that starts a
multi-word move. After the remap, the sequence that should have
become a no-op move starts by clobbering the original pseudo and then
moving its pieces onto themselves. The problem is the clobber: it
makes earlier sets of the original pseudo to be regarded as dead: if
the optional reload sequence was an output reload, the insn for which
the output reload was attempted may be regarded as dead and deleted.
I've arranged for undo_optional_reloads to accept SUBREGs and use
get_regno, like remove_inheritance_pseudo, adjusted its insn-removal
loop to tolerate iterating over a removed clobber, and added logic to
catch any left-over reload clobbers that could trigger the problem.
for gcc/ChangeLog
* lra-constraints.cc (undo_optional_reloads): Recognize and
drop insns of multi-word move sequences, tolerate removal
iteration on an already-removed clobber, and refuse to
substitute original pseudos into clobbers.
---
gcc/lra-constraints.cc | 37 ++++++++++++++++++++++++-------------
1 file changed, 24 insertions(+), 13 deletions(-)
diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc
index b2c4590153c4c..5cd89e7eeddc2 100644
--- a/gcc/lra-constraints.cc
+++ b/gcc/lra-constraints.cc
@@ -7261,15 +7261,17 @@ undo_optional_reloads (void)
continue;
src = SET_SRC (set);
dest = SET_DEST (set);
- if (! REG_P (src) || ! REG_P (dest))
+ if ((! REG_P (src) && ! SUBREG_P (src))
+ || (! REG_P (dest) && ! SUBREG_P (dest)))
continue;
- if (REGNO (dest) == regno
+ if (get_regno (dest) == (int) regno
/* Ignore insn for optional reloads itself. */
- && REGNO (lra_reg_info[regno].restore_rtx) != REGNO (src)
+ && (get_regno (lra_reg_info[regno].restore_rtx)
+ != get_regno (src))
/* Check only inheritance on last inheritance pass. */
- && (int) REGNO (src) >= new_regno_start
+ && get_regno (src) >= new_regno_start
/* Check that the optional reload was inherited. */
- && bitmap_bit_p (&lra_inheritance_pseudos, REGNO (src)))
+ && bitmap_bit_p (&lra_inheritance_pseudos, get_regno (src)))
{
keep_p = true;
break;
@@ -7291,18 +7293,22 @@ undo_optional_reloads (void)
bitmap_copy (insn_bitmap, &lra_reg_info[regno].insn_bitmap);
EXECUTE_IF_SET_IN_BITMAP (insn_bitmap, 0, uid, bi2)
{
+ /* We may have already removed a clobber. */
+ if (!lra_insn_recog_data[uid])
+ continue;
insn = lra_insn_recog_data[uid]->insn;
if ((set = single_set (insn)) != NULL_RTX)
{
src = SET_SRC (set);
dest = SET_DEST (set);
- if (REG_P (src) && REG_P (dest)
- && ((REGNO (src) == regno
- && (REGNO (lra_reg_info[regno].restore_rtx)
- == REGNO (dest)))
- || (REGNO (dest) == regno
- && (REGNO (lra_reg_info[regno].restore_rtx)
- == REGNO (src)))))
+ if ((REG_P (src) || SUBREG_P (src))
+ && (REG_P (dest) || SUBREG_P (dest))
+ && ((get_regno (src) == (int) regno
+ && (get_regno (lra_reg_info[regno].restore_rtx)
+ == get_regno (dest)))
+ || (get_regno (dest) == (int) regno
+ && (get_regno (lra_reg_info[regno].restore_rtx)
+ == get_regno (src)))))
{
if (lra_dump_file != NULL)
{
@@ -7310,7 +7316,7 @@ undo_optional_reloads (void)
INSN_UID (insn));
dump_insn_slim (lra_dump_file, insn);
}
- delete_move_and_clobber (insn, REGNO (dest));
+ delete_move_and_clobber (insn, get_regno (dest));
continue;
}
/* We should not worry about generation memory-memory
@@ -7319,6 +7325,11 @@ undo_optional_reloads (void)
we remove the inheritance pseudo and the optional
reload. */
}
+ if (GET_CODE (PATTERN (insn)) == CLOBBER
+ && REG_P (SET_DEST (insn))
+ && get_regno (SET_DEST (insn)) == (int) regno)
+ /* Refuse to remap clobbers to preexisting pseudos. */
+ gcc_unreachable ();
lra_substitute_pseudo_within_insn
(insn, regno, lra_reg_info[regno].restore_rtx, false);
lra_update_insn_regno_info (insn);
--
Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/
Free Software Activist GNU Toolchain Engineer
Disinformation flourishes because many people care deeply about injustice
but very few check the facts. Ask me about <https://stallmansupport.org>
