From 61bee6aed26eb30b798c75b9a595c9d51e080442 Mon Sep 17 00:00:00 2001
From: Jakub Jelinek <jakub@redhat.com>
Date: Wed, 6 Apr 2022 18:42:52 +0200
Subject: [PATCH] combine: Don't record for UNDO_MODE pointers into
regno_reg_rtx array [PR104985]
The testcase in the PR fails under valgrind on mips64 (but only Martin
can reproduce, I couldn't).
But the problem reported there is that SUBST_MODE remembers addresses
into the regno_reg_rtx array, then some splitter needs a new pseudo
and calls gen_reg_rtx, which reallocates the regno_reg_rtx array
and finally undo operation is done and dereferences the old regno_reg_rtx
entry.
The rtx values stored in regno_reg_rtx array seems to be created
by gen_reg_rtx only and since then aren't modified, all we do for it
is adjusting its fields (e.g. adjust_reg_mode that SUBST_MODE does).
So, I think it is useless to use where.r for UNDO_MODE and store
®no_reg_rtx[regno] in struct undo, we can store just
regno_reg_rtx[regno] (i.e. pointer to the REG itself instead of
pointer to pointer to REG) or could also store just the regno.
The following patch does the latter, and because SUBST_MODE no longer
needs to be a macro, changes all SUBST_MODE uses to subst_mode.
2022-04-06 Jakub Jelinek <jakub@redhat.com>
PR rtl-optimization/104985
* combine.cc (struct undo): Add where.regno member.
(do_SUBST_MODE): Rename to ...
(subst_mode): ... this. Change first argument from rtx * into int,
operate on regno_reg_rtx[regno] and save regno into where.regno.
(SUBST_MODE): Remove.
(try_combine): Use subst_mode instead of SUBST_MODE, change first
argument from regno_reg_rtx[whatever] to whatever. For UNDO_MODE, use
regno_reg_rtx[undo->where.regno] instead of *undo->where.r.
(undo_to_marker): For UNDO_MODE, use regno_reg_rtx[undo->where.regno]
instead of *undo->where.r.
(simplify_set): Use subst_mode instead of SUBST_MODE, change first
argument from regno_reg_rtx[whatever] to whatever.
---
gcc/combine.cc | 26 +++++++++++++-------------
1 file changed, 13 insertions(+), 13 deletions(-)
diff --git a/gcc/combine.cc b/gcc/combine.cc
index 8f06ee0e54f7..53dcac92abc2 100644
--- a/gcc/combine.cc
+++ b/gcc/combine.cc
@@ -382,7 +382,7 @@ struct undo
struct undo *next;
enum undo_kind kind;
union { rtx r; int i; machine_mode m; struct insn_link *l; } old_contents;
- union { rtx *r; int *i; struct insn_link **l; } where;
+ union { rtx *r; int *i; int regno; struct insn_link **l; } where;
};
/* Record a bunch of changes to be undone, up to MAX_UNDO of them.
@@ -761,10 +761,11 @@ do_SUBST_INT (int *into, int newval)
well. */
static void
-do_SUBST_MODE (rtx *into, machine_mode newval)
+subst_mode (int regno, machine_mode newval)
{
struct undo *buf;
- machine_mode oldval = GET_MODE (*into);
+ rtx reg = regno_reg_rtx[regno];
+ machine_mode oldval = GET_MODE (reg);
if (oldval == newval)
return;
@@ -775,15 +776,13 @@ do_SUBST_MODE (rtx *into, machine_mode newval)
buf = XNEW (struct undo);
buf->kind = UNDO_MODE;
- buf->where.r = into;
+ buf->where.regno = regno;
buf->old_contents.m = oldval;
- adjust_reg_mode (*into, newval);
+ adjust_reg_mode (reg, newval);
buf->next = undobuf.undos, undobuf.undos = buf;
}
-#define SUBST_MODE(INTO, NEWVAL) do_SUBST_MODE (&(INTO), (NEWVAL))
-
/* Similar to SUBST, but NEWVAL is a LOG_LINKS expression. */
static void
@@ -3186,7 +3185,7 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1, rtx_insn *i0,
newpat_dest = gen_rtx_REG (compare_mode, regno);
else
{
- SUBST_MODE (regno_reg_rtx[regno], compare_mode);
+ subst_mode (regno, compare_mode);
newpat_dest = regno_reg_rtx[regno];
}
}
@@ -3576,7 +3575,7 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1, rtx_insn *i0,
ni2dest = gen_rtx_REG (new_mode, REGNO (i2dest));
else
{
- SUBST_MODE (regno_reg_rtx[REGNO (i2dest)], new_mode);
+ subst_mode (REGNO (i2dest), new_mode);
ni2dest = regno_reg_rtx[REGNO (i2dest)];
}
@@ -3712,7 +3711,7 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1, rtx_insn *i0,
newdest = gen_rtx_REG (split_mode, REGNO (i2dest));
else
{
- SUBST_MODE (regno_reg_rtx[REGNO (i2dest)], split_mode);
+ subst_mode (REGNO (i2dest), split_mode);
newdest = regno_reg_rtx[REGNO (i2dest)];
}
}
@@ -4082,7 +4081,7 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1, rtx_insn *i0,
for (undo = undobuf.undos; undo; undo = undo->next)
if (undo->kind == UNDO_MODE)
{
- rtx reg = *undo->where.r;
+ rtx reg = regno_reg_rtx[undo->where.regno];
machine_mode new_mode = GET_MODE (reg);
machine_mode old_mode = undo->old_contents.m;
@@ -4755,7 +4754,8 @@ undo_to_marker (void *marker)
*undo->where.i = undo->old_contents.i;
break;
case UNDO_MODE:
- adjust_reg_mode (*undo->where.r, undo->old_contents.m);
+ adjust_reg_mode (regno_reg_rtx[undo->where.regno],
+ undo->old_contents.m);
break;
case UNDO_LINKS:
*undo->where.l = undo->old_contents.l;
@@ -6819,7 +6819,7 @@ simplify_set (rtx x)
new_dest = gen_rtx_REG (compare_mode, regno);
else
{
- SUBST_MODE (regno_reg_rtx[regno], compare_mode);
+ subst_mode (regno, compare_mode);
new_dest = regno_reg_rtx[regno];
}
--
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