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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
&regno_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.
This commit is contained in:
Jakub Jelinek 2022-04-06 18:42:52 +02:00
parent 9fd377a747
commit 61bee6aed2
1 changed files with 13 additions and 13 deletions
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26
gcc/combine.cc
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@ -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];
}