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Re: Fix PR rtl-optimization/27761 (miscompilation)
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Ian Lance Taylor <ian at airs dot com>, Jim Wilson <wilson at specifix dot com>
- Cc: Michael Matz <matz at suse dot de>, gcc-patches at gcc dot gnu dot org
- Date: Sun, 10 Dec 2006 06:32:45 -0500
- Subject: Re: Fix PR rtl-optimization/27761 (miscompilation)
- References: <Pine.LNX.firstname.lastname@example.org> <email@example.com>
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
On Fri, May 26, 2006 at 04:07:30PM -0700, Ian Lance Taylor wrote:
> Michael Matz <firstname.lastname@example.org> writes:
> > * combine.c (try_combine): Protect i1src and i2src from becoming
> > shared through subst().
> This patch is going to generate a lot of garbage.
> Suppose we instead eliminate the UNIQUE_COPY parameter to subst, and
> always copy TO if we are going to substitute it? That would at least
> cut down on the garbage a bit.
> Anybody else have any thoughts on this?
Jim apparently outlined a fix for this in bugzilla many months ago.
I have tested that this fixes the bug (on ia64 on both trunk and on
gcc-4_1-branch) and bootstrapped/regtested it on 7 linux arches.
I have also tried to add a temporary assertion to see when
i1pat RTL changed and it hits already several times in libgcc.a, though
in that case the RTL changes did not cause miscompilation.
Ok for trunk/4.2/4.1?
2006-12-08 Jim Wilson <email@example.com>
Jakub Jelinek <firstname.lastname@example.org>
* combine.c (try_combine): Don't create a useless garbage SET
if PATTERN (i2) is a PARALLEL. If added_sets_1, save
PATTERN (i1) resp. SET from i1src to i1dest in i1pat
and use it to prevent accidental modification of i1src.
--- gcc/combine.c.jj 2006-11-17 09:55:14.000000000 +0100
+++ gcc/combine.c 2006-12-07 15:33:37.000000000 +0100
@@ -1819,8 +1819,8 @@ try_combine (rtx i3, rtx i2, rtx i1, int
rtx i3dest_killed = 0;
/* SET_DEST and SET_SRC of I2 and I1. */
rtx i2dest, i2src, i1dest = 0, i1src = 0;
- /* PATTERN (I2), or a copy of it in certain cases. */
- rtx i2pat;
+ /* PATTERN (I1) and PATTERN (I2), or a copy of it in certain cases. */
+ rtx i1pat = 0, i2pat = 0;
/* Indicates if I2DEST or I1DEST is in I2SRC or I1_SRC. */
int i2dest_in_i2src = 0, i1dest_in_i1src = 0, i2dest_in_i1src = 0;
int i2dest_killed = 0, i1dest_killed = 0;
@@ -2218,12 +2218,21 @@ try_combine (rtx i3, rtx i2, rtx i1, int
rtx. If I2 is a PARALLEL, we just need the piece that assigns I2SRC to
- i2pat = (GET_CODE (PATTERN (i2)) == PARALLEL
- ? gen_rtx_SET (VOIDmode, i2dest, i2src)
- : PATTERN (i2));
- i2pat = copy_rtx (i2pat);
+ if (GET_CODE (PATTERN (i2)) == PARALLEL)
+ i2pat = gen_rtx_SET (VOIDmode, i2dest, copy_rtx (i2src));
+ i2pat = copy_rtx (PATTERN (i2));
+ if (added_sets_1)
+ if (GET_CODE (PATTERN (i1)) == PARALLEL)
+ i1pat = gen_rtx_SET (VOIDmode, i1dest, copy_rtx (i1src));
+ i1pat = copy_rtx (PATTERN (i1));
@@ -2418,9 +2427,7 @@ try_combine (rtx i3, rtx i2, rtx i1, int
- XVECEXP (newpat, 0, --total_sets)
- = (GET_CODE (PATTERN (i1)) == PARALLEL
- ? gen_rtx_SET (VOIDmode, i1dest, i1src) : PATTERN (i1));
+ XVECEXP (newpat, 0, --total_sets) = i1pat;