[Bug rtl-optimization/47612] New: RTL crash when cc0 setter moved away from cc0 user

[Bug rtl-optimization/47612] New: RTL crash when cc0 setter moved away from cc0 user

[ian at airs dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

           Summary: RTL crash when cc0 setter moved away from cc0 user
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: ian@airs.com


Consider this C file:

extern void e (int) __attribute__ ((noreturn));
void
f (char *p, int a, int b, int c)
{
  int i, j;

  j = 0;
  for (i = 0; i < 10; ++i)
    {
      switch (a)
    {
    case 0:
      p[i] = 0;
      break;
    case 1:
      if (c == 1)
        {
          if (j < 0 | b <= j)
        e (0);
          p[j] = 0;
        }
      else
        {
          if (j < 0 | b <= j)
        e (0);
          p[j] = 0;
        }
      j++;
    }
    }
}

When I use a compiler built for the m68k-rtems4.11 target, the compiler crashes
when I compile this file with the options -O2 -mcpu=5206 -fwrapv.

/home/iant/gcc/m68k-rtems-objdir/./gcc/xgcc
-B/home/iant/gcc/m68k-rtems-objdir/./gcc/ -O2 -mcpu=5206 -S -fwrapv foo.c
foo.c: In function 'f':
foo.c:31:1: internal compiler error: in maybe_add_or_update_dep_1, at
sched-deps.c:845
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.

I will describe what I think is happening, although I have not proved it.  The
crash occurs because try_head_merge_bb in cfgcleanup.c moves a CC0-setter away
from the CC0-user.  It finds a common sequence in two basic blocks--I believe
it is the finding of this common sequence which makes this test requires the
-mcpu=5206 -fwrapv options.  Finding the common sequence respects CC0
requirements.  However, it then calls can_move_insns_across.  That returns
false, because there is a register conflict--d0 is used by the predecessor
block and the common sequence.  However, can_move_insns_across also returns
move_upto, indicating which insns may be moved.  can_move_insns_across does not
check for cc0 when setting move_upto, and try_head_merge_bb doesn't check for
it when using move_upto.  The effect is that the cc0 setter is moved, leaving
the cc0 user behind.  This leads to the later crash.

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[joel at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

Joel Sherrill <joel at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2011.02.04 20:45:46
      Known to work|                            |4.3.2, 4.4.5, 4.5.2
     Ever Confirmed|0                           |1

--- Comment #1 from Joel Sherrill <joel at gcc dot gnu.org> 2011-02-04 20:45:46 UTC ---
Just a note that it happens with revision 169771.

This is a regression as it works with 4.5.2, 4.4.5, 4.3.2

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |http://gcc.gnu.org/bugzilla
                   |                            |/show_bug.cgi?id=47459

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-02-04 20:59:39 UTC ---
Related to PR 47459.

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[ian at airs dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

--- Comment #3 from Ian Lance Taylor <ian at airs dot com> 2011-02-04 21:27:40 UTC ---
It's similar to PR 46878 in that this is also CC0 related, but it is different
code that is splitting up the CC0 setter and the CC0 user.  My sources do
include the patch for PR 46878.

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

Mikael Pettersson <mikpe at it dot uu.se> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bernds at gcc dot gnu.org,
                   |                            |mikpe at it dot uu.se

--- Comment #4 from Mikael Pettersson <mikpe at it dot uu.se> 2011-02-05 20:48:53 UTC ---
I can reproduce the ICE with a cross to m68k-elf.  It's caused by r167779:

Author: bernds
Date: Tue Dec 14 00:23:40 2010
New Revision: 167779

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=167779
Log:
gcc/
    PR rtl-optimization/44374
    Reapply patch with fixes.
        ...

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[vincent.riviere at freesbee dot fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

Vincent Riviere <vincent.riviere at freesbee dot fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |vincent.riviere at freesbee
                   |                            |dot fr

--- Comment #5 from Vincent Riviere <vincent.riviere at freesbee dot fr> 2011-03-26 15:02:11 UTC ---
I confirm I have also hit this bug on GCC 4.6.0 release for the unofficial
m68k-atari-mint target with only "-mcpu=5475 -O2" on a rather big and
complicated file.

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[vincent.riviere at freesbee dot fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

--- Comment #6 from Vincent Riviere <vincent.riviere at freesbee dot fr> 2011-04-02 12:13:57 UTC ---
Created attachment 23850
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=23850
Testcase

Here is my simplified testcase. It looks weird, but I didn't manage to simplify
more. It fails with ICE when compiled using:
gcc -c bug.c -mcpu=5475 -O2

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[bernds at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

Bernd Schmidt <bernds at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |bernds at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #7 from Bernd Schmidt <bernds at gcc dot gnu.org> 2011-04-05 22:41:07 UTC ---
Created attachment 23890
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=23890
Potential fix.

Please test this patch.

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[vincent.riviere at freesbee dot fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

--- Comment #8 from Vincent Riviere <vincent.riviere at freesbee dot fr> 2011-04-06 17:07:26 UTC ---
Excellent! Your patch fixes both testcases here.

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[bernds at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

--- Comment #9 from Bernd Schmidt <bernds at gcc dot gnu.org> 2011-04-06 17:28:43 UTC ---
Any chance you can run the testsuite before/after the patch? m68k is
problematic due to lack of a simulator.

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[joel at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

--- Comment #10 from Joel Sherrill <joel at gcc dot gnu.org> 2011-04-06 17:52:00 UTC ---
(In reply to comment #9)
> Any chance you can run the testsuite before/after the patch? m68k is
> problematic due to lack of a simulator.

I can test with RTEMS on Qemu targeting an mc5282 Coldfire.  I just started a
build and test sweep without the patch.  Give me a bit to post test results
without and with the patch.  FWIW gcc 4.6.0 does fail with the test case and
5282 so this will be a good sweep.

$ m68k-rtems4.11-gcc -O2 -mcpu=5282 -fwrapv -c j2.c
j2.c: In function 'bug':
j2.c:19:1: internal compiler error: in maybe_add_or_update_dep_1, at
sched-deps.c:845
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[joel at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

--- Comment #11 from Joel Sherrill <joel at gcc dot gnu.org> 2011-04-07 11:44:54 UTC ---
In both cases, I built gcc + newlib multilib + rtems multilib to ensure the
entire software base was built with and without the patch.

$ m68k-rtems4.11-gcc --version
m68k-rtems4.11-gcc (GCC) 4.6.1 20110329 (prerelease)

Without patch.. results are at:

http://www.rtems.org/pipermail/rtems-tooltestresults/2011-April/000516.html
http://gcc.gnu.org/ml/gcc-testresults/2011-04/msg00525.html

        === gcc Summary ===

# of expected passes        67228
# of unexpected failures    386
# of expected failures        121
# of unresolved testcases    77
# of unsupported tests        1095

        === g++ Summary ===

# of expected passes        24705
# of unexpected failures    720
# of expected failures        162
# of unsupported tests        449

With the patch ... results are at:

http://www.rtems.org/pipermail/rtems-tooltestresults/2011-April/000517.html
http://gcc.gnu.org/ml/gcc-testresults/2011-04/msg00533.html

        === gcc Summary ===

# of expected passes        67231
# of unexpected failures    383
# of expected failures        121
# of unresolved testcases    77
# of unsupported tests        1095

        === g++ Summary ===

# of expected passes        24705
# of unexpected failures    720
# of expected failures        162
# of unsupported tests        449

It looks like it didn't make anything worse and fixed 3 C tests. :-D

I think this should be committed to the 4.6 branch and head.  If you like, we
can repeat the experiment on the 4.5 branch if that is desired.

FWIW I would be happy to help run down some of the failure cases if someone is
interested in trying to fix them. :-D

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[bernds at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

Bernd Schmidt <bernds at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #23890|0                           |1
        is obsolete|                            |

--- Comment #12 from Bernd Schmidt <bernds at gcc dot gnu.org> 2011-04-07 12:03:48 UTC ---
Created attachment 23909
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=23909
Better fix

Sorry to do this to you, but can you test this one? I looked at the code again
a bit more closely and I believe the previous patch was incorrect :-(

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[joel at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

--- Comment #13 from Joel Sherrill <joel at gcc dot gnu.org> 2011-04-07 15:28:39 UTC ---
Not a problem to redo.. just CPU time and if you don't use it, you lose it. :-D
I am repeating some information so it is all in one post.

In both cases, I built gcc + newlib multilib + rtems multilib to ensure the
entire software base was built with and without the patch.

$ m68k-rtems4.11-gcc --version
m68k-rtems4.11-gcc (GCC) 4.6.1 20110329 (prerelease)

Without patch.. results are at:

http://www.rtems.org/pipermail/rtems-tooltestresults/2011-April/000516.html
http://gcc.gnu.org/ml/gcc-testresults/2011-04/msg00525.html

        === gcc Summary ===

# of expected passes        67228
# of unexpected failures    386
# of expected failures        121
# of unresolved testcases    77
# of unsupported tests        1095

        === g++ Summary ===

# of expected passes        24705
# of unexpected failures    720
# of expected failures        162
# of unsupported tests        449

With the patch ... results are at:

http://www.rtems.org/pipermail/rtems-tooltestresults/2011-April/000518.html
http://gcc.gnu.org/ml/gcc-testresults/2011-04/msg00577.html

    === gcc Summary ===

# of expected passes        67230
# of unexpected failures    384
# of expected failures        121
# of unresolved testcases    77
# of unsupported tests        1095

        === g++ Summary ===

# of expected passes        24705
# of unexpected failures    720
# of expected failures        162
# of unsupported tests        449

Only an increase of two passes.  I don't know what was the 3rd test that passed
with the previous patch and not with this one.

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[bernds at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

--- Comment #14 from Bernd Schmidt <bernds at gcc dot gnu.org> 2011-04-07 15:35:34 UTC ---
>From the test results you posted, it appears to have been

+WARNING: program timed out.
+FAIL: gcc.dg/torture/fp-int-convert-double.c  -O2 -flto  execution test

Probably unrelated.

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[joel at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

--- Comment #15 from Joel Sherrill <joel at gcc dot gnu.org> 2011-04-07 15:44:16 UTC ---
(In reply to comment #14)
> From the test results you posted, it appears to have been
> 
> +WARNING: program timed out.
> +FAIL: gcc.dg/torture/fp-int-convert-double.c  -O2 -flto  execution test
> 
> Probably unrelated.

When I compiled it by hand and ran it, it passed.  I think that makes the test
results the same.  Strangely, none of the gcc.dg/torture tests that failed
appear to have left executables. :(

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[bernds at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

--- Comment #16 from Bernd Schmidt <bernds at gcc dot gnu.org> 2011-05-04 20:24:19 UTC ---
Author: bernds
Date: Wed May  4 20:24:15 2011
New Revision: 173393

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=173393
Log:
    PR rtl-optimization/47612
    * df-problems.c (can_move_insns_across): Don't pick a cc0 setter
    as the last insn of the sequence to be moved.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/df-problems.c

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[vincent.riviere at freesbee dot fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

--- Comment #17 from Vincent Riviere <vincent.riviere at freesbee dot fr> 2011-05-04 23:59:00 UTC ---
For me the bug seems to be fixed.

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[vincent.riviere at freesbee dot fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

--- Comment #18 from Vincent Riviere <vincent.riviere at freesbee dot fr> 2011-08-02 07:30:06 UTC ---
I have applied your patch to GCC 4.6.1 and it worked fine on all the software
I'm used to compile. You should apply it to the 4.6 branch.

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[joel at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

--- Comment #19 from Joel Sherrill <joel at gcc dot gnu.org> 2011-12-13 19:10:10 UTC ---
Time to close this?

[Bug rtl-optimization/47612] RTL crash when cc0 setter moved away from cc0 user

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

--- Comment #20 from Mikael Pettersson <mikpe at it dot uu.se> 2011-12-13 19:40:19 UTC ---
(In reply to comment #19)
> Time to close this?

Not until the patch gets applied to gcc-4.6 branch.

[Bug rtl-optimization/47612] [4.6 regression] RTL crash when cc0 setter moved away from cc0 user

[ebotcazou at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ebotcazou at gcc dot
                   |                            |gnu.org
   Target Milestone|---                         |4.6.3
            Summary|RTL crash when cc0 setter   |[4.6 regression] RTL crash
                   |moved away from cc0 user    |when cc0 setter moved away
                   |                            |from cc0 user
      Known to fail|                            |4.6.2, 4.7.0

--- Comment #21 from Eric Botcazou <ebotcazou at gcc dot gnu.org> 2011-12-13 22:54:20 UTC ---
Please properly mark regressions and backport the fix ASAP if appropriate.

[Bug rtl-optimization/47612] [4.6 regression] RTL crash when cc0 setter moved away from cc0 user

[tg at mirbsd dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

Thorsten Glaser <tg at mirbsd dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tg at mirbsd dot org

--- Comment #22 from Thorsten Glaser <tg at mirbsd dot org> 2012-02-27 19:23:11 UTC ---
The fix applies as-is to gcc-4.6 with only a fuzz in line offset.

[Bug rtl-optimization/47612] [4.6 regression] RTL crash when cc0 setter moved away from cc0 user

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.6.3                       |4.6.4

--- Comment #23 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-03-01 14:39:08 UTC ---
GCC 4.6.3 is being released.

[Bug rtl-optimization/47612] [4.6 regression] RTL crash when cc0 setter moved away from cc0 user

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47612

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|4.6.4                       |4.7.0

--- Comment #24 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-04-12 16:17:56 UTC ---
The 4.6 branch has been closed, fixed in GCC 4.7.0.