[Bug rtl-optimization/53908] New: [4.7 Regression] csa removes needed memory load

[Bug rtl-optimization/53908] New: [4.7 Regression] csa removes needed memory load

[hp at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

             Bug #: 53908
           Summary: [4.7 Regression] csa removes needed memory load
    Classification: Unclassified
           Product: gcc
           Version: 4.7.2
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: hp@gcc.gnu.org
              Host: x86_64-linux
            Target: x86_64-linux-gnu, cris-axis-elf,
                    crisv32-axis-linux-gnu


Created attachment 27768
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27768
Repeat with e.g. cc1 -O2 ba2.c

Observed with gcc-4_7-branch revision 189394.
The attached test-case calls
is_basic(user_name) < 0 && is_digest(user_name) < 0
with *user_name = NULL.
The call to is_basic "fails"; returns < 0 without writing to *user_name.
The call to is_digest is successful and furthermore writes *user_name (a char
**).  Next, *user_item = find_user(*user_name) is called, but the load of
*user_name after the is_digest call is lost; wrongly eliminated in favor of the
load after the call to is_basic.

A dump shows wrong code first in the ".207r.csa" pass (for
crisv32-axis-linux-gnu, likely for x86_64 as well).

The test-case does not expose the bug on trunk r189401.
Not observed with a gcc-4.3-based toolchain (cris-*), not observed with (host)
"Debian 4.4.5-8". Unknown 4.5, 4.6.

[Bug rtl-optimization/53908] [4.7 Regression] csa removes needed memory load

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mikpe at it dot uu.se

--- Comment #1 from Mikael Pettersson <mikpe at it dot uu.se> 2012-07-10 09:04:58 UTC ---
I can reproduce on sparc64-linux: gcc 4.4, 4.5, and 4.8 generate working code,
but 4.6 and 4.7 generate code that SEGVs.  I wasn't able to reproduce on ARMv5
or m68k.

[Bug rtl-optimization/53908] [4.7 Regression] csa removes needed memory load

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.7.2

[Bug rtl-optimization/53908] [4.7 Regression] csa removes needed memory load

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

--- Comment #2 from Mikael Pettersson <mikpe at it dot uu.se> 2012-07-10 10:11:15 UTC ---
I can't reproduce on x86_64-linux, nor with a cross to sparc64-linux (only
natively on sparc64-linux so far).

HP: are you sure it fails on x86_64?

I'll try to bisect natively on sparc64, but that will take ages...

[Bug rtl-optimization/53908] [4.7 Regression] csa removes needed memory load

[hp at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

--- Comment #3 from Hans-Peter Nilsson <hp at gcc dot gnu.org> 2012-07-10 17:03:14 UTC ---
(In reply to comment #2)
> I can't reproduce on x86_64-linux, 

Odd.  What does valgrind say / did you check the generated code?

> HP: are you sure it fails on x86_64?

Yes, as written.  N.B.: I used --disable-bootstrap, but that shouldn't have any
significance modulo bugs.  Host (native) compiler was the mentioned "Debian
4.4.5-8" x86_64 gcc, but not for all targets and only for pristine FSF code
checks.  Are you sure you used the gcc 4.7 branch for x86_64? ;)

It can't be ruled out of course that there's some address hash thing clouding
the issue, but the reproducibility seems stable (same gcc binary on different
targets; different host gcc).

[Bug rtl-optimization/53908] [4.7 Regression] csa removes needed memory load

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

--- Comment #4 from Mikael Pettersson <mikpe at it dot uu.se> 2012-07-10 19:55:25 UTC ---
My mistake, I can now reproduce the runtime SEGV on x86_64-linux with vanilla
gcc-4.7-20120707.

[Bug rtl-optimization/53908] [4.6/4.7 Regression] csa removes needed memory load

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

--- Comment #5 from Mikael Pettersson <mikpe at it dot uu.se> 2012-07-10 22:50:24 UTC ---
On x86_64-linux the SEGV went away on trunk with r186159:
http://gcc.gnu.org/ml/gcc-cvs/2012-04/msg00108.html
http://gcc.gnu.org/ml/gcc-patches/2012-04/msg00202.html

The patch description makes it sound more like a cleanup than fixing actual
bugs, but when I diff the assembly code for the test case with r186158 and
r186159 I see:

--- pr53908.s-r186158   2012-07-11 00:28:57.000000000 +0200
+++ pr53908.s-r186159   2012-07-11 00:34:32.000000000 +0200
...
        call    is_basic
        testl   %eax, %eax
-       movq    8(%rsp), %rbp
-       js      .L68
-.L29:
+       js      .L29
+.L33:
        movq    users(%rip), %rbx
+       movq    8(%rsp), %rbp
        testq   %rbx, %rbx
...

That is, a load is being moved across a control flow insn.  All other diffs
seem to just be changed label numbers.

I'll give it some more testing tomorrow.

[Bug rtl-optimization/53908] [4.6/4.7 Regression] csa removes needed memory load

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-07-11
     Ever Confirmed|0                           |1

--- Comment #6 from H.J. Lu <hjl.tools at gmail dot com> 2012-07-11 06:27:29 UTC ---
It is fixed on trunk by revision 186159:

http://gcc.gnu.org/ml/gcc-cvs/2012-04/msg00108.html

[Bug rtl-optimization/53908] [4.6/4.7 Regression] csa removes needed memory load

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bernds at gcc dot gnu.org

--- Comment #7 from H.J. Lu <hjl.tools at gmail dot com> 2012-07-11 08:04:48 UTC ---
It is caused by revision 167779:

http://gcc.gnu.org/ml/gcc-cvs/2010-12/msg00461.html

[Bug rtl-optimization/53908] [4.6/4.7 Regression] csa removes needed memory load

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

--- Comment #8 from Mikael Pettersson <mikpe at it dot uu.se> 2012-07-11 09:46:06 UTC ---
Backporting r186159 and its followup fix r186164 to 4.7.1 was easy and fixed
the test case there too (untested beyond this test case).  Backporting those
revisions to 4.6.3 required more elbow grease but didn't fix the test case
there.

I'm going to test the 4.7 backport properly now, in case a smaller more direct
fix doesn't emerge soon.

[Bug rtl-optimization/53908] [4.6/4.7 Regression] csa removes needed memory load

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                URL|                            |http://gcc.gnu.org/ml/gcc-p
                   |                            |atches/2012-07/msg00410.htm
                   |                            |l

--- Comment #9 from H.J. Lu <hjl.tools at gmail dot com> 2012-07-11 12:38:16 UTC ---
The fix is posted at

http://gcc.gnu.org/ml/gcc-patches/2012-07/msg00410.html

[Bug rtl-optimization/53908] [4.6/4.7 Regression] csa removes needed memory load

[hp at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

--- Comment #10 from Hans-Peter Nilsson <hp at gcc dot gnu.org> 2012-07-13 06:53:30 UTC ---
Created attachment 27783
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27783
patch from Richard Sandiford

Updated patch, from http://gcc.gnu.org/ml/gcc-patches/2012-07/msg00463.html
(which wasn't in patch form).

[Bug rtl-optimization/53908] [4.6/4.7 Regression] csa removes needed memory load

[hp at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

--- Comment #11 from Hans-Peter Nilsson <hp at gcc dot gnu.org> 2012-07-13 08:53:28 UTC ---
Author: hp
Date: Fri Jul 13 08:53:24 2012
New Revision: 189454

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=189454
Log:
    PR rtl-optimization/53908
    * df-problems.c (can_move_insns_across): When doing
    memory-reference book-keeping, handle call insns.

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

[Bug rtl-optimization/53908] [4.6/4.7 Regression] csa removes needed memory load

[hp at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

--- Comment #12 from Hans-Peter Nilsson <hp at gcc dot gnu.org> 2012-07-13 08:58:52 UTC ---
Author: hp
Date: Fri Jul 13 08:58:46 2012
New Revision: 189455

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=189455
Log:
    PR rtl-optimization/53908
    * gcc.dg/torture/pr53908.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/torture/pr53908.c
Modified:
    trunk/gcc/testsuite/ChangeLog

[Bug rtl-optimization/53908] [4.6/4.7 Regression] csa removes needed memory load

[hp at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

--- Comment #13 from Hans-Peter Nilsson <hp at gcc dot gnu.org> 2012-07-13 17:21:47 UTC ---
Author: hp
Date: Fri Jul 13 17:21:41 2012
New Revision: 189468

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=189468
Log:
    PR rtl-optimization/53908
    * df-problems.c (can_move_insns_across): When doing
    memory-reference book-keeping, handle call insns.

Modified:
    branches/gcc-4_7-branch/gcc/ChangeLog
    branches/gcc-4_7-branch/gcc/df-problems.c

[Bug rtl-optimization/53908] [4.6/4.7 Regression] csa removes needed memory load

[hp at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

--- Comment #14 from Hans-Peter Nilsson <hp at gcc dot gnu.org> 2012-07-13 17:23:02 UTC ---
Author: hp
Date: Fri Jul 13 17:22:55 2012
New Revision: 189469

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=189469
Log:
    PR rtl-optimization/53908
    * gcc.dg/torture/pr53908.c: New test.

Added:
    branches/gcc-4_7-branch/gcc/testsuite/gcc.dg/torture/pr53908.c
Modified:
    branches/gcc-4_7-branch/gcc/testsuite/ChangeLog

[Bug rtl-optimization/53908] [4.6/4.7 Regression] csa removes needed memory load

[hp at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

Hans-Peter Nilsson <hp at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED

--- Comment #15 from Hans-Peter Nilsson <hp at gcc dot gnu.org> 2012-07-13 17:27:11 UTC ---
Testing for 4.7 went well, as expected from the previous versions, so
committed.
Closing, but feel free to post test-results for 4.6 and permission for
back-port.

[Bug rtl-optimization/53908] [4.6 Regression] csa removes needed memory load

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

Steven Bosscher <steven at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch
           Priority|P3                          |P1
             Status|RESOLVED                    |REOPENED
         Resolution|FIXED                       |
            Summary|[4.6/4.7 Regression] csa    |[4.6 Regression] csa
                   |removes needed memory load  |removes needed memory load

--- Comment #16 from Steven Bosscher <steven at gcc dot gnu.org> 2012-07-13 17:39:21 UTC ---
GCC 4.6 is still maintained, so this regression report should stay open.

In fact, being wrong code on a primary target, and relatively trivial to fix,
I'd say this has to be a P1 bug for GCC 4.6.

[Bug rtl-optimization/53908] [4.6 Regression] csa removes needed memory load

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

Steven Bosscher <steven at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |ASSIGNED
                 CC|                            |steven at gcc dot gnu.org
         AssignedTo|unassigned at gcc dot       |steven at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #17 from Steven Bosscher <steven at gcc dot gnu.org> 2012-07-13 17:41:12 UTC ---
Will take care of GCC 4.6.

[Bug rtl-optimization/53908] [4.6 Regression] csa removes needed memory load

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

Steven Bosscher <steven at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|steven at gcc dot gnu.org   |
            Version|4.7.2                       |4.6.4
   Target Milestone|4.7.2                       |4.6.4

[Bug rtl-optimization/53908] [4.6 Regression] csa removes needed memory load

[hp at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

--- Comment #18 from Hans-Peter Nilsson <hp at gcc dot gnu.org> 2012-07-13 19:10:07 UTC ---
(In reply to comment #17)
> Will take care of GCC 4.6.

Thanks!

[Bug rtl-optimization/53908] [4.6 Regression] csa removes needed memory load

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

--- Comment #19 from Steven Bosscher <steven at gcc dot gnu.org> 2012-07-16 09:36:11 UTC ---
Author: steven
Date: Mon Jul 16 09:36:04 2012
New Revision: 189512

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=189512
Log:
Backport from trunk:

gcc/
    PR rtl-optimization/53908
    * df-problems.c (can_move_insns_across): When doing
    memory-reference book-keeping, handle call insns.

testsuite/
    PR rtl-optimization/53908
    * gcc.dg/torture/pr53908.c: New test.


Added:
    branches/gcc-4_6-branch/gcc/testsuite/gcc.dg/torture/pr53908.c
Modified:
    branches/gcc-4_6-branch/gcc/ChangeLog
    branches/gcc-4_6-branch/gcc/df-problems.c
    branches/gcc-4_6-branch/gcc/testsuite/ChangeLog

[Bug rtl-optimization/53908] [4.6 Regression] csa removes needed memory load

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

Steven Bosscher <steven at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #20 from Steven Bosscher <steven at gcc dot gnu.org> 2012-11-08 22:23:16 UTC ---
.