[Bug c/46693] New: incorrect code generation with -O2 optimization enabled

[Bug c/46693] New: incorrect code generation with -O2 optimization enabled

[geomatsi at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

           Summary: incorrect code generation with -O2 optimization
                    enabled
           Product: gcc
           Version: 4.5.2
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: geomatsi@gmail.com

[Bug c/46693] incorrect code generation with -O2 optimization enabled

[geomatsi at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

--- Comment #1 from Sergey Matyukevich <geomatsi at gmail dot com> 2010-11-28 15:48:05 UTC ---
Created attachment 22554
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22554
testcase

code example

[Bug c/46693] incorrect code generation with -O2 optimization enabled

[geomatsi at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

--- Comment #2 from Sergey Matyukevich <geomatsi at gmail dot com> 2010-11-28 15:48:48 UTC ---
Created attachment 22555
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22555
dumpspecs

gcc dumpspecs

[Bug c/46693] incorrect code generation with -O2 optimization enabled

[geomatsi at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

--- Comment #3 from Sergey Matyukevich <geomatsi at gmail dot com> 2010-11-28 15:49:27 UTC ---
Created attachment 22556
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22556
gcc version

[Bug c/46693] incorrect code generation with -O2 optimization enabled

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |arm-gnueabi

--- Comment #4 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-11-28 15:59:13 UTC ---
Works for me on x86_64-darwin.

[Bug c/46693] incorrect code generation with -O2 optimization enabled

[geomatsi at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

--- Comment #5 from Sergey Matyukevich <geomatsi at gmail dot com> 2010-11-28 16:12:47 UTC ---
I am using an arm gcc cross-toolchain created with OpenEmbedded. Toolchain
version and its dumpspecs are available in attachements. Wrong code for
attached simple testcase is generated when I use -O2 optimization option. When
optimization options are not used or when -O0 is in use then code is generated
correctly. Running testcase is straightforward: compile an example with -O2 and
without it, then run both examples (either on a suitable arm machine or under
qemu) and get two different outputs (OK and WRONG) for two binaries.

[Bug target/46693] incorrect code generation with -O2 optimization enabled

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c                           |target
           Severity|major                       |normal

[Bug c/46693] incorrect code generation with -O2 optimization enabled

[geomatsi at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

Sergey Matyukevich <geomatsi at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code
          Component|target                      |c
               Host|                            |i686-linux
              Build|                            |i686-linux
           Severity|normal                      |major

[Bug target/46693] incorrect code generation with -O2 optimization enabled

[geomatsi at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

Sergey Matyukevich <geomatsi at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c                           |target
           Severity|major                       |normal

[Bug target/46693] incorrect code generation with -O2 optimization enabled

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

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

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

--- Comment #6 from Mikael Pettersson <mikpe at it dot uu.se> 2010-11-28 22:36:37 UTC ---
This test case works for me on arm-linux-gnueabi with gcc-4.3.5 and gcc-4.4.6,
but fails with current gcc-4.5.2 and gcc-4.6.

[Bug target/46693] incorrect code generation with -O2 optimization enabled

[ramana at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

Ramana Radhakrishnan <ramana at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2010.12.03 09:42:32
                 CC|                            |ramana at gcc dot gnu.org
     Ever Confirmed|0                           |1

--- Comment #7 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> 2010-12-03 09:42:32 UTC ---
Confirmed.

[Bug target/46693] incorrect code generation with -O2 optimization enabled

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |raj.khem at gmail dot com

--- Comment #8 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-12-10 13:29:12 UTC ---
*** Bug 46882 has been marked as a duplicate of this bug. ***

[Bug target/46693] incorrect code generation with -O2 optimization enabled

[ramana at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

Ramana Radhakrishnan <ramana at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot       |ramana at gcc dot gnu.org
                   |gnu.org                     |
   Target Milestone|---                         |4.5.3

[Bug tree-optimization/46693] incorrect code generation with -O2 optimization enabled

[ramana at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

Ramana Radhakrishnan <ramana at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
          Component|target                      |tree-optimization

--- Comment #9 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> 2010-12-13 10:53:31 UTC ---
On trunk 

vrp converts the IR from :


<bb 3>:
  c_5 = D.2034_4;
  D.2026_6 = D.2034_4 == 13;
  D.2027_7 = D.2034_4 == 10;
  D.2028_8 = D.2026_6 || D.2027_7;
  if (D.2028_8 != 0)
    goto <bb 7>;
  else
    goto <bb 4>;

<bb 4>:
  D.2030_9 = D.2034_4 <= 31;
  D.2031_10 = D.2034_4 != 9;
  D.2032_11 = D.2030_9 && D.2031_10;
  if (D.2032_11 != 0)
    goto <bb 7>;
  else
    goto <bb 5>;

<bb 5>:
  str_12 = str_1 + 1;

<bb 6>:
  # str_1 = PHI <str_3(D)(2), str_12(5)>
  D.2034_4 = *str_1;
  if (D.2034_4 != 0)
    goto <bb 3>;
  else
    goto <bb 7>;

<bb 7>:
  # D.2033_2 = PHI <0(4), 1(6), 0(3)>
  return D.2033_2;


to

<bb 3>:
  c_5 = D.2034_4;
  D.2026_6 = D.2034_4 == 13;
  D.2027_7 = D.2034_4 == 10;
  D.2028_8 = D.2026_6 | D.2027_7;
  if (D.2028_8 != 0)
    goto <bb 7>;
  else
    goto <bb 4>;

<bb 4>:
  D.2030_9 = D.2034_4 <= 31;
  D.2031_10 = D.2034_4 != 9;
  D.2032_11 = D.2030_9 & D.2031_10;
  if (D.2032_11 != 0)
    goto <bb 7>;
  else
    goto <bb 5>;

<bb 5>:
  str_12 = str_1 + 1;

<bb 6>:
  # str_1 = PHI <str_3(D)(2), str_12(5)>
  D.2034_4 = *str_1;
  if (D.2034_4 != 0)
    goto <bb 3>;
  else
    goto <bb 7>;

<bb 7>:
  # D.2033_2 = PHI <0(4), 1(6), 0(3)>
  return D.2033_2;

After a while ifcombine comes along and removes basic block 5 and merges blocks
3 and 4 into 1 basic block because it thinks that the 


optimizing two comparisons to 1
Merging blocks 3 and 4
Removing basic block 5

and converts this to this form: 

<bb 2>:
  goto <bb 4>;


<bb 3>:
  D.2026_6 = D.2034_4 == 13;
  D.2027_7 = D.2034_4 == 10;
  D.2028_8 = D.2026_6 | D.2027_7;
  D.2030_9 = D.2034_4 <= 31;
  D.2031_10 = D.2034_4 != 9;
  D.2032_11 = D.2030_9 & D.2031_10;
  goto <bb 5>;

<bb 4>:
Invalid sum of incoming frequencies 873, should be 10000
  # str_1 = PHI <str_3(D)(2)>
  D.2034_4 = *str_1;
  if (D.2034_4 != 0)
    goto <bb 3>;
  else
    goto <bb 5>;

<bb 5>:
Invalid sum of incoming frequencies 10000, should be 873
  # D.2033_2 = PHI <0(3), 1(4)>
  return D.2033_2;

[Bug tree-optimization/46693] incorrect code generation with -O2 optimization enabled

[ramana at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

--- Comment #10 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> 2010-12-13 14:11:13 UTC ---
(In reply to comment #4)
> Works for me on x86_64-darwin.

Fails for me on x86_64 -linux with trunk as of today. 

Ramana

[Bug tree-optimization/46693] incorrect code generation with -O2 optimization enabled

[ramana at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

Ramana Radhakrishnan <ramana at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |NEW
      Known to work|                            |4.3.5, 4.4.6
      Known to fail|                            |4.5.1

--- Comment #11 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> 2010-12-14 09:27:58 UTC ---
So the problem on trunk atleast seems to be in gimple-fold 

maybe_fold_or_comparisons and friends where all the comparisons are folded out
into a single boolean node of 1 where ideally the result of the basic block
should be reduced to the (c <= 31) && (x != 9) check . The other 2 equality
comparisons are superfluous. 

I won't be able to look at this for a couple of days - hence unassigning
myself.


The problem for this file goes away with -fno-tree-vrp but that's a heavy
weight work around.



cheers
Ramana

[Bug tree-optimization/46693] incorrect code generation with -O2 optimization enabled

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

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

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

--- Comment #12 from Jakub Jelinek <jakub at gcc dot gnu.org> 2010-12-14 10:06:52 UTC ---
Maybe dup of PR46909?

[Bug tree-optimization/46693] incorrect code generation with -O2 optimization enabled

[ramana at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

--- Comment #13 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> 2010-12-14 12:07:54 UTC ---
(In reply to comment #12)
> Maybe dup of PR46909?

I can verify that the fix for PR46909 fixes the issue on trunk.

I'm looking into 4.5 branch right now.


cheers
Ramana

[Bug tree-optimization/46693] incorrect code generation with -O2 optimization enabled

[ramana at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

--- Comment #14 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> 2010-12-14 12:13:00 UTC ---
It doesn't seem to fail for me with the RC for GCC 4.5.2

with -march=armv5te -mthumb
     -march=armv5te
     -march=armv7-a
     -march=armv7-a -mthumb

at -O2, -O3 and -Os

[Bug tree-optimization/46693] incorrect code generation with -O2 optimization enabled

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46693

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

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

--- Comment #15 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-01-12 20:31:24 UTC ---
Fixed so closing as such.