[Bug c/42084] New: Wrong result with -Os -fno-delete-null-pointer-checks

[Bug c/42084] New: Wrong result with -Os -fno-delete-null-pointer-checks

[chenyang at cs dot utah dot edu]

We found an inconsistent result when we were testing the options used to build
Linux kernels. See the code below. BTW, I am using r154188.

yang@yang-working:~$ svngcc -O1 -o small_1 small.c
yang@yang-working:~$ ./small_1
g = 2
yang@yang-working:~$ svngcc -Os -fno-delete-null-pointer-checks -o small_s
small.c
yang@yang-working:~$ ./small_s
g = 1
yang@yang-working:~$ cat small.c
#include <stdio.h>

int g = 0;

static int
foo(int ui1, int ui2)
{
 if (ui2 == 0)
   return ui1;
 else
   return ui1 + ui2;
}

void func_2(long long p);
void func_2(long long p)
{
   if ((g > p) == (g <= foo(8, (&g != 0))))
   {
       g = 1;
   }
   else
   {
       g = 2;
   }
}

int main(void)
{
   func_2(1);
   printf("g = %d\n", g);
   return 0;
}
yang@yang-working:~$ svngcc -v
Using built-in specs.
COLLECT_GCC=svngcc
COLLECT_LTO_WRAPPER=/home/yang/compilers/libexec/gcc/i686-pc-linux-gnu/4.5.0/lto-wrapper
Target: i686-pc-linux-gnu
Configured with: ../configure --enable-lto --prefix=/home/yang/compilers
--program-prefix=svn --enable-languages=c,c++
--with-libelf=/home/yang/compilers : (reconfigured) ../configure --enable-lto
--prefix=/home/yang/compilers --program-prefix=svn
--with-libelf=/home/yang/compilers --enable-languages=c,lto,c++ --no-create
--no-recursion : (reconfigured) ../configure --enable-lto
--prefix=/home/yang/compilers --program-prefix=svn
--with-libelf=/home/yang/compilers --enable-languages=c,c++,lto --no-create
--no-recursion : (reconfigured) ../configure --enable-lto
--prefix=/home/yang/compilers --program-prefix=svn
--with-libelf=/home/yang/compilers --enable-languages=c,c++,lto --no-create
--no-recursion : (reconfigured) ../configure --enable-lto
--prefix=/home/yang/compilers --program-prefix=svn
--with-libelf=/home/yang/compilers --enable-languages=c,c++,lto --no-create
--no-recursion : (reconfigured) ../configure --enable-lto
--prefix=/home/yang/compilers --program-prefix=svn
--with-libelf=/home/yang/compilers --enable-languages=c,c++,lto --no-create
--no-recursion
Thread model: posix
gcc version 4.5.0 20091115 (experimental) (GCC)


-- 
           Summary: Wrong result with -Os -fno-delete-null-pointer-checks
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: chenyang at cs dot utah dot edu
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42084

[Bug c/42084] Wrong result with -Os -fno-delete-null-pointer-checks

[chenyang at cs dot utah dot edu]

------- Comment #1 from chenyang at cs dot utah dot edu  2009-11-17 21:13 -------
The inconsistent results also show up with the following combinations:

-O3 -fno-delete-null-pointer-checks
-O2 -fno-delete-null-pointer-checks


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42084

[Bug c/42084] Wrong result with -Os -fno-delete-null-pointer-checks

[chenyang at cs dot utah dot edu]

------- Comment #2 from chenyang at cs dot utah dot edu  2009-11-17 21:21 -------
I am sorry I should also mention that the code works with "-Os", or "-O3" or
"-O2", but not with the extra flag -fno-delete-null-pointer-checks. 


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42084

[Bug tree-optimization/42084] [4.5 Regression] Wrong result with -Os -fno-delete-null-pointer-checks

[rguenth at gcc dot gnu dot org]

------- Comment #3 from rguenth at gcc dot gnu dot org  2009-11-18 09:57 -------
Confirmed.  Only fails with -m32 on x86_64.  It is VRP that triggers the
miscompile, thus -O1 -ftree-vrp -fno-delete-null-pointer-checks is enough.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
          Component|c                           |tree-optimization
     Ever Confirmed|0                           |1
           Keywords|                            |wrong-code
      Known to fail|                            |4.5.0
      Known to work|                            |4.4.2
   Last reconfirmed|0000-00-00 00:00:00         |2009-11-18 09:57:53
               date|                            |
            Summary|Wrong result with -Os -fno- |[4.5 Regression] Wrong
                   |delete-null-pointer-checks  |result with -Os -fno-delete-
                   |                            |null-pointer-checks
   Target Milestone|---                         |4.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42084

[Bug tree-optimization/42084] [4.5 Regression] Wrong result with -Os -fno-delete-null-pointer-checks

[rguenth at gcc dot gnu dot org]

-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42084

[Bug rtl-optimization/42084] [4.5 Regression] Wrong result with -Os -fno-delete-null-pointer-checks

[rguenth at gcc dot gnu dot org]

------- Comment #4 from rguenth at gcc dot gnu dot org  2009-11-27 13:22 -------
Actually it is some RTL optimization pass that miscompiles this (func_2).
With -fno-delete-null-pointer-checks we defer evaluating &g != 0 until
expansion which then exposes CCP opportunities.

With -O1 -fno-delete-null-pointer-checks -m32 -ftree-vrp -fno-if-conversion we
generate

func_2:
        pushl   %ebp
        movl    %esp, %ebp
        cmpl    $9, g
        jg      .L5
        movl    $1, g
        jmp     .L1
.L5:
        movl    $2, g
.L1:
        popl    %ebp
        ret

which looks good apart from that we have deleted the comparison against p.
This seems to happen between initial/final RTL during expansion.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |matz at gcc dot gnu dot org
          Component|tree-optimization           |rtl-optimization


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42084

[Bug rtl-optimization/42084] [4.5 Regression] Wrong result with -Os -fno-delete-null-pointer-checks

[rguenth at gcc dot gnu dot org]

------- Comment #5 from rguenth at gcc dot gnu dot org  2009-11-27 13:22 -------
int g = 0;
static int
foo(int ui1, int ui2)
{
 if (ui2 == 0)
   return ui1;
 else
   return ui1 + ui2;
}
void func_2(long long p)
{
   if ((g > p) == (g <= foo(8, (&g != 0))))
     g = 1;
   else
     g = 2;
}
extern void abort (void);
int main(void)
{
   func_2(1);
   if (g != 2)
     abort ();
   return 0;
}


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42084

[Bug rtl-optimization/42084] [4.5 Regression] Wrong result with -Os -fno-delete-null-pointer-checks

[matz at gcc dot gnu dot org]

------- Comment #6 from matz at gcc dot gnu dot org  2009-11-27 14:25 -------
Mine.


-- 

matz at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |matz at gcc dot gnu dot org
                   |dot org                     |
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2009-11-18 09:57:53         |2009-11-27 14:25:12
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42084

[Bug rtl-optimization/42084] [4.5 Regression] Wrong result with -Os -fno-delete-null-pointer-checks

[matz at gcc dot gnu dot org]

------- Comment #7 from matz at gcc dot gnu dot org  2009-11-27 15:36 -------
Subject: Bug 42084

Author: matz
Date: Fri Nov 27 15:35:50 2009
New Revision: 154709

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=154709
Log:
        PR rtl-optimization/42084
        * cfgexpand.c (maybe_cleanup_end_of_block): Add new parameter,
        use it to stop walking.
        (expand_gimple_cond): Adjust call to above.

testsuite/
        * gcc.dg/pr42084.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/pr42084.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/cfgexpand.c
    trunk/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42084

[Bug rtl-optimization/42084] [4.5 Regression] Wrong result with -Os -fno-delete-null-pointer-checks

[matz at gcc dot gnu dot org]

------- Comment #8 from matz at gcc dot gnu dot org  2009-11-27 15:37 -------
Fixed.


-- 

matz at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42084

[Bug rtl-optimization/42084] [4.5 Regression] Wrong result with -Os -fno-delete-null-pointer-checks

[hjl at gcc dot gnu dot org]

------- Comment #9 from hjl at gcc dot gnu dot org  2009-12-11 23:38 -------
Subject: Bug 42084

Author: hjl
Date: Fri Dec 11 23:36:24 2009
New Revision: 155184

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=155184
Log:
Backport testcases from trunk.

2009-12-11  H.J. Lu  <hongjiu.lu@intel.com>

        Backport from mainline:
        2009-12-11  Dodji Seketeli  <dodji@redhat.com>

        PR c++/42225
        * g++.dg/template/typedef24.C: New test.
        * g++.dg/template/typedef25.C: New test.

        2009-12-11  Dodji Seketeli  <dodji@redhat.com>

        PR c++/42251
        * g++.dg/template/const3.C: New test.

        2009-12-10  Jakub Jelinek  <jakub@redhat.com>

        PR c++/42317
        * g++.dg/opt/dtor2.C: New test.
        * g++.dg/opt/dtor2.h: New file.
        * g++.dg/opt/dtor2-aux.cc: New file.

        2009-12-10  Jan Hubicka  <jh@suse.cz>

        PR middle-end/42110
        * g++.dg/torture/pr42110.C: new file.

        2009-12-07  Jakub Jelinek  <jakub@redhat.com>

        PR debug/42244
        * gcc.dg/debug/pr42244.c: New test.

        2009-12-04  David Daney  <ddaney@caviumnetworks.com>

        PR rtl-optimization/42164
        * gcc.c-torture/compile/pr42164.c: New test.

        2009-12-03  Jason Merrill  <jason@redhat.com>

        PR c++/41611
        * g++.dg/abi/guard2.C: New.

        2009-12-03  Dodji Seketeli  <dodji@redhat.com>

        PR c++/42217
        * g++.dg/other/bitfield4.C: New test.

        2009-12-03  Jakub Jelinek  <jakub@redhat.com>

        PR c++/42256
        * g++.dg/inherit/thunk11.C: New test.
        * g++.dg/inherit/thunk11.h: New file.
        * g++.dg/inherit/thunk11-aux.cc: New file.

        2009-12-01  Martin Jambor  <mjambor@suse.cz>

        PR tree-optimization/42237
        * gcc.c-torture/compile/pr42237.c: New test.

        2009-12-01  Paolo Carlini  <paolo.carlini@oracle.com>

        PR c++/42057
        * g++.dg/parse/crash54.C: New.

        2009-11-30  Martin Jambor  <mjambor@suse.cz>

        PR middle-end/42196
        * gcc.c-torture/compile/pr42196-1.c: New test.
        * gcc.c-torture/compile/pr42196-2.c: New test.
        * gcc.c-torture/compile/pr42196-3.c: New test.

        2009-11-30  Dodji Seketeli  <dodji@redhat.com>

        PR c++/42069
        * g++.dg/template/typedef23.C: New test.

        2009-11-29  H.J. Lu  <hongjiu.lu@intel.com>

        PR tree-optimization/41961
        * g++.dg/tree-ssa/pr41961.C: New.

        2009-11-29  Ira Rosen  <irar@il.ibm.com>

        PR tree-optimization/42193
        * gcc.dg/vect/pr42193.c: New test.

        2009-11-28  Richard Guenther  <rguenther@suse.de>

        PR tree-optimization/42183
        * g++.dg/torture/pr42183.C: New testcase.

        2009-11-27  Martin Jambor  <mjambor@suse.cz>

        PR middle-end/42006
        * gcc.c-torture/execute/pr42006.c: New test.

        2009-11-27  Michael Matz  <matz@suse.de>

        PR rtl-optimization/42084
        * gcc.dg/pr42084.c: New test.

        2009-11-27  Michael Matz  <matz@suse.de>

        PR c++/41906
        * g++.dg/tree-ssa/pr41906.C: New testcase.

        2009-11-26  Michael Matz  <matz@suse.de>

        PR tree-optimization/41905
        * g++.dg/tree-ssa/pr41905.C: New testcase.

        2009-11-24  Richard Guenther  <rguenther@suse.de>

        PR tree-optimization/42142
        * gcc.c-torture/execute/pr42142.c: New testcase.

        2009-11-24  Martin Jambor  <mjambor@suse.cz>

        PR tree-optimization/42154
        * gcc.c-torture/execute/pr42154.c: New test.

        2009-11-21  Martin Jambor  <mjambor@suse.cz>

        PR middle-end/42025
        * gcc.c-torture/compile/pr42025-1.c: New test.
        * gcc.c-torture/compile/pr42025-2.c: New test.

        2009-11-21  Jakub Jelinek  <jakub@redhat.com>

        PR tree-optimization/42078
        * gcc.dg/pr42078.c: New test.

Added:
    branches/gcc-4_4-branch/gcc/testsuite/g++.dg/abi/guard2.C
      - copied unchanged from r155170, trunk/gcc/testsuite/g++.dg/abi/guard2.C
    branches/gcc-4_4-branch/gcc/testsuite/g++.dg/inherit/thunk11-aux.cc
      - copied unchanged from r155170,
trunk/gcc/testsuite/g++.dg/inherit/thunk11-aux.cc
    branches/gcc-4_4-branch/gcc/testsuite/g++.dg/inherit/thunk11.C
      - copied unchanged from r155170,
trunk/gcc/testsuite/g++.dg/inherit/thunk11.C
    branches/gcc-4_4-branch/gcc/testsuite/g++.dg/inherit/thunk11.h
      - copied unchanged from r155170,
trunk/gcc/testsuite/g++.dg/inherit/thunk11.h
    branches/gcc-4_4-branch/gcc/testsuite/g++.dg/opt/dtor2-aux.cc
      - copied unchanged from r155170,
trunk/gcc/testsuite/g++.dg/opt/dtor2-aux.cc
    branches/gcc-4_4-branch/gcc/testsuite/g++.dg/opt/dtor2.C
      - copied unchanged from r155170, trunk/gcc/testsuite/g++.dg/opt/dtor2.C
    branches/gcc-4_4-branch/gcc/testsuite/g++.dg/opt/dtor2.h
      - copied unchanged from r155170, trunk/gcc/testsuite/g++.dg/opt/dtor2.h
    branches/gcc-4_4-branch/gcc/testsuite/g++.dg/other/bitfield4.C
      - copied unchanged from r155170,
trunk/gcc/testsuite/g++.dg/other/bitfield4.C
    branches/gcc-4_4-branch/gcc/testsuite/g++.dg/parse/crash54.C
      - copied unchanged from r155172,
trunk/gcc/testsuite/g++.dg/parse/crash54.C
    branches/gcc-4_4-branch/gcc/testsuite/g++.dg/template/const3.C
      - copied unchanged from r155170,
trunk/gcc/testsuite/g++.dg/template/const3.C
    branches/gcc-4_4-branch/gcc/testsuite/g++.dg/template/typedef23.C
      - copied unchanged from r155181,
trunk/gcc/testsuite/g++.dg/template/typedef23.C
    branches/gcc-4_4-branch/gcc/testsuite/g++.dg/template/typedef24.C
      - copied unchanged from r155170,
trunk/gcc/testsuite/g++.dg/template/typedef24.C
    branches/gcc-4_4-branch/gcc/testsuite/g++.dg/template/typedef25.C
      - copied unchanged from r155170,
trunk/gcc/testsuite/g++.dg/template/typedef25.C
    branches/gcc-4_4-branch/gcc/testsuite/g++.dg/torture/pr42110.C
      - copied unchanged from r155170,
trunk/gcc/testsuite/g++.dg/torture/pr42110.C
    branches/gcc-4_4-branch/gcc/testsuite/g++.dg/torture/pr42183.C
      - copied unchanged from r155181,
trunk/gcc/testsuite/g++.dg/torture/pr42183.C
    branches/gcc-4_4-branch/gcc/testsuite/g++.dg/tree-ssa/pr41905.C
      - copied unchanged from r155182,
trunk/gcc/testsuite/g++.dg/tree-ssa/pr41905.C
    branches/gcc-4_4-branch/gcc/testsuite/g++.dg/tree-ssa/pr41906.C
      - copied unchanged from r155182,
trunk/gcc/testsuite/g++.dg/tree-ssa/pr41906.C
    branches/gcc-4_4-branch/gcc/testsuite/g++.dg/tree-ssa/pr41961.C
      - copied unchanged from r155181,
trunk/gcc/testsuite/g++.dg/tree-ssa/pr41961.C
    branches/gcc-4_4-branch/gcc/testsuite/gcc.c-torture/compile/pr42025-1.c
      - copied unchanged from r155182,
trunk/gcc/testsuite/gcc.c-torture/compile/pr42025-1.c
    branches/gcc-4_4-branch/gcc/testsuite/gcc.c-torture/compile/pr42025-2.c
      - copied unchanged from r155182,
trunk/gcc/testsuite/gcc.c-torture/compile/pr42025-2.c
    branches/gcc-4_4-branch/gcc/testsuite/gcc.c-torture/compile/pr42164.c
      - copied unchanged from r155170,
trunk/gcc/testsuite/gcc.c-torture/compile/pr42164.c
    branches/gcc-4_4-branch/gcc/testsuite/gcc.c-torture/compile/pr42196-1.c
      - copied unchanged from r155181,
trunk/gcc/testsuite/gcc.c-torture/compile/pr42196-1.c
    branches/gcc-4_4-branch/gcc/testsuite/gcc.c-torture/compile/pr42196-2.c
      - copied unchanged from r155181,
trunk/gcc/testsuite/gcc.c-torture/compile/pr42196-2.c
    branches/gcc-4_4-branch/gcc/testsuite/gcc.c-torture/compile/pr42196-3.c
      - copied unchanged from r155181,
trunk/gcc/testsuite/gcc.c-torture/compile/pr42196-3.c
    branches/gcc-4_4-branch/gcc/testsuite/gcc.c-torture/compile/pr42237.c
      - copied unchanged from r155171,
trunk/gcc/testsuite/gcc.c-torture/compile/pr42237.c
    branches/gcc-4_4-branch/gcc/testsuite/gcc.c-torture/execute/pr42006.c
      - copied unchanged from r155181,
trunk/gcc/testsuite/gcc.c-torture/execute/pr42006.c
    branches/gcc-4_4-branch/gcc/testsuite/gcc.c-torture/execute/pr42142.c
      - copied unchanged from r155182,
trunk/gcc/testsuite/gcc.c-torture/execute/pr42142.c
    branches/gcc-4_4-branch/gcc/testsuite/gcc.c-torture/execute/pr42154.c
      - copied unchanged from r155182,
trunk/gcc/testsuite/gcc.c-torture/execute/pr42154.c
    branches/gcc-4_4-branch/gcc/testsuite/gcc.dg/debug/pr42244.c
      - copied unchanged from r155170,
trunk/gcc/testsuite/gcc.dg/debug/pr42244.c
    branches/gcc-4_4-branch/gcc/testsuite/gcc.dg/pr42078.c
      - copied unchanged from r155182, trunk/gcc/testsuite/gcc.dg/pr42078.c
    branches/gcc-4_4-branch/gcc/testsuite/gcc.dg/pr42084.c
      - copied unchanged from r155182, trunk/gcc/testsuite/gcc.dg/pr42084.c
    branches/gcc-4_4-branch/gcc/testsuite/gcc.dg/vect/pr42193.c
      - copied unchanged from r155181,
trunk/gcc/testsuite/gcc.dg/vect/pr42193.c
Modified:
    branches/gcc-4_4-branch/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42084