[Bug tree-optimization/61045] New: Wrong constant folding

[Bug tree-optimization/61045] New: Wrong constant folding

[ishiura-compiler at ml dot kwansei.ac.jp]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61045

            Bug ID: 61045
           Summary: Wrong constant folding
           Product: gcc
           Version: 4.10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ishiura-compiler at ml dot kwansei.ac.jp

GCC 4.4.7 - 4.10.0 for x86_64 miscompiles the following code.

   $ cat test.c

   int main (void)
   {
      long a = 0;
      long b = 0x7FFFFFFFFFFFFFFFL;
      int t = (a - 2) > (b - 1);
      if (t != 0) { __builtin_abort(); };
      return 0;
   }

   $ x86_64-unknown-linux-gnu-gcc-4.10.0 test.c -O2
   $ ./a.out 
   Aborted (core dumped)

   $ x86_64-unknown-linux-gnu-gcc-4.10.0 -v        
   Using built-in specs.
   COLLECT_GCC=x86_64-unknown-linux-gnu-gcc-4.10.0
  
COLLECT_LTO_WRAPPER=/usr/local/x86_64-tools/gcc-4.10.0/libexec/gcc/x86_64-unknown-linux-gnu/4.10.0/lto-wrapper
   Target: x86_64-unknown-linux-gnu
   Configured with: /home/hassy/gcc/configure
   --prefix=/usr/local/x86_64-tools/gcc-4.10.0/
   --with-gmp=/usr/local/gmp-5.1.1/ --with-mpfr=/usr/local/mpfr-3.1.2/
   --with-mpc=/usr/local/mpc-1.0.1/ --disable-multilib
   --disable-nls --enable-languages=c
   Thread model: posix
   gcc version 4.10.0 20140502 (experimental) (GCC)

[Bug tree-optimization/61045] Wrong constant folding

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61045

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-05-03
                 CC|                            |mpolacek at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Confirmed.  Fold introduces signed overflow:
    long int a = 0;
    long int b = 9223372036854775807;
    int t = b + 1 < a;

[Bug middle-end/61045] [4.7/4.8/4.9/4.10 Regression] Wrong constant folding

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61045

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|tree-optimization           |middle-end
   Target Milestone|---                         |4.7.4
            Summary|Wrong constant folding      |[4.7/4.8/4.9/4.10
                   |                            |Regression] Wrong constant
                   |                            |folding

[Bug middle-end/61045] [4.7/4.8/4.9/4.10 Regression] Wrong constant folding

[mikpelinux at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61045

Mikael Pettersson <mikpelinux at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mikpelinux at gmail dot com

--- Comment #2 from Mikael Pettersson <mikpelinux at gmail dot com> ---
Fails also with gcc 4.3.6, works with gcc 4.2.4 and 4.1.2.

[Bug middle-end/61045] [4.7/4.8/4.9/4.10 Regression] Wrong constant folding

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61045

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
I believe this started with addition of this folding in r117931, but didn't
verify it.

[Bug middle-end/61045] [4.7/4.8/4.9/4.10 Regression] Wrong constant folding

[mikpelinux at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61045

--- Comment #4 from Mikael Pettersson <mikpelinux at gmail dot com> ---
According to my bisection it did start with r117931.

[Bug middle-end/61045] [4.7/4.8/4.9/4.10 Regression] Wrong constant folding

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61045

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Mine then.

[Bug middle-end/61045] [4.7/4.8/4.9/4.10 Regression] Wrong constant folding

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61045

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
      /* Put the constant on the side where it doesn't overflow and is
         of lower absolute value than before.  */
      cst = int_const_binop (TREE_CODE (arg0) == TREE_CODE (arg1)
                             ? MINUS_EXPR : PLUS_EXPR,
                             const2, const1);
      if (!TREE_OVERFLOW (cst)
          && tree_int_cst_compare (const2, cst) == tree_int_cst_sgn (const2))

const2 is -1 here and cst is 1.  So that means just checking for
"lower absolute value" is wrong.  A sign-change is obviously not ok either.

[Bug middle-end/61045] [4.7/4.8/4.9/4.10 Regression] Wrong constant folding

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61045

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
Author: rguenth
Date: Wed May 28 12:44:11 2014
New Revision: 211018

URL: http://gcc.gnu.org/viewcvs?rev=211018&root=gcc&view=rev
Log:
2014-05-28  Richard Biener  <rguenther@suse.de>

    PR middle-end/61045
    * fold-const.c (fold_comparison): When folding
    X +- C1 CMP Y +- C2 to X CMP Y +- C2 +- C1 also ensure
    the sign of the remaining constant operand stays the same.

    * gcc.dg/pr61045.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.dg/pr61045.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/fold-const.c
    trunk/gcc/testsuite/ChangeLog

[Bug middle-end/61045] [4.7/4.8/4.9/4.10 Regression] Wrong constant folding

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61045

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
Author: rguenth
Date: Wed May 28 12:46:39 2014
New Revision: 211019

URL: http://gcc.gnu.org/viewcvs?rev=211019&root=gcc&view=rev
Log:
2014-05-28  Richard Biener  <rguenther@suse.de>

    Backport from mainline
    2014-05-28  Richard Biener  <rguenther@suse.de>

    PR middle-end/61045
    * fold-const.c (fold_comparison): When folding
    X +- C1 CMP Y +- C2 to X CMP Y +- C2 +- C1 also ensure
    the sign of the remaining constant operand stays the same.

    * gcc.dg/pr61045.c: New testcase.

    2014-05-05  Richard Biener  <rguenther@suse.de>

    PR middle-end/61010
    * fold-const.c (fold_binary_loc): Consistently avoid
    canonicalizing X & CST away from a CST that is the mask
    of a mode.

    * gcc.dg/torture/pr61010.c: New testcase.

    2014-04-28  Richard Biener  <rguenther@suse.de>

    PR tree-optimization/60979
    * graphite-scop-detection.c (scopdet_basic_block_info): Reject
    SCOPs that end in a block with a successor with abnormal
    predecessors.

    * gcc.dg/graphite/pr60979.c: New testcase.

Added:
    branches/gcc-4_9-branch/gcc/testsuite/gcc.dg/graphite/pr60979.c
    branches/gcc-4_9-branch/gcc/testsuite/gcc.dg/pr61045.c
    branches/gcc-4_9-branch/gcc/testsuite/gcc.dg/torture/pr61010.c
Modified:
    branches/gcc-4_9-branch/gcc/ChangeLog
    branches/gcc-4_9-branch/gcc/fold-const.c
    branches/gcc-4_9-branch/gcc/graphite-scop-detection.c
    branches/gcc-4_9-branch/gcc/testsuite/ChangeLog

[Bug middle-end/61045] [4.7/4.8 Regression] Wrong constant folding

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61045

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.7.4                       |4.8.4

--- Comment #9 from Richard Biener <rguenth at gcc dot gnu.org> ---
The 4.7 branch is being closed, moving target milestone to 4.8.4.

[Bug middle-end/61045] [4.8 Regression] Wrong constant folding

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61045

--- Comment #10 from Richard Biener <rguenth at gcc dot gnu.org> ---
Author: rguenth
Date: Tue Sep  9 13:17:51 2014
New Revision: 215073

URL: https://gcc.gnu.org/viewcvs?rev=215073&root=gcc&view=rev
Log:
2014-09-09  Richard Biener  <rguenther@suse.de>

    Backport from mainline
    2014-05-05  Richard Biener  <rguenther@suse.de>

    PR middle-end/61010
    * fold-const.c (fold_binary_loc): Consistently avoid
    canonicalizing X & CST away from a CST that is the mask
    of a mode.

    * gcc.dg/torture/pr61010.c: New testcase.

    2014-05-28  Richard Biener  <rguenther@suse.de>

    PR middle-end/61045
    * fold-const.c (fold_comparison): When folding
    X +- C1 CMP Y +- C2 to X CMP Y +- C2 +- C1 also ensure
    the sign of the remaining constant operand stays the same.

    * gcc.dg/pr61045.c: New testcase.

    2014-08-11  Richard Biener  <rguenther@suse.de>

    PR tree-optimization/62075
    * tree-vect-slp.c (vect_detect_hybrid_slp_stmts): Properly
    handle uses in patterns.

    * gcc.dg/vect/pr62075.c: New testcase.

Added:
    branches/gcc-4_8-branch/gcc/testsuite/gcc.dg/pr61045.c
    branches/gcc-4_8-branch/gcc/testsuite/gcc.dg/torture/pr61010.c
    branches/gcc-4_8-branch/gcc/testsuite/gcc.dg/vect/pr62075.c
Modified:
    branches/gcc-4_8-branch/gcc/ChangeLog
    branches/gcc-4_8-branch/gcc/fold-const.c
    branches/gcc-4_8-branch/gcc/testsuite/ChangeLog
    branches/gcc-4_8-branch/gcc/tree-vect-slp.c

[Bug middle-end/61045] [4.8 Regression] Wrong constant folding

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61045

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
      Known to work|4.10.0                      |4.8.4, 5.0
         Resolution|---                         |FIXED

--- Comment #11 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed.