[Bug tree-optimization/57656] New: Wrong constant folding

["ishiura-compiler at ml dot kwansei.ac.jp" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57656

            Bug ID: 57656
           Summary: Wrong constant folding
           Product: gcc
           Version: 4.8.2
            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 4.8.2 for i686 miscompiles the following code.

    $ cat error.c

    int main (void)
    {
        int a = -1;
        int b = 2147483647;
        int c = 2;
        int t = 1 - ((a - b) / c);   // t = 1 - ( -2147483648 / 2 )

        if (t != 1073741825) { __builtin_abort(); }
        return 0;
    }

    $ i686-pc-linux-gnu-gcc-4.8.2 error.c -O2
    $ ./a.out
    Aborted (core dumped)

There was no problem with an x86_64 target.

    $ i686-pc-linux-gnu-gcc-4.8.2 -v
    Using built-in specs.
    COLLECT_GCC=i686-pc-linux-gnu-gcc-4.8.2
   
COLLECT_LTO_WRAPPER=/usr/local/i686-tools/gcc-4.8.2/libexec/gcc/i686-pc-linux-gnu/4.8.2/lto-wrapper
    Target: i686-pc-linux-gnu
    Configured with: /home/hassy/gcc/configure
    --prefix=/usr/local/i686-tools/gcc-4.8.2/
    --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 4.8.2 20130607 (prerelease) (GCC)