[Bug c/38817] New: GCC wrongly optimize a modulo operation.

[jlerouge at apple dot com]

The following code seems to be wrongly optimized by GCC:

int main(int argc, char **argv) {
   unsigned int foo = 3;
   return ((838237499u * foo - 2137600414u) % 11u);
}

always return 0 on my machine, it should return 7. GCC seems to be optimizing
the modulo operation (even with -O0).

GCC version:
debian:~ $ gcc -v
Using built-in specs.
Target: i486-linux-gnu
Configured with: ../src/configure -v
--enable-languages=c,c++,fortran,objc,obj-c++,treelang --prefix=/usr
--enable-shared --with-system-zlib --libexecdir=/usr/lib
--without-included-gettext --enable-threads=posix --enable-nls
--with-gxx-include-dir=/usr/include/c++/4.2 --program-suffix=-4.2
--enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --enable-mpfr
--disable-libmudflap --enable-targets=all --enable-checking=release
--build=i486-linux-gnu --host=i486-linux-gnu --target=i486-linux-gnu
Thread model: posix
gcc version 4.2.3 (Debian 4.2.3-1)

Command line used:
debian:~ $ gcc -o t t.c

Thanks,
Julien


-- 
           Summary: GCC wrongly optimize a modulo operation.
           Product: gcc
           Version: 4.2.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jlerouge at apple dot com
 GCC build triplet: i486-linux-gnu
  GCC host triplet: i486-linux-gnu
GCC target triplet: i486-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38817