[Bug tree-optimization/70138] New: wrong code at -O3 on x86_64-linux-gnu

[helloqirun at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70138

            Bug ID: 70138
           Summary: wrong code at -O3 on x86_64-linux-gnu
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: helloqirun at gmail dot com
  Target Milestone: ---

The current gcc trunk mis-compiles the following code on x86_64-linux-gnu at
-O3 only in both 32-bit and 64-bit modes.

It should be a 6 regression.



$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/home/absozero/trunk/root-gcc/libexec/gcc/x86_64-pc-linux-gnu/6.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc/configure --prefix=/home/absozero/trunk/root-gcc
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 6.0.0 20160307 (experimental) [trunk revision 234026] (GCC)


$ gcc-trunk -O3 abc.c
$ ./a.out
Aborted (core dumped)
$ gcc-trunk  abc.c
$ ./a.out


$ cat abc.c
double u[1782225];
int a, b, d, e;
static void foo(int *p1) {
  double c = 0.0;
  for (; a < 1335; a++) {
    b = 0;
    for (; b < 1335; b++)
      c = c + u[a + 1335 * a];
    u[1336 * a] *= 2;
  }
  *p1 = c;
}
void abort();
int main() {
  for (; d < 1782225; d++)
    u[d] = 2;
  foo(&e);
  if (e != 3564450)
    abort();
}