[Bug tree-optimization/69951] New: wrong code at -O1 and above on x86_64-linux-gnu

[helloqirun at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69951

            Bug ID: 69951
           Summary: wrong code at -O1 and above 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
-O1 and above in both 32-bit and 64-bit modes.

It affects as early as gcc-4.4.3 (I don't have earlier gcc on my machine).


$ 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 20160224 (experimental) [trunk revision 233678] (GCC) 




$ gcc-trunk abc.c
$ ./a.out 
$ gcc-trunk -O1 abc.c
$ ./a.out 
Aborted (core dumped)



$ cat abc.c
int a = 1, c = 1;
extern int b __attribute__((alias("a")));
extern int d __attribute__((alias("c")));
int main(int argc) {
  int *p, *q;
  if (argc)
    p = &c, q = &d;
  else
    p = &b, q = &d;
  *p = 1;
  *q = 2;
  if (*p == 1)
    __builtin_abort();
  return 0;
}