[Bug tree-optimization/86066] New: wrong code at -Os and above on x86-64-linux-gnu

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86066

            Bug ID: 86066
           Summary: wrong code at -Os and above on x86-64-linux-gnu
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu
  Target Milestone: ---

This appears to be a recent regression.

$ gcctk -v
Using built-in specs.
COLLECT_GCC=gcctk
COLLECT_LTO_WRAPPER=/home/su/software/tmp/gcc/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/9.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-source-trunk/configure --enable-languages=c,c++,lto
--prefix=/home/su/software/tmp/gcc/gcc-trunk --disable-bootstrap
Thread model: posix
gcc version 9.0.0 20180606 (experimental) [trunk revision 261226] (GCC) 
$ 
$ gcctk -O1 small.c; ./a.out
$ 
$ gcctk -Os small.c
$ timeout -s 9 5 ./a.out
Killed
$ 

--------------------------------

struct A
{
  int b:2;
  int c:2;
  unsigned d:8;
};

int main ()
{
  struct A t = { 0, 0, 2 };
 L:
  t.d = ~(~(~0 % t.d) % 2);
  if (!t.d)
    goto L;
  return 0;
}