[Bug tree-optimization/88621] New: wrong code at -O1 and above on x86_64-linux-gnu in 64-bit mode (not in 32-bit mode)

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88621

            Bug ID: 88621
           Summary: wrong code at -O1 and above on x86_64-linux-gnu in
                    64-bit mode (not in 32-bit mode)
           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 seems 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 20181226 (experimental) [trunk revision 267421] (GCC) 
$ 
$ gcctk -O0 small.c; ./a.out
$ 
$ gcctk -O1 small.c
$ timeout -s 9 5 ./a.out
Killed
$ 


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


struct S
{
  int b:4;
  int c; 
} e = { -1, 0 };

int d, f;

int main ()
{
  while (f)
    {
      struct S g = { 0, 0 };
      e = g;
    }
L:
  while (e.b > 0)
    ;
  e.b = 0;
  if (d)
    goto L;
  return 0;
}