[Bug tree-optimization/87859] New: [8/9 Regression] store-merging miscompilation of mesa

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87859

            Bug ID: 87859
           Summary: [8/9 Regression] store-merging miscompilation of mesa
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jakub at gcc dot gnu.org
  Target Milestone: ---

struct S {
  union F {
    struct T {
#define A(n) unsigned n:1;
#define B(n) A(n##0) A(n##1) A(n##2) A(n##3) A(n##4) \
             A(n##5) A(n##6) A(n##7) A(n##8) A(n##9)
      B(f) B(f1) B(f2) B(f3) B(f4) B(f5)
      A(f60) A(f61) A(f62) A(f63) A(f64) A(f65) A(f66)
    } q;
    unsigned int i[3];
  } f;
};

struct S s = {
  .f.q.f0 = 1, .f.q.f1 = 1, .f.q.f2 = 1, .f.q.f5 = 1, .f.q.f6 = 1,
  .f.q.f7 = 1, .f.q.f8 = 1, .f.q.f9 = 1, .f.q.f13 = 1, .f.q.f14 = 1,
  .f.q.f15 = 1, .f.q.f16 = 1, .f.q.f17 = 1, .f.q.f19 = 1, .f.q.f21 = 1,
  .f.q.f66 = 1
};

__attribute__((noipa)) void
bar (unsigned *x)
{
  if (x[0] != s.f.i[0] || x[1] != s.f.i[1] || x[2] != s.f.i[2])
    __builtin_abort ();
}

__attribute__((noipa)) void
foo (unsigned char *state)
{
  struct S i;
  i.f.i[0] = 0;
  i.f.i[1] = 0;
  i.f.i[2] = 0;
  i.f.q.f7 = 1;
  i.f.q.f2 = 1;
  i.f.q.f21 = 1;
  i.f.q.f19 = 1;
  i.f.q.f14 = 1;
  i.f.q.f5 = 1;
  i.f.q.f0 = 1;
  i.f.q.f15 = 1;
  i.f.q.f16 = 1;
  i.f.q.f6 = 1;
  i.f.q.f9 = 1;
  i.f.q.f17 = 1;
  i.f.q.f1 = 1;
  i.f.q.f8 = 1;
  i.f.q.f13 = 1;
  i.f.q.f66 = 1;
  if (*state)
    {
      i.f.q.f37 = 1;
      i.f.q.f38 = 1;
      i.f.q.f39 = 1;
      i.f.q.f40 = 1;
      i.f.q.f41 = 1;
      i.f.q.f36 = 1;
    }
  bar (i.f.i);
}

int
main ()
{
  unsigned char z = 0;
  foo (&z);
  return 0;
}

started failing with r264232.