[Bug tree-optimization/93970] New: load via restricted pointer not eliminated after a store via a restricted pointer of incompatible type

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93970

            Bug ID: 93970
           Summary: load via restricted pointer not eliminated after a
                    store via a restricted pointer of incompatible type
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

In the test case below the test in f() is folded to false as expected, but the
similar test in g() is not folded, even though in both functions the pointers
are restricted and in g() they additionally point to incompatible types.

$ cat t.c && gcc -O2 -S -Wall -Wextra  -fdump-tree-optimized=/dev/stdout t.c
void f (int *__restrict p, int *__restrict q)
{
  int t = *q;
  *p = 0;
  if (t != *q)            // folded to false
    __builtin_abort ();
}

void g (int *__restrict p, double *__restrict q)
{ 
  double t = *q;
  *p = 0;
  if (t != *q)            // not folded
    __builtin_abort ();
}



;; Function f (f, funcdef_no=0, decl_uid=1931, cgraph_uid=1, symbol_order=0)

f (int * restrict p, int * restrict q)
{
  <bb 2> [local count: 1073741824]:
  *p_3(D) = 0;
  return;

}



;; Function g (g, funcdef_no=1, decl_uid=1936, cgraph_uid=2, symbol_order=1)

g (int * restrict p, double * restrict q)
{
  double t;

  <bb 2> [local count: 1073741824]:
  t_3 = *q_2(D);
  *p_4(D) = 0;
  if (t_3 != t_3)
    goto <bb 3>; [0.00%]
  else
    goto <bb 4>; [100.00%]

  <bb 3> [count: 0]:
  __builtin_abort ();

  <bb 4> [local count: 1073741824]:
  return;

}