[Bug tree-optimization/94234] New: missed ccp folding for (addr + 8 * n) - (addr + 8 * (n - 1))

[fxue at os dot amperecomputing.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94234

            Bug ID: 94234
           Summary: missed ccp folding for (addr + 8 * n) - (addr + 8 * (n
                    - 1))
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fxue at os dot amperecomputing.com
  Target Milestone: ---

CCP could not fold the following expression to a constant "8":

size_t foo (char *a, size_t n)
{
  char *b1 = a + 8 * n;
  char *b2 = a + 8 * (n - 1);

  return b1 - b2;
}

But if we change b1 and b2 to integer type, folding happens.

size_t foo (char *a, size_t n)
{
  size_t b1 = (size_t)(a + 8 * n);
  size_t b2 = (size_t)(a + 8 * (n - 1));

  return b1 - b2;
}