[tree-ssa] Remove useless null pointer checks

[Jeff Sturm]

On Wed, 30 Jul 2003 law@redhat.com wrote:
>  >Somehow the RTL optimizers never caught on to this.
> Odd.  We've got a pass do do this at the RTL level and from the structure
> of your code I'd expect it to remove the useless check.  Very odd.

Because delete_null_pointer_checks_1 can't cope with a COMPONENT_REF,
perhaps?  The test for loads:

          if (GET_CODE (SET_SRC (set)) == MEM
              && GET_CODE ((reg = XEXP (SET_SRC (set), 0))) == REG

won't match:

    (set (reg:SI 61)
        (mem/s:SI (plus:SI (reg/v/f:SI 59 [ a ])
                (const_int 8 [0x8])) [7 <variable>.i+0 S4 A32]))

Jeff