[PTR-PLUS] Fix up forwprop testcase

[Andrew_Pinski@PlayStation.Sony.Com]

Hi,
  This fixes up the new forwprop testcase which I added to the trunk.  The 
problem here was that we were checking for PLUS_EXPR and then also 
checking for a cast which is no longer there.


Committed after a bootstrap/test on i686-linux-gnu with 2 regressions (the 
2 regressions are due to forwprop doing a better job and data-ref not 
understanding the IR any more, see PR 31995 and 31996 for more details and 
a testcase for the mainline).

Thanks,
Andrew Pinski

ChangeLog:

        * tree-ssa-forwprop.c
        (forward_propagate_addr_into_variable_array_index):
        Don't expect there to be a cast for the index as that does not 
exist anymore.
        (forward_propagate_addr_expr_1): Check for
        POINTER_PLUS_EXPR instead of PLUS_EXPR.
        Don't check for the first operand of the
        POINTER_PLUS_EXPR was the index as it
        cannot be.

        * gcc.dg/tree-ssa/forwprop-1.c: New testcase.