Fix PR tree-optimization/77808, ICE in duplicate_ssa_name_ptr_info, at tree-ssanames.c:630 starting with r240439

[Matthew Fortune]

Richard Biener <richard.guenther@gmail.com> writes:
> On Sat, Oct 1, 2016 at 3:35 AM, Doug Gilmore <Doug.Gilmore@imgtec.com>
> wrote:
> > My commit r240439 didn't handle the situation where setting --param
> > prefetch-latency=0 can cause the prefetch address to be the same as
> > the original address.  In this case, no copying of points-to
> > information should be done.
> >
> > Bootstrapped and regression tested on x86_64-linux, ok for trunk?
> 
> Ok.
> 
> RIchard.

Committed as r240749.

(I updated the changelog to say what changed)

gcc/
        PR tree-optimization/77808
        * tree-ssa-loop-prefetch.c (issue_prefetch_ref): Check base_addr
        and addr are different before copying points-to information.

gcc/testsuite
        PR tree-optimization/77808
        * gcc.dg/tree-ssa/pr77808.c: New testcase.


Matthew