[Bug middle-end/39297] [4.4 Regression] gcc.dg/tree-ssa/loop-31.c

["rakdver at kam dot mff dot cuni dot cz" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #12 from rakdver at kam dot mff dot cuni dot cz  2009-02-25 22:41 -------
Subject: Re:  [4.4 Regression] gcc.dg/tree-ssa/loop-31.c

> ------- Comment #11 from hjl dot tools at gmail dot com  2009-02-25 19:18 -------
> (In reply to comment #10)
> > The difference between
> > 
> > >   D.1254 = &a[0] + ((long unsigned int) ((unsigned int) len + 4294967295) + 1)
> > > * 2;
> > 
> > (original) and
> > 
> > >   D.1255 = ((long unsigned int) &a + 2) + (long unsigned int) ((unsigned int)
> > >            len + 4294967295) * 2;
> > 
> > (current) is mostly cosmetical; the test in the testcase should be made more
> > robust, but other than that, there is no regression here.
> > 
> 
> The new loop is
> 
> .L3:
>         st2 [r14] = r33, 2
>         ;;
>         cmp.ne p6, p7 = r15, r14
>         (p6) br.cond.sptk .L3
> 
> The old loop is
> 
>        mov ar.lc = r15
> .L3:
>         st2 [r14] = r33, 2
>         ;;
>         br.cloop.sptk.few .L3
> 
> They are quite different.

nevertheless, loop-31.c test is not supposed to test this; it just
checks whether strength reduction is performed correctly.  I think we
already have another PR regarding the problem that strength reduction
and iv elimination on tree level may cause rtl level # of iterations
analysis to fail (which leads to the code difference).


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39297