On Fri, 22 Nov 2013, Richard Sandiford wrote:
> Richard Biener <rguent...@suse.de> writes:
> > This patch decrements nb_iterations_upper_bound by one after we copied
> > the loop header. This allows niter + 1 to more often not overflow.
> >
> > Bootstrapped and tested on x86_64-unknown-linux-gnu, installed to trunk.
> >
> > Richard.
> >
> > 2013-11-21 Richard Biener <rguent...@suse.de>
> >
> > * tree-ssa-loop-ch.c (copy_loop_headers): Decrement
> > nb_iterations_upper_bound by one.
>
> This seems to regress the following testcase, compiled at -O2 on
> x86_64-linux-gnu.
Thanks for the testcase, I have reverted the patch and installed
the testcase.
Thanks,
Richard.
> Thanks,
> Richard
>
>
> void __attribute__ ((noinline))
> f (long *s, long *t, int len1, int len2)
> {
> int i, j;
>
> j = 2;
> for (i = len1 - 1; i >= 0; i--)
> {
> s[j--] = (i < len2 ? t[i] : t[len2 - 1] < 0 ? -1 : 0);
> if (j < 0)
> break;
> }
> }
>
> long s[3];
> long t[3];
>
> int
> main (void)
> {
> t[0] = 1;
> t[1] = 2;
> t[2] = 3;
> f (s, t, 3, 3);
> if (memcmp (s, t, sizeof (s)) != 0)
> abort ();
> return 0;
> }
