[PATCH] Adjust nb_iterations_upper_bound in loop header copying
Richard Sandiford
rdsandiford@googlemail.com
Fri Nov 22 14:32:00 GMT 2013
Richard Biener <rguenther@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 <rguenther@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,
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;
}
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