http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55334
--- Comment #18 from Richard Biener <rguenth at gcc dot gnu.org> 2012-12-21
14:01:33 UTC ---
(In reply to comment #17)
> > Nothing to fix for me - it's the IPA-CP decision that pessimizes things.
> Well, replacing parameter by known constant should not pessimize in general...
True, but replacing restrict parameter with sth non-restrict may be.
The language spec allows me to write
void foo (int * restrict p, int * restrict q, int n)
{
for (i = 0; i < n; ++i)
p[i] = q[n-i];
}
and call it with foo (&a[0], &a[100], n) when I know that with this
particular n it will not alias.
But without knowing 'n' (like in the mgrid case) there is no chance
that we can re-discover this non-aliasing when you propagate &a[0]
and &a[100].
