[Bug tree-optimization/21734] [4.1 regression] ICE: -ftree-vectorize, segfault

["law at redhat dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From law at redhat dot com  2005-05-25 05:55 -------
Subject: Re:  [4.1 regression] ICE:
	-ftree-vectorize, segfault

On Tue, 2005-05-24 at 14:21 +0000, pinskia at gcc dot gnu dot org wrote:
> ------- Additional Comments From pinskia at gcc dot gnu dot org  2005-05-24 14:21 -------
> Here is a C testcase:
> struct a
> {
>   int aa[4];
> };
> struct b
> {
>   struct a aa;
> };
> 
> void foo(struct b *bb)
> {
>   int i;
>   for (i=0; i<4; ++i)
>     {
>       struct a *aa = &bb->aa;
>       struct a *aa1 = aa;
>       struct a *aa2 = aa1;
>       int *d = &aa2->aa[i];
>       *d = 0;
>     }
> }
> 
> I think this is caused by the forwprop changes.  (Notice the extra variables to reproduce this bug).
Actually, this is a bug in the vectorizer code to update PHIs in duplicate
loops.  forwprop AFAICT is just exposing the latent vectorizer bug.

>From what I've been able to determine so far, the vectorizer code to
update PHIs doesn't properly handle the case where a PHI is dead.  It
is likely someone with more experience in the vectorizer code is going
to need to fix this.


Jeff



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21734