[Bug tree-optimization/32230] [4.3 Regression] Segfault in set_bb_for_stmt with -O -ftree-vectorize

[rguenther at suse dot de]

------- Comment #7 from rguenther at suse dot de  2007-06-28 12:20 -------
Subject: Re:  [4.3 Regression] Segfault in
 set_bb_for_stmt with -O -ftree-vectorize

On Thu, 28 Jun 2007, irar at il dot ibm dot com wrote:

> 
> 
> ------- Comment #6 from irar at il dot ibm dot com  2007-06-28 11:41 -------
> ((float*) (&((sbuf_header_t *) ((buf) == &(buf)->buf[0]))->buf[0]))[i] = val;
> 
> is (after ommiting the casts)
> 
> *(1B + (i * 4)) = val;
> 
> Is that legal?

"Legal" as far as that you are not allowed to reject it at compile-time.
Of course runtime behavior looks completely undefined ;)

> Vectorizer assumes that every data-ref has base_address. In the above case we
> get the following data-ref structure:
>         base_address: 0B
>         offset from base address: 0
>         constant offset from base address: 1
>         step: 4
>         aligned to: 128
>         base_object: *0B
>         symbol tag: SMT.5
> 
> therefore, creating an empty stmt for the first access of the data-ref in the
> loop.
> 
> Before Zdenek's rewrite of data-refs analysis, it failed to create a dr here,
> and thus no segfault occurred.

I suppose rejecting NULL bases should work here?

Richard.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32230