[Bug tree-optimization/42652] vectorizer created unaligned vector insns

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

------- Comment #9 from law at redhat dot com  2010-01-12 15:18 -------
Subject: Re:  vectorizer created unaligned vector
 insns

On 01/12/10 01:08, irar at il dot ibm dot com wrote:
> ------- Comment #8 from irar at il dot ibm dot com  2010-01-12 08:08 -------
> So, to be on the safe side, we should assume that COMPONENT_REFs are not
> naturally aligned and never use peeling for them?
>    
If you can not *prove* at compile time that you're going to get the 
proper alignment, then you can't vectorize without a runtime check to 
select between a vectorized and unvectorized loop.

Proven alignement -- vectorize
Proven unaligned -- do not vectorize
Likely aligned, but not proven -- emit two loops, one vectorized, one 
not vectorized and runtime selection of the proper loop

Otherwise you run the risk of making conforming code segfault which is 
obviously unacceptable.

jeff


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42652