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Re: [patch, rfc] Semantics of attribute (aligned), misscompilation of crtstuff
Zdenek Dvorak wrote:
>> I agree that the vectorizer has the right to increase alignment, but why
>> does the vectorizer want to vectorize this loop?
>
> it does not; the vectorizer (more precisely, the increase_alignment pass
> that is run when vectorizer is enables) just unconditionally increases
> alignment of all arrays.
Oh, I see; it increases alignment in case it might be able to vectorize.
>> That doesn't seem like
>> much of a win, since there are no vectorizable accesses in the loop that
>> I can see. If there's not a speed improvement, then this is just a
>> speed/space pessimization -- compounded by the code that you're adding
>> to check for NULLs.
>
> I don't think the speed is important in this case. Space might be,
> though.
Both matter, but space is a bigger concern; we use GCC on systems with
just a couple of kilobytes, and we need to be reducing overhead for
these sorts of things, not increasing it.
So, I think we should just turn the vectorizer off when compiling this file.
Thanks,
--
Mark Mitchell
CodeSourcery
mark@codesourcery.com
(650) 331-3385 x713
- References:
- [patch, rfc] Semantics of attribute (aligned), misscompilation of crtstuff
- Re: [patch, rfc] Semantics of attribute (aligned), misscompilation of crtstuff
- Re: [patch, rfc] Semantics of attribute (aligned), misscompilation of crtstuff
- Re: [patch, rfc] Semantics of attribute (aligned), misscompilation of crtstuff
- Re: [patch, rfc] Semantics of attribute (aligned), misscompilation of crtstuff