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[Bug target/14552] compiled trivial vector intrinsic code is inefficient



------- Comment #27 from ubizjak at gmail dot com  2008-03-19 23:46 -------
(In reply to comment #25)
> Actually the first generates-
>         subl    $12, %esp
>         movq    _w, %mm0
>         paddw   %mm0, %mm0
>         movq    %mm0, _w
>         movq    _w, %mm0
>         movq    %mm0, _dw
>         addl    $12, %esp
>         ret
> 
> which is better than the code in the original report but still has a useless
> store/reload.

The store is not useless. Reload from "_w" is how gcc handles double stores
nowadays and is not mmx specific. It looks that some pass forgot to check where
the value came from.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14552


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