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[Bug c/56083] Vectorizer uses xor/movlps/movhps rather than movups


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56083

Marc Glisse <glisse at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |glisse at gcc dot gnu.org

--- Comment #2 from Marc Glisse <glisse at gcc dot gnu.org> 2013-01-23 16:17:02 UTC ---
(In reply to comment #1)
> This is tuning decision,

Uros, I completely agree, but note that the PR also mentions this line:

xorps    %xmm0, %xmm0

which appears rather useless since the low and high parts are overwritten on
the next 2 lines. Is this done on purpose to kill dependencies or something? Or
is it a missed optimization? (simplify-rtx (or another place) is indeed missing
a few things in that area)


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