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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug middle-end/103781] [AArch64, 11 regr.] Failed partial
 vectorization of mulv2di3
Date: Mon, 20 Dec 2021 20:59:43 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103781

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
>Side note: why not ldp in the loop?
Because of the way LDP formation is done, it is just badly done in general
(file a different bug for that). It is a known issue that ldp/stp formation=
 is
not good really.

>As of GCC 11, the AArch64 backend is very greedy in trying to vectorize mu=
lv2di3.

No, you are actually seeing SLP happening really and since mul does not exi=
st,
it does not do that.=