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Date: Fri, 07 Dec 2012 15:06:00 -0000
From: Richard Henderson <rth@redhat.com>
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To: Marc Glisse <marc.glisse@inria.fr>
CC: Michael Zolotukhin <michael.v.zolotukhin@gmail.com>,        Kirill Yukhin <kirill.yukhin@gmail.com>,        "H.J. Lu" <hjl.tools@gmail.com>, Uros Bizjak <ubizjak@gmail.com>,        gcc-patches List <gcc-patches@gcc.gnu.org>
Subject: Re: [i386] scalar ops that preserve the high part of a vector
References: <alpine.DEB.2.02.1210131032460.9651@stedding.saclay.inria.fr> <CAFULd4Z=8xeVScUM7JSqkHHXJrmO7qVa40q-h-mUE+Vehb86vw@mail.gmail.com> <alpine.DEB.2.02.1212021215330.3747@laptop-mg.saclay.inria.fr> <CAFULd4Z4Ywk+BQupB+=tDKiWx5QrCt9VL83XF4Xtgu03=y0VZw@mail.gmail.com> <alpine.DEB.2.02.1212030958050.3737@laptop-mg.saclay.inria.fr> <CAFULd4a5my_Hre6k5kTUm2UqpBX06kKKe9jjMiFisBJSUJPxyw@mail.gmail.com> <alpine.DEB.2.02.1212041436150.3790@laptop-mg.saclay.inria.fr> <alpine.DEB.2.02.1212041715370.22183@stedding.saclay.inria.fr> <CAFULd4aPuceLK0uBhoK-ZVvMi_TqkiwijNddYVL9B4iKaN358Q@mail.gmail.com> <CAMe9rOpdBqD3A+EVVqbkhaos7my2ZNkdOky89AOa8Ye0OkeEKQ@mail.gmail.com> <CAGs3Rfvy96savuHk-=tDU0ixkt4ahz2LsQpWATkPX0Sg87+8_w@mail.gmail.com> <CANtU07-4ce+_wHenrbJCP879rnAsP+B+P6GGdqeZ8A0drA11cA@mail.gmail.com> <alpine.DEB.2.02.1212070934550.3800@laptop-mg.saclay.i! nria.fr> <50C20079.8050001@redhat.com> <alpine.DEB.2.02.1212071552390.3800@laptop-mg.saclay.inria.fr>
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On 2012-12-07 09:00, Marc Glisse wrote:
> On Fri, 7 Dec 2012, Richard Henderson wrote:
> 
>> On 2012-12-07 02:49, Marc Glisse wrote:
>>> For 2-element vectors, vec_concat does seem more natural than
>>> vec_merge. If we chose vec_merge as the canonical representation, we
>>> should chose it for setting an element in a vector
>>> (ix86_expand_vector_set) everywhere, not just those scalarish
>>> operations.
>>
>> I'd hate to enshrine vec_merge over vec_concat for the benefit of x86,
>> and to the detriment of e.g. mips.  There are plenty of embedded simd
>> implementations that are V2xx only.
>>
>> If we simply pull the various x86 patterns into one common form, set
>> and extract included, does that buy us most of what we'd get for
>> playing games in combine?
> 
> I'm sorry, could you be more precise? I don't see clearly what you are suggesting.

Don't change combine?

Have I lost the plot somewhere here?


r~