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Re: Notes from tinkering with the autovectorizer (4.1.1)
- From: Dorit Nuzman <DORIT at il dot ibm dot com>
- To: "Erich Plondke" <eplondke at gmail dot com>
- Cc: gcc <gcc at gcc dot gnu dot org>
- Date: Thu, 28 Sep 2006 13:49:17 +0300
- Subject: Re: Notes from tinkering with the autovectorizer (4.1.1)
"Erich Plondke" <eplondke@gmail.com> wrote on 27/09/2006 18:17:55:
thanks for the detailed explanation,
> Indeed, in your paper (grin) "Multi-platform Auto-vectorization" you
>
> define the functionality of realign load in terms of mis - the
> misalignment
> of the address (i.e., address&(VS)), as follows: The last
> VS-mis bytes of
> vector vec1 are concatenated to the first mis bytes of the
> vector vec2.
>
> This is what the walign instruction does, but it's not quite what we
> ended up with in GCC.
> In the case that mis is 0, the GCC hook wants to end up with vec2, not
vec1.
>
yes, what we describe in the paper is a bit more general than what we ended
up implementing...
> So for architectures that can align both ways, the current method is
> fine, but if the
> architecture is designed for one endian only we are going to have
> trouble exploiting
> the alignment feature.
>
I agree we need to add the alternatives you pointed out to make it
applicable to more targets.
This is now PR26268.
dorit
> Thanks,
>
> Erich
>
> --
> Why are ``tolerant'' people so intolerant of intolerant people?