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Date: Mon, 06 Jun 2016 17:44:00 -0000
From: Jakub Jelinek <jakub@redhat.com>
To: Richard Biener <rguenther@suse.de>
Cc: Ilya Enkovich <enkovich.gnu@gmail.com>,        gcc-patches <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH] Fix SLP wrong-code with VECTOR_BOOLEAN_TYPE_P (PR tree-optimization/71259)
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Reply-To: Jakub Jelinek <jakub@redhat.com>
References: <20160111171343.GB18720@tucnak.redhat.com> <CAMbmDYaE0P0VEUu9mJT17SAZAtQhyFQ6VqPvS_-xjNqx9zGv0Q@mail.gmail.com> <20160603173343.GM7387@tucnak.redhat.com> <alpine.LSU.2.11.1606060949240.1493@t29.fhfr.qr>
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On Mon, Jun 06, 2016 at 10:05:57AM +0200, Richard Biener wrote:
> So this ends up generating { a ? -1 : 0, b ? -1 : 0, ... }.  That

Yes, that is already what we do now for loop vectorization.

> might be less optimal than doing { a, b, ... } ? { -1, -1 ... } : { 0, 0, 
> .. }

Well, it would need to be
{ a, b, ... } != { 0, 0, ... } ? { -1, -1, ... } : { 0, 0, ... }
then, doesn't VEC_COND_EXPR assume the condition is in canonical
VECTOR_BOOLEAN_TYPE_P form?

Anyway, if something like the above would be faster, perhaps generic vector
lowering or some similar pass could detect that case post-vectorization and
optimize?

	Jakub