From: Richard Biener <richard.guenther@gmail.com>
To: Marc Glisse <marc.glisse@inria.fr>
Cc: GCC Patches <gcc-patches@gcc.gnu.org>
Subject: Re: VEC_COND_EXPR optimizations v2
Date: Wed, 5 Aug 2020 16:24:15 +0200 [thread overview]
Message-ID: <CAFiYyc3Cw=sXXd8099p0J3FskkHDA2orUR5Qczkqz0aZ9rky=g@mail.gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.23.453.2008051443320.18411@stedding.saclay.inria.fr>
On Wed, Aug 5, 2020 at 3:33 PM Marc Glisse <marc.glisse@inria.fr> wrote:
>
> New version that passed bootstrap+regtest during the night.
>
> When vector comparisons were forced to use vec_cond_expr, we lost a number of
> optimizations (my fault for not adding enough testcases to prevent that).
> This patch tries to unwrap vec_cond_expr a bit so some optimizations can
> still happen.
>
> I wasn't planning to add all those transformations together, but adding one
> caused a regression, whose fix introduced a second regression, etc.
>
> Restricting to constant folding would not be sufficient, we also need at
> least things like X|0 or X&X. The transformations are quite conservative
> with :s and folding only if everything simplifies, we may want to relax
> this later. And of course we are going to miss things like a?b:c + a?c:b
> -> b+c.
>
> In terms of number of operations, some transformations turning 2
> VEC_COND_EXPR into VEC_COND_EXPR + BIT_IOR_EXPR + BIT_NOT_EXPR might not look
> like a gain... I expect the bit_not disappears in most cases, and
> VEC_COND_EXPR looks more costly than a simpler BIT_IOR_EXPR.
>
> I am a bit confused that with avx512 we get types like "vector(4)
> <signed-boolean:2>" with :2 and not :1 (is it a hack so true is 1 and not
> -1?), but that doesn't matter for this patch.
OK.
Thanks,
Richard.
> 2020-08-05 Marc Glisse <marc.glisse@inria.fr>
>
> PR tree-optimization/95906
> PR target/70314
> * match.pd ((c ? a : b) op d, (c ? a : b) op (c ? d : e),
> (v ? w : 0) ? a : b, c1 ? c2 ? a : b : b): New transformations.
> (op (c ? a : b)): Update to match the new transformations.
>
> * gcc.dg/tree-ssa/andnot-2.c: New file.
> * gcc.dg/tree-ssa/pr95906.c: Likewise.
> * gcc.target/i386/pr70314.c: Likewise.
>
> --
> Marc Glisse
next prev parent reply other threads:[~2020-08-05 14:24 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-30 7:49 VEC_COND_EXPR optimizations Marc Glisse
2020-07-31 11:18 ` Richard Sandiford
2020-07-31 11:38 ` Marc Glisse
2020-07-31 11:43 ` Richard Biener
2020-07-31 11:57 ` Marc Glisse
2020-07-31 12:50 ` Richard Sandiford
2020-07-31 12:59 ` Richard Biener
2020-07-31 13:01 ` Marc Glisse
2020-07-31 13:13 ` Marc Glisse
2020-07-31 11:35 ` Richard Biener
2020-07-31 11:39 ` Richard Biener
2020-07-31 11:47 ` Richard Biener
2020-07-31 12:08 ` Richard Biener
2020-07-31 12:12 ` Marc Glisse
2020-08-05 13:32 ` VEC_COND_EXPR optimizations v2 Marc Glisse
2020-08-05 14:24 ` Richard Biener [this message]
2020-08-06 8:17 ` Christophe Lyon
2020-08-06 9:05 ` Marc Glisse
2020-08-06 11:25 ` Christophe Lyon
2020-08-06 11:42 ` Marc Glisse
2020-08-06 12:00 ` Christophe Lyon
2020-08-06 18:07 ` Marc Glisse
2020-08-07 6:38 ` Richard Biener
2020-08-07 8:33 ` Marc Glisse
2020-08-07 8:47 ` Richard Biener
2020-08-07 12:15 ` Marc Glisse
2020-08-07 13:04 ` Richard Biener
2020-08-06 10:29 ` Richard Biener
2020-08-06 11:11 ` Marc Glisse
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