From: Eric Botcazou <ebotcazou@adacore.com>
To: Marc Glisse <marc.glisse@inria.fr>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: [RTL] Canonicalize commutative operations more
Date: Tue, 02 Apr 2013 11:44:00 -0000 [thread overview]
Message-ID: <5990842.GuiiquCisS@polaris> (raw)
In-Reply-To: <alpine.DEB.2.02.1304021202300.21244@stedding.saclay.inria.fr>
> I can, but then I am giving lshift higher priority than every other
> operation, not just rshift. And if I want to give (vec_select x 0) a
> higher precedence than (vec_select x 1) but lower than (vec_select
> (vec_concat a b) 1), the weights may become complicated, whereas the
> comparison function could just recurse.
You cannot have both transitivity and fast-tracks in the comparison function.
However it isn't clear (at least to me) if transitivity is really required.
(vec_select x 0) and (vec_select x 1) are the same pattern so they shouldn't
be distinguished here.
> I wonder if those issues might in most cases be bugs in the back-ends
> (optimizations missed depending on the order), that the canonicalization
> would make more noticable (and thus easier to fix).
There are certainly such issues in the back-ends (and even ??? comments about
it) so sensible canonicalization is desirable.
--
Eric Botcazou
next prev parent reply other threads:[~2013-04-02 10:55 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-19 17:14 Marc Glisse
2013-03-27 10:01 ` Eric Botcazou
2013-03-30 12:49 ` Marc Glisse
2013-04-02 9:23 ` Eric Botcazou
2013-04-02 11:12 ` Marc Glisse
2013-04-02 11:44 ` Eric Botcazou [this message]
2013-04-02 17:19 ` Jeff Law
2013-04-04 18:57 ` Mike Stump
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