From: Richard Henderson <rth@redhat.com>
To: Alex Rosenberg <alexr@spies.com>
Cc: gcc@gcc.gnu.org
Subject: Re: [lno] [RFC] if-conversion and auto vectorizer
Date: Mon, 15 Mar 2004 22:38:00 -0000 [thread overview]
Message-ID: <20040315223807.GA4850@redhat.com> (raw)
In-Reply-To: <7F249017-7628-11D8-A9FC-003065FC08E4@spies.com>
On Sun, Mar 14, 2004 at 06:28:51PM -0800, Alex Rosenberg wrote:
> Maybe I keep stating the obvious, but it seems to me that it would be
> better to remove the MIN/MAX nodes, in favor of the SELECT node that
> Dorit has suggested since MIN/MAX are just specific CMPs mated with a
> SELECT.
No.
(1) MIN/MAX have better floating-point properties than conditional move.
Consider
a = 0; b = NaN;
c = a < b ? b : a; // 0
vs
c = a > b ? a : b; // NaN
vs
c = max(a, b); // Undefined
Undefined is good because then the target md pattern doesn't have to
be careful to preserve one or the other of the values in the face of
unordered comparisons.
(2) I reiterate that we will NOT be adding a new SELECT node.
The sooner Dorit changes to use COND_EXPR as I asked, the better.
r~
next prev parent reply other threads:[~2004-03-15 22:38 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-03-14 10:57 Fw: " Dorit Naishlos
2004-03-14 19:22 ` Andrew Pinski
2004-03-14 22:31 ` Daniel Berlin
2004-03-15 2:29 ` Alex Rosenberg
2004-03-15 22:38 ` Richard Henderson [this message]
2004-03-15 23:08 ` Devang Patel
2004-03-15 23:20 ` Richard Henderson
2004-03-16 0:02 ` Devang Patel
2004-03-16 0:07 ` Diego Novillo
2004-03-16 0:45 ` Richard Henderson
2004-03-16 3:02 ` Diego Novillo
2004-03-16 3:33 ` Richard Henderson
2004-03-16 6:33 ` Devang Patel
-- strict thread matches above, loose matches on Subject: below --
2004-03-16 12:27 Robert Dewar
2004-03-16 18:32 ` Richard Henderson
2004-03-16 22:51 ` Toon Moene
2004-03-16 23:10 ` Joseph S. Myers
2004-03-16 23:28 ` Toon Moene
2004-03-16 23:37 ` Richard Henderson
2004-03-16 23:42 ` Toon Moene
2004-03-16 5:33 Robert Dewar
2004-03-16 6:54 ` Richard Henderson
2004-03-16 3:46 Chris Lattner
2004-03-15 22:42 Robert Dewar
2004-03-15 23:08 ` Richard Henderson
2004-03-04 19:59 Devang Patel
2004-03-04 20:12 ` Andrew Pinski
2004-03-04 20:39 ` Devang Patel
2004-03-04 21:03 ` Richard Henderson
2004-03-05 19:06 ` Devang Patel
2004-03-05 19:17 ` Diego Novillo
2004-03-05 19:22 ` Diego Novillo
2004-03-05 19:28 ` Devang Patel
2004-03-05 19:41 ` Diego Novillo
2004-03-05 19:44 ` Diego Novillo
2004-03-12 18:45 ` Devang Patel
2004-03-13 9:24 ` Zdenek Dvorak
2004-03-13 22:41 ` Devang Patel
2004-03-14 10:59 ` Dorit Naishlos
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