From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Subject: Re: GNAT (GCC) Profile Guided Compilation
Date: Sun, 15 Jul 2012 14:02:31 +0300
Date: 2012-07-15T14:02:31+03:00 [thread overview]
Message-ID: <a6fma7Fm6hU1@mid.individual.net> (raw)
In-Reply-To: <a6f90pFj55U1@mid.individual.net>
On 12-07-15 10:15 , Niklas Holsti wrote:
> It seems to me that the general belief, regarding the expected relative
> speeds of the short-circuit code versus the long-circuit code for
> Boolean expressions with simple operands, is that the branch penalties
> on modern processors are so large that the short-circuit form is not
> obviously faster. This may explain why the Ada compiler is not using the
> short-circuit code automatically.
>
> Clearly, if the expression is "(simple operand likely to be True) and
Oops, my brain fart: change that to "likely to be False".
> (longer and longer expression)", at some point the short-circuit code
> (or changing to "and then") will become faster than the long-circuit
> code, whatever the branch penalty. This point will come sooner if
> profile-guidance is used to reduce the branch penalty.
--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
. @ .
next prev parent reply other threads:[~2012-07-15 11:02 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-29 9:17 GNAT (GCC) Profile Guided Compilation Keean Schupke
2012-06-29 9:34 ` Dmitry A. Kazakov
2012-06-29 10:01 ` Keean Schupke
2012-06-29 10:24 ` Keean Schupke
2012-06-29 12:26 ` stefan-lucks
2012-06-29 12:51 ` Keean Schupke
2012-06-29 12:05 ` Dmitry A. Kazakov
2012-06-29 10:48 ` Simon Wright
2012-06-29 11:14 ` Keean Schupke
2012-06-29 12:39 ` gautier_niouzes
2012-06-29 12:52 ` Keean Schupke
2012-06-29 14:14 ` gautier_niouzes
2012-06-29 15:05 ` gautier_niouzes
2012-06-29 17:03 ` Keean Schupke
2012-07-01 9:29 ` Georg Bauhaus
2012-07-01 17:45 ` Georg Bauhaus
2012-07-01 22:57 ` Keean Schupke
2012-07-02 17:15 ` Georg Bauhaus
2012-07-02 17:26 ` Keean Schupke
2012-07-02 23:48 ` Keean Schupke
2012-07-04 10:38 ` Georg Bauhaus
2012-07-04 10:57 ` Keean Schupke
2012-07-04 12:36 ` Mark Lorenzen
2012-07-04 12:38 ` Georg Bauhaus
2012-07-14 20:17 ` Keean Schupke
2012-07-14 20:33 ` Keean Schupke
2012-07-14 20:43 ` Niklas Holsti
2012-07-14 22:32 ` Keean Schupke
2012-07-14 23:40 ` Keean Schupke
2012-07-15 7:15 ` Niklas Holsti
2012-07-15 8:27 ` Keean Schupke
2012-07-18 10:01 ` Georg Bauhaus
2012-07-18 17:36 ` Keean Schupke
2012-07-19 5:42 ` Georg Bauhaus
2012-07-19 10:18 ` Keean Schupke
2012-07-15 11:02 ` Niklas Holsti [this message]
2012-07-15 12:48 ` Keean Schupke
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