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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: GNAT (GCC) Profile Guided Compilation
Date: Sun, 15 Jul 2012 14:02:31 +0300
Organization: Tidorum Ltd
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Date: 2012-07-15T14:02:31+03:00
List-Id: <comp.lang.ada>

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
       .      @       .