OT: C perfomance

From: CBFalconer (cbfalconer_at_yahoo.com)
Date: 02/01/04 

Date: Sun, 01 Feb 2004 03:59:21 GMT

Chris Torek wrote:
>
... snip ...
>
> I think you are making unwarranted assumptions here, such as which
> version of gcc was involved, and whether the target CPU was the
> PowerPC or the older Mac CPU family, the 680x0. It is, however,
> true that the PowerPC has an unusual instruction set, with instructions
> like "bdnzf" (decrement count and branch if comparison result not
> equal and count not zero) and "rlwinm" (rotate and mask), and
> apparently many versions of gcc do not use it very effectively.
>
> About all that can be said with any certainty, when it comes to
> actual run time of various C source code constructs, is that "it
> depends". :-)

I consider that a prerequisite for building an efficient code
generator is a good assembly language programmer for that
machine. The next requirement is a good register allocation
scheme. These days things are complicated by pipelining and the
need to know jump probabilities. 

-- 
Chuck F (cbfalconer@yahoo.com) (cbfalconer@worldnet.att.net)
   Available for consulting/temporary embedded and systems.
   <http://cbfalconer.home.att.net>  USE worldnet address!

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