The lost art (Was: The VAX is running

Paul Koning Paul_Koning at Dell.com
Tue Apr 7 19:56:29 CDT 2009


> From: cctalk-bounces at classiccmp.org [mailto:cctalk-
> bounces at classiccmp.org] On Behalf Of William Donzelli
> Sent: Tuesday, April 07, 2009 5:44 PM
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: Re: The lost art (Was: The VAX is running
> 
> > And too few people who take the trouble to learn the assembly bother
> > to learn the machine representation of the instructions--or the
> > architecture of the implementation. Even fewer learn how to time
> > instruction execution--perhaps it's no longer relevant.
> 
> All of this is now the job of the compiler.
> 
> It ain't 1980 anymore.

True.  But it remains the case that there are tasks that push the limits
of what the available processors can do.  Or there may be special
considerations that you simply can't tell the compiler -- either it
doesn't know, or you can't say it in C.

I continue to do assembly language programming, occasionally.  It's a
small fraction of the total code but it has to be done that way for one
reason or another; the compiler just isn't an option.

For example, I have some cache flush code that runs about 10x the speed
of C code.  And it works correctly, which the C code can't because the
hardware has some very odd requirements that no compiler ever written
can cope with.

	paul




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