Re: Code quality (Tim Channon)
Thu, 7 Jan 1993 02:20:25 GMT

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Newsgroups: comp.compilers
From: (Tim Channon)
Organization: Compilers Central
Date: Thu, 7 Jan 1993 02:20:25 GMT
Keywords: optimize
References: 93-01-017

> How important is generated code quality these days? There are a lot of
> good optimization techniques that seem to be adequate for ordinary
> programming. But they still are at least 10% or 20% worse than the ideal.
> Is there much of a market for another 10% in speed of generated code?

It depends... I think that 10..20% is often very optimistic but will
depend very much on the processor.

A 2MHz 6502 will walk all over a 486/33 under certain cicumstances, same
algorithm, no choice about the data format and high speed bit twiddling of
the most awkward sort is not generally a HLL forte.

I've seen this sort of thing time and time again.

What does this mean: IMO understood problems can be solved by a compiler
because the compiler author or language designer knew a good solution,
move outside this area and we see the compiler for the dead thing it is.

Then there is the choice of source language. In general these seem to
cover a pretty narrow range of styles where the programmer has little
chance to use his brain to come up with imaginative solutions because of
the straightjacket of the HLL. How often do you see C programmers bending
their code to try and persuade the compiler to generate certain code?

I guess that some of you may be angry at me suggesting that compilers are
no good because they cannot produce efficent code for ancient 8 bit
processors. Look at it this way -- if you need large machine resources to
produce what you call efficient code you aren't within 20% of optimum in
the global sense.

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