Re: Code quality

drw@zermelo.mit.edu (Dale R. Worley) writes:


>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 seems to me that compile time is roughly exponential in the deficiency
of the generated code. So, to produce code that is 10% worse than optimal
takes twice as long as it does to produce code 20% less than optimal (if
your compiler is optimizer-bound). I suspect that programmer time required
to get the optimizer solid is also exponential.


So getting that last few percent requires a lot of resources.


Perhaps someone has collected some numbers on this? I am just making the
statement based on a gut feeling gotten from writing an optimizer.
[It varies all over the place. The Princeton/Bell Labs lcc compiler
is supposed to produce better code faster than GCC. Ken Thompson's Plan 9
compiler is supposed to be better still in both dimensions. -John]
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