Re: Debugging optimized code

Ralph Johnson <>
Mon, 30 Jul 90 18:02:11 GMT

          From comp.compilers

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Newsgroups: comp.compilers
From: Ralph Johnson <>
Keywords: code, debug
Organization: Compilers Central
Date: Mon, 30 Jul 90 18:02:11 GMT

One of the good reasons for posting to the net is that you can get information
that hasn't been published. This is especially important in the area of
programming languages, where there are not a lot of places to publish.

Larry Zurawski did his PhD thesis on debugging optimized code. We have a
(long) paper on the subject that I am polishing. I would be happy to send it
to people like Lyle Cool, especially if they criticize it. The basic idea is
to achieve the best optimizations possible while still ensuring that the
debugger behaves as expected. This is done by noting every point in the
program where the debugger could be invoked and ensuring that it can recover
the unoptimized state. The compiler stores recovery information for each of
these points in the program, and it occasionally omits an optimization.
However, it doesn't omit many; many programs are not slowed down at all by
omitting optimizations, while the worse case we found was 15% slower.

I can send paper if you send me your paper mail address, or LaTeX if that is

Ralph Johnson -- University of Illinois at Urbana-Champaign

[I am certainly not opposed to people asking for info on the net, but do think
it appropriate that there be some evidence that they have done some homework
before they send out a message. That's why you haven't seen any messages here
saying "Are there any books on how to write a compiler?" while we've had quite
a lot of discussion on the pros and cons of various books that people have
looked at. -John]

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