Re: Unsafe optimizations (Herman Rubin)
Thu, 21 Jun 90 18:47:34 GMT

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Newsgroups: comp.compilers
From: (Herman Rubin)
References: <>
Date: Thu, 21 Jun 90 18:47:34 GMT
Organization: Purdue University Statistics Department
Keywords: code, optimize,
Summary: So why not let the programmer decide? The compiler does not have to work in secrecy.

In article <>, (Dale Worley) writes:
> I find this whole discussion somewhat odd. While it may be possible for the
> programmer to "know what he is doing", if the compiler is doing serious
> optimizations, it is impossible for him to know what the optimizer is doing!

This is the place where a great deal of harm is done by the compiler writers
and language designers. There is no reason why there cannot be more
communication between the compiler and the programmer. This can even apply
to the inclusion of operations not envisioned by the language.


> My personal opinion is that when people want to allow "unsafe optimizations"
> they either want a semantic relaxation (as above) or want to make up for a
> deficient compiler that doesn't know how to prove enough about the program.
> When are people going to start puttting serious interprocedural analysis
> into optimizing compilers?

In my opinion, this is the case with all compilers and languages. I doubt
that silicon (or GaAs, or whatever) will ever be able to replace DNA and RNA.

Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907
Phone: (317)494-6054 (Internet, bitnet) {purdue,pur-ee}!!cik(UUCP)

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