Re: Architecture description languages for compilers?

pardo@cs.washington.edu (David Keppel) writes:
> It is an amusing exercise to compare the listed md sizes for the Thompson
> compiler to the GCC md sizes for the same machines. I can't say whether
> the code is comparable: Thompson claims the compile time is half that of
> GCC and run time is 75% that of GCC, but it shows only slightly better run
> times than lcc, and a previous comp.compilers article said lcc was
> substantially worse than GCC.


1) What programs are used for the execution time comparisons? If you are
willing to do a lot of hand optimization of C code, then you can get good
performance with relatively simple compilers. (E.g. should the compiler do
induction variable optimization/strength reduction or should the
programmer code pointer arithmetic?) My impression is that the Thompson
and friends lean towards the simpler compiler approach.


2) GCC's machine description language is notable for supporting a large
number of architectures and having good documentation. It also serves as
an opportunity to study the evolution of an intermediate language as the
number of architectures and optimization quality both increase. (In fact
it may be worth studying the "distributed software engineering" aspects of
the compiler but that's off the subject.)
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