Re: Simplistic Assemblers?

In article <789@ima.isc.com> Doug Pardee writes:
>There is a modern aphorism that "It's much harder to program in assembler
>than in a high-level language". That's no surprise ...


John Levine adds:
>It has always seemed to me that the main place that assembler loses is in data
>structuring -- typed data and pointers buy you a lot, particularly in the
>error checking department, and it'd take an awful lot of macro magic to give
>an assembler that.


Most people won't dispute that having a compiler do some of the
work such as register allocation and strong type checking really
does make programming easier. Even if you are using a fancy
assembler. Or maybe especially; programs which are mostly
sophisticated macros such as fancy assembler, troff packages, or
FORTH are notoriously hard to read. Personally, I suspect this is
due to difficulty of reproducing the train of thought the author
had while writing the code. Working in an very expressive medium
makes it easy to embody an idiosyncratic approach into the code.


Intermediate between assemblers and higher level languages is an
alternative which is often over looked. In the late '60s Don Knuth
called them "structured assemblers". IBM is using one to do space
shuttle software. Ed Ream published a lovely article in Dr. Dobbs
last year, showing how to use a rich subset of C as an assembly
language. His key point was that data structures, procedures, and
variables all have straightforward translations to assembly code. In
the absence of optimization, all you need to give you full assembly
language power with structured syntax is enough restrictions on the
variable declarations that you end up doing the register allocation
yourself.


Jim Leinweber jiml@uwslh.uucp jiml%uwslh.uucp@cs.wisc.edu
  ...!{rutgers, ucbvax, ihnp4, ...}!uwvax!uwslh!jiml
State Laboratory of Hygiene @ Univ. of Wisconsin - Madison; (608) 262-8092
[There used to be a lot of structured assemblers; I used one for the 360
called PL/360 which had a distinct Algol flavor. There used to be something
called LIL at Bell Labs which was sort of souped down C. The guy who wrote
LIL wrote a tech report in which he said that he considered LIL a failure
because there wasn't anything it did that you couldn't do about as well in
C. -John]
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