SCOUG-Programming Mailing List Archives

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Date:	Wed, 6 Aug 2003 22:56:50 PDT7
From:	Peter Skye <pskye@peterskye.com >
Reply-To:	scoug-programming@scoug.com
To:	scoug-programming@scoug.com
Subject:	SCOUG-Programming: Re: Warpstock 2003 Presentation

Content Type: text/plain

Lynn H. Maxson wrote:
>
> I'm sort of "iffy" with respect to Bob Blair's emphasis to
> the front end with respect to automating source mainteance
> away from the back end for automating code generation. You
> have to offer a complete package from the front end to the
> back end. Otherwise you won't get the full productivity
> impact.

Don't set Bob's experience aside. A smaller project is more likely to
eventually be successful.

> "faster, better, cheaper". All
> three, Peter. No tradeoffs.

Icarus went before you. Good luck.

> I don't care, because the software doesn't. It does one
> or a zillion without concern about the time, only the
> result. As it does it a zillion times faster than I can,
> I figure it's a wash.

Will you be creating a test bench model? Will you test your hypothesis?

> "As I recall, the original Level F compiler used 47 passes."
>
> Time for a little history lesson. IBM designated OS/360
> compilers by letters based on their design level: D for
> 16K, E for 32K, F for 64K, G for 128K, and H for 256K.
> The design level included the OS, in this instance PCP a
> single main task supporting multiple subtasks. The full
> function OS in smallest form took up 12K. For the F-level
> PL/I compiler this meant a 54K partition.
>
> The compiler phases were ordered sequentially, though if a
> phase was not needed it was skipped. Each phase completed
> its processing by determining its successor.
>
> It didn't have 47 phases, only something in the range of
> the alphabet (A - Z). To get to 47 it would have had too
> large a source file, which it segmented. It essentially
> swapped these segments for each necessary phase.

For speed the keywords were hashed (up to three times if collisions
occurred, then a sequential lookup was used). The compiler phases were
ordered sequentially as you say, but each phase only processed a small
number of keywords. Phases were skipped if none of their associated
keywords were found in the source. (There were a handful of
housekeeping phases as well, such as the preprocessor, the source
parser, and the disassembler which took the finished compile and created
pseudo-assembler from it.)

Somewhere around here I still have the SRL with the compiler's technical
details. I even still have my green-covered KWIC index. Life was so
much simpler back then, when IBM would hand me whatever I needed.

- Peter

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