optimizing compilers vs. optimizing programmers

[Marty Sasaki]

Warning! This posting contains a major digression from the discussion of
Pascal as a system implementation language. I thought it would be
interesting enough in general for a posting.

All of this talk about optimization of C code vs. Pascal code, and
Pascal as a system implementation language reminds me of the time I
asked someone in the VMS development group why they didn't choose C for
their system implementation language (they chose Bliss).  He answered
that C required an optimizing programmer in order to produce code that
was good enough for an operating system kernel.

The VMS folks also looked at Pascal, but felt that they didn't have
enough control of the machine in Pascal without seriously changing the
language.

In the discussion that followed the VMS guy basically said (please note
that these are my interpretations of the conversation):

     1.	They had to assume that the programmers that they used would
	be good, but not necessarily great. 

     2.	The language/compiler had to be very good to sell management
	on using a high level language for system implementation.

Point 2 is important all by itself, but point 1 implies that the programmer
would probably not be able to consistantly produce code that was efficient
and that worked in a timely fashion. An optimizing compiler was doubly
important.

To those that argue that Bliss is no better than assembly language let
me say that tests done by DEC indicate that the Bliss-32 compiler
produces code better than that written by experienced assembly language
programmers.
-- 
			Marty Sasaki
			Havard University Science Center
			sasaki at harvard.{arpa,uucp}
			617-495-1270