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From: dgary@ecsvax.UUCP (D Gary Grady)
Newsgroups: net.lang,net.arch
Subject: Re: Assembly VS HOL: Having it both ways
Message-ID: <1163@ecsvax.UUCP>
Date: Mon, 6-May-85 12:21:14 EDT
Article-I.D.: ecsvax.1163
Posted: Mon May  6 12:21:14 1985
Date-Received: Thu, 9-May-85 13:04:19 EDT
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Organization: Duke U Comp Ctr
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Can't recall if anyone has pointed this out before, but Burroughs
large systems (as of five or ten years ago when I was working with
Burroughs gear) has no assembly language.  Instead they used a
dialect of Algol that permitted complete control of the generated
code.

It might be noted that advantage of assembly language is only in its
power to control exactly what the object format will be (with the
possible exception of some assemblers for Intel 80x8x processors, which
still tend to surprise me with their inventive code productions).  If a
high-level language can be given the ability to specify exactly what
object code will be produced, we can have it both ways.  

It might even be possible to do this in a somewhat "machine independent"
fashion; that is, in a way that isolates the machine-specific
instructions.  A simple way of doing that is the #asm directive found in
some C compilers.  Burroughs medium systems Algol (BPL) allowed the use
of assembler mnemonics as statement modifiers; an assignment statement
might be followed by a :MW to force a move word to be generated (going
from memory, here).  Obviously, for this to work some degrading of
optimization might be necessary.  It might also be desirable to have a
sort of conversation between the compiler and the programmer during the
compile.  Critical sections of code could be marked by the programmer
and the compiler could say, "Here's what I've generated for this; what
changes do you want me to make?"

Sorry this is so vague; my real point is that rather than having to
choose between two unsatisfactory options, it would be nice to have a
third way to go that preserved the undeniable advantages of high-level
languages without preventing us from producing code as tight as we might
ever want.

-- 
D Gary Grady
Duke U Comp Center, Durham, NC  27706
(919) 684-3695
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