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From: jss@sjuvax.UUCP (J. Shapiro)
Newsgroups: net.arch,net.micro.68k
Subject: Re: Re: M680*0 "small model"
Message-ID: <1178@sjuvax.UUCP>
Date: Sat, 22-Jun-85 01:58:01 EDT
Article-I.D.: sjuvax.1178
Posted: Sat Jun 22 01:58:01 1985
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Organization: Haverford College, Haverford, Pa.
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"This" referring to address shrinking of span dependent code:

> Heck, guys, the UNIX PDP-11 assembler does this for branch instructions.  So
> does the UNIX VAX-11 assembler and the MIT and AT&T 68000 assemblers.
> 
> 	Guy Harris

Not quite right, Guy. As I understood it, the Perkin Elmer assembler was
described as doing an essentially arbitrary number of passes. With UNIX
it was decided that this approach was too slow, and that the break point
of cost effectiveness was at two passes, which catches about 80 percent
of such things. the PDP-11 compilers and the VAX compilers both make only
two passes.

You are correct that they will replace jump/branch as appropriate. This
is essentially an extension of the concept of span dependent optimization
of addressing modes.

I recently went off and looked into all of this, which is how I learned.

Jon Shapiro