#: 8975 S12/OS9/68000 (OSK)
    31-Dec-90  20:44:50
Sb: #8966-#68000 ASM Language
Fm: Jack Crenshaw 72325,1327
To: Kevin Darling (UG Pres) 76703,4227 (X)

Kev, I remember a project at work on the Z8000, which has 16 general-purpose
registers.  The program had to be super fast ... among other things, it had to
compute one sine, one cosine, an arctan, and a square root, in a millisecond.  
So I had to write almost all in-line code, and keep everything possible in
registers.   What an ordeal!  Basically, I was doing global register
optimization by hand.  Had to keep a map of what was in each register, and
deciding where to put the next item was like working out a chinese puzzle.  It
sure would have been nice for me to have been able to identify the registers by
their contents, too.

Which brings me to a thought:  You'd need error messages to tell you when
something's been overlaid, wouldn't you?

Well, I guess that would be taken care of by the assembler:  If you declare a
variable x to be in D0, and then later declare it to be y, the assembler must
remove x from the symbol table.  Unless, of course, you redeclare it as RAM.

Hm.  Have to think about implementation on that one.  I'd been thinking of a
syntax something like

   assign x to d0
   .
   .
   release d0

Perhaps I could set it up so that if there is an assignment x=d0 somewhere in
between, x would be automatically set to refer to the RAM variable rather than
the register.  Sounds feasible.

Jack



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