Re: Compiler for Z80/6510

["Robert I. Eachus" <eachus@mitre.org>]

Robert Dewar wrote:
> > I could go into details,

> Please at least give references!

    Do you have copies of the SPARC architecture Versions 7 and 8?

    There were many instructions added to version 8 of the
architecture.  Even though not all existing SPARC processors supported
them directly, version 8 added a number of instructions not in version
7.  To comple with version 8 (and now version 9) of the reference
manual, you had to support these instructions in a trap handler if they
were not supported by the processor.

   There was a window where SunOS did not support the new instructions--
even by emulation.  In fact the SunAda(VADS) 1.x compiler did not even
allow these instructions in code inserts.  However, I was able to create
a package that contained "legitmate" implementations of these
instructions and then edit the binary to use the new instructions.  I
couldn't use pragma INLINE on the operations, but when these functions
were called the only overhead incurred was a function call rather than a
call to a run-time routine that simulated integer multiplication and
division.  Of course I could and did override the Standard operators in
the body of the using packages.

   As you know, SPARC subroutine calls are very efficient when
everything can be  done without creating an new stack frame.

   So I could get a several fold speed increase over asm writing in
Ada.  This was very handy when I was working on multi-precision
arithmetic, prime numbers,
and random number generators.  One particularly useful pair of
instructions  did 32x32-->64 bit multiplies and 64/32-->32,32 divides. 
Of course, you had to be very careful since the Y register had a long
latency on loads and stores from other registers.


     
-- 

                                        Robert I. Eachus

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