Assembly or ....

[Keith Bierman - Sun Tactical Engineering]

In article <1039 at l.cc.purdue.edu> cik at l.cc.purdue.edu (Herman Rubin) writes:
>
>Can division be pipelined?  In scalar mode on the CYBER 205, division is not
>subject for pipelining.  I believe that this is the case because too much of
>the dividend must be retained throughout.

The cydra 5 had it pipelined, but the pipe was interlocked during
operation. This was said to be due to a lack of real estate (viz could
have been fully pipelined if (a) not for gradual underflow (the cydra
5 was a fully ieee compliant machine), (b) there was more space it
could have been done anyway.

>
>Even if CORDIC is not used, returning the sine and cosine would be faster in
>software than two function calls.  The corresponding function is in some of
>the libraries I know, but I have not seen any other implementation than the
>two calls.

DEC's famous math$sincos does this. SunFORTRAN takes two calls (in the
user code) and turns them into one call to the sun sincos routine.
Unless I am mistaken this is a very old and well known optimization
(which is typically invisible to the user).

On many machines the cost of both is only a couple of % more than the
cost of one.


Keith H. Bierman
It's Not My Fault ---- I Voted for Bill & Opus