68881 Floating Point Speed Increase on Sun 3/60

[Wayne Little]

One of the professors here at UMR discovered that he gained a 5 times
performance increase on some of his floating point intensive code with
complex numbers by using in-line expansion.

The problem was with the *humongous* amount of stack traffic that was
being generated by the 68881 coprocessor calls.

The fix is to designate the inline expansion library for the 68881 on the
compile line - 
e.g.
f77 -c -f68881 code.c -O code /usr/lib/68881/libm.il

The problem and solution are described in detail in section G
(Assembly-Level In-line Expansion) of Sun's Floating-Point Programmer's
Guide, pp. 105-113.

I hope this will be of help to others.

-- Wayne Little      Internet: rwl at ee.umr.edu      UUCP: uunet!umree!rwl
Phone: (314) 341-4546  USPS: Univ. of Missouri-Rolla, EE Dept., Rolla, MO 65401