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From: tcd@vax5.cit.cornell.edu
Newsgroups: comp.sys.mac.programmer
Subject: MPW C/fp performance
Message-ID: <1991Jan7.170126.1900@vax5.cit.cornell.edu>
Date: 7 Jan 91 21:01:26 GMT
Distribution: comp
Lines: 23


    I am using MPW C (v. 3.0) to write a program that involves
a lot of floating point calculation.  The code that is generated
appears incredibly inefficient (although I'll admit that I have
never looked at the output from another compiler before, so I
don't have much basis for comparison).  I have learned to use a lot
of temporary variables and eliminate explicit subscripting of arrays,
but some things appear impossible to get around.  A typical section of
code that really bothers me is something like the following:
  FMOVE   FP7,FP0
  FADD.X  (A3),FP0
  FMOVE   FP0,FP7

when   FADD.X  (A3),FP7   would produce the desired result.  What I am
wondering is the following:
1)  Does version 3.1 of MPW offer any improvement in this regard?
2)  How do other Macintosh compilers (C or otherwise) compare?
3)  Does anyone know of a book or other source that describes tips,
techniques, pitfalls, etc. for a Macintosh programmer interested in
execution speed for floating point calculations?

Thanks,
Tim Dorcey