From: semler@
Newsgroups: comp.os.msdos.djgpp
Subject: DJGPP Optimizing
Date: 30 Dec 1996 14:06:14 GMT
Organization: IBM Zurich Research Laboratory
Lines: 16
Message-ID: <5a8i8m$vgk@grimsel.zurich.ibm.com>
Reply-To: semler@
NNTP-Posting-Host: semler.dk.ibm.com
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp

Hi!

I have some troubles using the optimizing features in the compiler

1) When the compiler optimizes a tight inner loop, that uses only integer math
it inserts a bunch of floating point instructions (fxch) that doesn't seem to do
anything at all (I can remove them and my code works fine without). As these
instructions are inside the tight loop they eat up about 50% of the time spent here..

2) When using the trigonomic functions cos/sin in 3D graphics it seems that whenever
I use the -O# compiler option the functions are treated differently than without
the -O# option. Result is that the 3D space is skew'ed. Am I assuming something
about the trigonomic function (ie. angles can be outside [0 : 2*PI]) that does not 
hold when optimizing?

Kind regards, Henning Semler