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From: wdkirby AT ix DOT netcom DOT com (William D. Kirby)
Newsgroups: comp.os.msdos.djgpp
Subject: DJGPP v2beta4 creates slower code?
Date: 2 Jan 1996 20:05:25 GMT
Organization: Netcom
Lines: 20
Message-ID: <4cc365$3ce@cloner2.ix.netcom.com>
NNTP-Posting-Host: ix-dc15-01.ix.netcom.com
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp

I have just installed DJGPP compiler v2beta4, and noticed that compiled
programs run much slower than they did using DJGPP v1m4.

For example, I have a floating point FFT (Fast Fourier Transform) timer
program that I have compiled using both DJGPP versions using the same
makefile. The gcc options are -O3 -m486. For a 1024 real sample FFT the
transform average times on my machine (486/33) are v1m4=18.3, and
v2beta4=20.3 milliseconds. These times are established with 10,000
identical iterations. A 10% speed change is significant.

I suspect the speed changes are due to ggc version changes, since
v2beta3 gave run times close to
v1m4.

Any suggestions or explanations are welcome.


Bill Kirby