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From: | "Markus F.X.J. Oberhumer" <markus DOT oberhumer AT jk DOT uni-linz DOT ac DOT at> |
Newsgroups: | comp.os.msdos.djgpp |
Subject: | Re: gcc optimize performance, V2.7.2.1 versus V2.6.0 |
Date: | Thu, 03 Apr 1997 20:29:43 +0200 |
Organization: | Johannes Kepler University Linz |
Message-ID: | <3343F717.31B3@jk.uni-linz.ac.at> |
References: | <Pine DOT SUN DOT 3 DOT 91 DOT 970331181732 DOT 17577N-100000 AT is> |
NNTP-Posting-Host: | c210.edvz.uni-linz.ac.at |
Mime-Version: | 1.0 |
CC: | Dan Hirschberg <dan AT ics DOT uci DOT edu> |
Lines: | 23 |
To: | djgpp AT delorie DOT com |
DJ-Gateway: | from newsgroup comp.os.msdos.djgpp |
Eli Zaretskii wrote: > > On Sat, 29 Mar 1997, Dan Hirschberg wrote: > > > The same program compiled with the newer compiler had much worse > > performance (about 50% worse) on both my 486 and my Pentium Pro. > > The performance was even worse with -O2. I was able to improve > > the performance somewhat by using -O1 and adding a few of the > > -f options (found by reading the info file on gcc), but still about > > 40% worse than under the 2.6.0 version. > > > > Is this a common experience? > > No. People who tested this report that the optimization quality is the > same, and sometimes slightly better in 2.7.2.1. One reason that 2.7.2.1 compiled programs might be slower than 2.7.2 is that the specs do not contain '-fno-strength-reduce' anymore because the optimizer bug has been fixed in gcc 2.7.2.1. In fact all programs I tested (on the Intel platform) run slower with '-fstrength-reduce' enabled (read the Linux GCC-FAQ/Howto for more optimization tips).
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