Date: Fri, 10 Mar 2000 12:30:47 -0500 (EST)
Message-Id: <200003101730.MAA22032@indy.delorie.com>
From: Eli Zaretskii <eliz AT delorie DOT com>
To: djgpp AT delorie DOT com
CC: buers AT gmx DOT de (Dieter Buerssner)
In-reply-to: <8a65uu$39fkt$1@fu-berlin.de> (buers@gmx.de)
Subject: Re: [long] gcc performance and possible bug
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> To exclude, that there may be a (hardware) problem with my system:
> Could please anybody try, to reproduce my results by compiling
> the following program with 
> 
> gcc -O2 mwc32tst.c
> 
> and running a.exe, then uncomment the const close to the end
> of the listing and recompile and rerun. Please post or mail your
> results, maybe including your processor and versions of gcc and
> binutils (I have AMD K6-2, tried with various versions of gcc and
> binutils, including gcc 2.95.2 and binutils 2.9.5).

I did this on two machines: a P-166 running DOS 5.0 and a 400-MHz
Celeron running Windows 98, with two different versions of GCC.  Here
are the results:

      P166/gcc 2.7.2.1   P166/gcc 2.95.2   C400/2.7.2.1   C400/2.95.2

 non-const  0.18053          0.06059          0.05445       0.01515

  const     0.30990          0.17480          0.05486       0.01556

The version of Binutils in both case was 2.9.1.

I'm not sure what does this mean, but it looks like alignment-related
problems.  Otherwise, I cannot explain how come the same executable
runs with the same speed on one machine, but not on another.

There's no 1:10 speed difference, which seems to confirm what Salvador
said: you are seeing some K-6-specific effect.