Re: [Mingw-users] GCC compiled code very slow compared to MS Visual C

[Jeremy H. <gcc...@gm...>]

OK,

Its a console text editor that supports a scripting language.

The editor is about 11,250 lines of C and is self contained on Windows
(doesn't use any extra libraries).  Its been heavily optimized over
many years.

The "benchmark" is a (complex) regression test script reports the
elapsed time at the end.  It does a great deal
of work including a lot of arithmetic and memory access, but very
little disk access.

I realise its too big an example for specific suggestions.  I'll try
and create a small example with simple compiler
options for both compilers. I was really wondering if anyone else had
seen this and if so what were their conclusions?

FYI, the timings I had were (Windows XP SP3, on 1.6GHz Athlon XP, 1GB) :

MinGW GCC 4.5.2   -Os      173 seconds

MinGW GCC 4.5.2   -O3      105 seconds

MS Visual C++ 2010  -O1s   89 seconds

MS Visual C++ 2010  -O2t    87 seconds

The same script on a 32 bit Linux box (GCC) runs a little faster (143
secs -Os), but still not as fast as VC++.
The Linux 64 bit version on a 4GHz Core i7 executes in 20 seconds :-)

The VS 2010 compile looks like this:

D:\ge>cl -DFILE_TABS=4 -DSCREEN_TABS=2 /O1isyb2 /J /fp:fast /GFrS-
/Qfast_transcendentals /arch:SSE /Zp4 /W2
  g.c /Feg.exe /FAs
Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 16.00.30319.01 for 80x86

The MinGW  GCC (4.5.2) options are:-
gcc -pipe -std=c99 -funsigned-char -DFILE_TABS=4 -DSCREEN_TABS=2 g.c
-Os -Wall -Wextra -Wno-char-subscripts
 -ffast-math -mfpmath=387 -mpc80 -mhard-float -s -fno-ident
-fshort-enums -fwhole-program -minline-all-stringops
 -fmerge-all-constants -fomit-frame-pointer -fno-non-call-exceptions
-fno-asynchronous-unwind-tables -fno-exceptions
 -fno-unwind-tables -fira-loop-pressure -fstrict-aliasing
-fstrict-overflow -march=athlon-xp -mtune=athlon-xp -o g

Regards
Jeremy