Indeed ! I was waiting for warnings or errors while compiling to tell me I was doing something wrong but I should not.
Thanks for your time. Patrice > In message <[EMAIL PROTECTED]> you wrote: > > > > I was searching for the best mcpu option for amcc440, compiling and > > running a small program you can find here: > > http://magnux.free.fr/gcc/mandelbrot.c. My distro is a ppc fedora core 6, > > and results are obviously the same using DENX4.0. > > In general, you should need to meddle much with such options; the ELDK > default settings are usually OK. > > > -------------------- > > -bash-3.00# gcc -O2 ./mandelbrot.c -o ./mandelbrot && time ./mandelbrot && > > rm -f ./mandelbrot > > > > real 1m15.059s > > user 1m14.996s > > sys 0m0.060s > > -bash-3.00# gcc -O2 -mcpu=440 ./mandelbrot.c -o ./mandelbrot && time > > ./mandelbrot && rm -f ./mandelbrot > > > > real 0m39.606s > > user 0m39.552s > > sys 0m0.028s > > -bash-3.00# gcc -O2 -mcpu=440fp ./mandelbrot.c -o ./mandelbrot && time > > ./mandelbrot && rm -f ./mandelbrot > > > > real 1m15.016s > > user 1m14.988s > > sys 0m0.024s > > -bash-3.00# gcc -O2 -msoft-float ./mandelbrot.c -o ./mandelbrot && time > > ./mandelbrot && rm -f ./mandelbrot > > > > real 0m39.577s > > user 0m39.544s > > sys 0m0.032s > > This looks to me as if you have been runing all these tests in the > SAME environment, probably the /opt/eldk/ppc_4xx root file system, > which is soft-float based. You must not do this. > > For tests with FP instructions, you MUST use the /opt/eldk/ppc_4xxFP > root file system. For tests with soft-float, you MUST use the > /opt/eldk/ppc_4xx root file system. > > You CANNOT link an application build with one settings against > libraries using other settings, or you will run into trouble. You > would probably have seen the problems if you had used any test where > the results of the calculations would have been visible. > > > > * I do not explain why not using FPU gives better results ? > > Because you did not run the tests you thought yoiu were running. > > > * mcpu option seems to not have any effect ? > > Use "gcc -v" to see exactly which options get passed to the compiler > stages. > > > * My third test was to compile and run mplayer. > > - With default options (no mcpu specified), my test mpeg was smooth. > > - With mcpu=440fp, my test mpeg was not smooth. > > > > Can anybody bring me some lights about the right gcc mcpu option for > > amcc440 ? > > Just use the defaults, unless you know exactly what you are doing. > > Best regards, > > Wolfgang Denk > _______________________________________________ Linuxppc-embedded mailing list [email protected] https://ozlabs.org/mailman/listinfo/linuxppc-embedded
