I have made a test with all the CFLAGS explained in the GCC info pages, using povray as the benchmark app (because it does lot of memory/integer/floating point operations) and these are just a few of my conclusions (when I come back home I'll post the full research, I wanted to do this before but never have the time, so now I see such a thread on the mailing list, I think this is the best opportunity):-O3 (finline-functions to be exact) might create useless code that will polute cache and throws away the advantages of using trace caches.
I use -O2 and this works fine for me.
Kind regards,
Joao Seabra
On Tue, 28 Oct 2003, Chris Graves wrote:
OK, so some folks swear by "-O3" optimizations, but alot of what I've read suggests "-O2" produces "faster" binaries.
I have a Pentium III (coppermine) @ 900MHz with 512M RAM and 1G swap. What CFLAGS do I want? (questionably unstable optimizations that do produce better results are OK)
-chris
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(These are from my memory now, if I put (a little bit) wrong cflags, please apologize me.
-O3 = -O2 + -finline-functions -frename-regs
povray benchmarked faster with -O2, slower -O3, so I tested -O2 separatedly with these two additional -O3 CFLAGS:
-O2 -finline-functions = slower than -O2
-O2 -frename-regs = FASTER than -O2
I'll post my complete benchmarked results ASAP. It includes many more CFLAGS (but for my architecture only, an AMD Athlon-XP).
Salu2.
Javier Villavicencio.
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