GCC optimization
Hi, I would know which are the best optimization options for the GCC compiler to optimice for a pentium4 not HT, this is what I think:
-march=pentium4
-O2 -pipe
-fomit-frame-pointer
-mmx -sse -sse2
-ffast-math
-mfpmath=sse
-fprefetch-loop-arrays
-finline-functions
-frename-registers
-fforce-mem -fforce-addr
-malign-double
-falign-functions=64
-falign-loops=5
-falign-jumps=5
-falign-labels=5
just to know how you will do it if you want to optimice to the max for specific cpu (p4) and without using asm, I know that maybe will be only a very bit faster, but I want to know it. Thanks.
I''m not sure about the P4 specifically, but a lot of systems actually run slower with -finline-functions and -funroll-loops enabled. Just because something sounds like an improvement, doesn''t mean it actually is. You might do just as well with something like
In a lot of cases with recent systems, the processor isn''t the real bottleneck, so you''ll see a better improvement if you try to optimise memory and hard disk usage (hence -Os).
Also, beware of -ffast-math. On modern processors, the FPU math is quite fast enough, and -ffast-math can produce inaccurate results. As one of the Gentoo developers said: "If I want my math done wrong, I''ll ask my cat."
Disclaimer: I don''t have a P4, and I haven''t benchmarked any of these.
-march=pentium4 -Os -pipe -fomit-frame-pointer -msse2 -mfpmath=sse
In a lot of cases with recent systems, the processor isn''t the real bottleneck, so you''ll see a better improvement if you try to optimise memory and hard disk usage (hence -Os).
Also, beware of -ffast-math. On modern processors, the FPU math is quite fast enough, and -ffast-math can produce inaccurate results. As one of the Gentoo developers said: "If I want my math done wrong, I''ll ask my cat."
Disclaimer: I don''t have a P4, and I haven''t benchmarked any of these.
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