Messages in this thread | | | Date | Fri, 24 Apr 1998 19:12:30 +0200 | From | Alexander Kjeldaas <> | Subject | Re: faster strcpy() |
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On Fri, Apr 24, 1998 at 11:49:05AM -0400, Richard B. Johnson wrote: > > Directly using the built-in Intel macros such as: > > rep movsb > rep movsw > rep movslw > .... etc > > is not the most efficient way unless the strings are very short. Using > cache-aligned long-word instructions in which register operations can > occur at the same time memory accesses are happening, will be most > efficient.. > > The new glibc "knows" about this stuff. Also the kernel code "knows" > about this stuff. >
But this isn't true on all processors. It is true on the pentium, but probably not on the pentium pro/II. On the pentium pro, rep movsl is highly optimized microcode. It takes over the whole microarchitecture and utilizes all possible instruction units (that's why you can't run other instructions in parallell with a 'rep' instruction on a pentium pro). I haven't checked this, but take Andy Glew's word for it :-).
astor
-- Alexander Kjeldaas, Guardian Networks AS, Trondheim, Norway http://www.guardian.no/
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