[RC5] Runtime optimization??
Décio Luiz Gazzoni Filho
decio at decpp.net
Wed Mar 1 18:42:10 EST 2006
On Mar 1, 2006, at 8:20 PM, Fugu wrote:
> Why don't the cruncher cores compiled using fftw-like optimizations?
> Assembly code may be slightly faster, but in needs to be remade for
> every platform...
This technique is worthwhile in FFTW (and even then, specialized
packages handily beat FFTW) because of issues like memory/cache
organization, size, speed, etc. RC5 is immune to those variations --
it is only affected by register allocation and instruction scheduling.
An effective FFTW-like optimizer for RC5 would be pretty similar to a
general C compiler's code generator/optimizer. Not only is this an
overly complicated piece of software, but it can't schedule
instructions all that well anyway -- just look at the performance of
C cores. Plus I dare any compiler's code generator to produce
something like kakace's software pipelined Altivec+integer RC5 core.
By the way, `assembly code may be slightly faster' qualifies for
understatement of the year. Even generic assembly code, without
targeting a specific processor, would easily beat the C cores.
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