[bf1942] x86 optimizations?

ScratchMonkey ScratchMonkey at SewingWitch.com
Sat Dec 28 23:17:08 EST 2002


--On Saturday, December 28, 2002 5:12 AM -0500 "Ryan C. Gordon" 
<icculus at clutteredmind.org> wrote:

>> Will it be using this information in the (near) future to do any sort of
>> optimization for any specific CPU?
>
> If DICE adds it, but I wouldn't count on it. See below.

Optimization using special instructions is not that useful unless the code 
is designed for it. What *is* useful is to recompile critical code (eg. 
inner loops and other places that profiling reveals a lot of time is spent 
in) for specific CPU's so that instructions are correctly ordered. 
Different CPU's in the x86 family have different optimal instruction orders 
for common sequences, to maximize utilization of the chip's internal 
pipelines and parallelism not visible to the programmer.

Hence, it would be useful to build separate builds for each CPU to get 
instruction ordering optimizations in critical code.



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