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From Brian Pane <bp...@pacbell.net>
Subject Re: [PATCH] Re: 2.0 performance Re: Breaking something? Now is the time?
Date Sat, 29 Jun 2002 21:04:53 GMT
Cliff Woolley wrote:

>On Sat, 29 Jun 2002, Cliff Woolley wrote:
>
>  
>
>>some way that would allow us to coalesce the writes.
>>    
>>
>
>Alignment issues would kill us here, aren't they?  That sucks.  Grrrr.....
>  
>

We might be able to get some additional improvements by
doing word-at-a-time operations for half of the copy operation:
  - start with the current byte-at-a-time loop
  - as soon as "buf" points to a word-aligned address,
    switch to a mode in which we grab the next sizeof(int)
    bytes from the input string, pack them into an int
    (with ifdef'ed code for big- and little-endian machines),
    and write the int to the target address.

But that might or might not actually be faster (we'd be doing
more instructions in order to do fewer memory writes).  And
it's more complicated than the unrolled-loop code, of course.
So for now, I'll stick with the unrolled-loop implementation,
since it's showing good results in benchmark testing.

--Brian



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