[Mono-dev] Patch for IPAddress.cs

[Jonathan Gilbert]

At 12:04 PM 3/25/2007 +1000, Gareth Pearce wrote:
>> However, as a comparison, the MS.NET implementation
>> completes 15 loops of the benchmark in a mere 6718ms ;)
>
>On this point, I suspect AOT compilation of the .Net system assemblies 
>may be making the difference.  The AOT might be able to recognize 
>certain patterns are equivalent to rot instructions and replace a bunch 
>of shifts and masks with a set of unsigned rots.
>
>A 32bit reorder is rot 8 on each of the 16 bit sections and a rot 16 on 
>the full variable.  I think that can be done in 3 clocks on x86 - but my 
>assembly is rusty.

x86 actually has an instruction whose sole purpose is to invert the byte
order of a 32-bit value. Look up BSWAP. It requires at least a 486, though.
Does mono otherwise run on 386 CPUs presently? If it is okay to exclude 386
systems (or they can be detected on-the-fly and given the alternative 3
instructions), then perhaps it would be possible to do something like
marking it as an icall and having the JIT recognize that method and inline
it as just a BSWAP.

Jonathan Gilbert