> Nicolas concluded:
> 
>>>> Therefore,
>>>> the 3.6 codebase didn't need this hand-optimization any longer.
> 
> I assume that we want the binaries as fast as possible, so why should the
> hand-optimizations no longer be used if they are still faster?

	The whole point here exactly stands in your very last few words: are
those hand-optimizations *still* faster than the compiler-optimized code
on current processors?  According to our tests with both POV-Ray 3.6 for
Windows and for Linux -- they are not.
	To the contrary these hand-optimizations nowadays tend to slow down
the program execution.  For instance you can end up with at least a 25%
speed loss in rendering the official benchmark (that uses Noise quite a bit)
on current Pentium 4 processors, as compared to compiler-optimized binaries.
Most likely this disappointing result has to do with the micro-architecture
of those processors, in particular lengthy pipelines (think P4 Northwood /
Prescott and Pentium D in particular) that probably voids the benefit of
using SIMD parallel instructions.  However I'm not qualified enough to argue
on that matter...

	- NC

PS: Note that I didn't try the hand-optimizations on the AMD K8, but I don't
expect them to give anything better than on the P4; I couldn't test on a
Pentium-M either.  Also the latest architectures that Intel is currently
(Intel Core) or will soon (Conroe and Merom) be introducing might not even
change the deal, since the current and future compilers will most likely
produce much better output for them.

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