Nicolas Calimet <pov### [at] freefr> wrote:
>  AFAIK at the time 3.5 was released the available compilers were not
> able to automatically generate SSE2-optimized code for that particular peace
> of code, and Intel contributed the hand-optimized code you are referring to.
> Nowadays the situation is much different since, in particular, the Intel C++
> compiler greatly improved its optimization framework (the GCC compiler did
> also improve a lot, though it is still not as good as ICPC at optimizing on
> the P4 architecture; K8 might be slightly different though).  Therefore,
> the 3.6 codebase didn't need this hand-optimization any longer.

That is not true. I have recently studied the sse support of icc and gcc in
detail. It will not do that kind of optimization (performing the noise
calculation with SIMD parallel instructions) with the unmodified POV-Ray
noise code. It still needs much care to the code in order for the compiler
to do automatic optimization.

What the compilers currently do well is using the see2 registers (xmm)
instead of the floating point stack to do the floating point computations.
But when you look at the assembler you will see that all comuptations are
not done in parallel.

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