Luya Tshimbalanga wrote:
> Igor mentioned it is possible to build embree without that instruction
> which is beyond my current skills thus bringing more questions.
It is possible to build Embree without SSE3 and beyond (including AVX),
i.e., with only SSE2, but, as everything beyond SSE2 is runtime-detected, it
is not necessary to disable it completely.
> Considering the recent LuxRender required embree, won't building without
> these instructions set impact such dependancy?
The only impact it would have is on performance. But again, it is not
necessary nor desirable to disable runtime-detected support for vector
instructions. It is only a problem when they are used unconditionally.
The only issue is really that SSE2 is required unconditionally, but it
doesn't look like there is much that can be done about it. This is
unfortunate, because it also breaks support for all non-x86 architectures.
But it would be a lot of work to fix that. (And looking at LuxRender, I also
see hardcoded SSE2 usage there all over the place, both in hardcoded compile
flags and in the code. So Embree is not the only problem there.)
Also note that it is fine to require SSE2 (and also SSE(1) and MMX) on
x86_64. All x86_64 CPUs support SSE2 (and lower). It is only a problem on
i686 (and non non-x86 architectures where the code likely won't build at
all).
Kevin Kofler
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