[Opensim-dev] FYI: Mono's SIMD Support: Making Mono safe for Gaming

[Eugen Leitl]

http://tirania.org/blog/archive/2008/Nov-03.html

Mono's SIMD Support: Making Mono safe for Gaming

This week at the Microsoft PDC we introduced a new feature in the Mono virtual machine that we have been working on quietly and will appear in our upcoming Mono 2.2 release (due in early December).

I believe we are the first VM for managed code that provides an object-oriented API to the underlying CPU SIMD instructions.

In short, this means that developers will be able to use the types in the Mono.Simd library and have those mapped directly to efficient vector operations on the hardware that supports it.

With Mono.Simd, the core of a vector operations like updating the coordinates on an existing vector like the following example will go from 40-60 CPU instructions into 4 or so SSE instructions.

Vector4f Move (Vector4f [] pos, ref Vector4f delta)
{
	for (int i = 0; i < pos.Length; i++)
		pos [i] += delta;
}
	

Which in C# turns out to be a call into the method Vector4f.operator + (Vector4f a, Vector4f b) that is implemented like this:

Vector3f static operator + (Vector3f a, Vector3f b)
{
	return new Vector3f (a.x+b.x, a.y+b.y, a.z+b.z, a.w+b.w);
}
	

The core of the operation is inlined in the `Move' method and it looks like this:

movups (%eax),%xmm0
movups (%edi),%xmm1
addps  %xmm1,%xmm0
movups %xmm0,(%eax)
	
etc.

-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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