Runtime: Add float16 support to bigarray

[hhugo]

float16array is not widely supported.

[hhugo]

@vouillon, I think the wasm runtime needs to be updated somehow. Can you take a look ?

[hhugo]

@vouillon, I think there is a bug in the wasm runtime of bigarrays plus we need to add support for float16.
I'd like to include this in the 6.0 release. Can you take a look ?

[hhugo]

Thanks for the wasm support.
The js runtime uses Uint16Array which has the same memory layout as float16,
The wasm runtime uses Float32Array which has a larger memory footprint but saves us some conversion.
@vouillon, do you think we can leave it like this ? Should we unify the two ?

[vouillon]

@hhugo Maybe I should switch to using Uint16array typed arrays, actually. Eventually, we should use Float16Array, but it's still under a flag in Chrome, and cannot be used with WebGL in Safari:
https://github.com/WebKit/WebKit/blob/9fca11bf1d0cc85c923d86c2a8e71045c30dfc98/Source/WebCore/html/canvas/WebGLRenderingContextBase.cpp#L3767-L3769

[hhugo]

@hhugo Maybe I should switch to using Uint16array typed arrays, actually. Eventually, we should use Float16Array, but it's still under a flag in Chrome, and cannot be used with WebGL in Safari: https://github.com/WebKit/WebKit/blob/9fca11bf1d0cc85c923d86c2a8e71045c30dfc98/Source/WebCore/html/canvas/WebGLRenderingContextBase.cpp#L3767-L3769

Should I wait for this change ?

[hhugo]

(I've a commit that uses float16array in js if available but maybe we should sit on it given the safari situation, 5099f19)

[vouillon]

Should I wait for this change ?

I'll try to do that tomorrow