Add GL_EXT_subgroupuniform_qualifier extension

[allanmac]

Is the GL_EXT_subgroupuniform_qualifier extension implemented?

[johnkslang]

I don't see this in the code base.

[sheredom]

I've got a partial implementation but I'm still working on it.

[sheredom]

https://github.com/KhronosGroup/glslang/pull/1497

[allanmac]

Is there still interest in implementing this extension?

I have a large pile of compute shaders with subgroupuniformEXT annotations and am still curious if there will be a performance improvement (or bugs) due to reduced register pressure.

[greg-lunarg]

There are still a few unresolved requests on #1497 written by @sheredom. Not sure if he is still working on Vulkan issues. If not, we will need someone to pick this up.

[sheredom]

I've bailed on Khronos 1 & 1/2 years ago - so this isn't for me alas!

Good luck though.