An interesting article about it: http://www.g-truc.net/post-0714.html

I wonder in general will Apple and MS support SPIR-V or they'll play nasty and not support it just to make life harder for everyone?

Also, will Apple push Metal to OS X, or they'll support Vulkan going forward? Their support for OpenGL was very much lagging behind.

I suspect Apple's lagging OpenGL support is mainly due to their reliance on Intel GPUs and their reluctance to fragment the Mac hardware platform. They don't like it when users of their low-end or ultraportable machines complain that games won't run at any speed.

On the other hand, they created OpenCL and they obviously want their developers to have access to this kind of hardware capability. Their problem now is getting developers to actually make use of it, and for that they'll have to implement SPIR-V if that's what catches on. (Provided again that all of their hardware can support it.)

At least for Vulkan it seems you need Haswell and up in case of Intel (i.e. what supports OpenGL ES 3.1).

So SPIR-V is completely unrelated to the previous attempt at a portable IR layer for compute kernels, named SPIR? This is crazy. Why is Khronos trying to be confusing?

SPIR-V is clearly intended to be the successor and replacement for SPIR, and the name seems to be different enough to allow for breaking compatibility. (By one reading, it's incrementing the major version number by 3.)