[Mesa-dev] [PATCH 05/12] nir: rename global/local to private/function memory

[Kenneth Graunke]

On Tuesday, December 4, 2018 10:26:43 AM PST Karol Herbst wrote:
> the naming is a bit confusing no matter how you look at it. Within SPIR-V
> "global" memory is memory accessible from all threads. glsl "global" memory
> normally refers to shader thread private memory declared at global scope. As
> we already use "shared" for memory shared across all thrads of a work group
> the solution where everybody could be happy with is to rename "global" to
> "private" and use "global" later for memory usually stored within system
> accessible memory (be it VRAM or system RAM if keeping SVM in mind).
> glsl "local" memory is memory only accessible within a function, while SPIR-V
> "local" memory is memory accessible within the same workgroup.
> 
> v2: rename local to function as well
> 
> Signed-off-by: Karol Herbst <kherbst at redhat.com>

I strongly dislike this patch, and I think we ought to revert it.

This probably makes sense from an OpenCL memory-model view of the world,
but it's really confusing from a compiler or general programming point
of view.

/Everybody/ knows what a local variable is.  It's one of the most used
concepts in programming.  Calling it nir_var_function is very confusing.
The variable is a...function?  Maybe it's a function pointer?  Neither
of those things even exist in GLSL, so...what the heck is it?

Renaming global scope variables to "private" is also confusing IMO.
They're certainly not private to a function.  They're globally
accessible by anything in the whole shader.  I'll admit "global" isn't
a great name either.

I think we need to discuss this more.  There are people with large
series of outstanding work that now have to rebase on this flag day
rename, and I don't think two people is enough consensus for renaming
a core IR concept.  Can we find names we're all happy with?

--Ken
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