On Fri, Jan 11, 2019 at 10:19 AM Kenneth Graunke <kenn...@whitecape.org> wrote:
> On Wednesday, January 9, 2019 5:33:22 PM PST Ian Romanick wrote: > > On 1/8/19 9:57 PM, Kenneth Graunke wrote: > > > 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 <kher...@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. > > > > It seems like the concepts we're after a function local and thread > > local, so why not nir_var_thread_local (for old nir_var_global) and > > nir_var_function_local (for old nir_var_local). When "global" is > > reintroduced to mean thread global, we could add it as > > nir_var_thread_global. That seems to match at least one reasonable view > > of a storage hierarchy. > > Those names (nir_var_func_local, nir_var_thread_local, and > nir_var_thread_global) make more sense to me than private/function. > > Another option is `nir_var_local_temp` and `nir_var_shader_temp`, > indicating that they're just temporary variables, and not anything > with special semantics like memory. shader_temp would pair well with > the existing shader_in/shader_out, since they have the same scope. > > I might also consider adding 'mem' to variables representing memory. > > So that would look like... > > nir_var_shader_in > nir_var_shader_out > nir_var_shader_temp (formerly local/function) > nir_var_local_temp (formerly global/private) > Are those flipped? > nir_var_uniform > nir_var_system_value > nir_var_mem_ubo (added mem) > nir_var_mem_ssbo (added mem) > nir_var_mem_shared (added mem) > nir_var_mem_global (the new global memory type being introduced) > > How does that look? > I think I kind of like having "mem" be on external things. Shared is a little weird there because it never leaves the chip so is it mem or shader? > We may also want to rename the nir->globals list, or > nir_lower_global_vars_to_local and nir_opt_global_to_local. Not sure. > Yes, whatever we do, we should make those lists more consistent.
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