NV_shader_buffer_{load,store} is a 2010 extension that allows GL applications
to use what in Vulkan is known as physical pointers, this is basically C
pointers. On GLASM these is exposed through the LOAD/STORE/ATOM
instructions.
Up until now, assembly shaders were using NV_shader_storage_buffer_object.
These work fine, but have a (probably unintended) limitation that forces
us to have the limit of a single stage for all shader stages. In contrast,
with NV_shader_buffer_{load,store} we can pass GPU addresses to the
shader through local parameters (GLASM equivalent uniform constants, or
push constants on Vulkan). Local parameters have the advantage of being
per stage, allowing us to generate code without worrying about binding
overlaps.
Add code required to use OpenGL assembly programs based on
NV_gpu_program5. Decompilation for ARB programs is intended to be added
in a follow up commit. This does **not** include ARB decompilation and
it's not in an usable state.
The intention behind assembly programs is to reduce shader stutter
significantly on drivers supporting NV_gpu_program5 (and other required
extensions). Currently only Nvidia's proprietary driver supports these
extensions.
Add a UI option hidden for now to avoid people enabling this option
accidentally.
This code path has some limitations that OpenGL compatibility doesn't
have:
- NV_shader_storage_buffer_object is limited to 16 entries for a single
OpenGL context state (I don't know if this is an intended limitation, an
specification issue or I am missing something). Currently causes issues
on The Legend of Zelda: Link's Awakening.
- NV_parameter_buffer_object can't bind buffers using an offset
different to zero. The used workaround is to copy to a temporary buffer
(this doesn't happen often so it's not an issue).
On the other hand, it has the following advantages:
- Shaders build a lot faster.
- We have control over how floating point rounding is done over
individual instructions (SPIR-V on Vulkan can't do this).
- Operations on shared memory can be unsigned and signed.
- Transform feedbacks are dynamic state (not yet implemented).
- Parameter buffers (uniform buffers) are per stage, matching NVN and
hardware's behavior.
- The API to bind and create assembly programs makes sense, unlike
ARB_separate_shader_objects.
After a compute shader was set to the pipeline, no graphics shader was
invoked again. To address this use glUseProgram to bind compute shaders
(without state tracking) and call glUseProgram(0) when transitioning out
of it back to the graphics pipeline.
Emulates negative y viewports with ARB_clip_control. This allows us to
more easily emulated pipelines with tessellation and/or geometry shader
stages. It also avoids corrupting games with transform feedbacks and
negative viewports (gl_Position.y was being modified).
We can just pass in the Maxwell3D instance instead of going through the
system class to get at it.
This also lets us simplify the interface a little bit. Since we pass in
the Maxwell3D context now, we only really need to pass the shader stage
index value in.
Those implementations are quite costly, so there is no need to inline them to the caller.
Ressource deletion is often a performance bug, so in this way, we support to add breakpoints to them.
Namespaces all OpenGL code under the OpenGL namespace.
Prevents polluting the global namespace and allows clear distinction
between other renderers' code in the future.
We keep track of the current instance and update an uniform in the shaders to let them know which instance they are.
Instanced vertex arrays are not yet implemented.
Avoids performing unnecessary copies of 65560 byte sized ShaderSetup
instances, considering it's only used as part of lookup and not
modified.
Given the parameters were already const, it's likely taking these
parameters by reference was intended but the ampersand was forgotten.
All tested games that use a single texture show no regression.
Only Texture2D textures are supported right now, each shader gets its own "tex_fs/vs/gs" sampler array to maintain independent textures between shader stages, the textures themselves are reused if possible.
