This is probably the most ugly and controversial bit of API. I don't really know
if this is the right approach to solving this.
sm4 registers match by register index, such that shaders can mostly be compiled
in isolation. sm1 does not—registers may be specified in any order in the vertex
and pixel shaders, and will be matched by usage and usage index.
By itself this is not much of a problem. Where it gets hairy is that we want to
do some degree of caching, as well as pre-compilation, and avoid recompiling
either shader every time it's matched with a new one.
Wine currently deals with this problem, for GLSL, by generating a "main" GLSL
shader for the vertex shader, and then an extra function setup_vs_output(), and
linking the two together every time a new pixel shader is used. This could in
theory be used for SPIR-V, but it requires the use of extra, probably external,
code to link SPIR-V shaders together, which I do not particularly anticipate
being well-received.
(I'm not sure how Wine deals with this problem in the ARB backend. It seems to
take the pixel shader signature into account when generating the vertex shader—
cf. init_output_registers()—but it doesn't take it into account when looking up
a vertex shader variant? I didn't look too closely at the code, so maybe I'm
missing something.)
--
The vkd3d parts of this patch are quite straightforward, and looking at them, I
think the design is quite intuitive in isolation. There may be some room for
internal refactoring (in particular with an eye to not so much overloading
the "register_index" field of struct shader_signature_element) but I'm
relatively happy with the way it turned out. In isolation, that is.
The Wine part is worse. I've uploaded branches for vkd3d and Wine that use this
API, and correctly handle shaders with some nontrivial reordering:
https://gitlab.winehq.org/zfigura/vkd3d/-/commits/himavant5https://gitlab.winehq.org/zfigura/wine/-/commits/himavant_cb
The test can be run, as before, like so:
make tests/shader_runner.exe && WINE_D3D_CONFIG=renderer=vulkan wine tests/shader_runner.exe ../vkd3d/tests/hlsl/sm1-interstage-interface.shader_test
The interesting Wine parts are concentrated in a single patch, 5cfb9d930f11e.
The patch takes a few shortcuts, partly because I wanted not to block the vkd3d
API design questions, but also because while writing it I came up with a couple
of problems that I wasn't sure how to fix. There are two main problems I see:
(1) This patch has the user pass the signature from the pixel shader when
compiling the vertex shader, and looks up register indices already
arbitrarily allocated by the pixel shader. This is problematic when trying
to use this signature as a cache key, by virtue of it not being clear (or
even defined) which fields are key elements and which aren't. It's also not
particularly kind to lookup, on account of not being directly comparable
with memcmp(). There are a few options I see:
(a) Provide an internal function to compare key elements. This feels... odd,
like a very special-purpose function, but perhaps workable.
(b) Just make the user deal with it, and assert that all fields are key
elements.
(c) Use some alternative, perhaps shortened structure as a field of
vkd3d_shader_next_stage_info. This has the disadvantage that it is not
as simple for a hypothetical user to retrieve from the pixel shader, but
we would presumably provide a function to generate one from a shader
signature. This would probably also be kinder to cache lookup if it's
shorter.
(d) Make caching vkd3d's responsibility, to some degree. This seems
daunting, but the more we optimize, the more difficult it may be to
design API that allows for nice caching.
(2) Assuming we use signatures, there is a memory management problem that
5cfb9d930f11e spells out. This is probably a matter of "just fix it", but
I suppose another option is to take the GLSL or ARB architecture.
--
April is the cruellest month, breeding
Lilacs out of the dead land, mixing
Memory and desire, stirring
Dull roots with spring rain.
--
v8: vkd3d-shader: Introduce a function to build a varying map between sm1 stages.
vkd3d-shader/spirv: Make output varyings not consumed by the next stage private variables.
vkd3d-shader: Implement remapping shader output registers to match the next shader's semantics.
https://gitlab.winehq.org/wine/vkd3d/-/merge_requests/280
It's no problem to send fewer of these per MR. I have included the complete set because all but the last introduce no functional changes, and upstreaming a smaller set would leave the changes in a half-done state with unnecessary buffering.
--
This merge request has too many patches to be relayed via email.
Please visit the URL below to see the contents of the merge request.
https://gitlab.winehq.org/wine/vkd3d/-/merge_requests/294
Recap:
I implemented relative addressing in !229, but I was suggested to handle register indexes by moving all the registers to the heap, which I did in my [nonconst-offsets-6](https://gitlab.winehq.org/fcasas/vkd3d/-/commits/noncon… branch. A part of this implementation required !269, but I was asked to try to turn the sm4 register structs into the vkd3d-shader register structs instead, to get closer to a common low level IR.
This is the first part of that transformation. The whole thing is in my [use_vkd3d_reg](https://gitlab.winehq.org/fcasas/vkd3d/-/commits/use_vkd3d_r… branch.
~~This is built on top of !225 (the first two patches), so it may be good to get that upstream first.~~
---
This patch series aims to do the following replacements:
```
struct sm4_register -> struct vkd3d_shader_register
struct sm4_dst_register -> struct vkd3d_shader_dst_param
struct sm4_src_register -> struct vkd3d_shader_src_param
```
to get us closer to a common level IR and simplify the implementation of relative-addressing.
To achieve this, the fields in the sm4 register structs are replaced with fields in the vkd3d-shader structs or removed altogether, one at the time.
As can be seen when looking at the whole branch, it is possible to do this transformation without having to add additional fields to `struct vkd3d_shader_register`, by restricting each register type to a single `enum vkd3d_sm4_dimension` (and its src registers to a single `enum vkd3d_sm4_swizzle_type`) by default.
The only exception we need so far is for sampler registers: They always have dimension NONE, except when used as arguments of gather instructions, in which case they have dimension VEC4 and SCALAR swizzle. This, and similar exceptions we may find in the future, can be handled using the opcode_info, as in 7/8 [81e17506](https://gitlab.winehq.org/fcasas/vkd3d/-/commit/81e17506ba2cb1fbf….
--
v5: vkd3d-shader/tpf: Get rid of sm4_register.dim.
vkd3d-shader/tpf: Use 's' in src_info to expect sampler register with vec4 dimension.
vkd3d-shader/tpf: Separate dst register write function.
vkd3d-shader/tpf: Separate src register write function.
vkd3d-shader/tpf: Make register_type_table an array of structs with lookup tables.
vkd3d-shader/tpf: Introduce struct tpf_writer to group sm4 write arguments.
vkd3d-shader/tpf: Use struct vkd3d_shader_register_index in sm4_register.idx[].
vkd3d-shader/tpf: Allow passing NULL register type on hlsl_sm4_register_from_semantic().
vkd3d-shader/tpf: Use enum vkd3d_shader_register_type in sm4_register.type.
https://gitlab.winehq.org/wine/vkd3d/-/merge_requests/281