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The `TEST_INPUT` facility allows textual Slang test cases to provide two kinds of information to the `render-test` tool:
1. Information on what shader inputs exist
2. Information on what values/objects to bind into those shader inputs
Under the first category of information, there exists supporting for attaching a `dxbinding(...)` annotation to a `TEST_INPUT` which seemingly indicates what HLSL `register` the input uses. There is a similar `glbinding(...)` annotation, used for OpenGL and Vulkan.
It turns out that these annotations were, in practice, completely ignored and had no bearing on how `render-test` allocates or bindings graphics API objects. There was some amount of code attempting to validate that explicit registers/bindings were being set appropriately, but the actual values were being ignored.
The visible consequence of the `dxbinding` and `glbinding` annotations being ignored is issue #1036: the order of `TEST_INPUT` lines was *de facto* determining the registers/bindings that were being used by `render-test`.
This change simply removes the placebo features and strips things down to what is implemented in practice: the `TEST_INPUT` lines do not need target-API-specific binding/register numbers, because their order in the file implicitly defines them.
I added logic to the parsing of `TEST_INPUT` lines to make sure I got an error message on any leftover annotations, and went ahead and systematicaly deleted all of the placebo annotations from our test cases.
If we decide to make `TEST_INPUT` lines *not* depend on order of declaration in the future, we can build it up as a new and better considered feature.
The main alternative I considered was to keep the annotations in place, and change `render-test` and the `gfx` abstraction layer to properly respect them, but that path actually creates much more opportunity for breakage (since every single test case would suddenly be specifying its root signature / pipeline layout via a different path using data that has never been tested). The approach in this change has the benefit of giving me high confidence that all the test cases continue to work just as they had before.
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* Fix up handling of NumElements for D3D buffer views
For everything but structured buffers we'd been setting this to the size in bytes, but that isn't really valid at all.
The `NumElements` member in the view descs is supposed to be the number of buffer elements, so it would be capped at the byte size divided by the element size.
This change fixes the computation of `NumElements` to take the size of the format into account for non-structured views.
For the "raw" case, we use a size of 4 bytes since that matches the `DXGI_FORMAT_R32_TYPELESS` format we use (which seems to be required for raw buffers).
I also added support for the raw case for SRVs where it didn't seem to be supported before (not that any of our tests cover it).
* Fix handling of size padding for D3D11 buffers
The existing code was enforcing a 256-byte-aligned size for all buffers, but this can cause problems for a structured buffer.
A structured buffer must have a size that is a multiple of the stride, so a structured buffer with a 48-byte stride and a 96-byte size would get rounded up to 256 bytes, which is not an integer multiple of 48.
This change makes it so that we only apply the padding to constant buffers.
According to MSDN, constant buffers only require padding to a 16-byte aligned size, and no other restrictions are listed for D3D11, but it is difficult to know whether those constrains are exhaustive.
I've left in the 256-byte padding for now (rather than switch to 16-byte), even though I suspect that was only needed as a band-aid for the `NumElements` issue fixed by another commit.
* Fix an IR generation bug when indxing into a strutured buffer element
The problem here arises when we have a structured buffer of matrices (an array type would likely trigger it too):
```hlsl
RWStructuredBuffer<float3x4> gMatrices;
```
and then we index into it directly, rather than copying to a temporary:
```hlsl
// CRASH:
float v = gMatrices[i][j][k];
// OKAY:
float3x4 m = gMatrices[i];
float v = m[j][k];
```
The underlying issue is that our IR lowering pass tries to defer the decision about whether to use a `get` vs. `set` vs. `ref` accessor for a subscript until as late as possible (this is to deal with the fact that sometimes D3D can provide a `ref` accessor where GLSL can only provide a `get` or `set`).
We probably need to overhaul that aspect of IR codegen sooner or later, but this change uses some of the existing machinery to try to force the `gMatrices[i]` subexpression to take the form of a pointer when doing sub-indexing like this. This fixes the present case, and hopefully shouldn't break anything else that used to work (because the subroutines I'm using to coerce the `gMatrices[i]` expression should be idempotent on the cases that were already implemented).
* Add a test case to confirm fxc/dxc layout for structured buffers of matrices
Even when row-major layout is requested globally, fxc and dxc seem to lay out a `StructuredBuffer<float3x4>` with column-major layout on the elements.
This commit adds a test that confirms that behavior.
This commit does not try to implement a fix for the issue (either fixing Slang's layout reflection information to be correct for what fxc/dxc do in practice, or fixing Slang's HLSL output to work around the fxc/dxc behavior), but just documents the status quo.
If/when we decide how we'd like to handle the issue long-term, this test can/should be updated to match the decision we make.
* fixup: build breakage on clang/gcc
This is one of those cases where the Microsoft compiler is letting through some stuff that isn't technically valid C++ ("delayed template parsing").
Fixed by just moving some declarations to earlier in the file.
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