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<title>slang.git/tests/compute/global-type-param1.slang, branch master</title>
<subtitle>Making it easier to work with shaders</subtitle>
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<updated>2021-03-17T19:55:30+00:00</updated>
<entry>
<title>Remove old code paths from render-test (#1760)</title>
<updated>2021-03-17T19:55:30+00:00</updated>
<author>
<name>Tim Foley</name>
<email>tfoleyNV@users.noreply.github.com</email>
</author>
<published>2021-03-17T19:55:30+00:00</published>
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<id>urn:sha1:6e5d85efb9fa5f647f7f0c7ef784a9fd09b29023</id>
<content type='text'>
* Remove old code paths from render-test

Historically, the `render-test` tool was using three different code paths:

* One based on `gfx` and manual (non-reflection-based) parameter setting, used for OpenGL, D3D11, D3D12, and Vulkan
* One for CPU that used reflection-based parameter setting but shared no code with the first
* One for CUDA that used reflection-based parameter setting and shared some, but not all, code with the CPU path

Recently we've updated `render-test` to include a fourth option:

* Using `gfx` and the "shader object" system it exposes for a unified reflection-based parameter-setting system taht works across OpenGL, D3D11, D3D12, Vulkan, CUDA, and CPU

This change removes the first three options and leaves only the single unified path. A sa result, a bunch of code in `render-test` is no longer needed, and the codebase no longer relies on things like the `IDescriptorSet`-related APIs in `gfx`.

Several existing tests had to be disabled to make this change possible. Those tests will need to be audited and either re-enabled once we fix issues in the shader object system, or permanently removed if they don't test stuff we intend to support in the long run (e.g., global-scope type parameters, which aren't a clear necessity).

* fixup: CUDA detection logic</content>
</entry>
<entry>
<title>Add shader object parameter binding to renderer_test. (#1622)</title>
<updated>2020-12-03T16:23:05+00:00</updated>
<author>
<name>Yong He</name>
<email>yonghe@outlook.com</email>
</author>
<published>2020-12-03T16:23:05+00:00</published>
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<id>urn:sha1:44c0a56974b664e50b2cb8cb6f10740b19c4e02f</id>
<content type='text'>
* Add shader object parameter binding to renderer_test.

* remove multiple-definitions.hlsl

* Fix cuda implementation.

Co-authored-by: Tim Foley &lt;tfoleyNV@users.noreply.github.com&gt;</content>
</entry>
<entry>
<title>Remove support for explicit register/binding syntax on TEST_INPUT (#1132)</title>
<updated>2019-11-21T22:06:19+00:00</updated>
<author>
<name>Tim Foley</name>
<email>tfoleyNV@users.noreply.github.com</email>
</author>
<published>2019-11-21T22:06:19+00:00</published>
<link rel='alternate' type='text/html' href='https://git.yummers.dev/slang.git/commit/?id=2ea64ff4f2c7c43b72ff24650330fca79a87500f'/>
<id>urn:sha1:2ea64ff4f2c7c43b72ff24650330fca79a87500f</id>
<content type='text'>
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.</content>
</entry>
<entry>
<title>Allow entry points to have explicit generic parameters (#826)</title>
<updated>2019-02-06T00:47:25+00:00</updated>
<author>
<name>Tim Foley</name>
<email>tfoleyNV@users.noreply.github.com</email>
</author>
<published>2019-02-06T00:47:25+00:00</published>
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<id>urn:sha1:60cc9f24c4bec54561bea873ee943aa3d0973dc2</id>
<content type='text'>
* Allow entry points to have explicit generic parameters

Prior to this change, the Slang implementation required users to use global `type_param` declarations in order to specialize a full shader. For example:

```hlsl
type_param L : ILight;
ParameterBlock&lt;L&gt; gLight;

[shader("fragment")]
float4 fs(...)
{ ... gLight.doSomething() ... }
```

With this change we can rewrite code like the above using explicit generics, plus the ability to have `uniform` entry-point parameters:

```hlsl
[shader("fragment")]
float4 fs&lt;L : ILight&gt;(
    uniform ParameterBlock&lt;L&gt; light,
    ...)
{ ... light.doSomething() ... }
```

Having this support in place should make it possible for us to eliminate global generic type parameters and the complications they cause (both at a conceptual and implementation level).

The most central and visible piece of the change is that `EntryPointRequest` now holds a `DeclRef&lt;FuncDecl&gt;` instead of just ` RefPtr&lt;FuncDecl&gt;`, which allows it to refer to a specialization of a generic function.
Various places in the code that refer to the `EntryPointRequest::decl` member now use a `getFuncDecl()` or `getFuncDeclRef()` method as appropriate (see `compiler.h`).

In order to fill in the new data, the `findAndValidateEntryPoint` function has been greaterly overhauled.
The changes to its operation include:

* The by-name lookup step for the entry point function has been adapted to accept either a function or a generic function.

* The generic argument strings provided by API or command line are no longer parsed all the way to `Type`s, but instead just to `Expr`s in the first pass.

* There are now two cases for checking the global generic arguments against their matching parameters. The first case is the new one, where we plug the generic argument `Expr`s into the explicit generic parameters of an entry point (that case re-uses existing semantic checking logic).  The second case is the pre-existing code for dealing with global generic type arguments.

The `lower-to-ir.cpp` logic for hadling entry points then had to be extended. Making it deal with a full `DeclRef` instead of just a `Decl` was the easy part (just call `emitDeclRef` instead of `ensureDecl`).
The more interesting bits were:

* We need to carefully add the `IREntryPointDecoration` to the nested function and not the generic in the case where we have a generic entry point. There is a handy `getResolvedInstForDecorations` that can extract the return value for an IR generic so that we can decorate the right hting.

* We need to make sure that in the case where we emit a `specialize` instruction (which normally wouldn't get a linkage decoration), we attach an `[export(...)]` decoration to it with the mangled name of the decl-ref, so that it can be found during the linking step.

The IR linking step is then slightly more complicated because the mangled entry point name could either refer directly to an `IRFunc` or to a `specialize` instruction for a generic entry point. The logic was refactored to first clone the entry point symbol without concern for which case it is (the old code was specific to functions), and then *if* the result is a `specialize` instruction, we attempt to run generic specialization on-demand.

That on-demand specialization is a bit of a kludge, but it deals with the fact that all the downstream passing only expect to see an `IRFunc`. A future cleanup might try to split out that specialization step into its own pass, which ends up being a limited form of the specialization pass.

Since I was already having to touch a lot of the code around IR linking, I went ahead and refactored the signature of the operations. I eliminated the need for the caller to create, pass in, and then destroy an `IRSpecializationState` (really an IR *linking* state), and replaced it with a structure local to the pass (that data structure was a remnant of an older approach in the compiler), and then also renamed the main operation to `linkIR` to reflect what it is doing in our conceptual flow.

Smaller changes made along the way include:

* Refactored `visitGenericAppExpr` to create a subroutine `checkGenericAppWithCheckedArgs` so that it can be used by the entry-point validation logic described above).

* Refactored the declarations around the IR passes in `emitEntryPoint()` (`emit.cpp`), to show that things are more self-contained than they used to be (e.g., that the `TypeLegalizationContext` is now only needed by one pass).

* Refactored the generic specialization code so that there is a stand-along free function that can perform specialization on a `specialize` instruction without all the other context being required. This is only to support the limited specialization that needs to be done as part of linking.

* Updated the `global-type-param.slang` test to actually test entry-point generic parameters. In a later pass we can/should rework all the tests/examples for global type parameters over to use explicit entry-point generic parameters (at which point we should rename the tests as well). For now I am leaving thigns with just one test case, with the expectation that bugs will be found and ironed out as we expand to more tests.

* fixup

* Fixup: don't leave entry-point decorations on stuff we don't want to keep

The IR `[entryPoint]` decoration is effectively a "keep this alive" decoration, which means that attaching it to something we don't intend to keep around can lead to Bad Things.

The approach to generic entry points was attaching `[entryPoint]` to the underlying `IRFunc` because that seemed to make sense, but that meant that the `specialize` instruction at global scope scould instantiate that generic and then keep it alive, even if the resulting function wouldn't be valid according to the language rules.

As a quick fix, I'm attaching `[entryPoint]` to the `specialize` instruction instead in such cases, and then re-attaching it to the result of explicit specialization during linking.

* Port most of remaining test and rename global type parameters

This change ports as many as possible of the existing tests for global type parameters over to use entry-point generic parameters instead. For the most part this is a mechanical change.

A few test cases remain using global generic parameters, as does the `model-viewer` example application.
The reason for this is that the shaders have either or both the following features:

* A vertex and fragment shader that can/shold agree on their parameters

* A type declaration (e.g., a `struct`) that is dependent on one of the generic type parameters

In these cases, it would really only make sense to switch to explicit parameters once we support shader entry points nested inside of a `struct` type, so that we can use an outer generic `struct` as a mechanism to scope the entry points and other type-dependent declrations.

Since global-scope type parameters need to persist for at least a bit longer, I went ahead and renamed all the use sites over to use `type_param` for consistency.
</content>
</entry>
<entry>
<title>Add an error for global uniform parameter declarations (#773)</title>
<updated>2019-01-14T22:27:44+00:00</updated>
<author>
<name>Tim Foley</name>
<email>tfoleyNV@users.noreply.github.com</email>
</author>
<published>2019-01-14T22:27:44+00:00</published>
<link rel='alternate' type='text/html' href='https://git.yummers.dev/slang.git/commit/?id=5b0c5076326b98d0e9ee0f7bddda7f619676707c'/>
<id>urn:sha1:5b0c5076326b98d0e9ee0f7bddda7f619676707c</id>
<content type='text'>
A global uniform parameter in HLSL might canonically be defined like this:

```hlsl
uniform float gSomeParameter;
```

The fxc and dxc compilers automatically collect all such parameters into a synthesized constant buffer, along the lines of:

```hlsl
cbuffer $Globals
{
    float gSomeParameter;
}
```

Slang currently supports parsing and semantic checking of declarations like the above, and computes shader parameter layout/binding information that is appropriate for a constant buffer like `$Globals` above, but it does not include the support to emit HLSL or GLSL code that matches that layout, so that use of global uniforms in Slang is silently unsupported.

Making this problem worse, the HLSL language is quite lax, and will parse the following as shader parameters as well:

```hlsl
int gCounter = 0;
const float kScaleFactor = 2.0f;
```

Each of those declarations introduces a global shader parameter, and then provides a default value for it via the initializer. These declarations do *not* introduce an ordinary global variable or constant as might be expected.

(For anybody who wants to know, `static` is required to introduce a "real" global variable (although it will be a *thread-local* global in practice), while `static const` is required to introduce a global constant)

I was not too worried about users trying to use global-scope uniforms and failing (since that has fallen out of common HLSL/GLSL practice), but the possibility that users might try to declare global variables/constants and get shader parameters by mistake creates more of a risk so that this hole is worth plugging.

The right long-term fix is of course to support the intended semantics of global-scope uniforms, but that feature needs to be prioritized against other requests.

A few of the Slang tests were unwittingly relying on this functionality, including some compute tests that seemingly got away with it based on the DXBC generated from the HLSL output by Slang just happening to match the layout they expected. These tests have all been tweaked to use explicit `cbuffer`s or `ParameterBlock`s instead.</content>
</entry>
<entry>
<title>Remove non-IR codegen paths (#398)</title>
<updated>2018-02-03T15:30:54+00:00</updated>
<author>
<name>Tim Foley</name>
<email>tfoleyNV@users.noreply.github.com</email>
</author>
<published>2018-02-03T15:30:54+00:00</published>
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<id>urn:sha1:662f43fff6721c6cd013a8f1b2639c2e29fe6be3</id>
<content type='text'>
The basic change is simple: remove support for all code generation paths other than the IR.
There is a lot of vestigial code left, but the main logic in `ast-legalize.*` is gone.

Doing this breaks a *lot* of tests, for various reasons:

- We can no longer guarantee exactly matching DXBC or SPIR-V output after things pass through out IR

- Many builtins don't have matching versions defined for GLSL output via IR (even when they had versions defined via the earlier approach that worked with the AST)

- A lot of code creates intermediate values of opaque types in the IR, which turn into opaque-type temporaries that aren't allowed (this breaks many GLSL tests, but also some HLSL)

I implemented some small fixes for issues that I could get working in the time I had, but most of the above are larger than made sense to fix in this commit.

For now I'm disabling the tests that cause problems, but we will need to make a concerted effort to get things working on this new substrate if we are going to make good on our goals.</content>
</entry>
<entry>
<title>Add support for global generic parameters (#285)</title>
<updated>2017-11-18T02:26:21+00:00</updated>
<author>
<name>Yong He</name>
<email>yonghe@outlook.com</email>
</author>
<published>2017-11-18T02:26:21+00:00</published>
<link rel='alternate' type='text/html' href='https://git.yummers.dev/slang.git/commit/?id=54bf54bd0dda378f8400860b25855558f39cb52b'/>
<id>urn:sha1:54bf54bd0dda378f8400860b25855558f39cb52b</id>
<content type='text'>
* Add support for global generic parameters
(In-progress work)

This commit include:
1.  Update Slang API to allow specification of generic type arguments in an `EntryPointRequest`
2. Add parsing of `__generic_param` construct, which becomes a GlobalGenericParamDecl, contains members of `GenericTypeConstraintDecl`.
3. Semantics checking will check whether the provided type arguments conform to the interfaces as defined by the generic parameter, and store SubtypeWitness values in the EntryPointRequest, which will be used by `specializeIRForEntryPoint` when generating final IR.
4. Add a new type of substitution - `GlobalGenericParamSubstitution` for subsittuting references to `__generic_param` decls or to its member `GenericTypeConsraintDecl` with the actual type argument or witness tables.
5. Update `IRSpecContext` to apply `GlobalGenericParamSubstitution` when specializing the IR for an EntryPointRequest.
6. Update `render-test` to take additional `type` inputs, which specifies the type arguments to substitute into the global `__generic_param` types.

This commit does not include ProgramLayout specialization.

* IR: pass through `[unroll]` attribute (#284)

The initial lowering was adding an `IRLoopControlDecoration` to the instruction at the head of a loop, but this was getting dropped when the IR gets cloned for a particular entry point.
The fix was simply to add a case for loop-control decorations to `cloneDecoration`.

* fix warnings

* IR: support `CompileTimeForStmt` (#286)

This statement type is a bit of a hack, to support loops that *must* be unrolled.
The AST-to-AST pass handles them by cloning the AST for the loop body N times, and it was easy enough to do the same thing for the IR: emit the instructions for the body N times.
The only thing that requires a bit of care is that now we might see the same variable declarations multiple times, so we need to play it safe and overwrite existing entries in our map from declarations to their IR values.

Of course a better answer long-term would be to do the actual unrolling in the IR. This is especially true because we might some day want to support compile-time/must-unroll loops in functions, where the loop counter comes in as a parameter (but must still be compile-time-constant at every call site).

* Add support for global generic parameters
(In-progress work)

This commit include:
1.  Update Slang API to allow specification of generic type arguments in an `EntryPointRequest`
2. Add parsing of `__generic_param` construct, which becomes a GlobalGenericParamDecl, contains members of `GenericTypeConstraintDecl`.
3. Semantics checking will check whether the provided type arguments conform to the interfaces as defined by the generic parameter, and store SubtypeWitness values in the EntryPointRequest, which will be used by `specializeIRForEntryPoint` when generating final IR.
4. Add a new type of substitution - `GlobalGenericParamSubstitution` for subsittuting references to `__generic_param` decls or to its member `GenericTypeConsraintDecl` with the actual type argument or witness tables.
5. Update `IRSpecContext` to apply `GlobalGenericParamSubstitution` when specializing the IR for an EntryPointRequest.
6. Update `render-test` to take additional `type` inputs, which specifies the type arguments to substitute into the global `__generic_param` types.

progress on parameter binding

* Add a more contrived test case for specializing parameter bindings

* update render-test to align buffers to 256 bytes (to get rid of D3D complains on minimal buffer size).

* adding one more test case for parameter binding specialization.

* Cleanup according to @tfoleyNV 's suggestions.

* fix a bug introduced in the cleanup
</content>
</entry>
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