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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.
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* Work on getting rewriter + IR playing nice together.
There are a few different changes here, with the goal of improving the interaction between the "rewriter" code generation approach and the new IR and type legalization code.
The main changes are:
- Add a new pass that occurs before the AST legalization pass, which walks the (used) AST declarations and tries to discover (1) which declarations need to be specialized/lowered via the IR, and (2) which declarations need to be included in the resulting AST module.
- AST-based legalization now uses the generated list when in "rewriter" mode, so that we should be working around issues that users were seeing with types not getting emitted.
- TODO: we still need an equivalent fixup in the case of non-"rewriter" emit, so this may still be a problem for `.slang` files.
- IR type legalization now precedes AST legalization, so that we can record information on how any IR global values got legalized (e.g., if they got split). Then AST legalization includes logic to reconstruct suitable tuple expressions to reference a split global.
- When emitting using IR + AST, we walk all of the declarations that we decided belonged to the IR, but which were subsequently referenced in the AST, to make sure they get output (this would include `struct` types that are declared in a file compiled via IR, but never used in IR-based code).
The rewriter+IR use case still doesn't *quite* work, but the logic for walking the AST in a pre-pass ends up being needed/useful to fix some pure rewriter bugs, so I'm getting this checked in sooner rather than later.
* Fixup: walk arguments to generic declaration reference
The gotcha here is that the code for walking the AST would walk a line of code like:
SomeType a;
and know to traverse the declaration of `SomeType`, but if it saw a line of code like:
ParameterBlock<SomeType> b;
it would traverse the declaration of `ParameterBlock`, but fail to visit that of `SomeType`.
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* Revise type legalization so it can handle constant buffers
The existing legalization approach with "tuples" can handle scalarizing a `struct` type with resource-type fields in it, but it had several big gaps. The most notable is that given a type that mixes uniform and resource fields, we can't just blindly scalarize things:
```
struct P {
float4 a;
float4 b;
Texture2D t;
};
cbuffer C
{
P gParam[8];
};
```
The existing code was completely ignoring the declaration of `gParam` inside `C`, but even if we fixed that issue, we'd get something like:
```
cbuffer C
{
float4 gParam_a[8];
float4 gParam_b[8];
};
Texture2D gParam_t[8];
```
In this case we've completely changed the layout of the uniform buffer, by switching from AOS to SOA.
Even if we could get the type layout logic and the IR to agree on this, it would be a surprise to users, and "principle of least surprise" should be a big deal on a project with as many moving parts as ours.
The right thing to do is to have legalization create a "stripped" version of the original type `P` and use that:
```
struct P_stripped {
float4 a;
float4 b;
};
cbuffer C
{
P_stripped gParam[8];
};
Texture2D gParam_t[8];
```
Then at a call site, this:
```
foo(gParam);
```
becomes:
```
foo(gParam, gParam_t);
```
This is exactly how the current AST-to-AST legalization handles mixed uniform and resource types, but the way it does it involves some annoying kludges:
- That pass has a notion of a "tuple" similar to our legalization, but every tuple has an optional "primary" entry for all the uniform data, plus tuple elements for the resources, and a given field may be represented on one side, the other, or both. It makes the code for handling tuples very messy.
- That pass does the "stripping" of types by actually marking up the AST declarations (this is okay because it is constructing a new AST as it goes), so that when they get emitted certain fields don't actually show up. That is, we fix the problem with type `P` by actually *modifying* the user's declaration of `P`. That seems out of bounds for the IR.
This change fixes the problem in our IR type legalization while trying to avoid the problems of the AST-to-AST pass by using two new ideas:
1. We add a new case for `LegalType` (and `LegalVal`) that is a "pair" type, where a pair consists of both an "ordinary" type (for uniform data) and a "special" type (for resource data). E.g., after legalization, the type for `C` (which can be over-simplified to `ConstantBuffer<P>` for our purposes), will be a `LegalType::pair` where the ordinary side is `ConstantBuffer<P_stripped>` and the special side is a tuple containing the `Texture2D` field.
2. We add a new (and annoyingly hacky) AST-level type called `FilteredTupleType` which is semantically a sort of tuple type (it holds a list of elements, and the elements have their own types), but which remembers an "original type" that it was created from, and for each element remembers the field of the original type that it corresponds to. This is used to construct a type like `P_stripped` as an actual AST-level structural type.
The core logic for legalizing an aggregate type had to get more complicated just because of the new pair case, so there is now a `TupleTypeBuilder` that asists with taking an aggregate type, processing its fields, and then picking the right `LegalType` representation for the result.
Other smaller changes:
- Made the legalization logic actually legalize `PtrType<T>`. E.g., if `T` legalizes to a tuple, we need to construct a tuple of pointer types. The same exact thing needs to be applied to arrays, and any other generic type that should "distribute over" pairs/tuples.
- Made the legalization logic actually legalize `ConstantBuffer<T>` and similar. The basic idea there is if `T` maps to a pair, we wrap `ConstantBuffer<...>` around the ordinary side, and `implicitDeref` around the special side.
- Removed a bunch of `#ifdef`ed-out code from the end of `ir-legalize-types.cpp`. That was code from my first attempt at legalization that failed miserably (trying to do it via local changes and a work list instead of a global rewrite pass), but it had some code I wanted to reference when writing the version that actually got checked in (should have deleted the code earlier, though).
- Added a bunch of cases for `LegalType::none` (and the `LegalVal` equivalent) that helped simplify the logic fo the `pair` case by allowing me to *always* dispatch to both the "ordinary" and "special" sides, even if they might not actually be present.
- Renamed `TupleType` and `TupleVal` over to `TuplePseudoType` and `TuplePseudoval` to recognize the fact that we might actually need/want *real* tuples in the type system, to go along with these fake ones (that need to be optimized away).
The biggest doubt I have about this change is the whole `FilteredTupleType` thing; it seems like an obviously contrived type to add to the front-end type system that really only solves IR-level problems. A cleaner approach might have been to just add a plain old `TupleType` to the front-end type system (and initially I started with that), and then have yet another `LegalType`/`LegalVal` case that handles mapping from the fields of the original type to the numbered tuple elements.
I expect we'll actually want to make that change in the future (especially if we ever add true tuples to the front-end), but for right now I let myself be swayed by the desire to have these stripped/filtered types get names that explain their provenance ("where they came from") to make our output code more debuggable. The way I've done it is probably overkill, though, and we need a much more complete effort on the readability and debuggability of our output before anything like that is worth worrying about.
* Fixup: typo
* Fixup: fix output of "non-mangled" names for test cases
- Make sure to attach high-level decls to variables created as part of type legalization
- Also, try to share more of the code between the different cases of variables
- Fix up `parameter-blocks` test case that was passing `-no-mangle` but expecting mangled names in the output
- Fix up `multiple-parameter-blocks` to not rely on `-no-mangle` for now, because it would lead to two global variables with the same name (need to fix that underlying issue eventually).
- Also fix name generation logic so that we only use "original" names (from high-level decls) specifically when the `-no-mangle` flag is on, and otherwise use IR-level names.
* Fix: handle constant buffers better in render-test
- Don't request both CB and SRV usage for buffers, since that is illegal
- Also, don't try to create an SRV when user requested a CB (since the required usage flag won't be there)
- Record the input buffer type on the `D3DBinding` for a buffer, and use that to tell us when to bind a CB instead of SRV/UAV
- Fix expected output for `cbuffer-legalize` test now that we are actually feeding it correct cbuffer dta.
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* Don't auto-enable IR use for compute tests
The `COMPARE_COMPUTE` and `COMPARE_RENDER_COMPUTE` test fixtures were set up to always enable the `-use-ir` flag on Slang, which precludes having any tests that confirm functionality on the old non-IR path (which is still required by our main customer).
This change adds the `-xslang -use-ir` flags explicitly to any compute test cases that left them out, and makes the fixture no longer add it by default.
* Continue building out parameter block support
The initial front-end logic for parameter blocks was already added, but they are still missing a bunch of functionality. This change addresses some of the known issues:
- Bug fix: don't try to emit HLSL `register` bindings for variables that consume whole register spaces/sets
- Overhaul type layout logic so that it can make decisions based on a given code generation target (currently passed in as a `TargetRequest`), which allows us to decide whether or not a parameter block should get its own register set on a per-target basis.
- Always use a register space/set for Vulkan
- Never use a register space/set for HLSL SM 5.0 and lower
- By default, don't use register spaces/sets for HLSL output
- Add a command-line flag and some "target flags" to enable register-space usage for D3D targets
- Hackily add initial support for parameter blocks in the AST-to-AST path
- This just blindly lowers `ParameterBlock<T>` to `T`, which shouldn't quite work
- A more complete overhaul will probably need to wait until the AST-to-AST legalization is changed to use the `LegalType`s from the IR legalization pass.
- Add a compute-based test case to actually run code using parameter blocks
- This file runs test cases both with and without the IR
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* Rename existing ParameterBlock to ParameterGroup
We are planning to add a new `ParameterBlock<T>` type, which maps to the notion of a "parameter block" as used in the Spire research work.
Unfortunately, the compiler codebase already uses the term `ParameterBlock` as catch-all to encompass all of HLSL `cbuffer`/`tbuffer` and GLSL `uniform`/`buffer`/`in`/`out` blocks (all of which are lexical `{}`-enclosed blocks that define parameters...).
This change instead renames all of the existing concepts over to `ParameterGroup`, which isn't an ideal name, but at least doesn't directly overlap the new terminology or any existing terminology.
The new `ParameterBlockType` case will probably be a subclass of `ParameterGroupType`, since it is a logical extension of the underlying concept.
* Add Shader Model 5.1 profiles
The HLSL `register(..., space0)` syntax is only allowed on "SM5.1" and later profiles (which is supported by the newer version of `d3dcompiler_47.dll` that comes with the Win10 SDK, but not the older version of `d3dcompiler_47.dll` - good luck figuring out which you have!).
This change adds those profiles to our master list of profiles, and nothing else.
* First pass at support for `ParameterBlock<T>`
- Add the type declaration in stdlib
- Add a special case of `ParameterGroupType` for parameter blocks
- Handle parameter blocks in type layout (currently handling them identically to constant buffers for now, which isn't going to be right in the long term)
- Add an IR pass that basically replaces `ParameterBlock<T>` with `T`
- Eventually this should replace it with either `T` or `ConstantBuffer<T>`, depending on whether the layout that was computed required a constant buffer to hold any "free" uniforms
- Add first stab at an IR pass to "scalarize" global variables using aggregate types with resources inside.
- This currently only applies to global variables, so it won't handle things passed through functions, or used as local variables
- It also only supports cases where the references to the original variable are always references to its fields, and not the whole value itself
- Add a single test case that technically passes with this level of support, but probably isn't very representative of what we need from the feature
* Fold parameter-block desugaring into a more complete "type legalization" pass
The basic problem that was arising is that once you desugar `ParameterBlock<T>` into `T`, you then need todeal with splitting `T` into its constituent fields if it contains any resource types.
Handling those transformations by following the usual use-def chains wasn't really helping, because you might need systematic rewriting that can really only be handled bottom-up.
This change adds a new pass that is intended to perform multiple kinds of type "legalization" at once:
- It will turn `ParameterBlock<T>` into `T`
- It may at some point also convert `ConstantBuffer<T>` into `T` as well
- It will turn an value of an aggregate type that contains resources into N different values (one per field)
- As a result of this, it will also deal with AOS-to-SOA conversion of these types
Legalization is applied to *every* function/instruction/value, so that it can make large-scale changes that would be tough to manage with a work list.
This pass needs to be run *after* generics have been fully specialized, so that we know we are always dealing with fully concrete types, so that their legalization for a given target is completely known.
This is still work in progress; there's more to be done to get this working with all our test cases, and finish the remaining `ParameterBlock<T>` work.
* Improve binding/layout information when using parameter blocks
- When doing type layout for a parameter block, don't include the resources consumed by the element type in the resource usage for the parameter block
- Note that this is pretty much identical to how a `ConstantBuffer<T>` does not report any `LayoutResourceKind::Uniform` usage, except that `ParameterBlock<T>` is *also* going to hide underlying texture/sampler reigster usage
- The one exception here is that any nested items that use up entire `space`s or `set`s those need to be exposed in the resource usage of the parent (I don't have a test for this)
- When type legalization needs to scalarize things, it must propagate layout information down to the new leaf variables. In general, the register/index for a new leaf parameter should be the sum of the offsets for all of the parent variables along the "chain" from the original variable down to the leaf (we aren't dealing with arrays here just yet).
- When type legalization decides to eliminate a pointer(-like) type (e.g., desugar `ParameterBlock<T>` over to `T`), actually deal with that in terms of the `LegalVal`s created, so that we can know to turn a `load` into a no-op when applied to a value that got indirection removed.
- Hack up the "complex" parameter-block test so that it actually passes (the big hack here is that the HLSL baseline is using names that are generated by the IR, and are unlikely to be stable as we add/remove transformations).
- Note: I can't make these be compute tests right now, because regsiter spaces/sets are a feature of D3D12/Vulkan, and our test runner isn't using those APIs.
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