| Commit message (Collapse) | Author | Age |
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* Prefixing source files in source/slang with slang-
* Prefix source in source/slang with slang- prefix.
* Rename core source files with slang- prefix.
* Update project files.
* Fix problems from automatic merge.
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* Split front- and back-ends
This change is a major refactor of several of the types that provide the behind-the-scenes implementation of the public C API.
The goal of this refactor is primarily to allow for future API services that let the user operate both the front- and back-ends of the compiler in a more complex fashion.
For example, as user should be able to compile a bunch of source code into modules, look up types, functions, etc. in those modules, specialize generic types/functions to the types they've looked up, and then finally request target code to be gernerated for specialized entry points.
The back-end code generation they trigger should re-use the front-end compilation work (parsing, semantic checking, IR generation) that was already performed.
The most visible change is that `CompileRequest` has been split up into several smaller types that take responsibility for parts of what it did:
* The `Linkage` type owns the storage for `import`ed modules, and well as the `TargetRequest`s that represent code-generation targets. The intention is that an application could use a single `Linkage` for the duration of its runtime (so long as it was okay with the memory usage), so that each `import`ed module only gets loaded once. For now, this type needs to manage the search paths, file system, and source manager, because of its responsibility for loading files.
* A `FrontEndCompileRequest` owns the stuff related to parsing, semantic checking, and initial IR generation. This most notably includes the `TranslationUnitRequest`s and the `FrontEndEntryPointRequest`s (which used to be just `EntryPointRequest`s). It's main job is to produce AST and IR modules for each translation unit, and to find and validate the entry points. The front-end request does *not* interact with generic arguments for global or entry-point generic parameters.
* The main output of both `import` operations and front-end translation units is the `Module` type, which is just a simple container for both the AST module (to service the reflection/layout APIs, and also for semantic checking of code that `import`s the module) and the IR module (for linking and code generation). This type captures the commonalities between the old `LoadedModule` (which is now just an alias for `Module`) and `TranslationUnitRequest` (which now owns a `Module`).
* The secondary output of front-end compilation is a `Program`, which comprises a list of referenced `Module`s and validated `EntryPoint`s that will be used together. Layout and code generation both need a `Program` to tell them what modules and entry points will be used together (we don't want to just code-gen everythin that has ever been loaded into the linakge). The `Program`s created by the front-end do not include generic arguments, so they may provide incomplete layout information and/or be unsuitable for code generation.
* A `BackEndCompileRequest` owns stuff related to turning a `Program` into output kernels for the targets of a `Linkage`. Most of the data it owns beyond the `Program` to be compiled is minor, so this is a good candidate for demotion from a heap-allocated object to just a `struct` of options that gets passed around.
* The `CompileRequestBase` type is an attempt to wrap up the common functionality of both front-end and back-end compile requests. Most of it is just exposing the availability of a linkage and `DiagnosticSink`, so this type is a good candidate for subsequent removal. The main interesting thing it has is the flags related to dumping and validation of IR, so there is probably a good refactoring still to be made around deciding how options should be handled going forward.
* Behind the scenes, the `Program` type is set up to handle some level of on-line compilation and layout work. The `Program` knows the `Linkage` it belongs to, and allows for a `TargetProgram` to be looked up based on a specific `TargetRequest`. A `TargetProgram` then allows layout information and compiled kernel code to be asked for on-demand, in order to support eventual "live" compilation scenarios.
* The `EndToEndCompileRequest` type is a composition/coordination type that replaces the old `CompileRequest` in a way that uses the services of the various other types. It owns a few pieces of state that only make sense in the context of an end-to-end compile (e.g., there is really no way to "pass through" code when the front- and back-ends are run separately) or a command-line compile (everything to do with specifying output paths for files is really just for the benefit of `slangc`, and might even be moved there over time).
* One important detail is that the `EndToEndCompilRequest` owns all of the string-based generic arguments for both global and entry-point generic parameters. The logic in `check.cpp` for dealing with those arguments has been heavily refactored to separate out the parsings steps that are specific to end-to-end compilation with string-based type arguments, and the semantic checking steps that result in a specialized `Program` (which can be exposed through new APIs that aren't tied to end-to-end compilation).
It is perhaps not surprising that this change had a lot of consequences, so I'll briefly run over some of the main categories of changes required:
* I changed the way that global generic arguments are passed via API (use `spSetGlobalGenericArgs` instead of the generic arguments for `spAddEntryPointEx`, which are not just for entry-point generics), which has been a change that we've needed for a long time. This is technically a breaking API change, although we should have very few client applications that care about it.
* A bunch of places that used to take "big" objects like `CompileRequest` now just take the sub-pieces they care about (e.g., a function might have only needed a `Linkage` and a `DiagnosticSink`). This makes many subroutines or "context" struct types more generally useful, at the cost of taking more parameters.
* In a few cases the conceptually clean separation of the layers breaks down (often for edge-case or compatibility features), and so we may pass along additional objects that are allowed to be null, but are used when present. A big example of this is how the back-end code generation routines accept an `EndToEndCompileRequest` that is optional, and only used to check whether "pass through" compilation is needed. We should probably look into cleaning this kind of logic up over time so that we don't need to violate the apparent separation of phases of compilation.
* In cases where separation of layers was being broken for the sake of GLSL features, I went ahead and ripped them out, since all of that should be dead code anyway.
* In many cases I increased the encapsulation of data in the core types to help track down use sites and make sure they are following invariants better.
* In cases where code was doing, e.g., `context->shared->compileRequest->session->getThing()` I have tried to introduce convenience routines so that the usage site is just `context->getThing()` to improve encapsulation and allow changes to be made more easily going forward.
* The `noteInternalErrorLoc` functionality was moved off of the compile request and into `DiagnosticSink`, since that is the one type you can rely on having around when you want to note an internal error. We may consider going forward if (and how) it should reset the counter used for noting locations on internal errors.
* A few APIs now take `DiagnosticSink*` arguments where they didn't before, and as a result some public APIs need to create `DiagnosticSink`s to pass in, before going ahead and ignoring the messages. In the future there should be variations of these APIs that accept an `ISlangBlob**` parameter for the output.
* fixup: missing include for compilers with accurate template checking (non-VS)
* fixup: review feedback
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* 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<L> 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<L : ILight>(
uniform ParameterBlock<L> 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<FuncDecl>` instead of just ` RefPtr<FuncDecl>`, 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.
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* Support "modern" declaration syntax as an option
Fixed #202
This change adds four new declaration keywords:
The `let` and `var` keywords introduce immutable and mutable variables, respectively. They can only be used to declare a single variable at a time (unlike C declaration syntax), and they support inference of the variable's type from its initial-value expression.
Examples:
```
let a : int = 1; // immutable with explicit type and initial-value expression
let b = a + 1; // immutable, with type inferred
var c : float; // mutable, with explicit type
var d = b + c; // mutable, with type inferred
```
These declaration forms can be used wherever ordinary global, local, or member variable declarations appeared before. Right now they do not change rules about what is or is not considered a shader parameter. The `static` modifier should work on these forms as expected, but a `static let` variable is *not* the same as a `static const`, so an explicit `const` is still needed if you want that behavior.
A `typealias` declaration introduces a named type alias, similar to `typedef`, but with more reasonable syntax. It inherits from the same AST class that `typedef` uses, so all of the code after parsing should be able to treat them as equivalent. To give a simple example:
```
// typedef int MyArray[3];
typealais MyArray = int[3];
```
A `func` declaration introduces a function. Like `typealias` it re-uses the existing AST class, so there is no need for major changes after parsing. A `func` declaration uses a syntax similar to `let` variables for its parameters, and takes the (optional) result type in a trailing position. For example:
```
func myAdd(a: int, b: int) -> int { return a + b; }
```
If a `func` declaration leaves of the return type clause, the return type is assumed to be `void`.
The main difference (beyond the trailing return type) is that the parameters of a `func`-declared function are immutable (unless they are `out`/`inout`).
This change doesn't add support for declaring operator overloads with `func`, but that should be added later, and I'd like to make that the only way to declare such operations:
```
func +(left: MyType, right: MyType) -> MyType { ... }
```
The use of `:` for declaring parameter types here means that a function declared with modern syntax currently cannot include HLSL-style semantics on its parameters (or its result).
We might consider introducing an `[attribute]`-based syntax for adding semantics to parameters if we think this is important, but for now it is fine to insist that users declare their entry points using traditional syntax.
This change strives to avoid unecessary changes after parsing, but if the new syntax catches on with users there are some small ways we can take advantage of it for performance. In particular, since `let` declarations and parameters of modern-style functions are immutable, we do not need to generate read/write local temporaries for them during lowering to the IR (technically we can make the same optimization for `const` locals).
In the process of implementing these new forms I also added a few subroutines to help share code better between existing cases in the parser. In particular, parsing of generic parameter lists on declarations that can be generic is now simplified and more unified.
* Fixup: remove leftover debugging code
* fixup: typos
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The AST class hierarchy for variable declarations had a few messy bits.
First, there are more subclasses of `VarDeclBase` than seem strictly necessary; especially for stuff like `struct` member variable which use `StructField` even for `static` fields (which are effectively globals).
Second, the AST node type for the "cases" within an `enum` was made a subclass of `VarDeclBase` for expediency, but this isn't really semantically accurate (and doesn't seem to be paying off much in deduplication of code).
This change tries to address both of those problems.
First, we replace the existing `Variable` and `StructField` cases with a single `VarDecl` case that covers globals, locals, and member variables.
I haven't gone so far as to replace function parameters or generic value parameters, but that might be worth considering as a further clean-up.
Second, we change `EnumCaseDecl` to inherit directly from `Decl` instead of `VarDeclBase` and add an explicit case for handling them where they were previously handled as if they were variable declarations (this was done by manually surveying all locations in the code that referenced `VarDeclBase`).
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Slang `enum` declarations will always be scoped, e.g.:
```hlsl
enum Color
{
Red,
Green = 2,
Blue,
}
Color c = Color.Red; // Not just `Red`
```
A user can write `enum class` as a placebo for now (to ease sharing of headers with C++).
Slang does not currently support the `::` operator for static member lookup, so it must be `Color.Green` and not `Color::Green`. Support for `::` as an alternate syntax could be added later if there is strong user demand.
An `enum` type can have a declared "tag type" using syntax like C++ `enum class`:
```hlsl
enum MyThings : uint
{
First = 0,
// ...
}
```
The `enum` cases will store their values using that type. An `enum` that doesn't declare a tag type will use the type `int` by default.
Enum cases are assigned values just like in C/C++: cases can have explicit values, but otherwise default to one more than the previous case, or zero for the first case.
All `enum` types will automatically conform to a standard-library `interface` called `__EnumType`, which is used so that basic operators like equality testing can be defined generically for all `enum` types.
This change only adds one operator at first (the `==` comparison), but other should be added later.
An `enum` case needs to be explicitly converted to an integer where needed (e.g., `int(Color.Red)`).
This is implemented by having the main integer types (`int` and `uint`) support built-in initializers that can work for *any* `enum` type (or rather, anything conforming to `__EnumType`).
Eventually these will be restricted so that an `enum` type can only be converted to its associated tag type.
IR code generation completely eliminates `enum` types and their cases.
The `enum` type will be replaced with its tag type, and the cases will be replaced with the tag values.
Currently this could leave some mess in the IR where cast operations are applied between values that actually have the same type.
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* Introduce an IR-level type system
Up to this point, the Slang IR has used the front-end type system to represent types in the IR.
As a result (but ultimately more importantly) the IR representation of generics and specialization has used AST-level concepts embedded in the IR.
For example, to express the specialization of `vector<T,N>` to a concrete type `float` for `T`, we needed an IR operation that could represent the specialization, with operands that somehow represented the type argument `float`.
The whole thing was very complicated.
The big idea of this change is to introduce a new representation in which types in the IR are just ordinary instructions, so that using them as operands makes sense. The hierarchy of IR types closely mirrors the AST-side hierarchy for now, and that will probably be something we should maintain going forward.
In order to make these changes work, though, I also had to do major overhauls of things like the way substitutions are performed, how we check interface conformances, the way lookup through interface types is done, etc. etc. This is a big change, and unfortunately any attempt to summarize it in the commit message wouldn't do it justice.
* Fix 64-bit build warning
* Fix up some clang warnings/errors
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The existing code parsed all of the square-bracket `[attributes]` into `HLSLUncheckedAttribute`, and then went on to hand-convert some of them to specialized subclasses of `HLSLAttribute`. When attributes didn't check, they were left as-is, and no error message was issued, because at the time the compiler was focused on accepting arbitrary input.
This change greatly overhauls the handling of `[attributes]`. Attributes are now declared in the stdlib, with declarations like:
```hlsl
__attributeTarget(LoopStmt)
attribute_syntax [unroll(count: int = 0)] : UnrollAttribute;
```
In this syntax, the `unroll` part is giving the attribute name (the `[]` are just for flavor, to make the declaration look like a use site; we could drop it if we don't like the clutter), the `count` is a parameter of the attribute, which we expect to be of type `int`, and which has a default value of `0` if unspecified.
The `: UnrollAttribute` part specifies the meta-level C++ class that will implement this attribute (and corresponds to a class in `modifier-defs.h`). This syntax is similar to our current `syntax` declarations. I'm starting to think we should change it to something like a `__meta_class(UnrollAttribute)` modifier, and then use that uniformly across all cases (e.g., also replacing the curreent `__magic_type(Foo)` syntax).
The `__attributeTarget(LoopStmt)` is a modifier that specifies the meta-level C++ class for syntax that this attribute is allowed to attach to. It is legal to have more than one of these.
Attributes continue to be parsed in an unchecked form, so that we don't tie up semantic analysis and parsing more than necessary. During checking, we look up the attribute name in the current scope, and then replace the unchecked attribute with a more specific one *if* the checking passes.
Checking proceeds in generic and attribute-specific phases. The generic phase includes checking the number of arguments against those specified in the attribute declaration (I don't currently check types, or handle default arguments), and then checking that at least one `__attributeTarget(...)` modifier applies to the syntax node being modified.
The attribute-specific phase then applies to the specialized C++ subclass of `Attribute`, and does the actual checking right now (e.g., that step is responsible for actually type-checking things at present). This can obviously be improved over time.
With this support I went ahead and added declarations for all the HLSL attributes I could find documented on MSDN. I also added a provisional declaration for the `[shader(...)]` attribute that has been added to dxc, but which is not yet documented.
One important detail here is that lookup of attribute names needs to be done carefully, so that we don't let, e.g., local variables shadow an attribute declaration:
```hlsl
int unroll = 5;
// This attribute should *not* get confused by the local variable `unroll`
[unroll] for(...) { .. }
```
The lookup logic already has a notion of a `LookupMask` that can be used to filter declarations out of the result. In this change I surfaced that mask through the main lookup API (rather than requiring a second pass to "refine" lookup results), and made is so that the default lookup mask does *not* include attributes, while an explicit mask can be used to look up *only* attributes.
(An alternatie design we discussed was to follow the approach of C# and have the declaration of an attribute like `[unroll]` actually be `unrollAttribute`, with a suffix. I decided not to follow that approach for now because it seemed like printing good error messages in that case could require us to carefully trim the `Attribute` suffix off of names at times, and using the existing mask behavior seemed simpler.)
To verify that the shadowing behavior is indeed correct, I modified the `loop-unroll.slang` test case.
Smaller notes:
* Removed the `HLSL` prefix from several of the C++ attribute classes
* Made sure to actually validate the modifiers on statements
* Special-cased checking for `ParamDecl` with a null type, because I'm re-using `ParamDecl` for attribute parameters, but can't give a concrete type to some of them right now
* Deleting some old, dead emit-from-AST logic around attributes, rather than try to "fix" code that doesn't run (a more complete scrub of that code is still needed)
* Fixed AST inheritance hierarchy so that a `Modifier` is a `SyntaxNode` rather than a `SyntaxNodeBase`. I have *no* idea why we have both of those, and we need to clean that up soon.
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* IR: fixes for subscript accessors
Fixes #320
This is a bunch of fixes for handling of `__subscript` operations on builtin types (notably `RWStructuredBuffer` and `StructuredBuffer` at this point).
- Automatically add a `GetterDecl` to any subscript decalratio was declithout any accessors. This avoids hitting a null- dereference in the emit logic.
- Add a notion of a `RefAccessor` (declared with `ref`) as a peer to getters and setters. The idea is that a `ref` accessor returns a pointer to the element data, so that it can be used for both getting and setting values. This is closer to the behavior of `RWStructuredBuffer` element access in HLSL.
- Fixes for dealing with "access chains" where there might be a combination of a subscript (where the is a `get` and `set` but no `ref`) and member access, so that we have to read the base value into a temp, modify it, and then write it back.
- This logic is still a bit of a mess, so we will eventually want to take a more consistent pass over this to deal with how we "materialize" values for setters.
- Update `RWStructuredBuffer` to have a `ref` accessor, and then fix up the IR tests to handle the new opcode that I added for it.
- Note: I didn't handle this as an intrinsic simply because the `tests/ir/*` tests aren't really set up to handle builtins with ugly mangled names.
* Fixup: type error in VM for buffer element ref
I was using the result type of the op as the element type for computing the element address, but the result type is a pointer to the real element type.
This caused test failures on 64-bit platforms, where the stride of the buffer in the `ir/factorial` test needs to be 4.
The fix is to assume the result type is a pointer, and extract the pointed-to type out of that.
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* 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
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This change includes a lot of infrastructure work, but the main point is to allow code like the following:
```
// define an interface
interface Helper { float help(); }
// define a generic function that uses the interface
float test<T : Helper>( T t ) { return t.help(); }
// define a type that implements the interface
struct A : Helper { float help() { return 1.0 } }
// define an ordinary function that calls the
// generic function with a concrete type:
float doIt()
{
A a;
return test<A>(a);
}
```
Getting this to generate valid code involves a lot of steps. This change includes the initial version of all of these steps, but leaves a lot of gaps where more complete implementation is required.
The changes include:
- Member lookup on types has been centralized, and now handles the case where the type we are looking for a member in is a generic parameter (e.g., given `t.help()` we can now look up `help` in `Helper` by knowing that `t` is a `T` and `T` conforms to `Helper`).
- There is an obvious cleanup still to be done here where the same exact logic should be used to look up available "constructor" declarations inside a type when the type is used like a function.
- Add a notion of subtype constraint "wittnesses" to the type system. When a generic is declared as taking `<T : Helper>` it really takes two generic parameters: the type `T` and a proof that `T` conforms to `Helper`. The actual arguments to a generic will then include both the type argument and a suitable witness argument (both type-level values).
- As it stands right now, a witness wraps a `DeclRef` to the declaration that represents the appropriate subtype relationship. So if we have `struct A : Helper`, that `: Helper` part turns into an `InheritanceDecl` member, and a reference to that member can serve as a witness to the fact that `A` conforms to `Helper`.
- Make explicit generic application `G<A,B>` synthesize the additional arguments that represent conformances required by the generic.
- This does *not* yet deal with the case where a generic is implicitly specialized as part of an ordinary call `G(a,b)`
- A bug fix to not auto-specialize generics during lookup. The problem here was related to an attempted fix of an earlier issue.
During checking of a method nested in a generic type, we were running into problems where `DeclRefType::create()` was getting called on an un-specialized reference to `vector`, and this was leading to a crash when the code looked for the arguments for the generic. This was worked around by having name lookup automatically specialize any generics it runs into while going through lookup contexts.
That choice creates the problem that in a generic method like this:
```
void test<T>(T val) { ... }
```
any reference to `val` inside the body of `test` will end up getting specialized so that it is effectively `test<T>::val`, when that isn't really needed.
- Add front-end logic to check that when a type claims to conform to an interface it actually must provide the methods required by the interface. The checking process goes ahead and builds a front-end "witness table" that maps declarations in the interface being conformed to over to their concrete implementations for the type.
- At the moment the checking is completely broken and bad: it assumes that *any* member with the right name is an appropriate declaration to satisfy a requirement. That obviously needs to be fixed.
- Add an explicit operation to the IR for lookup of methods: `lookup_interface_method(w, r)` where `w` is a reference to the "witness" value and `r` is an `IRDeclRef` for the member we want to look up.
- Add an explicit notion of witness tables to the IR. These end up being the IR representation of an `InheritanceDecl` in a type, and they are generated by enumerating the members that satisfy the interface requirements (which were handily already enumerated by the front-end checking). The witness table is an explicit IR value, and so it will be referenced/used at the site where conformance is being exploited (e.g., as part of a `specialize` call), so it should be safe to eliminate witness tables that are unused (since they represent conformances that aren't actually exploited). Similarly, the entries in a witness table are uses of the functions that implement interface methods, and so keep those live.
- In order to implement the above, I did a bit of a cleanup pass on the IR representation so that there is an `IRUser` base that `IRInst` inherits from, so that we can have users of values that aren't instructions.
- One annoying thing is that because of how types and generics are handled in the IR, we needed a way to have a type-level `Val` that wraps an IR-level value: e.g., to allow an IR-level witness table to be used as one of the arguments for specialization of a generic. The design I chose here is to have a "proxy" `Val` subclass (`IRProxyVal`) that wraps an `IRValue*`. These should only ever appear as part of types and `DeclRef`s that are used by the IR.
- One annoying bit here is that an IR value might then have a use that is not manifest in the set of IR instructions, and instead only appears as part of a type somewhere.
- I'm not 100% happy with this design, but it seems like we'd have to tackle similar issues if/when we eventually allow functions to have `constexpr` or `@Constant` parameters
- Make generic specialization also propagate witness table arguments through to their use sites (this is mostly just the existing substitution machinery, once we have `IRProxyVal`), and then include logic to specialize `lookup_interface_method` instructions when their first operand is a concrete witness table.
All of this work allows a single limited test using generics with constraints to pass, but more work is needed to make the solution robust.
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* Checkpoint: interface conformance work
- Add explicit definition of `saturate` for the GLSL target, which calls through to `clamp`
- Needed to add explicit initializer to `__BuiltinFloatingPointType` to allow initialization from a single `float`, so that the `saturate` implementation can be sure that it can initialize a `T` from `0.0` or `1.0`.
- This triggered errors in overload resolution, because the logic in place could not figure out that the `T` of the outer generic (`saturate<T>()`) conformed to the interface required by the callee.
At this point I have the call to the scalar `clamp()` getting past type-checking, but not the vector or matrix cases.
* More fixups for overload resolution inside generics
- Make sure value parameters are treated the same as type parameters: we only want to solve for the parameters of the generic actually being applied, and not accidentally generate constraints for outer generics (e.g., when checking the body of a generic function).
- Make sure that the diagnostics stuff uses the correct source manager when expanding the location of a builtin.
* Fixes for function redeclaration
- Handle case of redeclaring a generic function
- Enumerate siblings in the parent of the *generic* not the parent of the *function*
- Add logic to compare generic signatures
- When generic signatures match, specialize functions to compatible generic arguments before comparing the function signatures
- Fix redeclaration logic to *not* detect prefix/postifx operators as redeclarations of one another
- Build an explicit representation of function redeclaration groups
- First declaration is the "primary" and others are stored in a linked list
- Make overload resolution handle redeclared functions
- Only consider the primary declaration and skip others
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Fixes #23
Up to this point, the compiler has used the ordinary `String` type to represent declaration names, which means a bunch of lookup structures throughout the compiler were string-to-whatever maps, which can reduce efficiency.
It also means that things like the `Token` type end up carying a `String` by value and paying for things like reference-counting.
This change adds a `Name` type that is used to represent names of variables, types, macros, etc.
Names are cached and unique'd globally for a session, and the string-to-name mapping gets done during lexing.
From that point on, most mapping is from pointers, which should make all the various table lookups faster.
More importantly (possibly), this brings us one step closer to being able to pool-allocate the AST nodes.
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This is in preparation for using `Name` as a type name.
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Just like the previous change did for declaration keywords, this change uses the lexical environment to drive the lookup and dispatch of modifier parsing.
This allows us to easily add modifiers to Slang, even when they might conflict with identifiers used in user code (because the modifier names are no longer special keywords, but ordinary identifiers).
There was already some support for ideas like this with `__modifier` declarations (`ModifierDecl`) used to introduce some GLSL-specific keywords (so that they wouldn't pollute the namespace of HLSL files).
The new approach changes these to be actual `syntax` declarations (`SyntaxDecl`) with the same representation as those used to introduce declaration keywords.
Because many modifiers just introduce a single keyword that maps to a simple AST node (no further tokens/data), I modified the handling of syntax declarations so that they can take a user-data parameter, and this allows the common case ("just create an AST node of this type...") to be handled with minimal complications.
This also adds in a general-purpose string-based lookup path for AST node classes, that should support programmatic creation in more cases.
Statements are now the main case of keywords that need to be made table driven.
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The existing parser code was doing string-based matching on the lookahead token to figure out how to parse a declaration, e.g.:
```
if(lookAhead == "struct") { /* do struct thing */ }
else if(lookAhead == "interface") { /* do interface thing * }
...
```
That approach has some annoying down-sides:
- It is slower than it needs to be
- It is annoying to deal with cases where the available declaration keywords might differ by language
- Most importantly, it is not possible for us to introduce "extended" keywords that the user can make use of, but which can be ignored by the user and treated as an ordinary identifier.
That last part is important. Suppose the user wanted to have a local variable named `import`, but we also had a Slang extension that added an `import` keyword. Then a line of code like `import += 1` would lead to a failure because we'd try to parse an import declaration, even when it is obvious that the user meant their local variable. This would mean that Slang can't parse existing user code that might clash with syntax extensions. This issue is the reason why we currently have keywords like `__import`.
A traditional solution in a compiler is to map keywords to distinct token codes as part of lexing, which eliminates the first conern (performance) because now we can dispatch with `switch`. It can also aleviate the second concern if we add/remove names from the string->code mapping based on language (the rest of the parsing logic doesn't have to know about keywords being added/removed).
The solution we go for here is more aggressive.
Instead of mapping keyword names to special token codes during lexing, we instead introduce logical "syntax declarations" into the AST, which are looked up using the ordinary scoping rules of the language.
Depending on what code is imported into the scope where parsing is going on, different keywords may then be visible.
This solves our last concern, since a user-defined variable that just happens to use the same name as a keyword is now allowed to shadow the imported declaration for syntax (this is akin to, e.g., Scheme where there really aren't any "keywords").
This also opens the door to the possibility of eventually allowing user to define their own syntax (again, like Scheme).
For now I'm only using this for the declaration keywords.
With this change it should be pretty easy to also add statement keywords in the same fashion.
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- `ExpressionSyntaxNode` becomes `Expr`
- `StatementSyntaxNode` becomes `Stmt`
- `StructSyntaxNode` becomes `StructDecl`
- `ProgramSyntaxNode` becomes `ModuleDecl`
- `ExpressionType` becomes `Type`
- Existing fields names `Type` become `type`
- There might be some collateral damage here if there were, e.g., `enum`s named `Type`, but I can live with that for now and fix those up as a I see them
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- The big change here is that all the definitions for syntax-node classes have been macro-ized, to that we can do light metaprogramming over them
- The use of macros for this has big down-sides, but I'm not quite ready to do anything more heavy-weight right now
- The macro-ized definitions can be included multiple times, to generate different declarations/code as needed
- The first example of using this meta-programming facility is a new visitor system
- The actual visitor base classes and the dispatch logic are all generated from the meta-files
- There was only one visitor left in the code: the semantics checker, so that was ported to the new system.
- All current test cases pass, so *of course* that means all is well.
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