| Age | Commit message (Collapse) | Author |
|---|
|
|
|
ExtractExitentialValueExpr. (#2541)
* Fix missing semantic highlighting in attributes and ExtractExitentialValueExpr.
* Fix regression on partially specialized generic expr highlighting.
* Add regression test.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
|
|
argument. (#2536)
* Fix non-static generic func call issue.
* Add test case.
* Revert unnecessary change.
* Update test comment.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
|
|
|
|
* Clean up type checking of higher order expressions.
* Replace `goto` with `break` to pacify clang.
* Fix.
* Fixes.
* Fix more tests.
* Fix lowerWitnessTable parameter error.
* Exclude attributes from ast printing.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
* Initial plumbing of backward autodiff in the frontend.
* More plumbing.
* Initial reverse autodiff working.
* Bug fixes.
* Misc.
* Remove redundant code.
* More clean up.
* Misc.
* Rebase and add backward diff test.
* Disable test.
* Clean up.
* Minor fix.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
* Add [ForwardDerivativeOf] attribute.
* Fix handling around phi nodes.
* Fixes.
* Remove IR opcode for ForwardDerivativeOfDecoration.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
* Rework differential conformance dictionary checking.
* Revert space changes.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
|
|
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
* Auto synthesis of IDifferntial interface methods.
* Add comments.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
|
|
`[DerivativeMember(DiffType.field)]` (#2460)
* wip: remove auto-diff for member access, add diff through property accessors.
* Fix getter-setter test.
* Fix getter-setter-multi test.
* Fix nested-jvp test.
* Use [DerivativeMember] attribute to differentiate through member access.
* Clean up.
* More cleanup.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
* Modified the new type system to support generic differentiable types and added support for differentiating overloaded functions.
* Changed a few asserts to release asserts to avoid unreferenced variable errors
* Fixed a naming issue with TypeWitnessBreadcumb::Flavor::Decl
* Added logic to avoid tracking differentiable types if the module does not use auto-diff or define differentiable types.
* Moved the auto-diff passes to after the specialization step, added a more complex generics test
* Added a generics stress test and fixed AST-side logic. IR side needs some more work
* Added differential getter and setter logic, fixed multiple issues with DifferentiableTypeDictionary, added support for loops and conditions
* Changed differential getters to use pointer types, added getter type checking
* Fixed some bugs related to diff type registration and differential getters
* Removed some superfluous code
* Removed some more unused code.
* Fixed an issue with witness substitution
* Minor fix
Co-authored-by: Yong He <yonghe@outlook.com>
|
|
* Changed all getEntryPointCode calls to use RendererBase::getEntryPointCodeFromShaderCache
* Hashing hooked up, tests pass but need to add more to fully test functionality
* checkpoint
* Checkpoint: File system creation seems functional, saving is broken
* checkpoint: Fixed filename generation from MD5 hash, shader blob might be going missing ahead of pipeline state creation
* Fixed a lot of bugs related to hash code generation, shader cache is likely working but needs further testing
* Added workaround for module loading by re-creating the test device, shader cache test functional
* Vulkan shader caching bug fixed, checkpoint commit before more refinement
* pre-ToT merge checkpoint
* checkpoint commit, improving cache keys
* Significantly expanded items included in the dependency hash for Module; Added dependency hash functions to SpecializedComponentType and RenamedEntryPointComponentType
* Temporarily disable shader cache test
* Mid cleanup changes, solution successfully builds
* Added several helper update functions to slang-md5 to help simplify usage; Added a function under ISession to compute a hash for all linkage-related items; Function renames and cleaned up some comments
* Ran premake.bat; Renamed getASTBasedHashCode to computeASTBasedHash
* Added slang unit tests for Checksum and MD5; Extended gfx shader cache test to test with multiple shader files and one shader file with multiple entry points
* Solution builds and shader cache tests pass, but at least a couple other tests now failing
* ran premake.bat
* More cleanup changes
* Added shaderCachePath field to IDevice desc in gfx.slang, gfx-smoke.slang should be functional
* ran premake
* cleanup changes; Adding test printf to getEntryPointCodeFromShaderCache to see if output can be seen in CI
* Removed debugging printfs; Added handling for getEntryPointCode() failing
* Cleanup changes; Jonathan's fixes to SerialWriter to zero initialize otherwise uninitialized memory; Change to SwizzleExpr creation to zero initialize elementCount
* Changed enable_if_t to enable_if
* Fixed enable_if
* Added test for import vs include and changes to included and imported files; Fixed build errors in CUDA; Renamed shader cache statistics fields
* cleanup changes
* Readd removed file
* Restructured computeDependencyBasedHash calls, added computeDependencyBasedHashImpl to all classes dervied from ComponentType
* Applied same restructuring to the AST hash functions
* Cleanup changes; Moved HashBuilder out to slang-digest.h and added some helper functions to streamline the process of adding items to a hash
* Cleanup; Fixed incorrect expected results for shader import and include test
|
|
* Language feature: pointer sized int types.
* Fix.
* small change to test.
* Fix stdlib.
* Fix.
* Fix.
* Add typedef for `size_t` in stdlib.
* Fix test.
* Add `intptr_t::size` constant.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
* Allow interface requirements to reference to the interface type itself.
* add comment explaining the change.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
* wip: dedup AST type nodes and cache lookup.
* Fix.
* Remove profiling.
* Fixes.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
* Multi parameter `__subscript`
* Fix.
* Fix bugs.
* Fix.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
(#2388)
|
|
|
|
* Compiler time evaluation of all int and bool operators.
* Fix linux compile error.
* Fix.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
* Warning on bool to float conversion.
* Fix test cases.
* Improve.
* LanguageServer: don't show constant value for non constant variables.
* Fix tests.
* Fix warnings in tests.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
|
|
* Add `none` literal that is convertible to `Optional`.
* Fix cpu code gen.
* Include vk and cpu test for is-as operator test.
* Inline comparison operators.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
* `is` and `as` operator and `Optional<T>`.
* Fix.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
* Merge slang-ir-diff-jvp.cpp
* Added support and tests for other float vector types
* Added swizzle test and code to handle it (tests failing currently)
* Fixed one test, the other is still pending
* Fixed instruction cloning logic to avoid modifying original function
* Fixed an issue with custom 'pow_jvp' and added support for vector contructor
* Minor update to comments
* Fixed support for division
* Fixed an issue with uninitialized diagnostic sink
* Moved derivative processing to after mandatory inlining.
Skip instructions that don't have side-effects and aren't used by anything.
* WIP: Handling unconditional control flow and multi-block functions
* Support for unconditional multi-block functions
* Added a dead code elimination step to the derivative pass
* Changed name of 'hasNoSideEffects()'
* Refactored variable names
* Added initial IR defs for new type system
* Added necessary logic for semantic checking
* Overhauled type system to use builtin pair types and conform to the IDifferentiable interface
* Automatically replace IRDifferentiablePairType to a custom IRStructType
* Added generics handling by expanding the conformance context functionality and allowing for type parameters
* Minor fix: early return in processPairTypes()
* Minor fixes to differentiable resolution on generic types
* Added new instructions for differential pairs. Basic tests work now.
Looking into generic types.
* Adjusted most tests to the new type system. OutType and InOutType are still not properly working.
* Updated __jvp to produce both primal and differential output
* Moved autodiff related declarations to diff.meta.slang
* Refactored variable names
* Added initial IR defs for new type system
* Added necessary logic for semantic checking
* Overhauled type system to use builtin pair types and conform to the IDifferentiable interface
* Automatically replace IRDifferentiablePairType to a custom IRStructType
* Added generics handling by expanding the conformance context functionality and allowing for type parameters
* Minor fix: early return in processPairTypes()
* Minor fixes to differentiable resolution on generic types
* Added new instructions for differential pairs. Basic tests work now.
Looking into generic types.
* Adjusted most tests to the new type system. OutType and InOutType are still not properly working.
* Updated __jvp to produce both primal and differential output
* Moved autodiff related declarations to diff.meta.slang
* Removed external changes
* Cleanup the transcription logic: each case returns a pair of insts for the primal and differential computation.
|
|
* Implicit pointer dereference when using member operator.
* Add expected test result
* Fix lookup.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
|
|
* Merge slang-ir-diff-jvp.cpp
* Added support and tests for other float vector types
* Added swizzle test and code to handle it (tests failing currently)
* Fixed one test, the other is still pending
* Fixed instruction cloning logic to avoid modifying original function
* Fixed an issue with custom 'pow_jvp' and added support for vector contructor
* Minor update to comments
* Fixed support for division
* Fixed an issue with uninitialized diagnostic sink
* Moved derivative processing to after mandatory inlining.
Skip instructions that don't have side-effects and aren't used by anything.
* WIP: Handling unconditional control flow and multi-block functions
* Support for unconditional multi-block functions
* Added a dead code elimination step to the derivative pass
* Changed name of 'hasNoSideEffects()'
|
|
* Added out/inout tests
* Added support for out and inout parameters. Still untested
* Fixed and tested support for out and inout types
* Removed some comments
|
|
* Support `class` types.
* Ignore class-keyword test
* Fix codereview comments and warnings.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
arithmetic on the float3 type (#2313)
* Added support for differentiating calls to basic functions, as well as arithmetic on the float3 type
* Added test expected result
|
|
* Language server: Inlay hints.
* Signature help for base exprs that is not a declref.
* Fix checking of jvp operator.
* Fix.
* Add clang-format based auto formatting.
* Fix clang error.
* Fix clang-format discovery logic.
* Fine tune auto formatting and completion experience.
* Update macos workflow.
* Fixes to configurations.
* Fix parser recovery to trigger completion for index exprs.
* Typo fix.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
arithmetic. Also added type-checking during the semantic stage. (#2303)
* Added JVPTranscriber to handle differentiation of load, store, var, param and return instructions, as well as conversion of data and function types
* Changed class names to be more in line with convention. Added correct type checking for __jvp() and verified that simple calls with only loads and stores are processed correctly
* Added logic to differentiate basic arithmetic and literals inside IRConstruct and fixed the way parameters are differentiated
Co-authored-by: Yong He <yonghe@outlook.com>
|
|
framework for passes to process them. (#2297)
* Added a decorator to mark functions for forward-mode differentiation
* Fill out support for calls to non-decl values
The existing compiler logic has a few places (semantic checking plus AST-to-IR lowering) where it assumes that function calls (`InvokeExpr`) are only ever made to expressions that resolve to a specific `Decl` (`DeclRefExpr`). This assumption allows semantic checking and lowering code to inspect things like the parameter list of an actual declaration, rather than just the type signature of the callee, and that infrastructure is used to support various features (e.g., default argument values on parameters).
The AST and IR representations themselves have no matching requirement, and the places where the more general case of call expressions would need to be supported were relatively clear in the code. This change attempts to add suitable logic into each of those places.
Note that this change does *not* surface any valid way to form input code that would cause these new code paths to be executed, so it is entirely possible that there are bugs in the logic as written here. The primary goal of this change is simply to get a sketch of the correct code checked in so that we have something to build on once we have language features that will require this support.
* fixup: warnings-as-errors
* Added parser logic for '__jvp(<fn-name>)' operator
* Fixed issue with missing overload candidate item and added basic parsing test for the __jvp syntax
* Added a blank JVP Auto-diff pass and a pass that replaces 'JVPDerivativeOf' calls with the differentiated function
* Added a couple comments
* Added parameter handling for the JVP pass
Co-authored-by: Theresa Foley <tfoley@nvidia.com>
|
|
|
|
* Major language server features.
* Include slangd in binary release.
* Fix compiler issues.
* Fix compiler error.
* Completion resolve.
* Various improvements.
* Update diagnostic test expected output.
* Bug fix for source locations.
* Adjust diagnostic update frequency.
* Update github actions to store artifacts.
* Fix infinite parser loop.
* Fix parser recovery.
* Fix parser recovery.
* Update test.
* Fix test.
* Disable IR gen for language server.
* Allow commit characters in auto completion.
* Fix lookup for invoke exprs.
* More parser robustness fixes.
* update solution file
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
* Clean up `IRReturnVoid`.
* Update gitignore.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
* New language feature: basic error handling.
* Fix.
* Fix `tryCall` encoding according to code review.
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
The problematic case is when an `interface` has a `[mutating]` method:
interface ICounter
{
[mutating] void increment();
}
and code tries to invoke that method on a value of existential type:
ICounter c = ...;
c.increment();
We know that the existential value `c` is conceptually a tuple of:
* A concrete type `X`
* A witness that `X : ICounter`
* A value `v` of type `X`
We simply want to invoke `increment()` on the `v` part, using the `X : ICounter` witness table.
The catch that the compiler faces is that the variable `c` is mutable, so we need to be careful that we "snapshot" its value (the tuple `X, X:ICounter, v`) at a single point.
The snapshotting behavior is important when invoking a method that involves `This` or associated types in its signature, so we cannot get rid of it.
The snapshotting we do relies on the idea of a `LetExpr` AST node, which cannot be written in the input syntax.
A `LetExpr` introduces a variable binding (with an initial-value expression) and then evaluates a body expression in the context of that binding.
For a call site like `c.increment()` the front-end makes an intermediate copy of `c` and then "opens" that immutable value to get at the elements of the tuple `X`, `X : ICounter`, `v`.
The resulting AST after checking looks something like:
ICounter c = ...;
(let tmp = c in extractExistentialValue(tmp)).increment();
In that form it is more clear why the attempt to call `increment()` fails:
1. The binding `tmp` sure looks immutable
2. There is no logic in the compiler to make `extractExistentialValue(x)` be an l-value if `x` is
3. There is seemingly no logic to write back from `tmp` to `c` when the operation completes
Let us walk through those problems in order.
Item (1) turns out to be a bit of a non-issue.
Despite the way that I've written out `let` expressions above, the logic in `moveTemp()` in the compiler actually introduces a *mutable* binding.
Item (2) can be fixed for the purposes of semantic checking by modifying `openExistential()`.
Simplistically, we make the overall expression be an l-value if the operand is.
Item (3) is handled at the level of AST->IR lowering. Each kind of expression that can form an l-value needs to have a way to represent the "location" of that l-value in the `LoweredValInfo` type.
This change adds a case to handle the `extractExistentialVal` operation, by tracking both the extract value (of concrete type) and the underlying l-value (of existential type).
Where all of this comes crashing against reality a bit is that the scoping I've drawn for the `let` expressions above kind of doesn't work once we look at types.
The basic problem is that the *type* of the `(let tmp = c in ...)` expression is the concrete type `X` that was extracted from the existential.
That type can conceptually be written as `ExtractExistentialType(tmp)` which, notably, references `tmp`.
That means that we end up with AST expression nodes that reference the variable `tmp` *outside* of its scope.
Furthermore, those references to `tmp` can end up being lowered to IR *before* we have lowered the `let ...` expression itself.
Fixing the scoping issue turns out to be a major undertaking.
The first (and more obvious) issue is needing to address the scoping problem.
The solution I implemented includes a bit of refactoring to make all the `SemanticsVisitor` types better able to pass around the contextual scope-dependent state that might be needed during semantic checking, but really only adds a single piece of state.
The semantic-checking state used for checking expressions is bottlenecked so that there will (or at least *should*) always be an explicit representation of a "scope" that surrounds a complete expression (as opposed to a sub-expression).
When a `LetExpr` needs to be introduced, it is added to a pending list on the active scope, rather than being added locally.
Once the complete expression is checked, the resulting expression is wrapped up in the pending `LetExpr`s so that their scope is as broad as possible.
Technically this solution doesn't cover all cases. For example:
interface ICell { associatedtype Content; Content getContent(); }
...
ICell cell = ...;
let content = cell.getContent();
In this case the type of `content` refers to the binding introduced by a `LetExpr` in the initial-value expression.
I am leaving such issues as a piece of future work, in the hopes that we can get at least a partial fix for the problem in place.
A future fix probably nees to extend the scoping even wider (e.g., by unwrapping the `LetExpr`s from the initial-value expression and turning them into distinct temporaries).
The second piece of the fix is that we need a way for the modified value of the extracted existential to be "written back" to the original location.
Well...
We are actually being a little slippery here, based on some logic in the compiler codebase that I guess Just Works.
When AST->IR lowering encounters a `LetExpr` that binds an l-value to a name, it actually ends up binding that name more or less as a *reference* to that l-value.
At this point the `let`-ness of `LetExpr` is very much in doubt: the binding can be mutable, and it can even be an *alias* of some location?!?
In any case, the result is that the AST->IR codegen logic implicitly handles the "write-back" because the `let`-bound temporary is actually an alias for the original location.
A more complete future fix might need to introduce a distinct case in `LoweredValInfo` to handle the case of copy of a mutable temporary.
|
|
* Support `[DllImport]`
* Fix.
* Fix.
* Fix array type emit in cpp.
* Fix.
* Fix.
* Fix
Co-authored-by: Yong He <yhe@nvidia.com>
|
|
An earlier refactoring pass over the compiler codebase split the
type that had been called `CompileRequest` into three distinct
pieces:
* `FrontEndCompileRequest` which was supposed to own state and
options related to running the compiler front end and producing
IR + reflection (e.g., what translation units and source
files/strings are included).
* `BackEndCompileRequest` which was supposed to own state and options
related to running the compiler back end to translate the IR
for a `ComponentType` (program) into output code. (Note that the
`BackEndCompileRequest` was conceived of as orthogonal to the
`TargetRequest`s, which store per-target and target-specific
options.)
* `EndToEndCompileRequest` which was an umbrella object that owns
separate front-end and back-end requests, plus any state that is
only relevant when doing a true end-to-end compile (such as the
kinds of compiles initiated with `slangc`). As originally conceived,
the only state that this type was supposed to own was stuff related
to "pass-through" compilation, as well as state related to writing
of generated code to output files.
That refactoring work was very useful at the time, because it allowed
us to "scrub" the back end compilation steps to remove all
dependencies on front-end and AST state (this was important for our
goals of enabling linking and codegen from serialized Slang IR).
At this point, however, it is clear that the hierarchy that was built
up serves very little purpose:
* The `BackEndCompileRequest` type is only used in two places:
* As part of an `EndToEndCompileRequest`, where the settings on
the `BackEndCompileRequest` can be configured, but only through
the `EndToEndCompileRequest`
* As part of on-demand code generation through the `IComponentType`
APIs. In this case, the settings stored on the
`BackEndCompileRequest` are not accessible to the application
at all, and will always use their default values, so that
instantiating a "request" object doesn't really make any sense.
* The `FrontEndCompileRequest` type has a similar situation:
* Front-end compilation as part of an `EndToEndCompileRequest`
supports user configuration of `FrontEndCompileRequest` settings,
but only through the `EndToEndCompileRequest`
* Front-end compilation triggered by an `import` or a `loadModule()`
call does not support user configuration of settings at all. It
will always derive all relevant settings from thsoe on the
session ("linkage").
In addition, subsequent changes have been made to the compiler that
show a bit of a "code smell" and/or forward-looking worries for this
decomposition:
* In some cases we've had to add the same setting to multiple types
in the breakdown (front-end, back-end, end-to-end, linkage, target,
etc.) which makes it harder for us to validate that all the possible
mixtures of state work correctly.
* Related to the above, in some cases we have manual logic that copies
state from one of the objects in the breakdown to another, in order
to ensure that the user's intention is actually followed.
* As a forward-looking concern, it seems that developers have sometimes
added new configuration options and state to places that don't really
make sense according to the rationale of the original decomposition
(e.g., we probably don't want to have a lot of state that is only
available via end-to-end requests, given that the API structure is
meant to push users *away* from end-to-end compiles).
As a result of all of the above, I've been planning a large refactor
with the following big-picture goals:
* Eliminate `BackEndCompileRequest`
* Move all relevant state/options from the back-end request to
the end-to-end request, since that is the only place they could
be set anyway.
* Introduce a transient "context" type to be used for the duration
of code generation that serves the main functions that back-end
requests really served in the codebase
* Make `EndToEndCompileRequest` be a subclass of
`FrontEndCompileRequest`
* Consider addding a transient "context" type for front-end
compiles that can be used in `import`-like cases rather than
needing a full front-end request object. If this works, then
eliminate `FrontEndCompileRequest` and be back to world with
just a single `CompileRequest` type
* Move *all* compiler configuration options to a distinct type (named
something like `CompilerConfig` or `CompilerOptions` or whatever)
which stores setting as key-value pairs, and has a notion of
"inheritance" such that one configuration can extend or build on top
of another. Make all the relevant types use this catch-all structure
instead of redundantly storing flags in many places.
This change deals with the first of those bullets: removeal of
`BackEndCompileRequest`. The addition of the `CodeGenContext` type is
perhaps an unncessary additional step, but making that change helps
clean up a bunch of the code related to per-target code generation,
so I think it is the right choice.
Co-authored-by: Yong He <yonghe@outlook.com>
|
|
Read/write resource types (what D3D/HLSL often refer to as UAVs) can be broadly categorized based on whether they require an underlying format (e.g., a `DXGI_FORMAT`) for reads, or not. D3D refers to the ones that require a format as "typed" UAVs (even though a `RWStructuredBuffer<MyData>` is clearly "typed" at the HLSL level). Vulkan refers to these cases as "storage images" and "storage texel buffers."
Under the D3D model, an application does not have to specify the exact format for a formatted/"typed" UAV in order for loads to work, but it *does* need to specify if an HLSL resource with a declared `float` or vector-of-`float` element type will be backed by data with a `*_UNORM` or `*_SNORM` format. This is where the `unorm` and `snorm` type modifiers come in.
Superficially, it might seem that adding this feature to the Slang compiler is "just" a matter of adding the two modifiers, which is easily done with a pair of one-line `syntax` declarations in `core.meta.slang` plus the corresponding AST node types.
Unfortunately the superficial view misses the detail that, to date, Slang has not had any support for *type modifiers* at all, and has only supported *declaration modifiers*. The distinction has so far not mattered, even with modifiers like `const` because, e.g., the difference between a "`const` array of `float`" and an "array of `const float`" doesn't really matter.
So, adding these two modifiers required introducing a lot of infrastructure along the way. Let's walk through what needed to happen:
* As described above, the actual `syntax` was added easily in the Slang stdlib
* I added a new subclass of `Modifier` for `TypeModifier`s in the AST, and added the AST nodes for `unorm` and `snorm` as subclasses of that.
* In order to syntactically support modifiers applied to types (e.g., `unorm float`), I needed to add a `ModifiedTypeExpr` subclass of `Expr` that represents a base type expression with one or more modifiers applied
* The parser needed some subtle new logic. There are two main cases where type modifiers will come up:
1. In contexts where we might be parsing a declaration (e.g., `const unorm float a`), we need to support a list of modifiers that might freely mix type modifiers and "declaration modifiers" which are not intended to apply to types. In this case we need to split the lis tof modifiers into the type-related ones and the declaration-related ones, and attach each subset to the appropriate place. This is very important for features like C-style pointers, where in `static const float* a;`, the `static` modifier applies to the entire declaration of `a`, but the `const` modifier *only* applies to the `float` type specifier, and *not* to the outer pointer type (the actual type of `a`).
2. In contexts where we are not parsing a declaration (e.g., a generic type argument), we need to support a list of modifiers and appy them *all* to the type specifier being parsed, even if some of them might not be appropriate.
* While working in the parser I implemented a certain amount of unrelated cleanup for code that was using raw `Modifier*`s to represent lists of modifiers, instead of the purpose-built `Modifiers` type.
* The `_parseGenericArg` case needed specific work, because it is an important case in the grammar where we need to parse *either* a type expression or a value exprssion, but cannot easily predict which we will see. The fix implemented for now is to always try to parse modifiers and, if we see any, to assume we are in the type case. Because of the rules for how modifiers in a C-like language inhere to the type specifier (and not necessarily the entire type), we need to refactor some of the type expression parsing routines to support parsing a "suffix" of a type expression.
* Note: I decided to be conservative and only make these changes in `_parseGenericArg` because that is place that is *needed* in order for user code with `unorm`/`snorm` to work, but in practice a user could still confuse our parser by using type modifiers as part of a cast (e.g., `x = (unorm float)y;`). While there is currently no reason why a user should want to do this, it *does* suggest that we need to be prepared to see type modifiers in other ambiguous "expression or type?" contexts. We have so far preferred to avoid looking up built-in syntax declarations like modifiers in expression contexts, because we want to allow users to create variable names that might conflict with some of the more surprising modifier keywords in HLSL (e.g., both `triangle` and `sample` are modifier keyword). A nuanced strategy may be required when we get around to closing this gap (which will be needed around when we want full pointer support, since a cast like `(const SomeType*)somePtr` is pretty common).
* In semantic checking, we now need a `visitModifiedTypeExpr`, which visits the base expression to produce a `Type` and then checks each of the `Modifier`s attached to it. During this process we need to translate the AST-level `Modifier`s into something that can exist properly in the universe of `Type`s. We introduce a `ModifiedType` subclass of `Type`, distinct from the `ModifiedTypeExpr` subclass of `Expr`. Furthermore, we introduce a `ModifierVal` subclass of `Val`, distinct from `Modifier`/`TypeModifier`.
* One unfortunate thing here is that it means we have both, e.g., `UNormModifier` to represent the parsed syntax, and `UNormModifierVal` to represent the `Type`/`Val`-level representation of the same concept. It is quite likely that we are near the point where we can/should consider having two distinct AST representations: one for freshly-parsed ASTs and one for semantically-checked ASTs. The `Type`/`Val` hierarchy clearly belongs to the latter.
* No actual semantic checking is currently being applied to the `unorm` and `snorm` modifiers, although we should in principle check that they are only being applied to `float` and vector-of-`float` types.
* In an attempt to simplify some of the creation logic and build a tiny bit of reusable infrastructure, I went ahead and added the skeleton of a dedupe-caching system in `ASTBuilder` so that we can easily ensure only a single `UNormModifierVal` and a single `SNormModifierVal` ever get created inside the scope of a single builder.
* TODO: Thinking about this, I'm now worried the deduplication does not mean I can make the simplifications I currently do in semantic checking by assuming that any two `UNormModifierVal`s will be pointer-identical. This is because we do not currently (IIRC) have the required "bottleneck" in the compiler where all ASTs get serialized after initial checking, and then deserialized when `import`ed into a downstream module, so that every AST node during a checking step comes from a single `ASTBuilder`. Hmm...
* If we can rely on deduplication to do its thing, then the `Val` and `Type` implementations of modifiers can be relatively simple.
* TODO: One issue here is that the equality comparison for `ModifiedType` currently checks for the same base type and the same modifiers in the same order. This works for now when we only have a small number of type modifiers and any given type will hae at most one, but in the longer run it relies on us to implement some kind of canonicalization scheme, which would both ensure that between `Modified(T, {A, B})` and `Modified(T, {B, A})` only one is allowed (that is, a canonical ordering on modifiers), and that we do not allow `Modified(Modified(T, {A}), {B})`.
* TODO: One other issues is that the `ModifiedType` case does not currently interact correctly with the `as()`-based casting for types (whereas that operation *does* interact in a semantically-correct fashion with `typedef`s). Fixing this issue in a robust way really depends on us re-architecting the `Type` system so that *any* `Type` can have modifiers attached, with modifiers affecting type identity/deduplication.
* The key place where `ModifiedType` creates a complication in semantic checking is type conversion/coercion. A user is likely to declare a `RWTexture2D<unorm float>`, fetch from it (producing a value of type `unorm float`) and then assign the result to a `float` variable, prompting for a conversion from `unorm float` to `float` (because they are distinct `Type`s).
* We handle this case in the core `_coerce()` operation by checking if either `toType` or `fromType` is a `ModifiedType`. If *either* one is a modified type, we apply logic to check for modifiers that are present on one and not the other. Basically we check which modifiers need to be "dropped" and which need to be "added" during conversion, and validate that these modifiers *can* be dropped/added without creating a semantic error. The only type modifiers we support right now *can* be dropped/added like this, so we are fine.
* TODO: When we add more complete pointer support, we could need logic here to validate when casts between, e.g., `const int*` and `int*` should/shouldn't be allowed.
* Note: Even opening the door to type modifiers at all creates the same kind of challenges for user-defined generic types (and functions!) since `MyType<int>` and `MyType<const int>` are distinct instantiations in a future where we support `const` as a type modifier. We *may* need to plan to restrict where modified types can be used, so that certain built-in generic types support modified types as arguments, but user-defined types don't (or at least might need to opt-in to get support).
* The result of a `_coerce()` that drops/adds modifiers is a `ModifierCastExpr`, which is a kind of no-op AST node that merely expresses that the conversion is allowed and valid.
* In IR lowering we currently do the simple thing and translate a `ModifiedType` to a distinct IR node called `AttributedType`.
* The change in terminology from "modifier" to "attribute" is to follow the way that these kinds of modifiers best map to the `IRAttr` case in the IR (rather than the `IRDecoration` case). We probably ought to do a careful terminology scrub here, because having this terminology mismatch between IR and AST could be a source of confusion.
* TODO: In principle, using `IRAttributedType` creates the same basic problems as using `ModifiedType`: code that is usin `as()` or similar operations to check for a specific subclass of `IRType` may not see the case they were looking for due to use of `IRAttributedType`.
* Initially I had hoped to avoid the problem by having the `IRAttr`s be attached directly as operands to an otherwise-ordinary `IRType`. E.g., a lowered `unorm float4` would be an `IRVectorType` with an "extra" operand that is an `IRUNormAttr`, something like: `Vector<Float, 4, UNorm>`. This sounds great (and looks great!), but runs into the problem that it is incompatible with the way we currently represent things like generic type parameters. A generic type parameter `T` is represented as an `IRParam`, and it does *not* make sense to have an additional `IRParam` to represent `const T` or `unorm T`, etc.
* The Right Way to solve this stuff at both the AST and IR levels is to avoid passing around bare `Type*` or `IRType*` in general, and instead use a value type that implements the needed policy more directly: something like a `TypeHolder` or `IRTypeHolder` (placeholder name). The `*Holder` type would abstract over the various "wrapper" nodes required to store all the additional data like attributes but, importantly, would *not* allow that extra information to be dropped or lost during operations like casting (e.g., note how the current `Type` implementation of `as()` loses information on `typedef` names, making our error messages slightly worse). This is actually quite similar to how we currently use the `DeclRef<T>` system to allow working with what is *usually* a `T*` under the hood, but in a way that ensures we don't lose track of any generic substitution information.
* During C-like code emit we have a process that turns an `IRType` into a chain of declarators as needed to emit a C-like declaration with pointers, arrays, etc. The `IRAttributedType` case needs to get folded into this logic. Basically, when we see an `IRAttributedType` we immediately emit any modifiers that are required to be in a prefix position, then recursively emit the underlying type with an extra layer of declarator that tracks the modifiers, so that we can emit any modifiers that should be placed in a postfix position *after* the type. As a specific example, our C/C++ back-end would want to use the postifx option to handle `const`, because then it can properly emit stuff like `int const * const *` and not the incorrect `const const int**`.
* The HLSL emit logic overrides the prefix case for handling type attributes, and uses it to emit `unorm` and `snorm` where they occur.
* One unfortunate detail is that (apparently) some downstream HLSL compilers do not allow the `unorm`/`snorm` modifiers to apply to `vector<float, *>` types, even though that should be semantically valid. Instead, they only support `float`, `float2`, `float3`, and `float4` explicitly. To work around this issue, we go ahead and change our HLSL emit logic so that when we encountered 1-to-4 component vectors of `float`, `int`, or `uint` we emit the type name using the typical HLSL shorthand. This is actually a signficicant change in our HLSL output, but it both seemed like a good fix to have anyway, and was also the only obvious way to address the downstream parser shortcomings without a massive kludge.
* As a result of this change the `half-texture.slang` test broke, since it was using raw HLSL as the expected output. I changed the test to do a DXIL comparison instead, which is our preferred way of testing cross-compilation behavior (since it is more robust in the face of small changes to our source output).
|
