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This is functionality required to support a Falcor bug fix.
Most of the code to compute the right semantic name/index for a parameter was already present.
This change adds:
- Storage for semantic name/index on every `VarLayout`
- Note: this is wasteful and should be optimized later
- A public API to query the semantic name/index
- The contract is that this API returns `NULL` if the parameter had no semantic
- A bit of work in `parameter-binding.cpp` to attach semantics to varying input/output when traversing varying parameters.
- Note: this is intentionally set up so that it associates semantics even with non-leaf parameters, so that an API user can query the semantic of a `struct` parameter and know that its members will be assigned sequential semantic indices from its starting value.
- Support for dumping this information in reflection tests
One notable thing that I did *not* change here is that the reflection test fixture doesn't report information on the output of an entry point, even though it really should. That should be fixed in a separate change, though, because it would affect many of the expected outputs.
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There are two big changes here:
- Add logic during the initial IR cloning pass for an entry point + target that tries to pick the best possible version of any target-overloaded function. This allows us to pick the intrinsic version of `saturate()` when compiling for HLSL output, but then pick the non-intrinsic version (that is implemented in terms of `clamp()`) when targetting GLSL.
- Add an initial specialization pass that tries to deal with generics. This required some fixing work to IR generation, so that we correctly generate explicit operations to specialize a generic for specific types (this is currently implemented as a `specialize` instruction that takes the generic to specialize plus a declaration-reference that represents the specialized form). With that work in place, we can scan for `specialize` instructions inside of non-generic functions, and use them to trigger generation of specialized code. We rely on the name-mangling scheme to help us find pre-existing specializations when possible.
There are also a bunch of cleanups encountered along the way:
- Don't use the explicit `layout(offset=...)` for uniforms, because it isn't supported by all current drivers. For now we will just assume that our layout rules compute the same values that the driver would for un-marked-up code. We can come back later and try to implement a workaround in the cases where this doesn't apply (e.g., by re-running the layout logic as part of emission, and dropping layout modifiers from variables that don't need explicit layout).
- Fix some issues in IR dump printing so that we print function declarations more nicely.
- Testing: print out failing pixel when image-diff fails
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The big addition here is that the Slang "bytecode" is no longer treated as just a "code generation target" (`CodeGenTarget`) akin to DX bytecode (DXBC) or SPIR-V, but instead is a `ContainerFormat` that can be used to emit all the results of a compile request (well, currently just the IR-as-BC, but the intention is there).
Getting to this goal involved some prior checkins that eliminated bogus "targets" that weren't really akin to SPIR-V or DXBC: `-target slang-ir-asm` and `-target reflection-json`. Those targets were really in place to support testing, and so they've been made more explicit testing/debug options.
This change eliminates `-target slang-ir` and instead tries to allow the user to specify `-o foo.slang-module` as an output file name, that indicates the intention to output a "container" file that will wrap up all the generated code.
I've also gone ahead and generalized the existing `-target` option so that we are actually building up a *list* of code generation targets. This is largely just a cleanup, since it forces code to be more aware of when it is doing something target-specific vs. target independent. For example, reflection layout information lives on a requested target, and not on the compile request as a whole, and similarly output code is per-target, per-entry-point.
As a cleanup, I eliminated support for per-translation-unit output. This was vestigial code from back when I used to try and do HLSL generation for a whole translation unit instead of per-entry-point (which turned out to be a lot of complexity for little gain), and it was only being used in the `hello` example and the `render-test` test fixture - in both cases fixing it up was easy enough. I've stubbed out the old `spGetTranslationUnitSource` API, but haven't removed it yet.
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* Get rid of the `-slang-ir-asm` target
This is really only useful for debugging, so I've replaced the functionality with a `-dump-ir` command line option (which dump's the IR for an entry point before doing codegen).
* fixup: use HLSL target, not DXBC, so test can run on Linux
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* Bug fix for vector initializer lists
When a vector was initialized with an initializer list:
float4 f = { 0, 1, 2, 3 };
we were following the logic for `struct` types (since `vector<T,N>` is technically a `struct` declaration in our stdlib...), but the type has no field, so we were (silently!) ignoring the actual operands.
I've applied a simple fix where we cast the operands to the element type of the vector, but a more complete fix will be needed sooner or later where we check the operand counts properly, etc.
* Create implicit cast AST nodes when calling initializers
The logic for dealing with implicit conversions was recently beefed up so that it would look at `__init` declarations in the target type, but in those cases the front-end would always create an `InvokeExpr` even when we would rather get an `ImplicitCastExpr` or (in the "rewrite" case) a `HiddenImplicitCastExpr`.
I've fixed this up for now by constructing a dummy expression to stand in for the "original" call expression when creating the final call (luckily our `TypeCastExpr` is already just a specialized `InvokeExpr`).
A better long-term solution might be to have implicit-ness or hidden-ness be modifiers or flags, rather than needing to use specialized forms of call nodes.
* Fix subscript operator for `RWTexture1D`
The index type was being declared as `uint1` instead of `uint`, and that created problems for downstream HLSL compilation when we introduced expressions like `uav[uint1(index)]` - the compiler would complain that a vector is not a valid index type.
* Fix up constant-folding of integer casts.
The old logic was checking for `InvokeExpr` before `TypeCastExpr`, but in the new setup a type cast *is* an `InvokeExpr`, so that case was never triggering.
All of the constant-folding code really needs to be revisited, though, so that it can use a more general-purpose evaluation scheme like the bytecode (so that we can handle a moral equivalent of `constexpr` in the long run).
* Fix implicit conversion costs for vector types
A recent change made it so that the logic for looking up implicit conversions now uses declarations of initializers in the standard library (rather than hand-coding all the cases in `check.cpp`).
One mistake made there was that we dropped the logic for computing implicit conversions between vectors of the same size, but different element types.
These conversions were still allowed by a catch-all (generic) declaration in the standard library, but that declaration didn't include any implicit conversion cost logic (since it was generic, there was no single cost to use).
This change explicitly enumerates the required conversions with their costs.
It is a bit unfortunate that this is an O(N^2) amount of code for N base types, but that seems unavoidable for now.
* Handle "lowering" of overloaded expressions
If we are in the `-no-checking` mode and the user calls an overloaded function from an `__import`ed file in a way such that Slang can't resolve the intended overload, we were failing to emit the definitions of the potential callees.
This change simply adds a case for `OverloadedExpr` in `lower.cpp` that explicitly lowers all the declarations that might have been referenced.
- There is a potentially for breakage here if we are outputting GLSL and one of the overloads is stage-specific.
- A more refined approach might try to recognize which over the overloaded options are even potentially applicable, and then output only those, but doing this would be way more complicated.
I've added a test case for this behavior, but it is a bit brittle because we need to confirm that we still produce the same error message as unmodified HLSL.
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* IR: overhaul IR design/implementation
Closes #192
Closes #188
This is a major overhaul of how the IR is implemented, with the primary goal of just using the AST-level type representation as the IR's type representation, rather than inventing an entire shadow set of types (as captured in issue #192).
One consequence of this choice is that types in the IR are no longer explicit "instructions" and are not represented as ordinary operands (so a bunch of `+ 1` cases end up going away when enumerating ordinary operands).
Along the way I also got rid of the embedded IDs in the IR (issue #188) because this wasn't too hard to deal with at the same time.
Another related change was to split the `IRValue` and `IRInst` cases, so that there are values that are not also instructions. Non-instruction values are now used to represent literals, references to declarations, and would eventually be used for an `undef` value if we need one. IR functions, global variables, and basic blocks are all values (because they can appear as operands), but not instructions.
The main benefit of this approach is that the top-level structure of a bytecode (BC) module is much simpler to understand and walk, and BC-level types are represented much more directly (such that we could conceivably use them for reflection soon).
* fixup: 64-bit build fix
* fixup: try to silence clang's pedantic dependent-type errors
* fixup: bug in VM loading of constants
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* First attempt at a Linux build
- Fix up places where C++ idioms were written assuming lenient behavior of Microsoft's compiler
- Add a few more alternatives for platform-specific behavior where Windows was the only platform accounted for.
- Add a basic Makefile that can at least invoke our build, even if it isn't going good dependency tracking, etc.
- Build `libslang.so` and `slangc` that depends on it, using a relative `RPATH` to make the binary portable (I hope)
- Add an initial `.travis.yml` to see if we can trigger their build process.
* Fixup: const bug in `List::Sort`
I'm not clear why this gets picked up by the gcc *and* clang that Travis uses, but not the (newer) gcc I'm using on Ubuntu here, but I'm hoping it is just some missing `const` qualifiers.
* Fixup: reorder specialization of "class info"
Clang complains about things being specialized after being instantiated (implicilty), and I hope it is just the fact that I generate the class info for the roots of the hierarchy after the other cases. We'll see.
* Fixup: add `platform.cpp` to unified/lumped build
* Fixup: Windows uses `FreeLibrary`
and not `UnloadLibrary`
* Fixup: fix Windows project file to include new source file
This obviously points to the fact that we are going to need to be generating these files sooner or later.
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The main interesting change here is around support for lowering of calls to "subscript" operations (what a C++ programmer would think of as `operator[]`).
An important infrastructure change here was to add an explicit AST-node representation for a "static member expression" which we use whenever a member is looked up in a type as opposed to a value. The implementation of this probably isn't robust yet, but it turns out to be important to be able to tell such cases apart.
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- Previously, there were a variety of rules in `check.cpp` to pick the conversion cost for various cases involving scalar, vector, and matrix types.
- The main problem of the previous approach is that any lowering pass would need to convert an arbitrary "type cast" node into the right low-level operation(s).
- The new approach is that a type conversion (implicit or explicit) always resolves as a call to a constructor/initializer for the destination type. This means that the existing rules around marking operations as builtins should work for lowering.
- The support this, the checking logic needs to perform lookup of intializers/constructors when asked to perform conversion between types. It does this by re-using the existing logic for lookup and overload resolution if/when a type was applied in an ordinary context.
- Next, we define a modifier that can be attached to constructors/initializers to mark them as suitable for implicit conversion, and associate them with the correct cost to be used when doing overload comparisons.
- We add the modifier to all the scalar-to-scalar cases in the stdlib, using the logic that previously existed in semantic checking.
- Next we add cases for general vector-to-scalar conversions that also convert type, using the same cost computation as above.
- This probably misses various cases, but at this point they can hopefully be added just in the stdlib.
- One gotcha here is that in lowering, we need to make sure to lower any kind of call expression to another call expression of the same AST node class, so that we don't lose information on what casts were implicit/hidden in teh source-to-source case.
Two notes for potential longer-term changes:
1. There is still some duplication between the type conversion declarations here and the "join" logic for types used for generic arguments. Ideally we'd eventually clean up the "join" logic to be based on convertability, but that isn't a high priority right now, as long as joins continue to pick the right type.
2. It is a bit gross to have to declare all the N^2 conversions for vector/matrix types to duplicate the cases for scalars. For the simple scalar-to-vector case, we might try to support multiple conversion "steps" where both a scalar-to-scalar and a scalar-to-vector step can be allowed (this could be tagged on the modifiers already introduced). That simple option doesn't scale to vector-to-vector element type conversions, though, where you'd really want to make it a generic with a constraint like:
vector<T,N> init<U>(vector<U,N> value) where T : ConvertibleFrom<U>;
Here the `ConvertibleFrom<U>` interface expresses the fact that a conforming type has an initializer that takes a `U`. What doesn't appear in this context is any notion of conversion costs. We'd need some kind of system for computing the conversion cost of the vector conversion from the cost of the `T` to `U` converion.
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The root of the problem here is that:
- We do a shallow copy of modifiers when "lowering" declarations/statements, by just copying over the head pointer of the linked list of modifiers
- During lowering we sometimes add additional modifiers (only used during lowering), and these can thus accidentally get added to the end of the list of modifiers for the original declaration (rather than just the lowered decl)
- If the same declaration is used by multiple entry points to be output, then a modifier added by the first entry point (which could reference entry-point-specific storage) will be earlier in the modifier list and might be picked up by a later entry point, so that we dereference already released memory
The simple fix for right now is the use the support for a "shared" modifier node to ensure that each lowered declaration/statement gets a unique modifier list.
A better long-term fix is:
1. Don't use modifiers to store general side-band information, and instead use proper lookup tables that own their contents.
2. Don't use a linked list to store modifiers (this was done to make splicing easy, but now we have a whole class of bugs related to bad splices), and be willing to clone them as needed.
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Fixes #171
Fixes #172
These two bugs related to bad logic in handling of splitting resource-containing `cbuffer` declarations.
- Issue #171 was the case where a `cbuffer` *only* had resource fields, in which case we crashed whenever referencing any field (some code was assuming there had to be non-resource fields)
- Issue #172 was a case where two fields were declared with a single declaration (`Texture2D a, b;`), and the logic we had for tracking resource-type fields was accidentally tagging *both* fields with a single modifier so that field `b` would get confused for `a` in some contexts, and attempts to access `b` would crash.
Both issues are now fixed, and regression tests have been added.
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The `-split-mixed-types` flag can be provided to command-line `slangc`, and the `SLANG_COMPILE_FLAG_SPLIT_MIXED_TYPE` flag can be passed to `spSetCompileFlags`.
Either of these turns on a mode where Slang will split types that included both resource and non-resource fields.
The declaration of such a type will just drop the resource fields, while a variable declare using such a type turns into multiple declararations: one for the non-resource fields, and then one for each resource field (recursively).
This behavior was already implemented for GLSL support, and this change just adds a flag so that the user can turn it on unconditionally.
Caveats:
- This does not apply in "full rewriter" mode, which is what happens if the user doesn't use any `import`s. I could try to fix that, but it seems like in that mode people are asking to bypass as much of the compiler as possible.
- When it *does* apply, it applies to user code as well as library/Slang code. So this will potentially rewrite the user's own HLSL in ways they wouldn't expect. I don't see a great way around it, though.
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- The changes introduced a new path where we don't even go through the current "lowering" (really an AST-to-AST legalization pass), but this exposed a few issues I didn't anticipate:
- First, we needed to make sure to pass in the computed layout information when emitting the original program (since the layout info is no longer automatically attached to AST nodes)
- Second, we needed to take the sample-rate input checks that were being done in lowering before, and move them to the emit logic (which is really ugly, but I don't see a way around it for GLSL).
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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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Fixes #24
So far the code has used a representation for source locations that is heavy-weight, but typical of research or hobby compilers: a `struct` type containing a line number and a (heap-allocated) string.
This is actually very convenient for debugging, but it means that any data structure that might contain a source location needs careful memory management (because of those strings) and has a tendency to bloat.
The new represnetation is that a source location is just a pointer-sized integer.
In the simplest mental model, you can think of this as just counting every byte of source text that is passed in, and using those to name locations.
Finding the path and line number that corresponds to a location involves a lookup step, but we can arrange to store all the files in an array sorted by their start locations, and do a binary search.
Finding line numbers inside a file is similarly fast (one you pay a one-time cost to build an array of starting offsets for lines).
More advanced compilers like clang actually go further and create a unique range of source locations to represent a file each time it gets included, so that they can track the include stack and reproduce it in diagnostic messages.
I'm not doing anything that clever here.
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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 so-called "lowering" pass (really a kind of AST-to-AST legalization pass right now) needs to handle some basic scalarization of structured types, and it does this by inventing what I call "pseuo-expressions" and "pseudo-declarations."
For example, there is a pseudo-expression node type that represents a tuple of N other expressions, and certain operations act element-wise over such tuples.
The problem was that the implementation introduced these out-of-band expression/declaration types into the existing AST hierarchy which led to a dilemma:
- If these new AST nodes were declared like all the others (and integrated into the visitor dispatch approach, etc.) then every pass would need to deal with them even though they are meant to be a transient implementation detail of this one pass
- But if the new nodes *aren't* declared like the others, then they can't meaningfully interact with visitor dispatch, and will just crash the compiler if they somehow "leak" through to latter passes. And because they are just ordinary AST nodes from a C++ type-system perspective, such leaking is entirely possible (if not probable)
Hopefully that setup helps make the solution clear: instead of having the "lowering" pass map an expression to an expression, it needs to map an expression to a new data type (here called `LoweredExpr`) that can wrap *either* an ordinary expression (the common case) or one of the new out-of-band values. Any code that accepts a `LoweredExpr` needs to handle all the cases, or explicitly decide that it can't/won't deal with anything other than ordinary expressions.
Most of the code changes are straightforward at that point, although the whole "lowering" approach is a bit fiddly right now, so gertting the tests passing took a bit of attention. I'm not sure our test coverage of all this code is great, so I wouldn't be surprised if some failures are lurking still.
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There were two main places where global variables were used in the Slang implementation:
1. The "standard library" code was generated as a string at run-time, and stored in a global variable so that it could be amortized across compiles.
2. The representation of types uses some globals (well, class `static` members) to store common types (e.g., `void`) and to deal with memory lifetime for things like canonicalized types.
In each case the "simple" fix is to move the relevant state into the `Session` type that controlled their lifetime already (the `Session` destructor was already cleaning up these globals to avoid leaks).
For the standard library stuff this really was easy, but for the types it required threading through the `Session` a bit carefully.
One more case that I found: there was a function-`static` variable used to generate a unique ID for files output when dumping of intermediates is enabled (this is almost strictly a debugging option).
Rather than make this counter per-session (which would lead to different sessions on different threads clobbering the same few files), I went ahead and used an atomic in this case.
Note that the remaining case I had been worried about was any function-`static` counter that might be used in generating unique names.
It turns out that right now the parser doesn't use such a counter (even in cases where it probably should), and the lowering pass already uses a counter local to the pass (again, whether or not this is a good idea).
This change should be a major step toward allowing an application to use Slang in multiple threads, so long as each thread uses a distinct `SlangSession`. The case of using a single session across multiple threads is harder to support, and will require more careful implementation work.
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There was a bug where the intialization expression for a variable was being lowered after the declaration was added to the output code, so that any sub-expressions that get hoisted out actually get computed *after* the original variable. This obviously led to downstream compilation failure.
I've updated the test case to stress this scenario.
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The basic bug there is that if you have a member of `struct` type in a `uniform` block and then pass a reference to that member directly to a call:
```
struct Foo { vec4 bar; };
uniform U { Foo foo; };
void main() { doSomething(foo); }
```
then glslang generates invalid SPIR-V which seems to cause an issue for some drivers.
This change works around the problem by detecting cases where an argument to a function call is a reference to `uniform` block member (of `struct` type) and then rewrites the code to move that value to a temporary before the call.
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Fixes #133
We already had logic to skip adding `flat` to a vertex input, and this just extends it to not adding `flat` to a fragment output.
Note that explicit qualifiers in the input HLSL/Slang will still be carried through to the output, so it is still possible for a Slang user to shoot themself in the foot with interpolation qualifiers.
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The requirements for using `gl_Layer` differ by stage, and so we need to pick an appropriate GL version based on the target stage, and then also require a specific extension for anything other than geometry or fragment.
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- The easy part here is treating `NV_` prefixed semantics as another case of "system-value" semantics
- Mapping the new semantics (`NV_X_RIGHT` and `NV_VIEWPORT_MASK`) to their GLSL equivalents is harder
- Instead of a single "right-eye vertex" output, GLSL defines an array of per-view positions
- Instead of a vector of masks, GLSL defines an array of per-view masks
- Another point here is that a lot of semantics that appear as `uint` in HLSL are `int` in GLSL, which can lead to conversion issues.
- The approach here is to have the lowering pass introduce a notion of assignment with "fixups," which will try to cast things as needed
- When assigning to a simple value with the "wrong" type, introduce a cast
- When assigning to an array from a vector, break out multiple assignments of individual vector/array elements
- In order to facilitate the above, I needed to add actual types to the magic expressions I introduce to represent GLSL builtin variables. These were taken by scanning the online documentation for GL, so they might not be perfect.
- Major issues with the approach in this change:
- No attempt is being made here to check that the original declaration used a type appropriate to the semantic. The assumption is that this logic only ever triggers for Slang entry points, or GLSL entry points using a Slang `struct` type for input/output (and for right now Slang code is only ever written by "understanding" developers)
- In the case of a Slang entry point, we always copy varying parameters in/out around the call to `main_`, so this approach should handle calls to functions with `out` or `in out` parameters okay, but it is *not* robust to cases where we don't want to copy in all the entry point parameters first thing (e.g., a GS), so that will have to change
- In the GLSL case (or if we revise the approach to Slang entry points), there is going to be a problem if these converted varying parameters are ever passed as arguments to `out` or `in out` parameters. In these cases we need to do more sleight-of-hand to reify a temporary variable and do the necessary copy-in/copy-out. Being able to do that logic relies on having correct information about callees, which requires having robust semantic analysis of the function body. There is only so much we can do...
- A better long-term approach would not rely on an ad-hoc "fixup" conversion during assignment, but would instead implement the GLSL builtin variables as, effectively, global "property" declarations that have both `get` and `set` accessors, and then tunnel a reference to such a property down through lowering, where it can lower to uses of the "getter" or "setter" as appropriate in context (and the result type of the getter/setter can be what we'd want/expect).
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The change is mostly about trying to make sure the compiler "fails safe" when it encounters an internal assumption that isn't met.
Most internal errors will now throw exceptions (yes, exceptions are evil, but this will work for now), and these get caught in `spCompile` so that they don't propagate to the user (they just see a message that compilation aborted due to an internal error).
Subsequent changes are going to need to work on diagnosing as many of these situations as possible, so that users can at least know what construct in their code was unexpected or unhandled by the compiler.
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Fixes #122
- In cases with an explicit mip level being specified, there was a mistake in how the argument for setting the mip level in the GLSL code was constructed that led to a parse error in GLSL
- Also, that argument is a `uint` in HLSL and an `int` in GLSL, so an explicit cast was needed
- The GLSL functions here seem to require a newer GLSL (at least higher than `420`), so I had to add in a capability for builtins to specify a required GLSL version. For now I made these ones require `450`.
- Added a test case to confirm that our lowering works (for some definition of "works")
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The basic syntax is:
$for(i in Range(0,99))
{
/* stuff goes here */
}
Note that the exact form is very restrictive. All that you are allowed to change is `i`, `0`, `99` or `/* stuff goes here */`.
As a tiny bit of syntax sugar, the following should work:
$for(i in Range(99))
{
/* stuff goes here */
}
Note that the range given is half-open (C++ iterator `[begin,end)` style).
Both the beginning and end of the range must be compile-time constant expressions that Slang knows how to constant-fold.
The implementation will basically generate code for `/* stuff goes here */` N times, once for each value in the half-open range.
Each time, the variable `i` will be replaced with a different compile-time-constant expression.
While I was working on a test case for this, I also found that our build of glslang had an issue with resource limits, so I fixed that.
Clients will need to build a new glslang to use the fix.
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GLSL technically supports varying (`in`, `out`) parameters of `struct` type, but there are some annoying constraints (not allowed for VS input), and it doesn't work with how an HLSL user would usually put "system-value" inputs/outputs into a `struct` together with ordinary inputs/outputs.
To work around this, this change adds support for using an imported Slang `struct` type for an `in` or `out` parameter, in which case it will (1) be scalarized and (2) will have system-value semantics mapped appropriately, just as for an entry-point parameter when cross-compiling an HLSL-style `main()`.
Changes:
- Add a notion of a `VaryingTupleExpr` and `VaryingTupleVarDecl`, similar to those for the resources-in-structs case
- Trigger use of these when we have a global-scope varying in/out using an imported `struct` type
- Also use these in the cross-compilation case for ordinary varying input/output (since this approach seems like it should be more general, and can hopefully handle stuff like GS input/output some day)
- When generating parameter binding information, special case global-scope input/output, and treat it the same as entry-point-parameter input/output
- Revamp how used resource ranges are computed so that we can eventually make this specific to an entry point
- Actually implement first signs of life for `maybeMoveTemp` so that assignments to the tuple-ified outputs will work better
- Add first test case that actually seems to work
- Add diagnostics for conflicting explicit bindings on a parameter
- Add diagnostic for different parameters with overlapping bindings
- Make global-scope varying input/output use a tracking data structure specific to the translation unit for computing locations (so that they are independent of other TUs)
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The basic idea is that an array of `struct`s will get scalarized into per-field arrays (for any fields that need to be scalarized). So given:
struct Foo { float x; Texture2D t; };
cbuffer C { Foo foo[4]; }
We'll get output like:
struct Foo { float x; };
cbuffer C { Foo foo[4]; }
Texture2D C_foo_t[4];
(Of course the output would also be translated over to GLSL, but I'm only concerned about this one transformation here).
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`gl_Layer` as a fragment input requires at least version 4.30 of GLSL, so we try to track that information when we see the name used.
Note that this does *not* override a user-specified `#version` line.
This required re-ordering when lowering happens relative to emitting the `#version` directive, since this code works by actually modifying the chosen profile for the entry point.
Yes, that is kind of gross and we should do something cleaner in the long term.
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Fixes #104
- Map HLSL `nointerpolation` to GLSL `flat`
- When lowering a `struct` type varying input/output, look for interpolation modifiers along the "chain" from the leaf field up to the original shader input variable (and take the first one found)
- Not sure if this is strictly needed, but it seems like a reasonable policy
- Add `flat` to varying input of integer type, with no other interpolation modifier
- Note: I do *not* do anything to ignore a manually imposed interpolation modifier that might be incorrect
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If we have something like to following in HLSL:
cbuffer C { Texture2D t; ... }
and we are compiling to GLSL, then both `C` and `C.t` consume the same kind of resource (a descriptor-table slot).
The way reflection was working right now, querying the index of `C` would return its binding (let's say it is `4` just to be concrete) and then a query on `C::t` would give its offset, which was being computed as `0` because it is the first field in the logical `struct` type.
That obviously leads to bad math and requires some subtle `+1`s in cases to get things right (e.g., when scalaring during lowering, I had to carefully add one in some cases).
It is unreasonable to expect users to deal with this.
This commit changes it so that the offset of field `C::t` is `1` so that hopefully more things Just Work.
The special-case logic in lowering is now gone.
One important catch here is that this pretty much only works in the case where the element type of a parameter block is a `struct` type (which is really all that makes sense right now).
If we ever want to generalize this in the future, then it will probably be necessary to change the `TypeLayout` case for parameter blocks to store a `VarLayout` for the element, rather than just a `TypeLayout`.
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- When assigning tuples `(a0, ...) = (b0, ...)` generate a tuple of assignments `(a0 = b0, ...)`
- Given an expression statement on a tuple `(a0, ...);` generate a sequence of statements `a0; ...`
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- This really just checks two basic things:
1. Was there any global variable declared with `in` and `sample`?
2. Did any code encountered during lowering referenece `gl_SampleIndex`?
- This doesn't cover what HLSL could need, nor what we would need for cross-compilation. Consider it GLSL-specific for now.
- In order to generate the information with even a reasonable chance of being accurate (not giving a ton of false positives) I tried to integrate the checks into the lowering process (so they only see code that is referenced, one hopes).
- For this to work with my testing setup, I needed to make sure that lowering is always performed, prior to emitting reflection info
- This change broke several reflection tests, because they had been using code that wouldn't actually pass the downstream compiler. I checked in fixes for those.
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- Don't try to extract the body layout for a field without a layout
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- The basic idea is that during the "lowering" pass, some types (notably: aggregate types that contain resource variables) will get turned into "tuple" types, which are pseduo-types that aren't meant to survive lowering.
- An attempt to declare a variable with a tuple type expands into a tuple of declarations
- An attempt to reference such a tuple-ified variable leads to a tuple of expressions
- An attempt to extract a member from such a tuple expression will pick the appropriate sub-element
- Dereference a tuple by dereferencing the primary expression
- Expand a tuple in the argument list to a call into N arguments (by recursively flattening the tuple)
- Don't create tuple types when not generating GLSL
- Make sure to preserve the specialized type of a call expression through lowering, since emission of unchecked calls relies on that info.
- TODO: maybe the infix/prefix/postifx/select information should come in as a side-band? Should we have modifiers on expressions?
- Make sure to offset the layout for a nested field based on teh base offset of its parent variable, when generating declarations for nested fields
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I haven't tried to be 100% exhaustie, but this should cover the main cases we are likely to encounter in library code.
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This helps avoid the problem where we emit a function that does a `discard` and thus get a GLSL compilation failure in a vertex shader (that doesn't even call the function).
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- Try to handle `ErrorType` gracefully when computing type layouts
- When outputting a `TypeExp`, if the type part is errorneous (or missing), try to use the expression part
- Make sure to lower the expressions side of a `TypeExp` during lowering
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I hadn't been lowering `SV_Position` outputs to `gl_Position`, and had somehow been relying on hidden driver behavior that I guess made things Just Work.
This change adds some infrastructure to handle `SV_` semantics during lowering of an entry point (currently only covering `SV_Position` and `SV_Target`, FWIW).
As a byproduct, this also means that a `VarLayout` stores semantic info, which could conceivably be exposed through reflection data now.
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- Add GLSL mappings for more `Texture*` methods
- The annoying one here is `Texture*.Load()` because it doesn't take a sampler, but the GLSL equivalent needs one (while the SPIR-V does *not*). I've hacked this pretty seriously for now.
- Try to ensure that we add `uniform` to global declarations that need it in GLSL
- When outputting an `in` or `out` variable that might have been created from an `inout` shader parameter, filter the layout qualifiers that we output to only cover the appropriate resource kind.
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If the user had a shader entry point with an `inout` parameter, we would end up lowering it to two GLSL global variables with the same name.
This change adds a `SLANG_in_` or `SLANG_out_` prefix to the two declarations.
Note: I haven't dealt with the issue that we end up printing two different `layout` qualifiers on such a variable...
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The earier changes to add sequence statements and change how the `isBuildingStmt` logic in lowering works doesn't work for this logic, which assumes it can just set `isBuildingStmt` and be sure that decls will go into the right place.
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The tricky bit here was that the `reflection-json` output format isn't really a code generation target like the others, and we need to be able to have multiple "targets" active to make sense of it. This needs cleaning-up.
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Code in Slang that is cross-compiled *might* introduce declarations that collide with language keywords that are reserved in the target.
This was previously being dealth with during final code emission, but the challenge there is that we want to allow user code that is being "rewritten" to use whatever identifiers it wants (they know better than us what is an error), and only apply renaming to our own code.
The approach here is to apply renaming during lowering - we validate each declaration to make sure its name is valid. Any expressions/types that refer to those declarations will automatically get emitted with the new name (while unchecked expressions will continue to be emitted with their existing name).
This isn't quite perfect, since we could in theory still rename a declaration in user code.
A more robust version down the line would try to determine if a declaration was nested inside code for the "rewriter."
Also note that this does *not* deal with any issues of name conflicts that might arise between modules. That would require a more complete and robust renaming pass, which seems tricky for me to pull off.
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If the user doesn't use any `import` declarations, there is no reason to parse their code at all, so having the option of falling back to `UnparsedStmt` can potentially save us some headaches down the road.
The new rule now is that if you have the "no checking" flag on, *and* the parser hasn't yet seen any `import` declarations, then it still used `UnparsedStmt` to avoid touching function bodies.
Otherwise, I go ahead and parse function bodies, and assume I can rewrite any code I can semantically understand.
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HLSL has the bad scoping behavior for `for` loops, and we need to respect that.
But, we need to have correct scoping for GLSL, and we'd like it for Slang.
We also need to ensure that `for` loops written in a "correct" language get the correct behavior when emitted as HLSL.
There was already code to handle this in the emit pass, but it was unfortunately using an `isRewrite` flag to try to tell if the HLSL behavior was wanted.
This doesn't work when the code being emitted might come from a mix of languages.
This change adds a distinct `UnscopedForStmt` syntax node type, and uses that when parsing HLSL input (bot not for other languages).
We make sure to preserve this node type through lowering, and then specialize our emit logic on this case.
With this, there are no more remaining uses of `isRewrite` in the emit logic, which is good because it didn't mean what I needed it to mean any more (since we now emit only a single module, that was merged during lowering).
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