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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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* Fix up emission of shader parameter semantics when using IR
- Make sure to propagate entry point parameter layouts down to IR parameters when doing the initial cloning to form target-specific IR
- When layout information is present on an IR node, prefer to use that over the original high-level declaration for outputting semantics in final HLSL
- Fix up test runner to generate `.actual` files when running compute tests, in cases where the `render-test` application errors out (e.g., because of a Slang compilation error)
- Add a first test of generics functionality, to show that they generate valid code through the IR
- Right now this test is *not* using any "interesting" operations on the type parameter, so this is not a test that can confirm that interface constraints work
* fixup: skip compute tests when running on Linux
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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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Move reflection JSON generation into separate test fixture
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This is intended to produce a better experience for end users when they encounter internal compiler errors.
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* Get tests running/passing under Linux
- Fix up `dlopen` abstraction
- Fix up some test cases to request hlsl (rather than default to dxbc) so they can run on non-Windows targets
- Fix up test runner ignore tests that can't run on current platform (and not count those as failure)
- Fix file handle leeak in process spawner absttraction
- Get additional test-related applications building
- More tweaks to Travis script; in theory deployment is set up now (yeah, right)
* fixup
* fixup: Travis environment variable syntax
* fixup: Buffer->begin
* fixup: actually run full tests on one config
* fixup: add build status badge for Travis
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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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The Slang API allows an expert user to feed in source code that the compiler then treats as if it came from the Slang "standard library."
They can use this to introduce new builtin types, functions, etc. - so long as they are careful, and are willing to deal with the lack of any compatibility guarantees across versions.
At some point I split the Slang standard library into distinct modules, so that GLSL and HLSL builtins wouldn't pollute each other's namespace.
In that change, I had to decide what module any new user-defined builtins should get added to, and I apparently decided they should go into the module for the Slang language, which would only affect `.slang` files.
This doesn't work at all if the user wants to declare new HLSL builtins.
I've gone ahead and made user extensions add to the "core" module (which is used by all of HLSL, GLSL, and Slang), but a better long-term fix would be to let the user pick the module/language the new builtins should apply to.
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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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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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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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Fixes #11
- This adds a `-o` command-line option for specifying an output file.
- The code tries to be a bit smart, to glean an output format from a file extension, and also to associate multiple `-o` options with multiple `-entry` options if needed.
- There is a restriction that all the output files need to agree on the code generation target. This is reasonable for now, but might be something to lift eventualy
- There is a restriction that only one output file is allowed per entry point
- Together with the previous item this means you can't output both a `.spv` and a `.spv.asm` in one pass, even though both should be possible
- There is currently a restriction that output paths only apply to entry points
- This means there is no way to output reflection JSON to a file with `-o` (but that is mostly just a debugging feature for now)
- This also means we don't support any "container" formats that can encapsulate multiple compiled entry points
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- API users can use this to get "clean" output to aid with debugging Slang issues
- Also changes the prefix on intermediate files that Slang dumps, to make them easier to ignore with a regexp
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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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Calling:
spSetDumpIntermedites(compileRequest, true);
will set up a mode where Slang tries to dump every intermediate HLSL, GLSL, DXBC, SPIR-V, etc. file it generates. If SPIR-V or DXBC is requested then we also dump assembly of those.
Right now the files are all named as `slang-<counter>.<ext>`, and get dropped in whatever the working directory is, but I'm open to ideas on how to improve that.
Note: this change introduces a new binary interface to `glslang`, so pulling it requires an updated `glslang.dll`.
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Fixes #77
- The `spGetEntryPointSource` function is now no longer needed, but I'm not going to "deprecate" it just yet
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EntryPointResult/TranslationUnitResult, added helper functionality; Ensure null termination when printing raw data
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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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This is in anticipation of needing to have more complete knowledge to be able to handle user code that `import`s library functionality.
The big picture of this change is just to remove the `UnparsedStmt` class that was used to hold the bodies of user functions as opaque token streams, and thus to let the full parser and compiler loose on that code. That is the easy part, of course, and the hard part is all the fixes that this requires in the rest of the compielr to make this even remotely work.
Subsequent commit address a lot of other issues, so this particular commit mostly represents work-in-progress.
One detail is that this change puts a conditional around nearly every diagnostic message in `check.cpp` to suppress thing when in rewriter mode.
I have yet to check how that works out if there are errors in anything we actually need to understand for the purposes of generating reflection data.
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The code should now compile cleanly with warnings as errors for VS2015 with `W3`.
Most of the changes had to do with propagating a real pointer-sized integer type through code that had been using `int`.
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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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Previously the code checked for a duplicate `#import` using a data structure attached to the compile request, but this would fail for nested imports.
It also wouldn't work for a combination of `#import` and `__import`.
This change makes it so that we instead track a set of already-imported modules in the semantic checking visitor, which is instantiated once per translation unit.
We also key this set on the actual module (AST) imported, rather than on path/name/whatever, so hopefully it will be robust to the same thing getting imported multiple ways.
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With this change, there is now a meaningful semantic difference between `__import` and `#import`.
An `__import` compiles the target file in a fresh environment, only providing it any macro definitions passed via command line or API. Any macros defined in the imported file are not made visible at the import site. One can think of an `__import` as a bit like `using namespace` in C++.
A `#import` will tokenize the input in the same preprocessor environment as the importing file, and any macros defined along the way will be visible in the parent file.
It is a *bit* like a `#include` with two big differences:
- The imported code is always parsed as Slang, and as its own module with default flags, etc. (so semantic checks are on even if we are in "rewriter" mode). It is pulled into the outer namespace just as for `__import`.
- A given file will only get `#import`ed once for a translation unit, so it behaves a bit like there is an implicit `#pragma once` in the target file
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Right now `#import` only differs from `#include` in that it takes a string literal for a file name instead of a raw identifier (to which `.slang` gets appended).
The next step is to make `#import` respect preprocessor state, while `__import` doesn't.
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- The basic idea is simple: be sure to enumerate code in `__import`ed modules when generating reflection info
- Note that we don't currently allow an entry point to appear in an imported module, so we only consider globlal-scope parameters
- Although there isn't currently a real implementation of namespacing, I went ahead and ensured that parameters in imported modules are treated as distinct from parameters in the user's code, even if they have the same name.
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The main user-visible change here is that instead of `spAddTranslationUnitEntryPoint` we have `spAddEntryPoint`, to reflect that the list of entry points is "global" to a compile request.
As a result, `spGetEntryPointSource` now only needs the entry point index, and not the translation unit index.
There are a bunch more behind-the-scenes changes, though, reflecting a streamlining of the concepts related to compilation into a smaller number of classes.
Now there is:
- `Session` (unchanged) to manage the lifetimes of shared stuff like the stdlib
- `CompileRequest` (merges in `CompileOptions`) to handle all the lifetime related to a single invocation of the compiler
- `TranslationUnitRequest` (merges `TranslationUnitOptions`, `CompileUnit`) to represent a single translation unit ("module") that the user is trying to compile. This is a single file for HLSL/GLSL, but can be multiple files for Slang.
- `EntryPointRequest` (merges `EntryPointOption` and a bit of `EntryPointResult`) to track a single entry point that the user is asking to compile (that entry point always comes from a single translation unit)
A lot of functions used to take some combination of these and end up with really long signatures.
I've given most of the objects "parent" pointers so that they can get back to all the context they need, so most functions don't need as many parameters.
It may eventually be important to tease these apart again, in particular:
- The code-generation side of things (the `*Result` types) might need to be pulled out in case we want to codegen multiple times from the same AST
- Similarly, the layout stuff may also need to be pulled out, in case we want to lay things out multiple times with different rules.
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That is, even if hte user specified the `-no-checking` option (or the equivalent via API), we still want/need to apply full semantic checks to Slang code, so that cross-compilation will be possible.
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The basic idea of this change is that user code can just write:
#include "foo.h"
and then if `foo.h` gets found in a list of registered directories for "auto-import," then it actually gets interpreted as if the user had writte, more or less:
__import foo;
That is, the code in `foo.h` will be treated as Slang, and will be fully parsed and checked (no matter what the source language had been), and the scoping rules will be those of `__import` instead of `#include`.
This is a really big hammer, and I could imagine it smashing fingers if used poorly.
I'm not sure this feature will pan out, but we need to try things to know.
One big piece of that that I'll likely keep in either case is an overhaul of command-line options parsing for `slangc`. In particular, this logic has been moved into the core `slang` library (so that users can just pass options in via the API), and it is all done on UTF-8 strings rather than wide strings (which was always going to be Windows-specific).
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Getting rid of more namespace complexity and stripping things down to the basics.
This also gets rid of some dead code in the "core" library.
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This gets rid of one unecessary namespace.
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This is a large change that contains many pieces:
- Update the `cross-compile0` test to actually make use of cross compilation.
Now the `cross-compile0.hlsl` file contains both HLSL and GLSL source code, and then imports code from `cross-compile0.slang`, which provides a "library" (one function) that can be shared between both the HLSL and GLSL version of things.
- Fixed a bug in the support for backslash-escaped newlines.
- Added a new `__import` declaration type (replaces the `using` directive that was still around in a vestigial form)
An `__import` causes the compiler to look for a Slang source file (currently using the ordinary `#include` lookup logic), and then parse/check the found file as an additional module ("translation unit"), before making its declarations visible in the current scope.
- Refactored the main compilation flow to be simpler. There were the `ShaderCompiler` and `ShaderCompilerImpl` classes that weren't relaly doing anything, but added complexity to the whole workflow.
- The `render-test` application has been heavily modified to better support testing cross-compilation workflows. At the most basic level we are starting to distinguish pass-through vs. rewriter workflows, and are passing various `#define`s down to the compiler(s) to let the source code be customized as needed for each case.
Several annoying corner cases are caused here by having to support the GLSL compilation model, which really wants each entry point in its own specific translation unit, whereas we really want to keep things nicely contained in single files.
- Added support for `__intrinsic` operations to have target-specific behavior.
This allows a function to be given a different name for some specific target (so a call gets emitted as a call to that other operation).
More generally, the library writer can put together an arbitrary format string that will be used in place of expressions that call the given function, e.g.:
__intrinsic(hlsl, "$1 - $0") __intrinsic int foo(int a, int b);
Given this declaration, a call like `foo(x,y)` will code generate as `x - y` for HLSL, and as `foo(x,y)` for all other targets.
Annoying things still to be dealt with:
- The way that I'm filtering the user-provided options when passing things down to the compilation of dynamically loaded modules is a bit ad hoc. It would be good to have a systematic notion of which options will be inherited and which won't. There is also more code duplication than I'd like, so we risk having the compiler behave differently when compiling a file at the top level, vs. because of `__import`.
- Adding target-specific behavior to intrinsics is all well and good, but the current approach means we can only add this to the original declaration, which limits the ability to easily extend the set of targets.
A better approach long-term would be to add a more robust notion of target-based overload resolution (which would happen after semantic checking). Then one mechanism would be used to find the right target-specific overload to use for an operation, and then each (target-specific) definition could use a simpler attribute to intercept code-generation behavior.
Note that we might eventually need a similar notion to deal with stage- or profile-specific functions and the overloading behavior around them, so using this for intrinsics doesn't seem like a bad idea.
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