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Fix CUDA global variable initialization with constructor calls
Resolves CUDA compilation failure where global variables with struct
constructor
initialization generated illegal `__device__` variable runtime
initialization.
**Problem:**
```cuda
// Generated invalid CUDA code:
__device__ static const Stuff_0 gStuff_0 = Stuff_x24init_0(args...);
// Error: "dynamic initialization is not supported for a __device__
variable"
Root Cause Discovered:
Through extensive debugging, found that
moveGlobalVarInitializationToEntryPoints
pass only handled kIROp_GlobalVar instructions, but global constants
with
constructor calls appeared as kIROp_Call instructions at module scope.
Solution:
1. IR Pipeline Fix: Extended moveGlobalVarInitializationToEntryPoints to
detect
and transform module-level constructor calls into proper global
variables with
entry-point initialization
2. Field Access Fix: Enhanced kIROp_FieldExtract logic to emit correct
->
syntax for pointer types and address-of operations
3. Constructor Emission: Added CUDA-specific handling for constructor
calls
Architecture:
- Transforms let %gStuff = call %Constructor(...) into kernel context
initialization
- Moves runtime initialization from global scope to entry-point
execution
- Follows CUDA best practices for global state management
Files:
- source/slang/slang-ir-explicit-global-init.cpp: Extended IR
transformation pass
- source/slang/slang-emit-c-like.cpp: Enhanced field access and foldable
value logic
- source/slang/slang-emit-cuda.cpp: Added CUDA-specific field extraction
handling
Result:
// Now generates proper CUDA code:
struct KernelContext_0 { Stuff_0 gStuff_1; };
// Runtime initialization in entry point:
kernelContext_1.gStuff_1 = constructor_call();
Fixes: tests/compute/type-legalize-global-with-init.slang
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* SP004: implement initialize list translation to ctor
- We synthesize a member-wise constructor for each struct follow
the rules described in SP004.
- Add logic to translate the initialize list to constructor invoke
- Add cuda-host decoration for the synthesized constructor
- Remove the default constructor when we have a valid member init constructor
- Disable -zero-initialize option, will re-implement it in followup (#6109).
- Fix the overload lookup issue
When creating invoke expression for ctor, we need to call
ResolveInvoke() to find us the best candidates, however
the existing lookup logic could find us the base constructor
for child struct, we should eliminate this case by providing
the LookupOptions::IgnoreInheritance to lookup, this requires
us to create a subcontext on SemanticsVisitor to indicate that
we only want to use this option on looking the constructor.
- Do not implicit initialize a struct that doesn't have explicit default
constructor.
Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>
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This change converts a large number of our existing tests to use the `ShaderObject` support that was added to the `gfx` layer.
In many cases, tests were just updated to pass `-shaderobj` and the result Just Worked.
In other cases, a `name` attribute had to be added to one or more `TEST_INPUT` lines.
For tests that did not work with shader objects "out of the box," I spent a little bit of time trying to get them work, but fell back to letting those tests run in the older mode.
Future changes to the infrastructure will be needed to get those additional tests working in the new path.
Along with the changes to test files, the following implementation changes were made to get additional tests working:
* Because the shader object mode uses explicit register bindings (from reflection), the hacky logic that was offseting `u` registers for D3D12 based on the number of render targets gets disabled (by another hack).
* The "flat" reflection information coming from Slang was not correctly reporting "binding ranges" for things that consumed only uniform data (which would be everything on CUDA/CPU), so it was refactored to properly include binding ranges for anything where the type of the field/variable implied a binding range should be created (even if the `LayoutResourceKind` was `::Uniform`).
* A few fixes were made to the CUDA implementation of `Renderer`, in order to get additional tests up and running. Most of these changes had to do with texture bindings, which hadn't really been tested previously.
In addition, a few changes were made that were attempts at getting more tests working, but didn't actually help. These could be dropped if requested:
* As a quality-of-life feature (not being used) the `object` style of `TEST_INPUT` line is upgraded to support inferring the type to use from the type of the input being set.
* Any `object` shader input lines get ignored in non-shader-object mode.
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The `TEST_INPUT` facility allows textual Slang test cases to provide two kinds of information to the `render-test` tool:
1. Information on what shader inputs exist
2. Information on what values/objects to bind into those shader inputs
Under the first category of information, there exists supporting for attaching a `dxbinding(...)` annotation to a `TEST_INPUT` which seemingly indicates what HLSL `register` the input uses. There is a similar `glbinding(...)` annotation, used for OpenGL and Vulkan.
It turns out that these annotations were, in practice, completely ignored and had no bearing on how `render-test` allocates or bindings graphics API objects. There was some amount of code attempting to validate that explicit registers/bindings were being set appropriately, but the actual values were being ignored.
The visible consequence of the `dxbinding` and `glbinding` annotations being ignored is issue #1036: the order of `TEST_INPUT` lines was *de facto* determining the registers/bindings that were being used by `render-test`.
This change simply removes the placebo features and strips things down to what is implemented in practice: the `TEST_INPUT` lines do not need target-API-specific binding/register numbers, because their order in the file implicitly defines them.
I added logic to the parsing of `TEST_INPUT` lines to make sure I got an error message on any leftover annotations, and went ahead and systematicaly deleted all of the placebo annotations from our test cases.
If we decide to make `TEST_INPUT` lines *not* depend on order of declaration in the future, we can build it up as a new and better considered feature.
The main alternative I considered was to keep the annotations in place, and change `render-test` and the `gfx` abstraction layer to properly respect them, but that path actually creates much more opportunity for breakage (since every single test case would suddenly be specifying its root signature / pipeline layout via a different path using data that has never been tested). The approach in this change has the benefit of giving me high confidence that all the test cases continue to work just as they had before.
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Before this change, global and function-scope `static const` declarations were represented as instructions of type `IRGlobalConstant`, which was represented similarly to an `IRGlobalVar`: with a "body" block of instructions that compute/return the initial value.
This representation inhibited optimizations (because a reference to a global constant would not in general be replaced with a reference to its value), and also caused problems for resource type legalization because the logic for type legalization did not (and still does not) handle initializers on globals (so global *variables* that contain resource types are still unsupported).
The change here is simple at the high level: we get rid of `IRGlobalConstant` and instead handle global-scope constants as "ordinary" instructions at the global scope. E.g., if we have a declaration like:
static const int a[] = { ... }
that will be represented in the IR as a `makeArray` instruction at the global scope, referencing other global-scope instructions that represent the values in the array.
This simple choice addresses both of the main limitations. A `static const` variable of integer/float/whatever type is now represented as just a reference to the given IR value and thus enables all the same optimizations. When a `static const` variable uses a type with resources, the existing legalization logic (which can handle most of the "ordinary" instructions already) applies.
Another secondary benefit of this approach is that the hacky `IREmitMode` enumeration is no longer needed to help us special-case source code emit for `static const` variables.
Beyond just removing `IRGlobalConstant`, and updating the lowering logic to use the initializer direclty, the main change here is to the emit logic to make it properly handle "ordinary" instructions that might appear at global scope.
One open issue with this change, that could be addressed in a follow-up change, is that "extern" global constants that need to be imported from another module (but which might not have a known value when the current module is compiled) aren't supported - we don't have a way to put a linkage decoration on them. A future change might re-introduce global constants as a distinct IR instruction type that just references the value as an operand (if it is available). We would then need to replace references to an IR constant with references to its value right after linking.
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