slang.git/source/slang/slang-emit-spirv.cpp, branch master

Immutable access qualifier for pointers and use `__ldg` on cuda. (#8710)

2025-10-16T03:59:47+00:00

This PR implements `Access.Immutable` to allow pointers to immutable data. The new type `ImmutablePtr` is defined as an alias of `Ptr`. By forming a immutable pointer, the programmer is conveying to the compiler that the data at the pointer address will never change during the execution of the current program. Therefore loads from immutable pointers can be deduplicated by the compiler, and will translate to `__ldg` when generating code for CUDA. The SPIRV backend is not changed in this PR, since the current SPIRV spec makes it very difficult to specify loads from immutable address without generating tons of wrappers and boilerplate type declarations. We would like to see the spec evolved a bit to around its support of `NonWritable` physical storage pointers or immutable loads before we attempt to express such immutability in SPIRV. For now we simply emit ordinary pointers and loads when generating spirv. --------- Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

Clean up Slang IR representation of undefined values (#8708)

2025-10-15T01:00:47+00:00

Prior to this change, the Slang IR used a single opcode (`kIROp_Undefined`) to encode all cases of undefined values. The particular motivation for this change was a need to distinguish those undefined values that represent a load from an uninitialized memory location versus other sorts of undefined values. If transforming a variable into SSA form results in `undefined` values in cases where the a `load` was executed without a prior `store`, that represents an error on the programmer's part, and should be diagnosed. However, other cases of undefined values can arise during program transformation and optimization, and should not typically result in diagnostics being emitted. While it was not the original motivation for this change, it is also worth noting that the LLVM project has transitioned from initially using only a single `undef` instruction to having a more nuanced model, and the same factors that motivated their shift also apply to the Slang IR. Counter-intuitively, the semantics of undefined values actually need to be carefully defined. Concretely, this change splits the pre-existing `undefined` opcode into two sub-cases: - `kIROp_LoadFromUninitializedMemory`, to represent the case of loading from a memory location (such as a local variable) that has not been initialized. - `kIROp_Poison`, corresponding to the LLVM `poison` value. Our poison instruction is intended to have semantics comparable to LLVM's equivalent. Conceptually, any operation that is invoked with a poison value as input will (with a few exceptions) produce a poison value as output. One can think of the behavior of `poison` as similar to how not-a-number values propagate in floating-point computations: by default they "infect" the result of any computation they are involved in. This semantic choice helps to ensure that many optimizations end up being correct in the presence of undefined values, even if they did not specifically account for them. The `kIROp_LoadFromUninitializedMemory` case is comparable to the combination of `freeze` and `undef` in LLVM. An LLVM `undef` value has semantics that allow *each* use of that value to be replaced with a *different* arbitrary value; these semantics cause many optimizations to only be correct in the absence of undefined values. An LLVM `freeze` instruction can take an undefined value as input, and produces a single value that is still arbitrary, but must be consistent across all uses. The latter semantics are what we want, since a given `load` from an uninitialized memory location will yield an arbitrary-but-fixed value. Note that we intentionally do not have a direct analogue to LLVM's `undef` instruction, because of the way that `undef` causes so many complications when trying to write optimizations. We also do not add a `kIROp_Freeze` instruction in this change, but that is simply because we currently have no need for it. Existing code that was creating `IRUndefined` values has been updated to create either `IRPoison` or `IRLoadFromUninitializedMemory` values, as appropriate to the use case. Code that was checking for the `kIROp_Undefined` opcode has been updated to either check for both of the new opcodes (in the case of `switch` statements), or to use `as` to perform a dynamic cast to the common base type of the two new instructions. Note that this change does not alter the way that instructions representing undefined values are typically emitted as ordinary instructions in the block that produces an undefined value. While emitting `IRLoadFromUninitializedMemory` as an ordinary instruction is exactly what we want, the `IRPoison` case would actually be better represented in Slang IR as a "hoistable" instruction, so that there would only be a singular `poison` value of each type. Changing `IRPoison` to be hoistable would be a good follow-up change, but might run into more challenges depending on what assumptions (if any) the codebase is making about where undefined values get emitted. --------- Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

Addition of `Load`/`Store` coherent operations (#8395)

2025-10-10T17:09:24+00:00

Fixes: https://github.com/shader-slang/slang/issues/7634 Duplicate of PR https://github.com/shader-slang/slang/pull/8052 Primary Changes: * Added `storeCoherent` and `loadCoherent` for coherent load/store via pointers. This is backed by `IRMemoryScopeAttr` which is an `IRAttr` attached to `IRLoad` and `IRStore` * Logic in `source\slang\slang-emit-spirv.cpp` for load/store emitting has been reworked to be less messy and more maintainable * Add to `hlsl.meta.slang` coop vector and coop matrix coherent load/store operations Secondary Changes: * Added a missing load/store test for coop matrix: `tests\cooperative-matrix\load-store-pointer.slang` --------- Co-authored-by: ArielG-NV Co-authored-by: ArielG-NV <159081215+ArielG-NV@users.noreply.github.com> Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com> Co-authored-by: Nathan V. Morrical

Update debug var when in-param proxy var is being updated. (#8671)

2025-10-10T06:27:57+00:00

Closes #8664. The problem is that when there is an `in` parameter, Slang will create a local variable to proxy the parameter, copy the value of the parameter into the proxy variable, and replace all uses of the parameter in the function body to use the proxy variable instead. This way all writes to the parameter become writes to the proxy variable. However, when there is debug info enabled, we are also going to create a "debugVariable" corresponding to the parameter, but this debugVariable isn't updated when the proxy variable is updated. The fix is to map the proxy var instead of the original param to the debug var during the `insertDebugValueStore` pass, so that any changes to the proxy var will result in additional stores being inserted to the debug var. Allowing function body to modify an `in` parameter is a bad legacy behavior we inherited from HLSL that we should really be moving away from. I would like us to completely treat an `in` parameter as immutable by default in the next language version (Slang 2026), and make it an error if the user tries to do so. This will allow us to generate much cleaner code and in many cases would help with performance.

Fix DerivativeGroupQuadsKHR workgroup size validation for texture sampling (#8647)

2025-10-08T23:18:50+00:00

Fixes #8545 where Slang generates SPIR-V with DerivativeGroupQuadsKHR execution mode but doesn't validate workgroup sizes when texture sampling triggers automatic derivative computation. **Root Cause**: Validation code was looking for IRNumThreadsDecoration on the wrong IR node **Fix**: One-line change in slang-emit-spirv.cpp to search decoration on entryPoint instead of entryPointDecor **Tests**: Added regression tests for both quad and linear derivative group validation Generated with [Claude Code](https://claude.ai/code) --------- Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com> Co-authored-by: Lujin Wang Co-authored-by: slangbot Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

Respect isShadow() flag when setting depth type in SPIR-V backend (#8604)

2025-10-04T12:50:56+00:00

This is important for SPIR-V targets that need to know if a texture is designated as a depth texture or not (for example WebGPU). I didn't change the default behavior for when isShadow() is not set, since I didn't want to make the change too invasive.

Rename some symbols related to pointers types (#8592)

2025-10-03T04:48:11+00:00

Note that while this change touched a large numer of files, there are no changes to functionality being made here. The only things being done are renaming various symbols and, in a few cases, updating or adding comments for consistency with the new names. The core of the naming changes are: * Most things named to refer to `OutType` (e.g., `IROutType`, `IRBuilder::getOutType()`, etc.) have been consistently renamed to refer to `OutParamType`, to emphasize that the relevant AST/IR node types are only intended for use to represent `out` parameters. * The same change as described above for `OutType` is also made for `RefType`, which becomes `RefParamType` in most cases. One mess that this exposes is the way that the `ExplicitRef` type in the core module currently lowers to `IRRefParamType`. This change sticks to the rule of not making functional changes, so that mess is left as-is for now. * Names referring to `InOutType` have been changed to instead refer to `BorrowInOutType`. The intention with this naming change is to emphasize that the Slang rules for `inout` are semantically those of a borrow (or at least our interpretation of what a borrow means). * Names referring to `ConstRefType` have been changed to instead refer to `BorrowInType`. This change starts work on clarifying that the existing `__constref` modifier was never intended to be a read-only analogue of `__ref`, and instead is the input-only analogue of `inout`. * The `ParameterDirection` enum type has been changed to `ParamPassingMode`, to reflect the fact that the concept of "direction" fails to capture what is actually being encoded, particularly once we have modes beyond simple `in`/`out`/`inout`. While this change does not alter behavior in any case (the user-exposed Slang language is unchanged), it is intended to set up subsequence changes that will work to make the handling of these types in the compiler more nuanced and correct. Breaking this part of the change out separately is primarily motivated by a desire to minimize the effort for reviewers. --------- Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

Rewriting the lower-buffer-element-type pass to avoid unnecessary packing/unpacking. (#8526)

2025-09-30T00:45:08+00:00

Part of the effort to improve the performance of generated SPIRV code. The existing lower-buffer-element-type pass works by loading the entire buffer element content from memory, and translate it to logical type stored in a local variable at the earliest reference of a buffer handle. This means that is can generate inefficient code that reads more than necessary. Consider this example: ``` struct BigStruct { bool values[1024]; } ConstantBuffer cb; void test(BigStruct v) { if (v.values[0]) { printf("ok"); } } [numthreads(1,1,1)] void computeMain() { test(cb); } ``` In IR, the `computeMain` function before lower-buffer-element-type pass is something like following: ``` func test: %v = param : BigStruct %barr = fieldExtract(%v, "values") %element = elementExtract(%barr, 0) ... // uses %element func computeMain: %v = load(cb) call %test %v ``` The existing lower-buffer-element-type pass will rewrite the bool array in `BigStruct` into `int` array so it is legal in SPIRV. However, it does so by inserting the translation on the first `load` of the constant buffer: ``` struct BigStruct_std430 { int values[1024]; } var cb : ConstantBuffer; func computeMain: %tmpVar : var call %unpackStorage(%tmpVar, cb) %v : BigStruct = load %tmpVar call %test %v ``` This means that the entire array will be loaded and translated to int, before calling `test`, which only uses one element. It turns out that the downstream compiler isn't always able to optimize out this inefficient translation/copy. This PR completely rewrites the way buffer-element-type lowering is handled to avoid producing this inefficient code. It works in two parts: first we turn on the `transformParamsToConstRef` pass for SPIRV target as well, so we will translate the `test` function to take the `v` parameter as `constref`. The second part is a redesigned buffer-element-type pass that defers the storage-type to logical-type translation until a value is actually used by a `load` instruction. In this example, after `transformParamsToConstRef`, the IR is: ``` func test: %v = param : ConstRef %barr = fieldAddr(%v, "values") %elementPtr = elementAddr(%barr, 0) %element = load(%elementPtr) ... // uses %element func computeMain: call %test %cb ``` The new `buffer-element-type-lowering` pass will take this IR, and insert translation at latest possible time across the entire call graph, and translate the IR into: ``` func test: %v = param : ConstRef %barr = fieldAddr(%v, "values") %elementPtr : ptr = elementAddr(%barr, 0) %element_int = load(%elementPtr) %element = cast(%element_int) : %bool ... // uses %element func computeMain: call %test %cb ``` In this new IR, there is no longer a load and conversion of the entire array. See new comment in `slang-ir-lower-buffer-element-type.cpp` for more details of how the pass works. This PR also address many other issues surfaced by turning on `transformParamsToConstRef` pass on SPIRV backend. --------- Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

Add SPV_NV_bindless_texture support (#8534)

2025-09-26T23:07:13+00:00

Treat DescriptorHandle as uint64_t instead of uint2. Implement target-specific SPIR-V emission with the bindless texture support. For OpImageTexelPointer, Image must have a type of OpTypePointer with Type OpTypeImage. Fix the issue by using [constref] in __subscript. Add a test coverage for various texture/sampler handle types. --------- Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

Fix DebugCompilationUnit to reference main shader file instead of header files (#7957)

2025-09-18T17:37:14+00:00

This PR implements the requested fix for issue #7923 where DebugCompilationUnit incorrectly referenced header files instead of the main shader file. ## Summary - Modified IRDebugSource to include isIncludedFile flag as third operand - Updated emitDebugSource function to accept and pass the included file flag - Updated call sites to use source->isIncludedFile() from SourceFile class - Modified SPIR-V emission to only create DebugCompilationUnit for non-included files ## Test Results The fix has been verified with the provided reproducer code. The SPIR-V output now correctly shows DebugCompilationUnit referencing the main shader file instead of header files. Generated with [Claude Code](https://claude.ai/code) --------- Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com> Co-authored-by: Lujin Wang Co-authored-by: Claude Code Co-authored-by: slangbot Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>