[Jonathan Zakharov (jzakharovnv)]

Building off of #8517, this PR extends the SPV_EXT_descriptor_heap native heap lowering to cover RaytracingAccelerationStructure resources loaded from ResourceDescriptorHeap. It is part 2/4 in a series.

Acceleration structure descriptors are accessed via OpUntypedAccessChainKHR into a runtime array of OpTypeAccelerationStructureKHR, consistent with the image and sampler paths added in the previous commit.

Assisted by an AI agent

Diego Novillo (@dnovillo)

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[Jonathan Zakharov (jzakharovnv)]

@microsoft-github-policy-service agree company="NVIDIA"

[Diego Novillo (dnovillo)]

Only a question left on detecting RT usage of the heap.

[Copilot]

Pull request overview

Extends native SPIR-V descriptor-heap lowering to acceleration structures and broader resource operations.

Changes:

• Adds descriptor-size-based heap strides, including acceleration structures.
• Adds native buffer, image, sampler, atomic, and alias lowering.
• Expands SPIR-V tests and documentation.

Reviewed changes

Copilot reviewed 51 out of 51 changed files in this pull request and generated 15 comments.

Show a summary per file

File	Description
tools/clang/unittests/SPIRV/SpirvContextTest.cpp	Extends runtime-array uniqueness tests.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.typed-formats.hlsl	Tests typed image formats.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.texturecube.hlsl	Tests cube textures and samplers.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.texture.hlsl	Tests texel buffers.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.texture-sampler-assignment.hlsl	Tests resource reassignment.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.texture-ms.hlsl	Tests multisampled textures.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.texture-dims.hlsl	Tests sampled-texture dimensions.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.structured-buffer-atomic.hlsl	Tests structured-buffer atomics.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.static-global.hlsl	Tests static global resources.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.sampler-comparison.hlsl	Tests comparison samplers.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.sample-grad-bias.hlsl	Tests gradient and bias sampling.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.rwtexture-dims.hlsl	Tests storage-texture dimensions.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.rwtexture-atomics.hlsl	Tests untyped image atomics.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.rwbyteaddressbuffer.hlsl	Tests writable byte buffers.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.nonuniform.hlsl	Tests nonuniform-index handling.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.mixed-bound.hlsl	Tests bound and heap resources together.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.load-offset.hlsl	Tests texture-load offsets.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.groupshared.hlsl	Tests groupshared interoperability.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.gather.hlsl	Tests texture gather operations.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.function-params.hlsl	Tests resource function parameters.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.discarded.error.hlsl	Tests discarded-access diagnostics.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.counter-ops.error.hlsl	Tests unsupported counter diagnostics.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.constant-texture-buffer.hlsl	Tests constant and texture buffers.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.constant-buffer-assignment.hlsl	Tests constant-buffer reassignment.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.buffer.hlsl	Tests native buffer lowering.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.array-stride.hlsl	Tests shared heap strides.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.array-stride.accelstruct.hlsl	Tests acceleration-structure stride inclusion.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.append-consume.error.hlsl	Tests append/consume diagnostics.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.acceleration-structure.stride.error.hlsl	Tests missing acceleration stride diagnostics.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.acceleration-structure.hlsl	Tests acceleration-structure heap loads.
tools/clang/test/CodeGenSPIRV/resource-heap-ext-texture.hlsl	Removes the superseded aggregate test.
tools/clang/lib/SPIRV/SpirvType.cpp	Includes stride IDs in type equality.
tools/clang/lib/SPIRV/SpirvInstruction.cpp	Implements new SPIR-V instructions.
tools/clang/lib/SPIRV/SpirvEmitter.h	Declares heap-lowering and alias state.
tools/clang/lib/SPIRV/SpirvEmitter.cpp	Implements native heap lowering and acceleration support.
tools/clang/lib/SPIRV/SpirvContext.cpp	Canonicalizes buffer and runtime-array types.
tools/clang/lib/SPIRV/SpirvBuilder.cpp	Builds descriptor-size constants and strides.
tools/clang/lib/SPIRV/LowerTypeVisitor.cpp	Lowers untyped image pointers.
tools/clang/lib/SPIRV/EmitVisitor.h	Declares new emission handlers.
tools/clang/lib/SPIRV/EmitVisitor.cpp	Emits new instructions and decorations.
tools/clang/lib/SPIRV/DeclResultIdMapper.h	Declares function-variable aliases.
tools/clang/lib/SPIRV/DeclResultIdMapper.cpp	Registers function-variable aliases.
tools/clang/lib/SPIRV/CapabilityVisitor.cpp	Enforces Vulkan 1.3 for native heaps.
tools/clang/lib/SPIRV/AstTypeProbe.cpp	Recognizes acceleration-structure types.
tools/clang/include/clang/SPIRV/SpirvVisitor.h	Adds visitor methods.
tools/clang/include/clang/SPIRV/SpirvType.h	Stores runtime-array stride IDs.
tools/clang/include/clang/SPIRV/SpirvInstruction.h	Defines new instruction classes.
tools/clang/include/clang/SPIRV/SpirvContext.h	Extends type-context APIs.
tools/clang/include/clang/SPIRV/SpirvBuilder.h	Exposes descriptor-stride builders.
tools/clang/include/clang/SPIRV/AstTypeProbe.h	Declares acceleration-type probing.
docs/SPIR-V.rst	Documents native descriptor heaps.

Comments suppressed due to low confidence (1)

tools/clang/lib/SPIRV/SpirvEmitter.cpp:7072

• Only casts are stripped here, so a syntactically valid parenthesized heap base such as (ResourceDescriptorHeap)[i] is diagnosed as unsupported even though it still refers directly to the builtin variable. Use IgnoreParenCasts() consistently when resolving the base declaration.

      const auto *declRefExpr = dyn_cast<DeclRefExpr>(baseExpr->IgnoreCasts());
      const auto *decl =
          declRefExpr ? dyn_cast<VarDecl>(declRefExpr->getDecl()) : nullptr;
      if (!decl) {
        emitError("unsupported ResourceDescriptorHeap/SamplerDescriptorHeap "
                  "expression",
                  baseExpr->getExprLoc());
        return nullptr;

---

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[Damyan Pepper (damyanp)]

[Auto-generated note from Damyan Pepper (@damyanp)]

This looks like a user-visible bug fix/feature change. Please add (or point to) the corresponding entry in docs/ReleaseNotes.md.

If release-note coverage is planned in a related PR (including one that hasn’t been submitted yet), please mention that plan/link so we can avoid duplicate notes.

[Copilot]

Pull request overview

Copilot reviewed 52 out of 52 changed files in this pull request and generated 1 comment.

Suppressed comments (3)

tools/clang/lib/SPIRV/SpirvEmitter.cpp:5315

• A heap-to-heap reassignment of RaytracingAccelerationStructure also reaches this branch because mixingDetected includes (isASType && wasHeap) regardless of srcIsHeap. That assignment does not mix bound and heap resources, so this diagnostic is misleading; report the unsupported AS reassignment separately.

    emitError("mixing bound and descriptor heap resources in the same variable "
              "is not supported with SPV_EXT_descriptor_heap",
              loc);

tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.array-stride.hlsl:62

• Use the possessive “its” rather than “it's” (“it is”).

// The sampler array just uses the sampler size as it's stride.

docs/SPIR-V.rst:2089

• This is a significant user-visible compiler feature, but docs/ReleaseNotes.md has no native descriptor-heap entry. Please add release-note coverage, or point to the shared release note planned for this four-PR series.

When ``-fspv-use-descriptor-heap`` is specified, DXC lowers
``ResourceDescriptorHeap`` and ``SamplerDescriptorHeap`` through
``SPV_EXT_descriptor_heap`` instead of the default emulated heap path. This
also requires ``SPV_KHR_untyped_pointers`` and ``-fspv-target-env=vulkan1.3``

[Diego Novillo (dnovillo)]

Added an analysis on this series: #8517 (comment)

[Copilot]

🔵 Needs a closer look

Writable function parameters can bypass alias reassignment diagnostics and silently leave subsequent accesses using the original descriptor.

6 open issues

• Use a consistent resource-heap stride across shader stages
• Register placeholder after failed lowering to avoid internal diagnostic
• Suppress debug lines for module-level specialization operations
• Avoid DebugLine emission for OpSpecConstantOp outside functions
• Remove unused acceleration-structure load from capability test
• Provide complete extension options for default-mode shader test

1 previously missed issue

In code that hasn't changed since last review

Reject writable arguments referencing heap-initialized aliases

tools/​clang/​lib/​SPIRV/​SpirvEmitter.cpp:2091

Passing a heap-initialized acceleration structure to an out or inout parameter bypasses the reassignment diagnostic. processCall creates a temporary but does not copy resource parameters back, so later uses of the alias still read the original heap handle after the helper assigns a different resource. Reject writable arguments that refer to these aliases until their updated values can be represented correctly.

_{Review effort: Balanced}

[Copilot]

🔵 Needs a closer look

Per-shader stride selection can cause shaders sharing a heap to address different slots and silently read the wrong descriptors.

4 open issues

• Register placeholder after failed lowering to avoid internal diagnostic
• Avoid DebugLine emission for OpSpecConstantOp outside functions
• Remove unused acceleration-structure load from capability test
• Provide complete extension options for default-mode shader test

2 resolved since last review

• Use a consistent resource-heap stride across shader stages
• Suppress debug lines for module-level specialization operations

_{Review effort: Balanced}

[Copilot]

🔵 Needs a closer look

Heap stride varies by shader stage, so separately compiled shaders sharing a heap can read different descriptors at the same index.

1 open issue

• Remove unused acceleration-structure load from capability test

3 resolved since last review

• Register placeholder after failed lowering to avoid internal diagnostic
• Avoid DebugLine emission for OpSpecConstantOp outside functions
• Provide complete extension options for default-mode shader test

_{Review effort: Balanced}

[Gregory Roth (pow2clk)]

I don't know why copilot is not acknowledging the change to sm6_6.descriptorheap.ext.array-stride.accelstruct-ext.hlsl, but it all looks good to me!

[Gregory Roth (pow2clk)]

/azp run

[azure-pipelines]

Azure Pipelines:
Successfully started running 1 pipeline(s).

[Jonathan Zakharov (jzakharovnv)]

Looks like one of the tests I added is failing on Azure. Investigating

[Jonathan Zakharov (jzakharovnv)]

Seems the issue was that a test was hitting an unexpected assert in debug builds, should be fixed now

[Jonathan Zakharov (jzakharovnv)]

/azp run

[azure-pipelines]

Commenter does not have sufficient privileges for PR 8518 in repo microsoft/DirectXShaderCompiler

[Copilot]

🔵 Needs a closer look

Heap stride varies by shader stage and extension settings, potentially causing shaders sharing a heap to read different descriptors for the same index.

No open issues 🎉

1 resolved since last review

• Remove unused acceleration-structure load from capability test

_{Review effort: Balanced}

[Jonathan Zakharov (jzakharovnv)]

🔵 Needs a closer look

Heap stride varies by shader stage and extension settings, potentially causing shaders sharing a heap to read different descriptors for the same index.

No open issues 🎉

Thank you Copilot lol

[Gregory Roth (pow2clk)]

/azp run

[Gregory Roth (pow2clk)]

/azp run

[azure-pipelines]

Azure Pipelines:
Successfully started running 1 pipeline(s).

[Copilot]

🔵 Needs a closer look

Heap stride varies by shader stage and extension list, so shaders sharing a heap can address different descriptors at the same index.

No open issues 🎉

_{Review effort: Balanced}

[Gregory Roth (pow2clk)]

/azp run

[azure-pipelines]

Azure Pipelines:
Successfully started running 1 pipeline(s).