[Jonathan Zakharov (jzakharovnv)]

Building off of #8518, this PR adds two new command-line flags that override the ArrayStride of the descriptor heap runtime arrays emitted by -fspv-use-descriptor-heap. It is part 3/4 in a series.

-fvk-resource-heap-stride and -fvk-sampler-heap-stride sets the stride for ResourceDescriptorHeap SamplerDescriptorHeap arrays respectively. N and M must be a power of two in [8, 256]. When set, the CLI value takes the highest precedence.

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)]

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[Diego Novillo (dnovillo)]

Thanks for the fixes. LGTM now.

[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

Adds configurable resource and sampler descriptor-heap strides while expanding native SPV_EXT_descriptor_heap lowering.

Changes:

• Adds and validates the two stride CLI options.
• Supports literal and computed descriptor-array strides, including acceleration structures.
• Expands documentation and SPIR-V regression coverage.

Reviewed changes

Copilot reviewed 57 out of 57 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
tools/clang/unittests/SPIRV/SpirvContextTest.cpp	Tests runtime-array uniquing.
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.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.texture.hlsl	Tests buffer textures.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.texture-sampler-assignment.hlsl	Tests texture/sampler 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.stride-cli.hlsl	Tests literal CLI strides.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.stride-cli-permute.hlsl	Tests stride values and validation.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.static-global.hlsl	Tests static resource aliases.
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 divergent heap indexing.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.mixed-bound.hlsl	Tests bound/heap coexistence.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.mixed-alias.error.hlsl	Tests mixed-alias diagnostics.
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 gathers.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.function-params.hlsl	Tests resource 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/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 buffer heap lowering.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.array-stride.hlsl	Tests computed default strides.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.array-stride.accelstruct.hlsl	Tests acceleration-structure strides.
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 acceleration-stride errors.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.acceleration-structure.hlsl	Tests acceleration-structure loads.
tools/clang/test/CodeGenSPIRV/resource-heap-ext-texture.hlsl	Removes superseded coverage.
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 descriptor-heap helpers/state.
tools/clang/lib/SPIRV/SpirvEmitter.cpp	Implements native heap lowering and strides.
tools/clang/lib/SPIRV/SpirvContext.cpp	Uniques extended descriptor types.
tools/clang/lib/SPIRV/SpirvBuilder.cpp	Builds computed heap 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 types, constants, and decorations.
tools/clang/lib/SPIRV/DeclResultIdMapper.h	Declares function alias support.
tools/clang/lib/SPIRV/DeclResultIdMapper.cpp	Implements function aliases.
tools/clang/lib/SPIRV/CapabilityVisitor.cpp	Requires Vulkan 1.3 for native heaps.
tools/clang/lib/SPIRV/AstTypeProbe.cpp	Detects acceleration structures.
tools/clang/include/clang/SPIRV/SpirvVisitor.h	Extends visitor dispatch.
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	Exposes extended type uniquing.
tools/clang/include/clang/SPIRV/SpirvBuilder.h	Exposes stride construction APIs.
tools/clang/include/clang/SPIRV/AstTypeProbe.h	Declares acceleration-type detection.
lib/DxcSupport/HLSLOptions.cpp	Parses and validates stride options.
include/dxc/Support/SPIRVOptions.h	Stores stride overrides.
include/dxc/Support/HLSLOptions.td	Defines the CLI flags.
docs/SPIR-V.rst	Documents native heaps and strides.

[Copilot]

🟡 Changes recommended

Image atomic lowering now reverses base and coordinate evaluation order, potentially changing shaders with side effects.

Get a fresh assessment by requesting another Copilot review.

Review details

Suppressed comments (1)

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

• Use the possessive “its” here.

• Files reviewed: 64/64 changed files
• Comments generated: 1
• Review effort level: Balanced

[Copilot]

🟡 Changes recommended

Passing a heap-initialized acceleration structure to an out/inout helper can bypass reassignment diagnostics and leave later traces using the original heap handle after reassignment.

8 open issues

• This now evaluates the coordinate expression before the image/base expression. The previous path…
• Including SPV_NV_ray_tracing here makes every native-heap shader build an acceleration-structure…
• Writable helper arguments bypass heap resource reassignment diagnostics · New
• The fallback chooses the stride from the element type instead of the heap selected by…
• These stride values are consumed only by the native -fspv-use-descriptor-heap path, but option…
• The guard only recognizes a local alias DeclRefExpr, so a direct argument such as…
• Test does not exercise the resource heap stride exemption · New
• For append/consume declarations, the first doExpr emits the unsupported-resource error and…

4 resolved since last review

• The definition no longer matches the new two-argument declaration or either call site, so this…
• This guard only catches a heap buffer after it has been assigned to a DeclRefExpr alias. Passing…
• For an acceleration-structure alias, this condition is true for every reassignment, including…
• This overstates the implementation: buffer aliases are re-derived from the saved index on every…

_{Review effort: Balanced}

[Copilot]

🔵 Needs a closer look

Acceleration-structure aliases passed to out/inout helpers can silently lose updates, leaving subsequent ray queries using stale handles; this path needs a fix and regression coverage.

3 open issues

• Writable helper arguments bypass heap resource reassignment diagnostics
• Test does not exercise the resource heap stride exemption
• For append/consume declarations, the first doExpr emits the unsupported-resource error and…

5 resolved since last review

• This now evaluates the coordinate expression before the image/base expression. The previous path…
• Including SPV_NV_ray_tracing here makes every native-heap shader build an acceleration-structure…
• The fallback chooses the stride from the element type instead of the heap selected by…
• These stride values are consumed only by the native -fspv-use-descriptor-heap path, but option…
• The guard only recognizes a local alias DeclRefExpr, so a direct argument such as…

_{Review effort: Balanced}

[Copilot]

🟢 Approval recommended

No active review issues are reported for the descriptor-heap stride changes.

1 open issue

• For append/consume declarations, the first doExpr emits the unsupported-resource error and…

2 resolved since last review

• Writable helper arguments bypass heap resource reassignment diagnostics
• Test does not exercise the resource heap stride exemption

_{Review effort: Balanced}

[Copilot]

🟡 Changes recommended

The stride tests can miss regressions because the buffer override check can match a texture array, while the forbidden-instruction checks do not cover the full disassembly.

3 open issues

• Check forbidden instructions across the full disassembly · New
• Bind the stride check to the buffer runtime array · New
• For append/consume declarations, the first doExpr emits the unsupported-resource error and…

_{Review effort: Balanced}

[Copilot]

🔵 Needs a closer look

Both regression tests scope their negative checks too narrowly, allowing forbidden stride-related SPIR-V instructions emitted before or between positive matches to go undetected.

3 open issues

• Bind the stride check to the buffer runtime array
• Check forbidden instructions across the full disassembly
• For append/consume declarations, the first doExpr emits the unsupported-resource error and…

_{Review effort: Balanced}

[Copilot]

🔵 Needs a closer look

Human assessment is needed for an unpublished concern about the release-note entry exceeding the contribution guidelines’ single-sentence limit.

1 open issue

• For append/consume declarations, the first doExpr emits the unsupported-resource error and…

2 resolved since last review

• Bind the stride check to the buffer runtime array
• Check forbidden instructions across the full disassembly

_{Review effort: Balanced}

[Gregory Roth (pow2clk)]

It looks good overall! I'd like to understand the need for the new onSamplerHeap parameter before I sign off.

The copy editing suggestions are purely optional.

[Gregory Roth (pow2clk)]

I'm not actually suggesting these just get deleted, but these would be replaced by my suggestion above

Suggested change

	descriptors; otherwise compilation fails, unless `-fvk-resource-heap-stride`
	is given.

[Copilot]

🔵 Needs a closer look

Human judgment is needed to determine whether the unpublished release-note formatting concern should affect approval.

1 open issue

• For append/consume declarations, the first doExpr emits the unsupported-resource error and…

_{Review effort: Balanced}