[SPIR-V] Add descriptor heap RaytracingAccelerationStructure support by jzakharovnv · Pull Request #8518 · microsoft/DirectXShaderCompiler

Jonathan Zakharov (jzakharovnv) · 2026-06-04T21:53:18Z

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 · 2026-06-04T21:55:04Z

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

Jonathan Zakharov (jzakharovnv) · 2026-06-04T23:02:33Z

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

Diego Novillo (dnovillo) · 2026-07-17T17:05:45Z

+    return true;
+  }
+
+  if (isRaytracingAccelerationStructure(decl->getType())) {


Since acceleration structures are distinct from image and buffers, do they still fit in max(sizeof(image), sizeof(buffer))? If not, the stride will be too small and heap indexing will land in the wrong spot.

Maybe we need to incorporate acceleration structures when computing the default stride if RT is used?

Good catch, it would be correct to include acceleration structures in the computation for the resource heap stride. Will address this in my next set of commits.

Addressed with Included AccelerationStructure in resource heap stride calculation

Diego Novillo (dnovillo) · 2026-07-17T17:07:36Z

@@ -0,0 +1,42 @@
+// RUN: %dxc -T lib_6_6 -fspv-use-descriptor-heap -fspv-target-env=vulkan1.3 -fvk-resource-heap-stride 64 -fvk-sampler-heap-stride 32 -fspv-extension=SPV_KHR_ray_tracing -fspv-extension=SPV_EXT_descriptor_heap -fspv-extension=SPV_KHR_untyped_pointers -spirv %s | FileCheck %s


This is using flags introduced in #8519. It will break if the PRs get merged in order. Perhaps move this test to #8519 and add only default stride tests here?

Another result of some clumsy commits and now outdated commits! Should be able to remove the usage of these flags now that strides are computed automatically. Will address next set of commits.

Addressed with removed erronous CLI options from test

Diego Novillo (dnovillo)

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

Diego Novillo (dnovillo) · 2026-07-24T13:00:09Z

+      if (shaderModelKindIsRayTracing(fi->shaderModelKind)) {
+        needsAccelStruct = true;
+        break;
+      }


This would fail for compute/graphics shaders that need to use RayQuery and have AS on the heap. I think this should be a translation unit walk looking for a vardecls and setting the flag on the first match.

This ended up being a much harder problem than I anticipated. I filed an issue with #8714 and have provided some work arounds in a revised Included AccelerationStructure in resource heap stride calculation. There also exists the work around of using the options provided in [SPIR-V] Add -fvk-resource-heap-stride / -fvk-sampler-heap-stride.

This ended up being a much harder problem than I anticipated. I filed an issue with #8714 and have provided some work arounds in a revised Included AccelerationStructure in resource heap stride calculation. There also exists the work around of using the options provided in [SPIR-V] Add -fvk-resource-heap-stride / -fvk-sampler-heap-stride.

Sure. Thanks for documenting workarounds. I think this is now ready.

Building off of microsoft#8281, this commit adds a native lowering via SPV_EXT_descriptor_heap and SPV_KHR_untyped_pointers. ResourceDescriptorHeap and SamplerDescriptorHeap are lowered to untyped variables decorated with ResourceHeapEXT and SamplerHeapEXT. Each heap access emits OpUntypedAccessChainKHR into a runtime array of the appropriate descriptor type. Buffer-like resources (StructuredBuffer, ByteAddressBuffer, ConstantBuffer, TextureBuffer) use OpTypeBufferEXT and OpBufferPointerEXT; image and sampler resources use OpLoad. Interlocked operations on RWTexture use OpUntypedImageTexelPointerEXT. Requires -fspv-target-env=vulkan1.3. Assisted-by: Claude.

…TODO

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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Jonathan Zakharov (jzakharovnv) · 2026-07-30T22:19:55Z

+// (Dim2D, depth=0, not-arrayed, non-MS, sampled, Unknown format), so
+// %[[TexDesc]] serves as both the placeholder for the size calculation and
+// the real descriptor type for the Texture2D access below.
+// CHECK-DAG:        %[[TexDesc:[a-zA-Z0-9_]+]] = OpTypeImage %float 2D 0 0 0 1 Unknown


Fixing test in next set of commits

Jonathan Zakharov (jzakharovnv) · 2026-07-30T22:19:59Z

+
+// --- Types (user-declared + stride-computation placeholders) ---------------
+// CHECK-DAG:    %[[Accel:[a-zA-Z0-9_]+]] = OpTypeAccelerationStructureKHR
+// CHECK-DAG:      %[[Img:[a-zA-Z0-9_]+]] = OpTypeImage %float 2D 0 0 0 1 Unknown


Fixing test in next set of commits

Jonathan Zakharov (jzakharovnv) · 2026-07-30T19:30:12Z

+    if (!needsAccelStruct && !spirvOptions.allowedExtensions.empty())
+      needsAccelStruct =
+          featureManager.isExtensionEnabled(Extension::KHR_ray_tracing) ||
+          featureManager.isExtensionEnabled(Extension::NV_ray_tracing) ||
+          featureManager.isExtensionEnabled(Extension::KHR_ray_query);


Jonathan Zakharov (jzakharovnv) · 2026-07-30T22:20:10Z

+The concrete descriptor type is selected at each heap access. For image,
+sampler, and texel buffer resources, DXC forms a runtime array of that
+descriptor type and decorates the array with a byte ``ArrayStride``, then uses
+``OpUntypedAccessChainKHR`` followed by ``OpLoad``:


Fixing documentation in next set of commits

Jonathan Zakharov (jzakharovnv) · 2026-07-30T22:20:22Z

+
+// Three distinct descriptor heap sizes exist:
+// the image/Texture2D type (%[[TexDesc]]), the Uniform buffer, and the sampler.
+// Regression test: make sure of no per-element nor per acces behavior exists


Fixing test in next set of commits

+  auto &alias = descriptorHeapImageAliasVars[dstVar];
+  if (!alias.indexVar)
+    alias.indexVar = createDescriptorHeapIndexVar(dstVar);
+  alias.imageType = found->second.imageType;
+  alias.arrayType = found->second.arrayType;
+  alias.heap = found->second.heap;
+  storeDescriptorHeapIndex(alias.indexVar, found->second.index,
+                           found->second.indexType, srcExpr);


+This path supports texture, RWTexture, sampler, Buffer/RWBuffer,
+StructuredBuffer/RWStructuredBuffer without associated counter operations,
+ByteAddressBuffer/RWByteAddressBuffer, ConstantBuffer, and TextureBuffer heap
+loads, including direct field and array-element accesses for
+``ConstantBuffer<T>`` and ``TextureBuffer<T>``. ``NonUniformResourceIndex`` is


+      // The heap index expression must be immediately converted to a concrete
+      // resource type (an implicit cast inserted by the front-end). If the
+      // parent is missing or is not a cast (e.g. the result is discarded as
+      // a statement, or used in a context with no target resource type) we
+      // cannot determine the resource type.
+      const auto *parentExpr =
+          dyn_cast_or_null<CastExpr>(parentMap->getParent(expr));
+      if (!parentExpr) {
+        emitError("ResourceDescriptorHeap/SamplerDescriptorHeap indexing must "
+                  "be used as a resource",
+                  expr->getExprLoc());
+        return nullptr;


+          emitError("acceleration structure loaded from ResourceDescriptorHeap "
+                    "requires the resource heap stride to account for "
+                    "acceleration structure descriptors; compile with "
+                    "-fspv-extension=SPV_KHR_ray_tracing or "
+                    "-fspv-extension=SPV_KHR_ray_query",
+                    expr->getExprLoc());


Jonathan Zakharov (jzakharovnv) · 2026-07-30T22:25:14Z

+
+  EXPECT_NE(spvContext.getRuntimeArrayType(int32, llvm::None),
+            spvContext.getRuntimeArrayType(int32, 32));


Will fix in next set of commits.

Damyan Pepper (damyanp) · 2026-07-30T16:48:09Z

[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``

Jonathan Zakharov (jzakharovnv) · 2026-08-05T20:30:20Z

+    (void)doExpr(init->IgnoreParenCasts());
+    tryToAssignDescriptorHeapBufferAlias(decl, init);
+    return true;


Good catch, will fix

Diego Novillo (dnovillo) · 2026-08-06T22:37:34Z

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

…t alias-to-alias

CapabilityVisitor::visitInstructionAllTypes was dropping the bool return of requestTargetEnv, so a vk<1.3 target-env would emit the diagnostic but keep lowering. Added sm6_6.descriptorheap.ext.targetenv.error.hlsl to cover rejection of -fspv-use-descriptor-heap with -fspv-target-env=vulkan1.2.

…microsoft#8517)

…tructure support (microsoft#8518)

Copilot

Pull request overview

Copilot reviewed 59 out of 59 changed files in this pull request and generated 1 comment.

Suppressed comments (3)

tools/clang/unittests/SPIRV/SpirvContextTest.cpp:1

These integer-to-pointer casts are implementation-defined and can be problematic on platforms with non-integral pointer representations or with sanitizers enabled. Prefer using stable, non-dereferenced addresses as tokens (e.g., alignas(SpirvInstruction) static char token1, token2; and cast &tokenN), which preserves the intent (pointer identity) without relying on integer pointer values.
tools/clang/include/clang/SPIRV/SpirvContext.h:1
getHashValue() hashes only getStride().hasValue() (not the stride value when present). With many runtime arrays that differ by literal stride, this will create avoidable hash collisions and slow lookups/uniquing. Include the stride value in the hash when getStride() has a value (and still include getArrayStrideId() when present) while keeping operator== as the source of truth.

//===-- SpirvContext.h - Context holding SPIR-V codegen data ----*- C++ -*-===//

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

Fix grammar: use the possessive 'its' (not the contraction 'it's').

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

      // do not need to mark the "param.var.*" variables as precise.
      const bool isPrecise = false;
      const bool isNoInterp = param->hasAttr<HLSLNoInterpolationAttr>() ||
                              (argInst && argInst->isNoninterpolated());

      auto *tempVar = spvBuilder.addFnVar(varType, arg->getLocStart(), varName,
                                          isPrecise, isNoInterp);



Copilot

Pull request overview

Copilot reviewed 59 out of 59 changed files in this pull request and generated 1 comment.

Suppressed comments (2)

tools/clang/unittests/SPIRV/SpirvContextTest.cpp:1

Using integer-to-pointer reinterpret_cast for sentinel identities is implementation-defined and can be problematic under some sanitizers/toolchains. Prefer using addresses of real objects with stable storage (e.g., two distinct local dummy objects and reinterpret_cast<SpirvInstruction *>(&dummy)), which preserves the “pointer identity only” intent without relying on invalid pointer values.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.array-stride.hlsl:62
Correct the grammar: use the possessive 'its' instead of 'it's'.

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

+      // instead of crashing. TODO: implement full buffer-alias function-call
+      // support (VariablePointersStorageBuffer + matching createFnParam type).
+      const auto *var = dyn_cast<VarDecl>(declRefExpr->getDecl());
+      if (var && descriptorHeapBufferAliasVars.count(var)) {
+        emitError("heap buffer alias cannot be passed to a user function; "
+                  "access the buffer element directly at the call site",
+                  arg->getLocStart());
+        // emitError does not halt codegen; returning nullptr here propagates
+        // to spvBuilder and causes an access violation before the diagnostic
+        // surfaces. Return a zero uint placeholder so downstream expression
+        // consumers remain valid. The emitted error ensures the shader is
+        // rejected even if codegen continues with the placeholder.
+        QualType retTy = callExpr->getCallReturnType(astContext);
+        if (retTy->isVoidType())
+          return nullptr;
+        return spvBuilder.getConstantInt(astContext.UnsignedIntTy,
+                                         llvm::APInt(32, 0), false);
+      }
      argInfo = declIdMapper.getDeclEvalInfo(declRefExpr->getDecl(),
                                             arg->getLocStart());


Extends the SPV_EXT_descriptor_heap native heap lowering to cover RaytracingAccelerationStructure resources loaded from ResourceDescriptorHeap. 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.

…tructure support (microsoft#8518)

Copilot

Pull request overview

Copilot reviewed 59 out of 59 changed files in this pull request and generated 2 comments.

Suppressed comments (3)

tools/clang/unittests/SPIRV/SpirvContextTest.cpp:1

Casting small integers like 1/2 to pointers is implementation-defined and can trip sanitizers even if never dereferenced. A safer way to get stable distinct pointer identities is to take the addresses of two dummy objects (e.g., int dummy1, dummy2; and reinterpret_cast<SpirvInstruction*>(&dummy1) / &dummy2) so the test remains robust across platforms and tooling.
tools/clang/test/CodeGenSPIRV/sm6_6.descriptorheap.ext.targetenv.error.hlsl:1
This checked diagnostic string reads incomplete (it doesn’t say what target env is being used / why it’s “not permitted”). If the underlying diagnostic can include the selected target environment (e.g., Vulkan 1.2) and the required one (Vulkan 1.3), the test should be updated to match the more actionable message.
tools/clang/lib/SPIRV/SpirvEmitter.cpp:3104
The early-return diagnostic for returning heap buffer aliases only triggers when the returned expression resolves to a VarDecl recorded in descriptorHeapBufferAliasVars. Returning a heap-sourced buffer-like value directly (e.g., return ResourceDescriptorHeap[i]; for StructuredBuffer/ByteAddressBuffer/ConstantBuffer/TextureBuffer) can still reach loadIfGLValue() and risks emitting the same invalid whole-resource load that this code is trying to prevent. Consider extending this rejection to cover direct heap subscripts of buffer-like resource types as well, not just alias variables.

    if (isHeapSourcedValue(srcExpr)) {
      if (isDescriptorHeap(srcExpr)) {
        // Direct heap subscript: register the heap variable so the declaration
        // mapper can resolve it for the return instruction.
        const Expr *base = nullptr;
        getDescriptorHeapOperands(srcExpr, &base, /* index= */ nullptr);
        const Expr *parentExpr = cast<CastExpr>(parentMap->getParent(srcExpr));
        QualType resourceType = parentExpr->getType();
        const auto *declRefExpr = dyn_cast<DeclRefExpr>(base->IgnoreCasts());
        declIdMapper.createResourceHeap(cast<VarDecl>(declRefExpr->getDecl()),
                                        resourceType);
      }
      // Buffer alias: emitting a load of the whole resource (runtime-array
      // struct) produces invalid SPIR-V.  emitError does not halt codegen,
      // so terminate the basic block with an undef return value before
      // returning to prevent loadIfGLValue from emitting an invalid load and
      // leaving the block without a terminator.
      // TODO: implement cross-function alias propagation for buffer aliases
      //       using VariablePointersStorageBuffer (tracked as follow-up).
      else if (const auto *var =
                   dyn_cast_or_null<VarDecl>(getReferencedDef(srcExpr))) {
        if (descriptorHeapBufferAliasVars.count(var)) {
          emitError("heap buffer alias cannot be returned from a function; "
                    "access the buffer element directly at the return site",
                    retVal->getLocStart());
          spvBuilder.createReturnValue(
              spvBuilder.getUndef(curFunction->getReturnType()),
              stmt->getReturnLoc());
          return;
        }
      }
    }

+  // consume the assignment to prevent a null-deref. Image aliases do have a
+  // backing function variable, so they can fall through to the plain handle
+  // store.
+  if (descriptorHeapBufferAliasVars.count(dstVar) ||
+      declIdMapper.hasFnVarAlias(dstVar))
+    return static_cast<SpirvInstruction *>(nullptr);


+            tryToAssignToDescriptorHeapAlias(expr))
+      return aliasResult.getValue();
+


github-project-automation Bot added this to HLSL Roadmap Jun 4, 2026

github-project-automation Bot moved this to New in HLSL Roadmap Jun 4, 2026

Jonathan Zakharov (jzakharovnv) mentioned this pull request Jun 4, 2026

[SPIR-V] Add descriptor heap -fvk-resource-heap-stride / -fvk-sampler-heap-stride CLI flags #8519

Open

Jonathan Zakharov (jzakharovnv) force-pushed the pr2-raytracing-accel-struct branch 3 times, most recently from d899b05 to b12b9ea Compare June 4, 2026 22:59

Damyan Pepper (damyanp) requested a review from Chris B (llvm-beanz) July 14, 2026 17:48

Jonathan Zakharov (jzakharovnv) force-pushed the pr2-raytracing-accel-struct branch from b12b9ea to 23eca97 Compare July 14, 2026 19:46

Diego Novillo (dnovillo) suggested changes Jul 17, 2026

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github-project-automation Bot moved this from New to In progress in HLSL Roadmap Jul 17, 2026

Diego Novillo (dnovillo) added the spirv Work related to SPIR-V label Jul 17, 2026

Jonathan Zakharov (jzakharovnv) force-pushed the pr2-raytracing-accel-struct branch 2 times, most recently from 23aff82 to 02f3581 Compare July 23, 2026 19:39

Diego Novillo (dnovillo) suggested changes Jul 24, 2026

View reviewed changes

Jonathan Zakharov (jzakharovnv) added 6 commits July 28, 2026 13:51

Added OpConstantSizeOfEXT

c7d2389

clang-format

153e928

Shared max(image,buffer) stride for descriptor heap resource arrays

eb4a9bc

Fixed correct StorageClass for descriptor heap buffer alias pointers …

25c5a0a

…TODO

Ammend keyword usage to follow LLVM Coding Standards

88bd33c

Jonathan Zakharov (jzakharovnv) force-pushed the pr2-raytracing-accel-struct branch 2 times, most recently from 6293723 to 20dd181 Compare July 29, 2026 17:23

Jonathan Zakharov (jzakharovnv) mentioned this pull request Jul 29, 2026

[SPIR-V] SPV_EXT_descriptor_heap: acceleration structure heap stride computed before codegen causes false rejections and over-wide strides #8714

Open

Diego Novillo (dnovillo) approved these changes Jul 29, 2026

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Damyan Pepper (damyanp) requested a balanced review from Copilot July 29, 2026 22:44

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Jonathan Zakharov (jzakharovnv) added 3 commits August 3, 2026 11:07

fix stride test

1007865

Cover arrayStrideId uniquing in SpirvContextTest

f502bcf

Diagnose mixed bound/heap aliasing and correct documentation

034f3c5

Copilot AI review requested due to automatic review settings August 4, 2026 00:41

Jonathan Zakharov (jzakharovnv) force-pushed the pr2-raytracing-accel-struct branch from 20dd181 to 568efbb Compare August 4, 2026 00:41

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Diego Novillo (dnovillo) mentioned this pull request Aug 6, 2026

[SPIR-V] Add SPV_EXT_descriptor_heap + SPV_KHR_untyped_pointers codegen #8517

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Jonathan Zakharov (jzakharovnv) added 6 commits August 16, 2026 12:31

Diagnose heap buffer alias use in function calls + returns and suppor…

d8fdf44

…t alias-to-alias

Remove useless scope block in tryToAssignDescriptorHeapImageAlias

6a75ed5

Remove dead append/consume guard in incDecRWACSBufferCounter

7f89640

Remove unreachable !decl guard in heap index codegen path

8dc7484

[SPIR-V] Add release note for SPV_EXT_descriptor_heap native lowering (…

dab0e1e

…microsoft#8517)

Jonathan Zakharov (jzakharovnv) added a commit to jzakharovnv/DirectXShaderCompiler that referenced this pull request Aug 16, 2026

[SPIR-V] Add release note for descriptor heap RaytracingAccelerationS…

3255c18

…tructure support (microsoft#8518)

Copilot AI review requested due to automatic review settings August 16, 2026 21:42

Jonathan Zakharov (jzakharovnv) force-pushed the pr2-raytracing-accel-struct branch from 568efbb to 3255c18 Compare August 16, 2026 21:42

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Copilot AI review requested due to automatic review settings August 16, 2026 21:44

Copilot AI reviewed Aug 16, 2026

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Jonathan Zakharov (jzakharovnv) added 6 commits August 16, 2026 22:39

nit fixes

fae23d7

removed erronous CLI options from test

c5909ae

Included AccelerationStructure in resource heap stride calculation

f69efdb

Added AS reassignment diagnostic, fixed tests and docs

b3c27b3

[SPIR-V] Add release note for descriptor heap RaytracingAccelerationS…

abba0d5

…tructure support (microsoft#8518)

Copilot AI review requested due to automatic review settings August 17, 2026 05:45

Jonathan Zakharov (jzakharovnv) force-pushed the pr2-raytracing-accel-struct branch from 3255c18 to abba0d5 Compare August 17, 2026 05:45

Copilot AI reviewed Aug 17, 2026

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		@@ -0,0 +1,42 @@
		// RUN: %dxc -T lib_6_6 -fspv-use-descriptor-heap -fspv-target-env=vulkan1.3 -fvk-resource-heap-stride 64 -fvk-sampler-heap-stride 32 -fspv-extension=SPV_KHR_ray_tracing -fspv-extension=SPV_EXT_descriptor_heap -fspv-extension=SPV_KHR_untyped_pointers -spirv %s \| FileCheck %s


		EXPECT_NE(spvContext.getRuntimeArrayType(int32, llvm::None),
		spvContext.getRuntimeArrayType(int32, 32));

		tryToAssignToDescriptorHeapAlias(expr))
		return aliasResult.getValue();

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github-actions Bot commented Jun 4, 2026 •

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