Add groundwork for GLSL_EXT_structured_descriptor_heap in glslang by Guang-035 · Pull Request #4272 · KhronosGroup/glslang

Guang-035 · 2026-05-13T08:42:11Z

This PR implements GLSL_EXT_structured_descriptor_heap support in glslang.

It builds on the existing GL_EXT_descriptor_heap lowering and extends the frontend/backend metadata model so structured heap layout can distinguish ordinary POD members from real descriptor payloads.

Spec reference: https://github.com/KhronosGroup/GLSL/pull/299/changes

Task Breakdown

Guang-035 · 2026-05-19T09:06:58Z

NOTE: These validation failures are expected for now and should be fixed in SPIRV-Tools validation.

spv.structuredDescriptorHeap.Buffer.comp.out:
The shader has a struct member containing a buffer descriptor:
struct Material {
vec4 data0;
DataBuffer dataBuffer;
};
Current validation incorrectly treats Material as a non-descriptor resource and rejects the structured descriptor heap decorations. This should be accepted for structs that contain descriptor members.

Fix is available here [Merged].

Guang-035 · 2026-05-19T15:19:53Z

ping for review

Apply heap_offset as an access-time descriptor heap base offset for literal, spec-constant, and push-constant values, with tests covering buffer, image, texture, and sampler heap access.

Allow inline buffer_reference blocks in structured descriptor heap declarations and reduce duplicate shifted heap base generation. Add SPIR-V coverage for buffer reference heap members and update affected baselines.

Cover acceleration structure, matrix layout, and heap buffer layout qualifier cases for structured descriptor heaps. Emit matrix layout decorations for descriptor heap structs that use OffsetIdEXT.

…n failure

Guang-035 · 2026-05-21T09:38:07Z

Rebase Guang-035:structured_descriptor_heap branch.

ShchchowAMD

LGTM, just some small points I don't fully understand.
Thanks very much for helping refining those codes!

Issue: KhronosGroup#4238 Propagate readonly/writeonly qualifiers for descriptor heap resources to valid SPIR-V decoration targets. 1. For buffer descriptors, preserve the qualifiers on OpBufferPointerEXT results using NonWritable for readonly buffers and NonReadable for writeonly buffers. 2. For direct descriptor heap image arrays, synthesize one-member wrapper block types so NonReadable/NonWritable can be emitted as member decorations instead of decorating OpLoad results, which is not valid SPIR-V. 3. Add regression coverage for descriptor heap buffer and image qualifier lowering.

Guang-035 · 2026-06-03T07:55:37Z

The new commit handles readonly / writeonly qualifiers for resources loaded from descriptor heaps. Issue reported here .

dnovillo · 2026-06-05T12:52:54Z

    extensionBehavior[E_GL_EXT_texture_cube_map_array]               = EBhDisable;
    extensionBehavior[E_GL_EXT_null_initializer]                     = EBhDisable;
    extensionBehavior[E_GL_EXT_descriptor_heap]                      = EBhDisable;
+    extensionBehavior[E_GL_EXT_structured_descriptor_heap]           = EBhDisable;


Is the GLSL spec stable already? Or is this PR blocked until the spec is merged.

The GLSL spec is stable, but it has not been merged yet. This PR is intended to track the current implementation and gather review feedback. I will keep it open and not merge it until the spec lands.

dnovillo · 2026-06-05T12:54:40Z

        parseContext.setLayoutQualifier($1.loc, $$, *$1.string);
    }
-    | IDENTIFIER EQUAL constant_expression {
+    | IDENTIFIER EQUAL assignment_expression {


Related to the previous comment here. Could you add a test that produces a diagnostic if the expression is not constant? (not sure if you have one already).

Good point, I missed adding coverage for this when resolving the previous comment. I added spv.layoutQualifierExpression.error.comp to verify that non-constant expressions used with regular layout qualifiers still produce the expected constant expression required diagnostic.

dnovillo · 2026-06-05T12:55:48Z

-            StorageClass descHeapStorageClass;  // for descriptor heap, record its basic storage class.
-            uint32_t descHeapBaseArrayStride;   // for descriptor heap, record its explicit array stride.
+            Id descHeapBaseOffset;              // byte offset applied to the heap base before descriptor lookup.
+            std::vector<Id> descHeapindexChain;


spelling nit: descHeapIndexChain is more consistent with the spelling of other fields (capital I in index).

Guang-035 changed the title ~~Refine descriptor heap type metadata and SPIR-V layout generation~~ Add groundwork for GLSL_EXT_structured_descriptor_heap in glslang May 13, 2026

Guang-035 force-pushed the structured_descriptor_heap branch 3 times, most recently from 64b6b98 to 284dd8c Compare May 15, 2026 07:55

Guang-035 commented May 15, 2026

View reviewed changes

Comment thread Test/spv.structuredDescriptorHeap.Buffer.comp

Guang-035 force-pushed the structured_descriptor_heap branch 4 times, most recently from ad639fd to 5262583 Compare May 19, 2026 08:58

Guang-035 force-pushed the structured_descriptor_heap branch from 5262583 to 658e0cf Compare May 19, 2026 09:51

spencer-lunarg added the Descriptor Heaps GL_EXT_descriptor_heap label May 20, 2026

Guang-035 added 7 commits May 21, 2026 17:29

enable GLSL_EXT_structured_descriptor_heap

c929698

Refine descriptor heap type metadata and SPIR-V layout generation

e7e1461

Support structured descriptor heap offsets

cd3926d

Apply heap_offset as an access-time descriptor heap base offset for literal, spec-constant, and push-constant values, with tests covering buffer, image, texture, and sampler heap access.

Support structured descriptor heap buffer references

3b0ea87

Allow inline buffer_reference blocks in structured descriptor heap declarations and reduce duplicate shifted heap base generation. Add SPIR-V coverage for buffer reference heap members and update affected baselines.

Test structured descriptor heap layouts

0a027b5

Cover acceleration structure, matrix layout, and heap buffer layout qualifier cases for structured descriptor heaps. Emit matrix layout decorations for descriptor heap structs that use OffsetIdEXT.

Fix spv.descriptorHeap.heaps.frag

f627f6e

Fix spv.structuredDescriptorHeap.AccelerationStructure.comp validatio…

dce6815

…n failure

Guang-035 force-pushed the structured_descriptor_heap branch from 5f25599 to dce6815 Compare May 21, 2026 09:36

ShchchowAMD reviewed May 31, 2026

View reviewed changes

Guang-035 added 2 commits June 1, 2026 16:41

review fix

fdde8a3

dnovillo requested changes Jun 5, 2026

View reviewed changes

review fix

47f8e97

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