fix crash from static members of cbuffers

[Brendan Duncan (brendan-duncan)]

static members of cbuffers, tbuffers, and structs are crashing the SPIR-V generator for DXC due to incorrectly being considered members of the struct and throwing off the actual member indices. DXC should not include static members when evaluating members.

Fixes #8537.
Unlike the related fix in #8538, which solves the main problem, this PR makes sure the statics are still emitted in SpirvEmitter.cpp.

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

[Copilot]

Pull request overview

Fixes SPIR-V generation crashes caused by static buffer members consuming layout indices.

Changes:

• Excludes static declarations from buffer layouts and indices.
• Emits static buffer members as globals.
• Adds cbuffer regression coverage.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
tools/clang/lib/SPIRV/DeclResultIdMapper.cpp	Skips static layout members.
tools/clang/lib/SPIRV/SpirvEmitter.cpp	Emits static members separately.
tools/clang/test/CodeGenSPIRV/cbuffer.static.member.hlsl	Tests layout and access indices.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

Suppressed comments (3)

tools/clang/lib/SPIRV/DeclResultIdMapper.cpp:1577

• This check occurs after the resource branch, so a static resource declared in a cbuffer/tbuffer is still passed to createExternVar() and treated as a descriptor; doHLSLBufferDecl() then emits the same declaration again as a static global. Move the static check ahead of the resource handling so every static member bypasses buffer/resource registration.

    if (isStaticBufferDecl(varDecl))
      continue;

tools/clang/lib/SPIRV/SpirvEmitter.cpp:2188

• This is a user-visible compiler crash fix, so it warrants an entry in docs/ReleaseNotes.md under the release-note policy in CONTRIBUTING.md:117-128. Please add the entry, or point to planned shared release-note coverage if this is part of a larger effort.

    if (decl->getStorageClass() != StorageClass::SC_Static) {
      // This is a VarDecl of cbuffer/tbuffer type.
      doHLSLBufferDecl(bufferDecl);
      return;

tools/clang/lib/SPIRV/DeclResultIdMapper.cpp:1752

• The new shader-record indexing path is not exercised by cbuffer.static.member.hlsl, which only reaches createCTBuffer(). Please add a shader-record cbuffer regression with a static declaration between ordinary members and verify the later access-chain indices, since this branch had the same out-of-bounds indexing failure.

    if (isStaticBufferDecl(varDecl))
      continue;

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated no new comments.

Suppressed comments (2)

docs/ReleaseNotes.md:61

• The release note overstates this fix by including ordinary structs. Struct layout already excluded static VarDecls at the check now wrapped by isStaticBufferDecl, and this PR does not otherwise change struct handling; the functional changes are limited to HLSL buffers. Remove /struct here, or include the missing struct behavior change and regression test.

- Fixed a crash from `static` members of a `cbuffer`/`tbuffer`/struct, which were

docs/ReleaseNotes.md:64

• This links to a specific pull request, which the release-note policy explicitly disallows (CONTRIBUTING.md:136-140). End the sentence on the preceding line and omit this PR link; a bug link can be used instead if one exists.

  [#8731](https://github.com/microsoft/DirectXShaderCompiler/pull/8731).

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated no new comments.

Suppressed comments (1)

tools/clang/test/CodeGenSPIRV/cbuffer.static.member.hlsl:22

• These regression cases only use builtin static const values. Even without the new eager-emission loop, getDeclEvalInfo() can lazily recover each declaration through tryToCreateConstantVar() (DeclResultIdMapper.cpp:1015-1023), so this test would still pass and would not protect the stated SpirvEmitter.cpp:1985-1988 behavior. Please include a static that cannot be lazily constant-folded (for example, an uninitialized mutable static that is read or written) and check its Private OpVariable.

  static const uint a_mode = 10;

[Brendan Duncan (brendan-duncan)]

copilot notes have been addressed.

[Damyan Pepper (damyanp)]

/azp run

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[Damyan Pepper (damyanp)]

Can you rebase or merge main into this branch please? The release note added here gets auto-merged into the wrong section.

[Brendan Duncan (brendan-duncan)]

Can you rebase or merge main into this branch please? The release note added here gets auto-merged into the wrong section.

Yup, merged main and moved the release not up to the new upcoming section.

[Damyan Pepper (damyanp)]

/azp run

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated no new comments.

Suppressed comments (1)

tools/clang/lib/SPIRV/SpirvEmitter.cpp:1980

• The new tests do not isolate this eager-emission path: every static is a referenced scalar constant, so getDeclEvalInfo() can recreate it lazily through tryToCreateConstantVar() even if this loop is removed. Please add a case that cannot pass via lazy constant creation (for example, an unused static whose emitted declaration is checked, or a valid non-constant static) so the stated requirement that buffer statics remain emitted is regression-tested.

  for (const auto *member : bufferDecl->decls()) {
    const auto *varMember = dyn_cast<VarDecl>(member);
    if (varMember && varMember->getStorageClass() == StorageClass::SC_Static)
      doVarDecl(varMember);