Make strings intangible types by llvm-beanz · Pull Request #9108 · microsoft/DirectXShaderCompiler

Chris B (llvm-beanz) · 2026-11-10T01:35:37Z

This updates the implementation of the built-in string type to be an intangible type. Aligning on the intangible semantics allows strings to be used in contexts that were allowed in FXC and some contexts supported by SPIRV.

This change does not expose any new things users can do with strings, but it is a neccessary basis for extending string operations.

Copilot

🟡 Changes recommended

Critical issues remain: non-literal local string initializers crash the SPIR-V backend, and casts between structs containing strings generate invalid GEP indices during code generation.

2 open issues

What changed in this PR

This PR aligns HLSL string handling with intangible-type semantics, laying groundwork for broader string support while restricting use in externally visible storage.

Changes:

Allows string locals, fields, and parameters, with storage-context validation.
Updates code generation and type annotations to preserve string values in aggregates.
Adds regression tests, updates diagnostic expectations, and documents the change.

File	Description
tools/clang/test/SemaHLSL/subobjects-syntax.hlsl	Updates diagnostics to expect `const string`.
tools/clang/test/SemaHLSL/subobjects-ast-dump.hlsl	Updates string field type expectations.
tools/clang/test/SemaHLSL/string.hlsl	Revises accepted declarations and diagnostics.
tools/clang/test/SemaHLSL/string-storage.hlsl	Tests string storage restrictions and private uses.
tools/clang/test/HLSLFileCheckLit/hlsl/intrinsics/string-empty-aggregates.hlsl	Covers traversal of deeply nested shared aggregate types.
tools/clang/test/HLSLFileCheckLit/hlsl/intrinsics/string-constant-initializers.hlsl	Tests string initialization, aggregate copies, and parameters.
tools/clang/lib/Sema/SemaHLSL.cpp	Adjusts string declaration, conversion, and storage checks.
tools/clang/lib/Sema/SemaDecl.cpp	Removes the blanket string-parameter rejection.
tools/clang/lib/CodeGen/CGHLSLMS.cpp	Preserves string pointers during aggregate initialization.
tools/clang/lib/CodeGen/CGDecl.cpp	Handles string pointer values in parameter emission.
tools/clang/lib/AST/ASTContext.cpp	Represents strings as pointers to const characters.
tools/clang/include/clang/AST/ASTContext.h	Changes string type storage to `QualType`.
lib/HLSL/HLLegalizeParameter.cpp	Exempts string pointers from input-parameter write patching.
lib/DXIL/DxilTypeSystem.cpp	Prevents string-containing structs from being marked empty.
docs/ReleaseNotes.md	Documents intangible string semantics under the upcoming release.

_{Review effort: Balanced}

This updates the implementation of the built-in `string` type to be an intangible type. Aligning on the intangible semantics allows strings to be used in contexts that were allowed in FXC and some contexts supported by SPIRV. This change does not expose any new things users can do with strings, but it is a neccessary basis for extending string operations. ../tools/clang/test/CodeGenSPIRV/type.string.initializer.hlsl ../tools/clang/test/HLSLFileCheckLit/hlsl/intrinsics/string-constant-ini tializers.hlsl ../tools/clang/test/HLSLFileCheckLit/hlsl/intrinsics/string-empty-aggreg ates.hlsl ../tools/clang/test/SemaHLSL/subobjects-ast-dump.hlsl

Co-authored-by: Chris B <beanz@abolishcrlf.org>

Copilot

🟡 Changes recommended

String-parameter calls can generate invalid SPIR-V, and referencing a rejected local can trigger a fatal unregistered-declaration error instead of recovering cleanly.

2 open issues

2 resolved since last review

_{Review effort: Balanced}

Copilot

🔵 Needs a closer look

String parameters can now produce invalid SPIR-V, while scalar-string-to-aggregate casts can generate invalid GEPs, leaving critical correctness issues unresolved.

2 open issues

1 previously missed issue

In code that hasn't changed since last review

Handle string leaves when splatting into aggregates

tools/clang/lib/CodeGen/CGHLSLMS.cpp:4163

For struct StringOnly { string Text; };, casting a string variable with (StringOnly)text now reaches the single-value splat path in EmitHLSLFlatConversion. EmitHLSLSplat descends into the field's i8* and builds an invalid GEP instead of copying the string value. Handle string leaves with a direct store before pointer recursion, bypassing the numeric conversion helper, and add a scalar-string-to-aggregate cast regression test.

_{Review effort: Balanced}

../tools/clang/test/CodeGenSPIRV/type.string.initializer.hlsl ../tools/clang/test/CodeGenSPIRV/type.string.parameter.hlsl ../tools/clang/test/HLSLFileCheckLit/hlsl/intrinsics/string-constant-ini tializers.hlsl

Copilot

🔵 Needs a closer look

Human assessment is needed to evaluate string copy-in paths that can trigger assertions and SPIR-V error recovery that can produce fatal errors.

No open issues 🎉

2 resolved since last review

_{Review effort: Balanced}

../tools/clang/test/CodeGenSPIRV/type.string.uninitialized.hlsl ../tools/clang/test/HLSLFileCheckLit/hlsl/intrinsics/string-constant-ini tializers.hlsl

Copilot

🟡 Changes recommended

Casting a string literal to an aggregate with a string field flattens it into characters instead of a string pointer, causing an assertion failure or a type-mismatched store in release builds.

1 open issue

Decay string literals to pointers before aggregate flattening · New

_{Review effort: Balanced}

+    if (hlsl::IsStringType(DstQualTy)) {
+      DXASSERT_NOMSG(hlsl::IsStringType(SrcQualTy));
+      CGF.Builder.CreateStore(SrcVal, DstPtr);


../tools/clang/test/HLSLFileCheckLit/hlsl/intrinsics/string-constant-ini tializers.hlsl

Copilot

🔵 Needs a closer look

Human assessment is needed because the changes can produce invalid SPIR-V for string fields and reject previously accepted forward-declared buffer element types.

1 open issue

Decay string literals to pointers before aggregate flattening

_{Review effort: Balanced}

Disallow strings as fields when targeting spirv Fix up handling of typedefs ../tools/clang/include/clang/Basic/DiagnosticSemaKinds.td ../tools/clang/test/CodeGenSPIRV/type.string.field.hlsl ../tools/clang/test/HLSLFileCheckLit/hlsl/intrinsics/structured-buffer-f orward-declaration.hlsl

Copilot

🔵 Needs a closer look

Human assessment is needed because arrays of forward-declared resource aliases can bypass validation, leaving forbidden string elements undiagnosed.

1 open issue

Decay string literals to pointers before aggregate flattening

_{Review effort: Balanced}

github-project-automation Bot added this to HLSL Roadmap Nov 10, 2026

Copilot AI balanced review requested due to automatic review settings November 10, 2026 01:35

github-project-automation Bot moved this to New in HLSL Roadmap Nov 10, 2026

Copilot started reviewing on behalf of Chris B (llvm-beanz) November 10, 2026 01:36

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Comment thread tools/clang/lib/CodeGen/CGHLSLMS.cpp Resolved

Comment thread tools/clang/lib/Sema/SemaHLSL.cpp Resolved

Chris B (llvm-beanz) marked this pull request as draft November 10, 2026 15:54

Chris B (llvm-beanz) force-pushed the cbieneman/intangible-strings branch from 2474067 to 34f3ade Compare November 10, 2026 16:56

Chris B (llvm-beanz) requested a balanced review from Copilot November 10, 2026 20:18

Copilot started reviewing on behalf of Chris B (llvm-beanz) November 10, 2026 20:19

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Comment thread tools/clang/lib/CodeGen/CGDecl.cpp Resolved

Comment thread tools/clang/lib/CodeGen/CGDecl.cpp Resolved

Apply batched suggestions from code review

13a0075

Co-authored-by: Chris B <beanz@abolishcrlf.org>

Chris B (llvm-beanz) marked this pull request as ready for review November 10, 2026 20:24

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Comment thread tools/clang/lib/SPIRV/DeclResultIdMapper.cpp Resolved

Comment thread tools/clang/lib/Sema/SemaDecl.cpp Resolved

Copilot AI balanced review requested due to automatic review settings November 10, 2026 20:24

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Address PR feedback

5824d39

../tools/clang/test/CodeGenSPIRV/type.string.initializer.hlsl ../tools/clang/test/CodeGenSPIRV/type.string.parameter.hlsl ../tools/clang/test/HLSLFileCheckLit/hlsl/intrinsics/string-constant-ini tializers.hlsl

Copilot AI balanced review requested due to automatic review settings November 11, 2026 18:15

Copilot started reviewing on behalf of Chris B (llvm-beanz) November 11, 2026 18:16

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Fix a few minor diagnostic issues to not produce fatal errors

2119c76

../tools/clang/test/CodeGenSPIRV/type.string.uninitialized.hlsl ../tools/clang/test/HLSLFileCheckLit/hlsl/intrinsics/string-constant-ini tializers.hlsl

Copilot AI balanced review requested due to automatic review settings November 11, 2026 18:47

Copilot started reviewing on behalf of Chris B (llvm-beanz) November 11, 2026 18:49

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Comment thread tools/clang/lib/CodeGen/CGHLSLMS.cpp

Comment on lines +5713 to +5715

if (hlsl::IsStringType(DstQualTy)) {

DXASSERT_NOMSG(hlsl::IsStringType(SrcQualTy));

CGF.Builder.CreateStore(SrcVal, DstPtr);

Handle aggregate casts of strings

2b37f58

../tools/clang/test/HLSLFileCheckLit/hlsl/intrinsics/string-constant-ini tializers.hlsl

Copilot AI balanced review requested due to automatic review settings November 13, 2026 17:18

Copilot started reviewing on behalf of Chris B (llvm-beanz) November 13, 2026 17:19

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Copilot AI balanced review requested due to automatic review settings November 13, 2026 19:26

Copilot started reviewing on behalf of Chris B (llvm-beanz) November 13, 2026 19:27

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Make strings intangible types - #9108

Make strings intangible types#9108
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