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[HLSL] Allow input semantics on structs #159047

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445bdaf
[HLSL] Add support for input semantics in structs
Keenuts Aug 12, 2025
6b55b1e
add maybe_unused on fixme location
Keenuts Sep 9, 2025
29ea2a4
move all diagnostics to sema
Keenuts Sep 15, 2025
5f5c43a
sema: move to a flat attribute list per entrypoint
Keenuts Sep 19, 2025
cb816bd
rename function
Keenuts Sep 19, 2025
bf3a90c
fix AST dump so semantic params are showing
Keenuts Sep 19, 2025
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2 changes: 2 additions & 0 deletions clang/include/clang/Basic/Attr.td
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Original file line number Diff line number Diff line change
Expand Up @@ -787,6 +787,8 @@ class HLSLSemanticAttr<bit Indexable> : HLSLAnnotationAttr {
let Spellings = [];
let Subjects = SubjectList<[ParmVar, Field, Function]>;
let LangOpts = [HLSL];
let Args = [DeclArgument<Named, "Target">, IntArgument<"SemanticIndex">,
BoolArgument<"SemanticExplicitIndex">];
}

/// A target-specific attribute. This class is meant to be used as a mixin
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14 changes: 6 additions & 8 deletions clang/include/clang/Sema/SemaHLSL.h
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Expand Up @@ -174,19 +174,17 @@ class SemaHLSL : public SemaBase {
bool handleResourceTypeAttr(QualType T, const ParsedAttr &AL);

template <typename T>
T *createSemanticAttr(const AttributeCommonInfo &ACI, Decl *TargetDecl,
T *createSemanticAttr(const AttributeCommonInfo &ACI, NamedDecl *TargetDecl,
std::optional<unsigned> Location) {
T *Attr = ::new (getASTContext()) T(getASTContext(), ACI);
T *Attr =
::new (getASTContext()) T(getASTContext(), ACI, TargetDecl,
Location.value_or(0), Location.has_value());

if (Attr->isSemanticIndexable())
Attr->setSemanticIndex(Location ? *Location : 0);
else if (Location.has_value()) {
if (!Attr->isSemanticIndexable() && Location.has_value()) {
Diag(Attr->getLocation(), diag::err_hlsl_semantic_indexing_not_supported)
<< Attr->getAttrName()->getName();
return nullptr;
}

Attr->setTargetDecl(TargetDecl);
return Attr;
}

Expand Down Expand Up @@ -258,7 +256,7 @@ class SemaHLSL : public SemaBase {
void checkSemanticAnnotation(FunctionDecl *EntryPoint, const Decl *Param,
const HLSLSemanticAttr *SemanticAttr);
HLSLSemanticAttr *createSemantic(const SemanticInfo &Semantic,
Decl *TargetDecl);
DeclaratorDecl *TargetDecl);
bool determineActiveSemanticOnScalar(FunctionDecl *FD, DeclaratorDecl *D,
SemanticInfo &ActiveSemantic);
bool determineActiveSemantic(FunctionDecl *FD, DeclaratorDecl *D,
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2 changes: 1 addition & 1 deletion clang/lib/Sema/SemaHLSL.cpp
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Expand Up @@ -770,7 +770,7 @@ void SemaHLSL::ActOnTopLevelFunction(FunctionDecl *FD) {
}

HLSLSemanticAttr *SemaHLSL::createSemantic(const SemanticInfo &Info,
Decl *TargetDecl) {
DeclaratorDecl *TargetDecl) {
std::string SemanticName = Info.Semantic->getAttrName()->getName().upper();

if (SemanticName == "SV_DISPATCHTHREADID") {
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5 changes: 5 additions & 0 deletions clang/test/SemaHLSL/Semantics/entry_parameter.hlsl
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Expand Up @@ -11,4 +11,9 @@ void CSMain(int GI : SV_GroupIndex, uint ID : SV_DispatchThreadID, uint GID : SV
// CHECK-NEXT: HLSLSV_GroupIDAttr
// CHECK-NEXT: ParmVarDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> col:96 GThreadID 'uint'
// CHECK-NEXT: HLSLSV_GroupThreadIDAttr

// CHECK: HLSLSV_GroupIndexAttr 0x{{[0-9a-fA-F]+}} <{{.*}}> ParmVar 0x{{[0-9a-fA-F]+}} 'GI' 'int' 0
// CHECK-NEXT: HLSLSV_DispatchThreadIDAttr 0x{{[0-9a-fA-F]+}} <{{.*}}> ParmVar 0x{{[0-9a-fA-F]+}} 'ID' 'uint':'unsigned int' 0
// CHECK-NEXT: HLSLSV_GroupIDAttr 0x{{[0-9a-fA-F]+}} <{{.*}}> ParmVar 0x{{[0-9a-fA-F]+}} 'GID' 'uint':'unsigned int' 0
// CHECK-NEXT: HLSLSV_GroupThreadIDAttr 0x{{[0-9a-fA-F]+}} <{{.*}}> ParmVar 0x{{[0-9a-fA-F]+}} 'GThreadID' 'uint':'unsigned int' 0
}
4 changes: 3 additions & 1 deletion clang/test/SemaHLSL/Semantics/position.ps.hlsl
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@@ -1,7 +1,9 @@
// RUN: %clang_cc1 -triple dxil-pc-shadermodel6.0-pixel -x hlsl -finclude-default-header -o - %s -ast-dump | FileCheck %s

float4 main(float4 a : SV_Position) {
float4 main(float4 a : SV_Position2) {
// CHECK: FunctionDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> line:[[@LINE-1]]:8 main 'float4 (float4)'
// CHECK-NEXT: ParmVarDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> col:20 a 'float4':'vector<float, 4>'
// CHECK-NEXT: HLSLSV_PositionAttr 0x{{[0-9a-fA-F]+}} <{{.*}}>

// CHECK: HLSLSV_PositionAttr 0x{{[0-9a-fA-F]+}} <{{.*}}> ParmVar 0x{{[0-9a-fA-F]+}} 'a' 'float4':'vector<float, 4>' 2 SemanticExplicitIndex
}
18 changes: 18 additions & 0 deletions clang/test/SemaHLSL/Semantics/position.ps.struct.hlsl
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@@ -0,0 +1,18 @@
// RUN: %clang_cc1 -triple dxil-pc-shadermodel6.0-pixel -x hlsl -finclude-default-header -o - %s -ast-dump | FileCheck %s

struct S {
float4 f0 : SV_Position;
// CHECK: FieldDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> col:10 f0 'float4':'vector<float, 4>'
// CHECK: HLSLSV_PositionAttr 0x{{[0-9a-fA-F]+}} <col:15> <<<NULL>>> 0
float4 f1 : SV_Position3;
// CHECK: FieldDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> col:10 f1 'float4':'vector<float, 4>'
// CHECK: HLSLSV_PositionAttr 0x{{[0-9a-fA-F]+}} <col:15> <<<NULL>>> 3 SemanticExplicitIndex
};

float4 main(S s) {
// CHECK: FunctionDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> line:[[@LINE-1]]:8 main 'float4 (S)'
// CHECK-NEXT: ParmVarDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> col:15 s 'S'

// CHECK: HLSLSV_PositionAttr 0x{{[0-9a-fA-F]+}} <{{.*}}> Field 0x{{[0-9a-fA-F]+}} 'f0' 'float4':'vector<float, 4>' 0
// CHECK: HLSLSV_PositionAttr 0x{{[0-9a-fA-F]+}} <{{.*}}> Field 0x{{[0-9a-fA-F]+}} 'f1' 'float4':'vector<float, 4>' 3 SemanticExplicitIndex
}
11 changes: 11 additions & 0 deletions clang/utils/TableGen/ClangAttrEmitter.cpp
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Expand Up @@ -3078,6 +3078,17 @@ static void emitAttributes(const RecordKeeper &Records, raw_ostream &OS,

OS << " {\n";

// The generator puts the arguments for each attribute in the child class,
// even if those are set in the inherited attribute class (in the TD
// file). This means I cannot access those from the parent class, and have
// to do this weirdness. Maybe the generator should be changed to
// arguments are put in the class they are declared in inside the TD file?
if (HLSLSemantic) {
OS << " if (SemanticExplicitIndex)\n";
OS << " setSemanticIndex(SemanticIndex);\n";
OS << " setTargetDecl(Target);\n";
}

Comment on lines +3081 to +3091
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Someone with more knowledge will have to comment on the best way to do this.

for (auto const &ai : Args) {
if (!shouldEmitArg(ai))
continue;
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