[HLSL] Add support for user semantics

clang/include/clang/AST/Attr.h

@@ -239,6 +239,8 @@ class HLSLSemanticAttr : public HLSLAnnotationAttr {
   LLVM_PREFERRED_TYPE(bool)
   unsigned SemanticExplicitIndex : 1;
 
+  Decl *TargetDecl = nullptr;
+
 protected:
   HLSLSemanticAttr(ASTContext &Context, const AttributeCommonInfo &CommonInfo,
                    attr::Kind AK, bool IsLateParsed,
@@ -259,6 +261,11 @@ class HLSLSemanticAttr : public HLSLAnnotationAttr {
 
   unsigned getSemanticIndex() const { return SemanticIndex; }
 
+  bool isSemanticIndexExplicit() const { return SemanticExplicitIndex; }
+
+  void setTargetDecl(Decl *D) { TargetDecl = D; }
+  Decl *getTargetDecl() const { return TargetDecl; }
+
   // Implement isa/cast/dyncast/etc.
   static bool classof(const Attr *A) {
     return A->getKind() >= attr::FirstHLSLSemanticAttr &&

clang/include/clang/Basic/Attr.td

@@ -4967,6 +4967,10 @@ def HLSLUnparsedSemantic : HLSLAnnotationAttr {
   let Documentation = [InternalOnly];
 }
 
+def HLSLUserSemantic : HLSLSemanticAttr</* Indexable= */ 1> {
+  let Documentation = [InternalOnly];
+}
+
 def HLSLSV_Position : HLSLSemanticAttr</* Indexable= */ 1> {
   let Documentation = [HLSLSV_PositionDocs];
 }

clang/include/clang/Basic/DiagnosticFrontendKinds.td

@@ -400,10 +400,6 @@ def warn_hlsl_langstd_minimal :
           "recommend using %1 instead">,
   InGroup<HLSLDXCCompat>;
 
-def err_hlsl_semantic_missing : Error<"semantic annotations must be present "
-                                      "for all input and outputs of an entry "
-                                      "function or patch constant function">;
-
 // ClangIR frontend errors
 def err_cir_to_cir_transform_failed : Error<
     "CIR-to-CIR transformation failed">, DefaultFatal;

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -13123,13 +13123,15 @@ def err_hlsl_duplicate_parameter_modifier : Error<"duplicate parameter modifier
 def err_hlsl_missing_semantic_annotation : Error<
   "semantic annotations must be present for all parameters of an entry "
   "function or patch constant function">;
+def note_hlsl_semantic_used_here : Note<"%0 used here">;
 def err_hlsl_unknown_semantic : Error<"unknown HLSL semantic %0">;
 def err_hlsl_semantic_output_not_supported
     : Error<"semantic %0 does not support output">;
 def err_hlsl_semantic_indexing_not_supported
     : Error<"semantic %0 does not allow indexing">;
 def err_hlsl_init_priority_unsupported : Error<
   "initializer priorities are not supported in HLSL">;
+def err_hlsl_semantic_index_overlap : Error<"semantic index overlap %0">;
 
 def warn_hlsl_user_defined_type_missing_member: Warning<"binding type '%select{t|u|b|s|c}0' only applies to types containing %select{SRV resources|UAV resources|constant buffer resources|sampler state|numeric types}0">, InGroup<LegacyConstantRegisterBinding>;
 def err_hlsl_binding_type_mismatch: Error<"binding type '%select{t|u|b|s|c}0' only applies to %select{SRV resources|UAV resources|constant buffer resources|sampler state|numeric variables in the global scope}0">;

clang/include/clang/Sema/SemaHLSL.h

@@ -20,9 +20,12 @@
 #include "clang/Basic/DiagnosticSema.h"
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Sema/SemaBase.h"
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringSet.h"
 #include "llvm/TargetParser/Triple.h"
 #include <initializer_list>
+#include <unordered_set>
 
 namespace clang {
 class AttributeCommonInfo;
@@ -130,9 +133,6 @@ class SemaHLSL : public SemaBase {
   bool ActOnUninitializedVarDecl(VarDecl *D);
   void ActOnEndOfTranslationUnit(TranslationUnitDecl *TU);
   void CheckEntryPoint(FunctionDecl *FD);
-  bool isSemanticValid(FunctionDecl *FD, DeclaratorDecl *D);
-  void CheckSemanticAnnotation(FunctionDecl *EntryPoint, const Decl *Param,
-                               const HLSLAnnotationAttr *AnnotationAttr);
   void DiagnoseAttrStageMismatch(
       const Attr *A, llvm::Triple::EnvironmentType Stage,
       std::initializer_list<llvm::Triple::EnvironmentType> AllowedStages);
@@ -177,9 +177,10 @@ class SemaHLSL : public SemaBase {
   bool handleResourceTypeAttr(QualType T, const ParsedAttr &AL);
 
   template <typename T>
-  T *createSemanticAttr(const ParsedAttr &AL,
+  T *createSemanticAttr(const AttributeCommonInfo &ACI, Decl *TargetDecl,
                         std::optional<unsigned> Location) {
-    T *Attr = ::new (getASTContext()) T(getASTContext(), AL);
+    T *Attr = ::new (getASTContext()) T(getASTContext(), ACI);
+
     if (Attr->isSemanticIndexable())
       Attr->setSemanticIndex(Location ? *Location : 0);
     else if (Location.has_value()) {
@@ -188,6 +189,7 @@ class SemaHLSL : public SemaBase {
       return nullptr;
     }
 
+    Attr->setTargetDecl(TargetDecl);
     return Attr;
   }
 
@@ -246,10 +248,27 @@ class SemaHLSL : public SemaBase {
 
   IdentifierInfo *RootSigOverrideIdent = nullptr;
 
+  llvm::DenseMap<FunctionDecl *, llvm::StringSet<>> ActiveInputSemantics;
+
+  struct SemanticInfo {
+    HLSLSemanticAttr *Semantic;
+    std::optional<uint32_t> Index;
+  };
+
 private:
   void collectResourceBindingsOnVarDecl(VarDecl *D);
   void collectResourceBindingsOnUserRecordDecl(const VarDecl *VD,
                                                const RecordType *RT);
+
+  void checkSemanticAnnotation(FunctionDecl *EntryPoint, const Decl *Param,
+                               const HLSLSemanticAttr *SemanticAttr);
+  HLSLSemanticAttr *createSemantic(const SemanticInfo &Semantic,
+                                   Decl *TargetDecl);
+  bool isSemanticOnScalarValid(FunctionDecl *FD, DeclaratorDecl *D,
+                               SemanticInfo &ActiveSemantic);
+  bool isSemanticValid(FunctionDecl *FD, DeclaratorDecl *D,
+                       SemanticInfo &ActiveSemantic);
+
   void processExplicitBindingsOnDecl(VarDecl *D);
 
   void diagnoseAvailabilityViolations(TranslationUnitDecl *TU);

clang/lib/CodeGen/CGHLSLRuntime.cpp

@@ -553,6 +553,16 @@ static void addSPIRVBuiltinDecoration(llvm::GlobalVariable *GV,
   GV->addMetadata("spirv.Decorations", *Decoration);
 }
 
+static void addLocationDecoration(llvm::GlobalVariable *GV, unsigned Location) {
+  LLVMContext &Ctx = GV->getContext();
+  IRBuilder<> B(GV->getContext());
+  MDNode *Operands =
+      MDNode::get(Ctx, {ConstantAsMetadata::get(B.getInt32(/* Location */ 30)),
+                        ConstantAsMetadata::get(B.getInt32(Location))});
+  MDNode *Decoration = MDNode::get(Ctx, {Operands});
+  GV->addMetadata("spirv.Decorations", *Decoration);
+}
+
 static llvm::Value *createSPIRVBuiltinLoad(IRBuilder<> &B, llvm::Module &M,
                                            llvm::Type *Ty, const Twine &Name,
                                            unsigned BuiltInID) {
@@ -566,17 +576,79 @@ static llvm::Value *createSPIRVBuiltinLoad(IRBuilder<> &B, llvm::Module &M,
   return B.CreateLoad(Ty, GV);
 }
 
+static llvm::Value *createSPIRVLocationLoad(IRBuilder<> &B, llvm::Module &M,
+                                            llvm::Type *Ty, unsigned Location,
+                                            StringRef Name = "") {
+  auto *GV = new llvm::GlobalVariable(
+      M, Ty, /* isConstant= */ true, llvm::GlobalValue::ExternalLinkage,
+      /* Initializer= */ nullptr, /* Name= */ Name, /* insertBefore= */ nullptr,
+      llvm::GlobalVariable::GeneralDynamicTLSModel,
+      /* AddressSpace */ 7, /* isExternallyInitialized= */ true);
+  GV->setVisibility(llvm::GlobalValue::HiddenVisibility);
+  addLocationDecoration(GV, Location);
+  return B.CreateLoad(Ty, GV);
+}
+
+llvm::Value *
+CGHLSLRuntime::emitSPIRVUserSemanticLoad(llvm::IRBuilder<> &B, llvm::Type *Type,
+                                         HLSLSemanticAttr *Semantic,
+                                         std::optional<unsigned> Index) {
+  Twine BaseName = Twine(Semantic->getAttrName()->getName());
+  Twine VariableName = BaseName.concat(Twine(Index.value_or(0)));
+
+  unsigned Location = SPIRVLastAssignedInputSemanticLocation;
+
+  // DXC completely ignores the semantic/index pair. Location are assigned from
+  // the first semantic to the last.
+  llvm::ArrayType *AT = dyn_cast<llvm::ArrayType>(Type);
+  unsigned ElementCount = AT ? AT->getNumElements() : 1;
+  SPIRVLastAssignedInputSemanticLocation += ElementCount;
+  return createSPIRVLocationLoad(B, CGM.getModule(), Type, Location,
+                                 VariableName.str());
+}
+
 llvm::Value *
-CGHLSLRuntime::emitSystemSemanticLoad(IRBuilder<> &B, llvm::Type *Type,
-                                      const clang::DeclaratorDecl *Decl,
-                                      SemanticInfo &ActiveSemantic) {
-  if (isa<HLSLSV_GroupIndexAttr>(ActiveSemantic.Semantic)) {
+CGHLSLRuntime::emitDXILUserSemanticLoad(llvm::IRBuilder<> &B, llvm::Type *Type,
+                                        HLSLSemanticAttr *Semantic,
+                                        std::optional<unsigned> Index) {
+  Twine BaseName = Twine(Semantic->getAttrName()->getName());
+  Twine VariableName = BaseName.concat(Twine(Index.value_or(0)));
+
+  // DXIL packing rules etc shall be handled here.
+  // FIXME: generate proper sigpoint, index, col, row values.
+  // FIXME: also DXIL loads vectors element by element.
+  SmallVector<Value *> Args{B.getInt32(4), B.getInt32(0), B.getInt32(0),
+                            B.getInt8(0),
+                            llvm::PoisonValue::get(B.getInt32Ty())};
+
+  llvm::Intrinsic::ID IntrinsicID = llvm::Intrinsic::dx_load_input;
+  llvm::Value *Value = B.CreateIntrinsic(/*ReturnType=*/Type, IntrinsicID, Args,
+                                         nullptr, VariableName);
+  return Value;
+}
+
+llvm::Value *CGHLSLRuntime::emitUserSemanticLoad(
+    IRBuilder<> &B, llvm::Type *Type, const clang::DeclaratorDecl *Decl,
+    HLSLSemanticAttr *Semantic, std::optional<unsigned> Index) {
+  if (CGM.getTarget().getTriple().isSPIRV())
+    return emitSPIRVUserSemanticLoad(B, Type, Semantic, Index);
+
+  if (CGM.getTarget().getTriple().isDXIL())
+    return emitDXILUserSemanticLoad(B, Type, Semantic, Index);
+
+  llvm_unreachable("Unsupported target for user-semantic load.");
+}
+
+llvm::Value *CGHLSLRuntime::emitSystemSemanticLoad(
+    IRBuilder<> &B, llvm::Type *Type, const clang::DeclaratorDecl *Decl,
+    Attr *Semantic, std::optional<unsigned> Index) {
+  if (isa<HLSLSV_GroupIndexAttr>(Semantic)) {
     llvm::Function *GroupIndex =
         CGM.getIntrinsic(getFlattenedThreadIdInGroupIntrinsic());
     return B.CreateCall(FunctionCallee(GroupIndex));
   }
 
-  if (isa<HLSLSV_DispatchThreadIDAttr>(ActiveSemantic.Semantic)) {
+  if (isa<HLSLSV_DispatchThreadIDAttr>(Semantic)) {
     llvm::Intrinsic::ID IntrinID = getThreadIdIntrinsic();
     llvm::Function *ThreadIDIntrinsic =
         llvm::Intrinsic::isOverloaded(IntrinID)
@@ -585,7 +657,7 @@ CGHLSLRuntime::emitSystemSemanticLoad(IRBuilder<> &B, llvm::Type *Type,
     return buildVectorInput(B, ThreadIDIntrinsic, Type);
   }
 
-  if (isa<HLSLSV_GroupThreadIDAttr>(ActiveSemantic.Semantic)) {
+  if (isa<HLSLSV_GroupThreadIDAttr>(Semantic)) {
     llvm::Intrinsic::ID IntrinID = getGroupThreadIdIntrinsic();
     llvm::Function *GroupThreadIDIntrinsic =
         llvm::Intrinsic::isOverloaded(IntrinID)
@@ -594,7 +666,7 @@ CGHLSLRuntime::emitSystemSemanticLoad(IRBuilder<> &B, llvm::Type *Type,
     return buildVectorInput(B, GroupThreadIDIntrinsic, Type);
   }
 
-  if (isa<HLSLSV_GroupIDAttr>(ActiveSemantic.Semantic)) {
+  if (isa<HLSLSV_GroupIDAttr>(Semantic)) {
     llvm::Intrinsic::ID IntrinID = getGroupIdIntrinsic();
     llvm::Function *GroupIDIntrinsic =
         llvm::Intrinsic::isOverloaded(IntrinID)
@@ -603,8 +675,7 @@ CGHLSLRuntime::emitSystemSemanticLoad(IRBuilder<> &B, llvm::Type *Type,
     return buildVectorInput(B, GroupIDIntrinsic, Type);
   }
 
-  if (HLSLSV_PositionAttr *S =
-          dyn_cast<HLSLSV_PositionAttr>(ActiveSemantic.Semantic)) {
+  if (HLSLSV_PositionAttr *S = dyn_cast<HLSLSV_PositionAttr>(Semantic)) {
     if (CGM.getTriple().getEnvironment() == Triple::EnvironmentType::Pixel)
       return createSPIRVBuiltinLoad(B, CGM.getModule(), Type,
                                     S->getAttrName()->getName(),
@@ -615,29 +686,59 @@ CGHLSLRuntime::emitSystemSemanticLoad(IRBuilder<> &B, llvm::Type *Type,
 }
 
 llvm::Value *
-CGHLSLRuntime::handleScalarSemanticLoad(IRBuilder<> &B, llvm::Type *Type,
-                                        const clang::DeclaratorDecl *Decl,
-                                        SemanticInfo &ActiveSemantic) {
-
-  if (!ActiveSemantic.Semantic) {
-    ActiveSemantic.Semantic = Decl->getAttr<HLSLSemanticAttr>();
-    if (!ActiveSemantic.Semantic) {
-      CGM.getDiags().Report(Decl->getInnerLocStart(),
-                            diag::err_hlsl_semantic_missing);
-      return nullptr;
+CGHLSLRuntime::handleScalarSemanticLoad(IRBuilder<> &B, const FunctionDecl *FD,
+                                        llvm::Type *Type,
+                                        const clang::DeclaratorDecl *Decl) {
+
+  HLSLSemanticAttr *Semantic = nullptr;
+  for (HLSLSemanticAttr *Item : FD->specific_attrs<HLSLSemanticAttr>()) {
+    if (Item->getTargetDecl() == Decl) {
+      Semantic = Item;
+      break;
     }
-    ActiveSemantic.Index = ActiveSemantic.Semantic->getSemanticIndex();
   }
+  // Sema must create one attribute per scalar field.
+  assert(Semantic);
 
-  return emitSystemSemanticLoad(B, Type, Decl, ActiveSemantic);
+  std::optional<unsigned> Index = std::nullopt;
+  if (Semantic->isSemanticIndexExplicit())
+    Index = Semantic->getSemanticIndex();
+
+  if (auto *UserSemantic = dyn_cast<HLSLUserSemanticAttr>(Semantic))
+    return emitUserSemanticLoad(B, Type, Decl, Semantic, Index);
+  return emitSystemSemanticLoad(B, Type, Decl, Semantic, Index);
 }
 
 llvm::Value *
-CGHLSLRuntime::handleSemanticLoad(IRBuilder<> &B, llvm::Type *Type,
-                                  const clang::DeclaratorDecl *Decl,
-                                  SemanticInfo &ActiveSemantic) {
-  assert(!Type->isStructTy());
-  return handleScalarSemanticLoad(B, Type, Decl, ActiveSemantic);
+CGHLSLRuntime::handleStructSemanticLoad(IRBuilder<> &B, const FunctionDecl *FD,
+                                        llvm::Type *Type,
+                                        const clang::DeclaratorDecl *Decl) {
+  const llvm::StructType *ST = cast<StructType>(Type);
+  const clang::RecordDecl *RD = Decl->getType()->getAsRecordDecl();
+
+  assert(std::distance(RD->field_begin(), RD->field_end()) ==
+         ST->getNumElements());
+
+  llvm::Value *Aggregate = llvm::PoisonValue::get(Type);
+  auto FieldDecl = RD->field_begin();
+  for (unsigned I = 0; I < ST->getNumElements(); ++I) {
+    llvm::Value *ChildValue =
+        handleSemanticLoad(B, FD, ST->getElementType(I), *FieldDecl);
+    assert(ChildValue);
+    Aggregate = B.CreateInsertValue(Aggregate, ChildValue, I);
+    ++FieldDecl;
+  }
+
+  return Aggregate;
+}
+
+llvm::Value *
+CGHLSLRuntime::handleSemanticLoad(IRBuilder<> &B, const FunctionDecl *FD,
+                                  llvm::Type *Type,
+                                  const clang::DeclaratorDecl *Decl) {
+  if (Type->isStructTy())
+    return handleStructSemanticLoad(B, FD, Type, Decl);
+  return handleScalarSemanticLoad(B, FD, Type, Decl);
 }
 
 void CGHLSLRuntime::emitEntryFunction(const FunctionDecl *FD,
@@ -684,8 +785,25 @@ void CGHLSLRuntime::emitEntryFunction(const FunctionDecl *FD,
     }
 
     const ParmVarDecl *PD = FD->getParamDecl(Param.getArgNo() - SRetOffset);
-    SemanticInfo ActiveSemantic = {nullptr, 0};
-    Args.push_back(handleSemanticLoad(B, Param.getType(), PD, ActiveSemantic));
+    llvm::Value *SemanticValue = nullptr;
+    if ([[maybe_unused]] HLSLParamModifierAttr *MA =
+            PD->getAttr<HLSLParamModifierAttr>()) {
+      llvm_unreachable("Not handled yet");
+    } else {
+      llvm::Type *ParamType =
+          Param.hasByValAttr() ? Param.getParamByValType() : Param.getType();
+      SemanticValue = handleSemanticLoad(B, FD, ParamType, PD);
+      if (!SemanticValue)
+        return;
+      if (Param.hasByValAttr()) {
+        llvm::Value *Var = B.CreateAlloca(Param.getParamByValType());
+        B.CreateStore(SemanticValue, Var);
+        SemanticValue = Var;
+      }
+    }
+
+    assert(SemanticValue);
+    Args.push_back(SemanticValue);
   }
 
   CallInst *CI = B.CreateCall(FunctionCallee(Fn), Args, OB);