[HLSL] Rewrite semantics parsing

This is the first PR to implement the semantics proposal:
https://github.com/llvm/wg-hlsl/blob/main/proposals/0031-semantics.md

This PR focuses on the changes required to handle user semantics, but
tried to be almost NFC.
What changes is the error messages as the semantics case is not kept
when reporting error messages.

You might notice the SV_GroupIndex semantic is not properly validated as
are others. This is an existing behavior that we'll need to fix, but
wanted to keep this separated from this rewrite to stay as-close as an
NFC as possible.

The next PR will add support on the different kinds of I/O we can have
using semantics (input, inout param, structs).

Author: Keenuts

clang/include/clang/AST/Attr.h

@@ -232,6 +232,41 @@ class HLSLAnnotationAttr : public InheritableAttr {
   }
 };
 
+class HLSLSemanticAttr : public HLSLAnnotationAttr {
+  unsigned SemanticIndex : 30;
+  LLVM_PREFERRED_TYPE(bool)
+  unsigned SemanticIndexable : 1;
+  LLVM_PREFERRED_TYPE(bool)
+  unsigned SemanticExplicitIndex : 1;
+
+protected:
+  HLSLSemanticAttr(ASTContext &Context, const AttributeCommonInfo &CommonInfo,
+                   attr::Kind AK, bool IsLateParsed,
+                   bool InheritEvenIfAlreadyPresent, bool SemanticIndexable)
+      : HLSLAnnotationAttr(Context, CommonInfo, AK, IsLateParsed,
+                           InheritEvenIfAlreadyPresent) {
+    this->SemanticIndexable = SemanticIndexable;
+    this->SemanticIndex = 0;
+    this->SemanticExplicitIndex = 0;
+  }
+
+public:
+  bool isSemanticIndexable() const { return SemanticIndexable; }
+
+  void setSemanticIndex(unsigned SemanticIndex) {
+    this->SemanticIndex = SemanticIndex;
+    this->SemanticExplicitIndex = true;
+  }
+
+  unsigned getSemanticIndex() const { return SemanticIndex; }
+
+  // Implement isa/cast/dyncast/etc.
+  static bool classof(const Attr *A) {
+    return A->getKind() >= attr::FirstHLSLSemanticAttr &&
+           A->getKind() <= attr::LastHLSLSemanticAttr;
+  }
+};
+
 /// A parameter attribute which changes the argument-passing ABI rule
 /// for the parameter.
 class ParameterABIAttr : public InheritableParamAttr {

clang/include/clang/Basic/Attr.td

@@ -396,7 +396,7 @@ class ClangGCC<string name, bit allowInC = 1, int version = 1>
 }
 
 // HLSL Annotation spellings
-class HLSLAnnotation<string name> : Spelling<name, "HLSLAnnotation">;
+class HLSLAnnotation<string name> : Spelling<name, "HLSLAnnotation"> {}
 
 class Accessor<string name, list<Spelling> spellings> {
   string Name = name;
@@ -779,6 +779,16 @@ class DeclOrStmtAttr : InheritableAttr;
 /// An attribute class for HLSL Annotations.
 class HLSLAnnotationAttr : InheritableAttr;
 
+class HLSLSemanticAttr<bit Indexable> : HLSLAnnotationAttr {
+  bit SemanticIndexable = Indexable;
+  int SemanticIndex = 0;
+  bit SemanticExplicitIndex = 0;
+
+  let Spellings = [];
+  let Subjects = SubjectList<[ParmVar, Field, Function]>;
+  let LangOpts = [HLSL];
+}
+
 /// A target-specific attribute.  This class is meant to be used as a mixin
 /// with InheritableAttr or Attr depending on the attribute's needs.
 class TargetSpecificAttr<TargetSpec target> {
@@ -4873,27 +4883,6 @@ def HLSLNumThreads: InheritableAttr {
   let Documentation = [NumThreadsDocs];
 }
 
-def HLSLSV_GroupThreadID: HLSLAnnotationAttr {
-  let Spellings = [HLSLAnnotation<"sv_groupthreadid">];
-  let Subjects = SubjectList<[ParmVar, Field]>;
-  let LangOpts = [HLSL];
-  let Documentation = [HLSLSV_GroupThreadIDDocs];
-}
-
-def HLSLSV_GroupID: HLSLAnnotationAttr {
-  let Spellings = [HLSLAnnotation<"sv_groupid">];
-  let Subjects = SubjectList<[ParmVar, Field]>;
-  let LangOpts = [HLSL];
-  let Documentation = [HLSLSV_GroupIDDocs];
-}
-
-def HLSLSV_GroupIndex: HLSLAnnotationAttr {
-  let Spellings = [HLSLAnnotation<"sv_groupindex">];
-  let Subjects = SubjectList<[ParmVar, GlobalVar]>;
-  let LangOpts = [HLSL];
-  let Documentation = [HLSLSV_GroupIndexDocs];
-}
-
 def HLSLResourceBinding: InheritableAttr {
   let Spellings = [HLSLAnnotation<"register">];
   let Subjects = SubjectList<[HLSLBufferObj, ExternalGlobalVar], ErrorDiag>;
@@ -4943,13 +4932,35 @@ def HLSLResourceBinding: InheritableAttr {
   }];
 }
 
-def HLSLSV_Position : HLSLAnnotationAttr {
-  let Spellings = [HLSLAnnotation<"sv_position">];
-  let Subjects = SubjectList<[ParmVar, Field]>;
+def HLSLUnparsedSemantic : HLSLAnnotationAttr {
+  let Spellings = [];
+  let Args = [DefaultIntArgument<"Index", 0>,
+              DefaultBoolArgument<"ExplicitIndex", 0>];
+  let Subjects = SubjectList<[ParmVar, Field, Function]>;
   let LangOpts = [HLSL];
+  let Documentation = [InternalOnly];
+}
+
+def HLSLSV_Position : HLSLSemanticAttr</* Indexable= */ 1> {
   let Documentation = [HLSLSV_PositionDocs];
 }
 
+def HLSLSV_GroupThreadID : HLSLSemanticAttr</* Indexable= */ 0> {
+  let Documentation = [HLSLSV_GroupThreadIDDocs];
+}
+
+def HLSLSV_GroupID : HLSLSemanticAttr</* Indexable= */ 0> {
+  let Documentation = [HLSLSV_GroupIDDocs];
+}
+
+def HLSLSV_GroupIndex : HLSLSemanticAttr</* Indexable= */ 0> {
+  let Documentation = [HLSLSV_GroupIndexDocs];
+}
+
+def HLSLSV_DispatchThreadID : HLSLSemanticAttr</* Indexable= */ 0> {
+  let Documentation = [HLSLSV_DispatchThreadIDDocs];
+}
+
 def HLSLPackOffset: HLSLAnnotationAttr {
   let Spellings = [HLSLAnnotation<"packoffset">];
   let LangOpts = [HLSL];
@@ -4962,13 +4973,6 @@ def HLSLPackOffset: HLSLAnnotationAttr {
   }];
 }
 
-def HLSLSV_DispatchThreadID: HLSLAnnotationAttr {
-  let Spellings = [HLSLAnnotation<"sv_dispatchthreadid">];
-  let Subjects = SubjectList<[ParmVar, Field]>;
-  let LangOpts = [HLSL];
-  let Documentation = [HLSLSV_DispatchThreadIDDocs];
-}
-
 def HLSLShader : InheritableAttr {
   let Spellings = [Microsoft<"shader">];
   let Subjects = SubjectList<[HLSLEntry]>;

clang/include/clang/Basic/DiagnosticFrontendKinds.td

@@ -393,6 +393,14 @@ def warn_hlsl_langstd_minimal :
           "recommend using %1 instead">,
   InGroup<HLSLDXCCompat>;
 
+def err_hlsl_semantic_index_overlap : Error<"semantic index overlap %0">;
+
+def err_hlsl_semantic_missing : Error<"semantic annotations must be present "
+                                      "for all input and outputs of an entry "
+                                      "function or patch constant function">;
+
+def note_hlsl_semantic_used_here : Note<"%0 used here">;
+
 // ClangIR frontend errors
 def err_cir_to_cir_transform_failed : Error<
     "CIR-to-CIR transformation failed">, DefaultFatal;

clang/include/clang/Basic/DiagnosticParseKinds.td

@@ -1851,9 +1851,8 @@ def note_max_tokens_total_override : Note<"total token limit set here">;
 
 def err_expected_semantic_identifier : Error<
   "expected HLSL Semantic identifier">;
-def err_invalid_declaration_in_hlsl_buffer : Error<
-  "invalid declaration inside %select{tbuffer|cbuffer}0">;
-def err_unknown_hlsl_semantic : Error<"unknown HLSL semantic %0">;
+def err_invalid_declaration_in_hlsl_buffer
+    : Error<"invalid declaration inside %select{tbuffer|cbuffer}0">;
 def err_hlsl_separate_attr_arg_and_number : Error<"wrong argument format for hlsl attribute, use %0 instead">;
 def ext_hlsl_access_specifiers : ExtWarn<
   "access specifiers are a clang HLSL extension">,

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -13058,6 +13058,11 @@ 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 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">;
 

clang/include/clang/Parse/Parser.h

@@ -5188,6 +5188,14 @@ class Parser : public CodeCompletionHandler {
       ParseHLSLAnnotations(Attrs, EndLoc);
   }
 
+  struct ParsedSemantic {
+    StringRef Name;
+    unsigned Index;
+    bool Explicit;
+  };
+
+  ParsedSemantic ParseHLSLSemantic();
+
   void ParseHLSLAnnotations(ParsedAttributes &Attrs,
                             SourceLocation *EndLoc = nullptr,
                             bool CouldBeBitField = false);

clang/include/clang/Sema/SemaHLSL.h

@@ -17,6 +17,7 @@
 #include "clang/AST/Attr.h"
 #include "clang/AST/Type.h"
 #include "clang/AST/TypeLoc.h"
+#include "clang/Basic/DiagnosticSema.h"
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Sema/SemaBase.h"
 #include "llvm/ADT/SmallVector.h"
@@ -129,6 +130,7 @@ 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(
@@ -161,16 +163,31 @@ class SemaHLSL : public SemaBase {
   void handleNumThreadsAttr(Decl *D, const ParsedAttr &AL);
   void handleWaveSizeAttr(Decl *D, const ParsedAttr &AL);
   void handleVkConstantIdAttr(Decl *D, const ParsedAttr &AL);
-  void handleSV_DispatchThreadIDAttr(Decl *D, const ParsedAttr &AL);
-  void handleSV_GroupThreadIDAttr(Decl *D, const ParsedAttr &AL);
-  void handleSV_GroupIDAttr(Decl *D, const ParsedAttr &AL);
-  void handleSV_PositionAttr(Decl *D, const ParsedAttr &AL);
   void handlePackOffsetAttr(Decl *D, const ParsedAttr &AL);
   void handleShaderAttr(Decl *D, const ParsedAttr &AL);
   void handleResourceBindingAttr(Decl *D, const ParsedAttr &AL);
   void handleParamModifierAttr(Decl *D, const ParsedAttr &AL);
   bool handleResourceTypeAttr(QualType T, const ParsedAttr &AL);
 
+  template <typename T>
+  T *createSemanticAttr(const ParsedAttr &AL,
+                        std::optional<unsigned> Location) {
+    T *Attr = ::new (getASTContext()) T(getASTContext(), AL);
+    if (Attr->isSemanticIndexable())
+      Attr->setSemanticIndex(Location ? *Location : 0);
+    else if (Location.has_value()) {
+      Diag(Attr->getLocation(), diag::err_hlsl_semantic_indexing_not_supported)
+          << Attr->getAttrName()->getName();
+      return nullptr;
+    }
+
+    return Attr;
+  }
+
+  void diagnoseSystemSemanticAttr(Decl *D, const ParsedAttr &AL,
+                                  std::optional<unsigned> Index);
+  void handleSemanticAttr(Decl *D, const ParsedAttr &AL);
+
   void handleVkExtBuiltinInputAttr(Decl *D, const ParsedAttr &AL);
 
   bool CheckBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall);

clang/lib/Basic/Attributes.cpp

@@ -189,7 +189,12 @@ AttributeCommonInfo::Kind
 AttributeCommonInfo::getParsedKind(const IdentifierInfo *Name,
                                    const IdentifierInfo *ScopeName,
                                    Syntax SyntaxUsed) {
-  return ::getAttrKind(normalizeName(Name, ScopeName, SyntaxUsed), SyntaxUsed);
+  AttributeCommonInfo::Kind Kind =
+      ::getAttrKind(normalizeName(Name, ScopeName, SyntaxUsed), SyntaxUsed);
+  if (SyntaxUsed == AS_HLSLAnnotation &&
+      Kind == AttributeCommonInfo::Kind::UnknownAttribute)
+    return AttributeCommonInfo::Kind::AT_HLSLUnparsedSemantic;
+  return Kind;
 }
 
 AttributeCommonInfo::AttrArgsInfo