[clang] Ensure that Attr::Create(Implicit) chooses a valid syntax

The purpose of this patch and follow-on patches is to ensure that
AttributeCommonInfos always have a syntax that is appropriate for
their kind (i.e. that it matches one of the entries in Attr.td).

The attribute-specific Create and CreateImplicit methods had four
overloads, based on their tail arguments:

(1) no extra arguments
(2) an AttributeCommonInfo
(3) a SourceRange
(4) a SourceRange, a syntax, and (where necessary) a spelling

When (4) had a spelling argument, it defaulted to
SpellingNotCalculated.

One disadvantage of this was that (1) and (3) zero-initialized
the syntax field of the AttributeCommonInfo, which corresponds
to AS_GNU.  But AS_GNU isn't always listed as a possibility
in Attr.td.

This patch therefore removes (1) and (3) and instead provides
the same functionality using default arguments on (4) (a bit
like the existing default argument for the spelling).
The default syntax is taken from the attribute's first valid
spelling.

Doing that raises the question: what should happen for attributes
like AlignNatural and CUDAInvalidTarget that are only ever created
implicitly, and so have no source-code manifestation at all?
The patch adds a new AS_Implicit "syntax" for that case.
The patch also removes the syntax argument for these attributes,
since the syntax must always be AS_Implicit.

For similar reasons, the patch removes the syntax argument if
there is exactly one valid spelling.

Doing this means that AttributeCommonInfo no longer needs the
single-argument constructors.  It is always given a syntax instead.

Differential Revision: https://reviews.llvm.org/D148101

clang/include/clang/Basic/Attr.td

@@ -834,7 +834,7 @@ def Annotate : InheritableParamAttr {
     return AnnotateAttr::Create(Ctx, Annotation, nullptr, 0, CommonInfo);
   }
   static AnnotateAttr *CreateImplicit(ASTContext &Ctx, llvm::StringRef Annotation, \
-              const AttributeCommonInfo &CommonInfo = AttributeCommonInfo{SourceRange{}}) {
+              const AttributeCommonInfo &CommonInfo) {
     return AnnotateAttr::CreateImplicit(Ctx, Annotation, nullptr, 0, CommonInfo);
   }
   }];

clang/include/clang/Basic/AttributeCommonInfo.h

@@ -51,6 +51,10 @@ class AttributeCommonInfo {
 
     /// <vardecl> : <semantic>
     AS_HLSLSemantic,
+
+    /// The attibute has no source code manifestation and is only created
+    /// implicitly.
+    AS_Implicit
   };
   enum Kind {
 #define PARSED_ATTR(NAME) AT_##NAME,
@@ -76,14 +80,6 @@ class AttributeCommonInfo {
   static constexpr unsigned SpellingNotCalculated = 0xf;
 
 public:
-  explicit AttributeCommonInfo(SourceRange AttrRange)
-      : AttrRange(AttrRange), ScopeLoc(), AttrKind(0), SyntaxUsed(0),
-        SpellingIndex(SpellingNotCalculated) {}
-
-  explicit AttributeCommonInfo(SourceLocation AttrLoc)
-      : AttrRange(AttrLoc), ScopeLoc(), AttrKind(0), SyntaxUsed(0),
-        SpellingIndex(SpellingNotCalculated) {}
-
   AttributeCommonInfo(const IdentifierInfo *AttrName,
                       const IdentifierInfo *ScopeName, SourceRange AttrRange,
                       SourceLocation ScopeLoc, Syntax SyntaxUsed)

clang/lib/Sema/SemaDecl.cpp

@@ -10125,9 +10125,8 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
   NewFD->setParams(Params);
 
   if (D.getDeclSpec().isNoreturnSpecified())
-    NewFD->addAttr(C11NoReturnAttr::Create(Context,
-                                           D.getDeclSpec().getNoreturnSpecLoc(),
-                                           AttributeCommonInfo::AS_Keyword));
+    NewFD->addAttr(
+        C11NoReturnAttr::Create(Context, D.getDeclSpec().getNoreturnSpecLoc()));
 
   // Functions returning a variably modified type violate C99 6.7.5.2p2
   // because all functions have linkage.
@@ -10142,7 +10141,7 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
       !NewFD->hasAttr<SectionAttr>())
     NewFD->addAttr(PragmaClangTextSectionAttr::CreateImplicit(
         Context, PragmaClangTextSection.SectionName,
-        PragmaClangTextSection.PragmaLocation, AttributeCommonInfo::AS_Pragma));
+        PragmaClangTextSection.PragmaLocation));
 
   // Apply an implicit SectionAttr if #pragma code_seg is active.
   if (CodeSegStack.CurrentValue && D.isFunctionDefinition() &&
@@ -10163,8 +10162,7 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
   if (StrictGuardStackCheckStack.CurrentValue && D.isFunctionDefinition() &&
       !NewFD->hasAttr<StrictGuardStackCheckAttr>())
     NewFD->addAttr(StrictGuardStackCheckAttr::CreateImplicit(
-        Context, PragmaClangTextSection.PragmaLocation,
-        AttributeCommonInfo::AS_Pragma));
+        Context, PragmaClangTextSection.PragmaLocation));
 
   // Apply an implicit CodeSegAttr from class declspec or
   // apply an implicit SectionAttr from #pragma code_seg if active.
@@ -14210,8 +14208,7 @@ void Sema::CheckCompleteVariableDeclaration(VarDecl *var) {
     // attribute.
     if (CurInitSeg && var->getInit())
       var->addAttr(InitSegAttr::CreateImplicit(Context, CurInitSeg->getString(),
-                                               CurInitSegLoc,
-                                               AttributeCommonInfo::AS_Pragma));
+                                               CurInitSegLoc));
   }
 
   // All the following checks are C++ only.
@@ -14313,23 +14310,19 @@ void Sema::FinalizeDeclaration(Decl *ThisDecl) {
     if (PragmaClangBSSSection.Valid)
       VD->addAttr(PragmaClangBSSSectionAttr::CreateImplicit(
           Context, PragmaClangBSSSection.SectionName,
-          PragmaClangBSSSection.PragmaLocation,
-          AttributeCommonInfo::AS_Pragma));
+          PragmaClangBSSSection.PragmaLocation));
     if (PragmaClangDataSection.Valid)
       VD->addAttr(PragmaClangDataSectionAttr::CreateImplicit(
           Context, PragmaClangDataSection.SectionName,
-          PragmaClangDataSection.PragmaLocation,
-          AttributeCommonInfo::AS_Pragma));
+          PragmaClangDataSection.PragmaLocation));
     if (PragmaClangRodataSection.Valid)
       VD->addAttr(PragmaClangRodataSectionAttr::CreateImplicit(
           Context, PragmaClangRodataSection.SectionName,
-          PragmaClangRodataSection.PragmaLocation,
-          AttributeCommonInfo::AS_Pragma));
+          PragmaClangRodataSection.PragmaLocation));
     if (PragmaClangRelroSection.Valid)
       VD->addAttr(PragmaClangRelroSectionAttr::CreateImplicit(
           Context, PragmaClangRelroSection.SectionName,
-          PragmaClangRelroSection.PragmaLocation,
-          AttributeCommonInfo::AS_Pragma));
+          PragmaClangRelroSection.PragmaLocation));
   }
 
   if (auto *DD = dyn_cast<DecompositionDecl>(ThisDecl)) {

clang/lib/Sema/SemaDeclCXX.cpp

@@ -3567,8 +3567,7 @@ Sema::ActOnCXXMemberDeclarator(Scope *S, AccessSpecifier AS, Declarator &D,
   }
 
   if (VS.isOverrideSpecified())
-    Member->addAttr(OverrideAttr::Create(Context, VS.getOverrideLoc(),
-                                         AttributeCommonInfo::AS_Keyword));
+    Member->addAttr(OverrideAttr::Create(Context, VS.getOverrideLoc()));
   if (VS.isFinalSpecified())
     Member->addAttr(FinalAttr::Create(
         Context, VS.getFinalLoc(), AttributeCommonInfo::AS_Keyword,

clang/lib/Serialization/ASTReaderDecl.cpp

@@ -4617,9 +4617,8 @@ void ASTDeclReader::UpdateDecl(Decl *D,
       break;
 
     case UPD_DECL_MARKED_OPENMP_THREADPRIVATE:
-      D->addAttr(OMPThreadPrivateDeclAttr::CreateImplicit(
-          Reader.getContext(), readSourceRange(),
-          AttributeCommonInfo::AS_Pragma));
+      D->addAttr(OMPThreadPrivateDeclAttr::CreateImplicit(Reader.getContext(),
+                                                          readSourceRange()));
       break;
 
     case UPD_DECL_MARKED_OPENMP_ALLOCATE: {
@@ -4629,8 +4628,7 @@ void ASTDeclReader::UpdateDecl(Decl *D,
       Expr *Alignment = Record.readExpr();
       SourceRange SR = readSourceRange();
       D->addAttr(OMPAllocateDeclAttr::CreateImplicit(
-          Reader.getContext(), AllocatorKind, Allocator, Alignment, SR,
-          AttributeCommonInfo::AS_Pragma));
+          Reader.getContext(), AllocatorKind, Allocator, Alignment, SR));
       break;
     }
 
@@ -4651,7 +4649,7 @@ void ASTDeclReader::UpdateDecl(Decl *D,
       unsigned Level = Record.readInt();
       D->addAttr(OMPDeclareTargetDeclAttr::CreateImplicit(
           Reader.getContext(), MapType, DevType, IndirectE, Indirect, Level,
-          readSourceRange(), AttributeCommonInfo::AS_Pragma));
+          readSourceRange()));
       break;
     }
 

clang/unittests/AST/DeclTest.cpp

@@ -88,12 +88,8 @@ TEST(Decl, AsmLabelAttr) {
   NamedDecl *DeclG = *(++DeclS->method_begin());
 
   // Attach asm labels to the decls: one literal, and one not.
-  DeclF->addAttr(::new (Ctx) AsmLabelAttr(
-      Ctx, AttributeCommonInfo{SourceLocation()}, "foo",
-      /*LiteralLabel=*/true));
-  DeclG->addAttr(::new (Ctx) AsmLabelAttr(
-      Ctx, AttributeCommonInfo{SourceLocation()}, "goo",
-      /*LiteralLabel=*/false));
+  DeclF->addAttr(AsmLabelAttr::Create(Ctx, "foo", /*LiteralLabel=*/true));
+  DeclG->addAttr(AsmLabelAttr::Create(Ctx, "goo", /*LiteralLabel=*/false));
 
   // Mangle the decl names.
   std::string MangleF, MangleG;

clang/utils/TableGen/ClangAttrEmitter.cpp

@@ -2505,15 +2505,8 @@ static void emitAttributes(RecordKeeper &Records, raw_ostream &OS,
           return &R == P.second;
         });
 
-    enum class CreateKind {
-      WithAttributeCommonInfo,
-      WithSourceRange,
-      WithNoArgs,
-    };
-
     // Emit CreateImplicit factory methods.
-    auto emitCreate = [&](bool Implicit, bool DelayedArgsOnly,
-                          bool emitFake, CreateKind Kind) {
+    auto emitCreate = [&](bool Implicit, bool DelayedArgsOnly, bool emitFake) {
       if (Header)
         OS << "  static ";
       OS << R.getName() << "Attr *";
@@ -2537,10 +2530,7 @@ static void emitAttributes(RecordKeeper &Records, raw_ostream &OS,
         OS << ", ";
         DelayedArgs->writeCtorParameters(OS);
       }
-      if (Kind == CreateKind::WithAttributeCommonInfo)
-        OS << ", const AttributeCommonInfo &CommonInfo";
-      else if (Kind == CreateKind::WithSourceRange)
-        OS << ", SourceRange R";
+      OS << ", const AttributeCommonInfo &CommonInfo";
       OS << ")";
       if (Header) {
         OS << ";\n";
@@ -2549,12 +2539,7 @@ static void emitAttributes(RecordKeeper &Records, raw_ostream &OS,
 
       OS << " {\n";
       OS << "  auto *A = new (Ctx) " << R.getName();
-      if (Kind == CreateKind::WithAttributeCommonInfo)
-        OS << "Attr(Ctx, CommonInfo";
-      else if (Kind == CreateKind::WithSourceRange)
-        OS << "Attr(Ctx, AttributeCommonInfo{R}";
-      else if (Kind == CreateKind::WithNoArgs)
-        OS << "Attr(Ctx, AttributeCommonInfo{SourceLocation{}}";
+      OS << "Attr(Ctx, CommonInfo";
 
       if (!DelayedArgsOnly) {
         for (auto const &ai : Args) {
@@ -2606,7 +2591,14 @@ static void emitAttributes(RecordKeeper &Records, raw_ostream &OS,
         OS << ", ";
         DelayedArgs->writeCtorParameters(OS);
       }
-      OS << ", SourceRange Range, AttributeCommonInfo::Syntax Syntax";
+      OS << ", SourceRange Range";
+      if (Header)
+        OS << " = {}";
+      if (Spellings.size() > 1) {
+        OS << ", AttributeCommonInfo::Syntax Syntax";
+        if (Header)
+          OS << " = AttributeCommonInfo::AS_" << Spellings[0].variety();
+      }
       if (!ElideSpelling) {
         OS << ", " << R.getName() << "Attr::Spelling S";
         if (Header)
@@ -2626,7 +2618,13 @@ static void emitAttributes(RecordKeeper &Records, raw_ostream &OS,
       else
         OS << "NoSemaHandlerAttribute";
 
-      OS << ", Syntax";
+      if (Spellings.size() == 0)
+        OS << ", AttributeCommonInfo::AS_Implicit";
+      else if (Spellings.size() == 1)
+        OS << ", AttributeCommonInfo::AS_" << Spellings[0].variety();
+      else
+        OS << ", Syntax";
+
       if (!ElideSpelling)
         OS << ", S";
       OS << ");\n";
@@ -2651,19 +2649,9 @@ static void emitAttributes(RecordKeeper &Records, raw_ostream &OS,
       OS << "}\n\n";
     };
 
-    auto emitBothImplicitAndNonCreates = [&](bool DelayedArgsOnly,
-                                             bool emitFake, CreateKind Kind) {
-      emitCreate(true, DelayedArgsOnly, emitFake, Kind);
-      emitCreate(false, DelayedArgsOnly, emitFake, Kind);
-    };
-
     auto emitCreates = [&](bool DelayedArgsOnly, bool emitFake) {
-      emitBothImplicitAndNonCreates(DelayedArgsOnly, emitFake,
-                                    CreateKind::WithNoArgs);
-      emitBothImplicitAndNonCreates(DelayedArgsOnly, emitFake,
-                                    CreateKind::WithAttributeCommonInfo);
-      emitBothImplicitAndNonCreates(DelayedArgsOnly, emitFake,
-                                    CreateKind::WithSourceRange);
+      emitCreate(true, DelayedArgsOnly, emitFake);
+      emitCreate(false, DelayedArgsOnly, emitFake);
       emitCreateNoCI(true, DelayedArgsOnly, emitFake);
       emitCreateNoCI(false, DelayedArgsOnly, emitFake);
     };
@@ -3468,6 +3456,10 @@ void EmitClangAttrHasAttrImpl(RecordKeeper &Records, raw_ostream &OS) {
   OS << "case AttributeCommonInfo::Syntax::AS_ContextSensitiveKeyword:\n";
   OS << "  llvm_unreachable(\"hasAttribute not supported for keyword\");\n";
   OS << "  return 0;\n";
+  OS << "case AttributeCommonInfo::Syntax::AS_Implicit:\n";
+  OS << "  llvm_unreachable (\"hasAttribute not supported for "
+        "AS_Implicit\");\n";
+  OS << "  return 0;\n";
 
   OS << "}\n";
 }