Ignore the "novtable" declspec when not using the Microsoft C++ ABI.

Clang used to silently ignore __declspec(novtable). It is implemented
now, but leaving the vtable uninitialized does not work when using the
Itanium ABI, where the class layout for complex class hierarchies is
stored in the vtable. It might be possible to honor the novtable
attribute in some simple cases and either report an error or ignore
it in more complex situations, but it’s not clear if that would be
worthwhile. There is also value in having a simple and predictable
behavior, so this changes clang to simply ignore novtable when not using
the Microsoft C++ ABI.

llvm-svn: 242730

clang/include/clang/Basic/Attr.td

@@ -241,14 +241,18 @@ def COnly : LangOpt<"CPlusPlus", 1>;
 class TargetArch<list<string> arches> {
   list<string> Arches = arches;
   list<string> OSes;
+  list<string> CXXABIs;
 }
 def TargetARM : TargetArch<["arm", "thumb"]>;
+def TargetMips : TargetArch<["mips", "mipsel"]>;
 def TargetMSP430 : TargetArch<["msp430"]>;
 def TargetX86 : TargetArch<["x86"]>;
 def TargetWindows : TargetArch<["x86", "x86_64", "arm", "thumb"]> {
   let OSes = ["Win32"];
 }
-def TargetMips : TargetArch<["mips", "mipsel"]>;
+def TargetMicrosoftCXXABI : TargetArch<["x86", "x86_64", "arm", "thumb"]> {
+  let CXXABIs = ["Microsoft"];
+}
 
 class Attr {
   // The various ways in which an attribute can be spelled in source
@@ -1820,7 +1824,7 @@ def TypeTagForDatatype : InheritableAttr {
 
 // Microsoft-related attributes
 
-def MSNoVTable : InheritableAttr {
+def MSNoVTable : InheritableAttr, TargetSpecificAttr<TargetMicrosoftCXXABI> {
   let Spellings = [Declspec<"novtable">];
   let Subjects = SubjectList<[CXXRecord]>;
   let Documentation = [MSNoVTableDocs];

clang/include/clang/Basic/Attributes.h

@@ -11,7 +11,7 @@
 #define LLVM_CLANG_BASIC_ATTRIBUTES_H
 
 #include "clang/Basic/LangOptions.h"
-#include "llvm/ADT/Triple.h"
+#include "clang/Basic/TargetInfo.h"
 
 namespace clang {
 
@@ -31,7 +31,7 @@ enum class AttrSyntax {
 /// \brief Return the version number associated with the attribute if we
 /// recognize and implement the attribute specified by the given information.
 int hasAttribute(AttrSyntax Syntax, const IdentifierInfo *Scope,
-                 const IdentifierInfo *Attr, const llvm::Triple &T,
+                 const IdentifierInfo *Attr, const TargetInfo &Target,
                  const LangOptions &LangOpts);
 
 } // end namespace clang

clang/include/clang/Sema/AttributeList.h

@@ -16,11 +16,11 @@
 #define LLVM_CLANG_SEMA_ATTRIBUTELIST_H
 
 #include "clang/Basic/SourceLocation.h"
+#include "clang/Basic/TargetInfo.h"
 #include "clang/Basic/VersionTuple.h"
 #include "clang/Sema/Ownership.h"
 #include "llvm/ADT/PointerUnion.h"
 #include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/Triple.h"
 #include "llvm/Support/Allocator.h"
 #include <cassert>
 
@@ -464,7 +464,7 @@ public:
   bool hasVariadicArg() const;
   bool diagnoseAppertainsTo(class Sema &S, const Decl *D) const;
   bool diagnoseLangOpts(class Sema &S) const;
-  bool existsInTarget(const llvm::Triple &T) const;
+  bool existsInTarget(const TargetInfo &Target) const;
   bool isKnownToGCC() const;
 
   /// \brief If the parsed attribute has a semantic equivalent, and it would

clang/lib/Basic/Attributes.cpp

@@ -4,8 +4,8 @@
 using namespace clang;
 
 int clang::hasAttribute(AttrSyntax Syntax, const IdentifierInfo *Scope,
-                         const IdentifierInfo *Attr, const llvm::Triple &T,
-                         const LangOptions &LangOpts) {
+                        const IdentifierInfo *Attr, const TargetInfo &Target,
+                        const LangOptions &LangOpts) {
   StringRef Name = Attr->getName();
   // Normalize the attribute name, __foo__ becomes foo.
   if (Name.size() >= 4 && Name.startswith("__") && Name.endswith("__"))

clang/lib/Lex/PPMacroExpansion.cpp

@@ -1633,13 +1633,13 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
       Value = FeatureII->getBuiltinID() != 0;
     } else if (II == Ident__has_attribute)
       Value = hasAttribute(AttrSyntax::GNU, nullptr, FeatureII,
-                           getTargetInfo().getTriple(), getLangOpts());
+                           getTargetInfo(), getLangOpts());
     else if (II == Ident__has_cpp_attribute)
       Value = hasAttribute(AttrSyntax::CXX, ScopeII, FeatureII,
-                           getTargetInfo().getTriple(), getLangOpts());
+                           getTargetInfo(), getLangOpts());
     else if (II == Ident__has_declspec)
       Value = hasAttribute(AttrSyntax::Declspec, nullptr, FeatureII,
-                           getTargetInfo().getTriple(), getLangOpts());
+                           getTargetInfo(), getLangOpts());
     else if (II == Ident__has_extension)
       Value = HasExtension(*this, FeatureII);
     else {

clang/lib/Parse/ParseDecl.cpp

@@ -387,7 +387,7 @@ bool Parser::ParseMicrosoftDeclSpecArgs(IdentifierInfo *AttrName,
   // If the attribute isn't known, we will not attempt to parse any
   // arguments.
   if (!hasAttribute(AttrSyntax::Declspec, nullptr, AttrName,
-                    getTargetInfo().getTriple(), getLangOpts())) {
+                    getTargetInfo(), getLangOpts())) {
     // Eat the left paren, then skip to the ending right paren.
     ConsumeParen();
     SkipUntil(tok::r_paren);

clang/lib/Parse/ParseDeclCXX.cpp

@@ -3612,7 +3612,7 @@ bool Parser::ParseCXX11AttributeArgs(IdentifierInfo *AttrName,
   // If the attribute isn't known, we will not attempt to parse any
   // arguments.
   if (!hasAttribute(AttrSyntax::CXX, ScopeName, AttrName,
-                    getTargetInfo().getTriple(), getLangOpts())) {
+                    getTargetInfo(), getLangOpts())) {
     // Eat the left paren, then skip to the ending right paren.
     ConsumeParen();
     SkipUntil(tok::r_paren);

clang/lib/Sema/AttributeList.cpp

@@ -17,6 +17,7 @@
 #include "clang/AST/DeclTemplate.h"
 #include "clang/AST/Expr.h"
 #include "clang/Basic/IdentifierTable.h"
+#include "clang/Basic/TargetInfo.h"
 #include "clang/Sema/SemaInternal.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringSwitch.h"
@@ -155,7 +156,7 @@ struct ParsedAttrInfo {
   bool (*DiagAppertainsToDecl)(Sema &S, const AttributeList &Attr,
                                const Decl *);
   bool (*DiagLangOpts)(Sema &S, const AttributeList &Attr);
-  bool (*ExistsInTarget)(const llvm::Triple &T);
+  bool (*ExistsInTarget)(const TargetInfo &Target);
   unsigned (*SpellingIndexToSemanticSpelling)(const AttributeList &Attr);
 };
 
@@ -195,8 +196,8 @@ bool AttributeList::isTypeAttr() const {
   return getInfo(*this).IsType;
 }
 
-bool AttributeList::existsInTarget(const llvm::Triple &T) const {
-  return getInfo(*this).ExistsInTarget(T);
+bool AttributeList::existsInTarget(const TargetInfo &Target) const {
+  return getInfo(*this).ExistsInTarget(Target);
 }
 
 bool AttributeList::isKnownToGCC() const {

clang/lib/Sema/SemaDeclAttr.cpp

@@ -4583,7 +4583,7 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
   // which do not apply to the current target architecture are treated as
   // though they were unknown attributes.
   if (Attr.getKind() == AttributeList::UnknownAttribute ||
-      !Attr.existsInTarget(S.Context.getTargetInfo().getTriple())) {
+      !Attr.existsInTarget(S.Context.getTargetInfo())) {
     S.Diag(Attr.getLoc(), Attr.isDeclspecAttribute()
                               ? diag::warn_unhandled_ms_attribute_ignored
                               : diag::warn_unknown_attribute_ignored)

clang/test/Parser/MicrosoftExtensions.cpp

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 %s -triple i386-mingw32 -std=c++14 -fsyntax-only -Wno-unused-getter-return-value -Wno-unused-value -Wmicrosoft -verify -fms-extensions -fms-compatibility -fdelayed-template-parsing
+// RUN: %clang_cc1 %s -triple i386-pc-win32 -std=c++14 -fsyntax-only -Wno-unused-getter-return-value -Wno-unused-value -Wmicrosoft -verify -fms-extensions -fms-compatibility -fdelayed-template-parsing
 
 /* Microsoft attribute tests */
 [repeatable][source_annotation_attribute( Parameter|ReturnValue )]

clang/test/SemaCXX/ms-novtable.cpp

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 %s -fsyntax-only -verify -fms-extensions -Wno-microsoft -std=c++11
+// RUN: %clang_cc1 -triple i386-pc-win32 %s -fsyntax-only -verify -fms-extensions -Wno-microsoft -std=c++11
 
 struct __declspec(novtable) S {};
 enum __declspec(novtable) E {}; // expected-warning{{'novtable' attribute only applies to classes}}

clang/test/SemaCXX/ms-unsupported.cpp

@@ -0,0 +1,5 @@
+// RUN: %clang_cc1 -triple x86_64-pc-windows-gnu %s -fsyntax-only -verify -fms-extensions -Wno-microsoft -std=c++11
+
+// "novtable" is ignored except with the Microsoft C++ ABI.
+// MinGW uses the Itanium C++ ABI so check that it is ignored there.
+struct __declspec(novtable) S {}; // expected-warning{{__declspec attribute 'novtable' is not supported}}

clang/utils/TableGen/ClangAttrEmitter.cpp

@@ -1885,7 +1885,8 @@ static void GenerateHasAttrSpellingStringSwitch(
       }
     }
 
-    // It is assumed that there will be an llvm::Triple object named T within
+    // It is assumed that there will be an llvm::Triple object
+    // named "T" and a TargetInfo object named "Target" within
     // scope that can be used to determine whether the attribute exists in
     // a given target.
     std::string Test;
@@ -1902,6 +1903,7 @@ static void GenerateHasAttrSpellingStringSwitch(
       }
       Test += ")";
 
+      // If the attribute is specific to particular OSes, check those.
       std::vector<std::string> OSes;
       if (!R->isValueUnset("OSes")) {
         Test += " && (";
@@ -1916,6 +1918,21 @@ static void GenerateHasAttrSpellingStringSwitch(
         Test += ")";
       }
       
+      // If one or more CXX ABIs are specified, check those as well.
+      if (!R->isValueUnset("CXXABIs")) {
+        Test += " && (";
+        std::vector<std::string> CXXABIs =
+          R->getValueAsListOfStrings("CXXABIs");
+        for (auto AI = CXXABIs.begin(), AE = CXXABIs.end(); AI != AE; ++AI) {
+          std::string Part = *AI;
+
+          Test += "Target.getCXXABI().getKind() == TargetCXXABI::" + Part;
+          if (AI + 1 != AE)
+            Test += " || ";
+        }
+        Test += ")";
+      }
+
       // If this is the C++11 variety, also add in the LangOpts test.
       if (Variety == "CXX11")
         Test += " && LangOpts.CPlusPlus11";
@@ -1962,6 +1979,7 @@ void EmitClangAttrHasAttrImpl(RecordKeeper &Records, raw_ostream &OS) {
     }
   }
 
+  OS << "const llvm::Triple &T = Target.getTriple();\n";
   OS << "switch (Syntax) {\n";
   OS << "case AttrSyntax::GNU:\n";
   OS << "  return llvm::StringSwitch<int>(Name)\n";
@@ -2464,7 +2482,7 @@ static std::string GenerateLangOptRequirements(const Record &R,
 }
 
 static void GenerateDefaultTargetRequirements(raw_ostream &OS) {
-  OS << "static bool defaultTargetRequirements(const llvm::Triple &) {\n";
+  OS << "static bool defaultTargetRequirements(const TargetInfo &) {\n";
   OS << "  return true;\n";
   OS << "}\n\n";
 }
@@ -2533,6 +2551,20 @@ static std::string GenerateTargetRequirements(const Record &Attr,
     Test += ")";
   }
 
+  // Test for the C++ ABI, if specified.
+  if (!R->isValueUnset("CXXABIs")) {
+    Test += " && (";
+    std::vector<std::string> CXXABIs = R->getValueAsListOfStrings("CXXABIs");
+    for (auto I = CXXABIs.begin(), E = CXXABIs.end(); I != E; ++I) {
+      std::string Part = *I;
+      Test += "Target.getCXXABI().getKind() == TargetCXXABI::" + Part;
+      if (I + 1 != E)
+        Test += " || ";
+      FnName += Part;
+    }
+    Test += ")";
+  }
+
   // If this code has already been generated, simply return the previous
   // instance of it.
   static std::set<std::string> CustomTargetSet;
@@ -2540,7 +2572,8 @@ static std::string GenerateTargetRequirements(const Record &Attr,
   if (I != CustomTargetSet.end())
     return *I;
 
-  OS << "static bool " << FnName << "(const llvm::Triple &T) {\n";
+  OS << "static bool " << FnName << "(const TargetInfo &Target) {\n";
+  OS << "  const llvm::Triple &T = Target.getTriple();\n";
   OS << "  llvm::Triple::ArchType Arch = T.getArch();\n";
   if (UsesOS)
     OS << "  llvm::Triple::OSType OS = T.getOS();\n";