r227796 - MS ABI: Implement support for 'novtable'

[David Majnemer]

Author: majnemer
Date: Mon Feb  2 04:22:20 2015
New Revision: 227796

URL: http://llvm.org/viewvc/llvm-project?rev=227796&view=rev
Log:
MS ABI: Implement support for 'novtable'

It is common for COM interface classes to be marked as 'novtable' to
tell the compiler that constructors and destructors should not reference
virtual function tables.

This commit implements this feature in clang.

Modified:
    cfe/trunk/include/clang/Basic/Attr.td
    cfe/trunk/lib/CodeGen/CGClass.cpp
    cfe/trunk/lib/CodeGen/MicrosoftCXXABI.cpp
    cfe/trunk/lib/Sema/SemaDeclAttr.cpp
    cfe/trunk/test/Parser/MicrosoftExtensions.cpp

Modified: cfe/trunk/include/clang/Basic/Attr.td
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/Attr.td?rev=227796&r1=227795&r2=227796&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/Attr.td (original)
+++ cfe/trunk/include/clang/Basic/Attr.td Mon Feb  2 04:22:20 2015
@@ -1761,6 +1761,12 @@ def TypeTagForDatatype : InheritableAttr
 
 // Microsoft-related attributes
 
+def MsNoVTable : InheritableAttr {
+  let Spellings = [Declspec<"novtable">];
+  let Subjects = SubjectList<[CXXRecord]>;
+  let Documentation = [Undocumented];
+}
+
 def MsProperty : IgnoredAttr {
   let Spellings = [Declspec<"property">];
 }

Modified: cfe/trunk/lib/CodeGen/CGClass.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGClass.cpp?rev=227796&r1=227795&r2=227796&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGClass.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGClass.cpp Mon Feb  2 04:22:20 2015
@@ -1949,6 +1949,14 @@ CodeGenFunction::InitializeVTablePointer
                                          const CXXRecordDecl *NearestVBase,
                                          CharUnits OffsetFromNearestVBase,
                                          const CXXRecordDecl *VTableClass) {
+  const CXXRecordDecl *RD = Base.getBase();
+
+  // Don't initialize the vtable pointer if the class is marked with the
+  // 'novtable' attribute.
+  if ((RD == VTableClass || RD == NearestVBase) &&
+      VTableClass->hasAttr<MsNoVTableAttr>())
+    return;
+
   // Compute the address point.
   bool NeedsVirtualOffset;
   llvm::Value *VTableAddressPoint =

Modified: cfe/trunk/lib/CodeGen/MicrosoftCXXABI.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/MicrosoftCXXABI.cpp?rev=227796&r1=227795&r2=227796&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/MicrosoftCXXABI.cpp (original)
+++ cfe/trunk/lib/CodeGen/MicrosoftCXXABI.cpp Mon Feb  2 04:22:20 2015
@@ -1582,7 +1582,8 @@ void MicrosoftCXXABI::emitVirtualInherit
   for (unsigned I = 0, E = VBGlobals.VBTables->size(); I != E; ++I) {
     const VPtrInfo *VBT = (*VBGlobals.VBTables)[I];
     llvm::GlobalVariable *GV = VBGlobals.Globals[I];
-    emitVBTableDefinition(*VBT, RD, GV);
+    if (GV->isDeclaration())
+      emitVBTableDefinition(*VBT, RD, GV);
   }
 }
 
@@ -1609,6 +1610,9 @@ MicrosoftCXXABI::getAddrOfVBTable(const
   else if (RD->hasAttr<DLLExportAttr>())
     GV->setDLLStorageClass(llvm::GlobalValue::DLLExportStorageClass);
 
+  if (!GV->hasExternalLinkage())
+    emitVBTableDefinition(VBT, RD, GV);
+
   return GV;
 }
 

Modified: cfe/trunk/lib/Sema/SemaDeclAttr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDeclAttr.cpp?rev=227796&r1=227795&r2=227796&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaDeclAttr.cpp (original)
+++ cfe/trunk/lib/Sema/SemaDeclAttr.cpp Mon Feb  2 04:22:20 2015
@@ -4689,6 +4689,9 @@ static void ProcessDeclAttribute(Sema &S
     break;
 
   // Microsoft attributes:
+  case AttributeList::AT_MsNoVTable:
+    handleSimpleAttribute<MsNoVTableAttr>(S, D, Attr);
+    break;
   case AttributeList::AT_MsStruct:
     handleSimpleAttribute<MsStructAttr>(S, D, Attr);
     break;

Modified: cfe/trunk/test/Parser/MicrosoftExtensions.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Parser/MicrosoftExtensions.cpp?rev=227796&r1=227795&r2=227796&view=diff
==============================================================================
--- cfe/trunk/test/Parser/MicrosoftExtensions.cpp (original)
+++ cfe/trunk/test/Parser/MicrosoftExtensions.cpp Mon Feb  2 04:22:20 2015
@@ -339,7 +339,7 @@ void TestProperty() {
 //expected-warning at +1 {{C++ operator 'and' (aka '&&') used as a macro name}}
 #define and foo
 
-struct __declspec(uuid("00000000-0000-0000-C000-000000000046")) __declspec(novtable) IUnknown {}; // expected-warning{{__declspec attribute 'novtable' is not supported}}
+struct __declspec(uuid("00000000-0000-0000-C000-000000000046")) __declspec(novtable) IUnknown {};
 
 typedef bool (__stdcall __stdcall *blarg)(int);