DebugInfo: Emit "LocalToUnit" flag on local member function decls.

[jyknight]

Summary

Previously, the definition was so-marked, but the declaration was
not. This resulted in LLVM's dwarf emission treating the function as
being external, and incorrectly emitting DW_AT_external.

[dblaikie]

Sounds good. Out of curiosity, how'd you come across this/do you have any particular use case that uses DW_AT_external?

clang/test/CodeGenCXX/debug-info-class.cpp

27–34

Might be better to add a separate class to test this case - modifying this class may reduce coverage of existing features (the vtable homing (well, lack of homing due to ~D being virtual and inline) would no longer be tested here, since the type is internal and that'd override the other logic.

clang/lib/CodeGen/CGDebugInfo.cpp

if (CXXC->isExplicit())
       Flags |= llvm::DINode::FlagExplicit;
   }
   if (Method->hasPrototype())
     Flags |= llvm::DINode::FlagPrototyped;
   if (Method->getRefQualifier() == RQ_LValue)
     Flags |= llvm::DINode::FlagLValueReference;
   if (Method->getRefQualifier() == RQ_RValue)
     Flags |= llvm::DINode::FlagRValueReference;
+  if (!Method->isExternallyVisible())
+    SPFlags |= llvm::DISubprogram::SPFlagLocalToUnit;
   if (CGM.getLangOpts().Optimize)
     SPFlags |= llvm::DISubprogram::SPFlagOptimized;
 
   // In this debug mode, emit type info for a class when its constructor type
   // info is emitted.
   if (DebugKind == codegenoptions::DebugInfoConstructor)
     if (const CXXConstructorDecl *CD = dyn_cast<CXXConstructorDecl>(Method))
       completeUnusedClass(*CD->getParent());

clang/test/CodeGenCXX/debug-info-class.cpp

 struct C {
   static int s;
   virtual ~C();
 };
 
 C::~C() {
 }
 
+namespace {
 struct D {
-  D();
-  virtual ~D();
+  D() {}
+  virtual ~D() {}
   void func() {
   }
 };
+} // namespace
 
 struct E {
   E();
   virtual ~E();
   virtual void func() {
   }
 };
 

 // CHECK: [[C_MEM]] = !{[[C_VPTR:![0-9]*]], [[C_S:![0-9]*]], [[C_DTOR:![0-9]*]]}
 // CHECK: [[C_VPTR]] = !DIDerivedType(tag: DW_TAG_member, name: "_vptr$C"
 // CHECK-SAME:                        DIFlagArtificial
 // CHECK: [[C_S]] = !DIDerivedType(tag: DW_TAG_member, name: "s"
 // CHECK-SAME:                     baseType: ![[INT]]
 // CHECK-SAME:                     DIFlagStaticMember
 // CHECK: [[C_DTOR]] = !DISubprogram(name: "~C"
 
-// CHECK: [[D:![0-9]+]] = !DICompositeType(tag: DW_TAG_structure_type, name: "D"
+// CHECK: [[D:![0-9]+]] = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "D"
 // CHECK-SAME:             size:
-// CHECK-SAME:             DIFlagFwdDecl
 // CHECK-NOT:              identifier:
 // CHECK-SAME:             ){{$}}
+// CHECK: [[D_FUNC_DECL:![0-9]*]] = !DISubprogram(name: "func",{{.*}} scope: [[D]]
+// CHECK-SAME:             DISPFlagLocalToUnit
+
 // CHECK: !DICompositeType(tag: DW_TAG_structure_type, name: "E"
 // CHECK-SAME:             DIFlagFwdDecl
 // CHECK-NOT:              identifier:
 // CHECK-SAME:             ){{$}}
 
 // CHECK: !DICompositeType(tag: DW_TAG_structure_type, name: "K"
 // CHECK-SAME:             identifier: "_ZTS1K"
 // CHECK-SAME:             ){{$}}
 
 // CHECK: !DISubprogram(name: "func",{{.*}} scope: [[D]]
-// CHECK-SAME:          DISPFlagDefinition
-// CHECK-SAME:          declaration: [[D_FUNC_DECL:![0-9]*]]
-// CHECK: [[D_FUNC_DECL]] = !DISubprogram(name: "func",{{.*}} scope: [[D]]
+// CHECK-SAME:          DISPFlagLocalToUnit | DISPFlagDefinition
+// CHECK-SAME:          declaration: [[D_FUNC_DECL]]
 
-// CHECK: !DICompositeType(tag: DW_TAG_structure_type, name: "inner",{{.*}} line: 50
+// CHECK: !DICompositeType(tag: DW_TAG_structure_type, name: "inner",{{.*}} line: 52
 // CHECK-NOT: DIFlagFwdDecl
 // CHECK-SAME: elements: [[G_INNER_MEM:![0-9]*]]
 // CHECK-SAME: identifier: "_ZTSN1G5innerE"
 
 // CHECK: !DICompositeType(tag: DW_TAG_structure_type, name: "G"
 // CHECK-SAME:             DIFlagFwdDecl
 // CHECK-NOT:              identifier:
 // CHECK-SAME:             ){{$}}
 // CHECK: [[G_INNER_MEM]] = !{[[G_INNER_I:![0-9]*]]}
 // CHECK: [[G_INNER_I]] = !DIDerivedType(tag: DW_TAG_member, name: "j"
 // CHECK-SAME:                           baseType: ![[INT]]
 
 // CHECK: !DICompositeType(tag: DW_TAG_structure_type, name: "A"
 // CHECK: !DIDerivedType(tag: DW_TAG_member, name: "HdrSize"
 //
-// CHECK: ![[EXCEPTLOC]] = !DILocation(line: 91,
-// CHECK: ![[RETLOC]] = !DILocation(line: 90,
+// CHECK: ![[EXCEPTLOC]] = !DILocation(line: 93,
+// CHECK: ![[RETLOC]] = !DILocation(line: 92,