Module debugging: Defer emitting tag types until their definition

was visited and all decls have been merged.

We only get a single chance to emit the types for virtual classes because
CGDebugInfo::completeRequiredType() categorically doesn't complete them.

llvm-svn: 256962

clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp

@@ -59,8 +59,10 @@ class PCHContainerGenerator : public ASTConsumer {
   struct DebugTypeVisitor : public RecursiveASTVisitor<DebugTypeVisitor> {
     clang::CodeGen::CGDebugInfo &DI;
     ASTContext &Ctx;
-    DebugTypeVisitor(clang::CodeGen::CGDebugInfo &DI, ASTContext &Ctx)
+    bool SkipTagDecls;
-        : DI(DI), Ctx(Ctx) {}
+    DebugTypeVisitor(clang::CodeGen::CGDebugInfo &DI, ASTContext &Ctx,
+                     bool SkipTagDecls)
+        : DI(DI), Ctx(Ctx), SkipTagDecls(SkipTagDecls) {}
 
     /// Determine whether this type can be represented in DWARF.
     static bool CanRepresent(const Type *Ty) {
@@ -75,6 +77,12 @@ class PCHContainerGenerator : public ASTConsumer {
     }
 
     bool VisitTypeDecl(TypeDecl *D) {
+      // TagDecls may be deferred until after all decls have been merged and we
+      // know the complete type. Pure forward declarations will be skipped, but
+      // they don't need to be emitted into the module anyway.
+      if (SkipTagDecls && isa<TagDecl>(D))
+          return true;
+
       QualType QualTy = Ctx.getTypeDeclType(D);
       if (!QualTy.isNull() && CanRepresent(QualTy.getTypePtr()))
         DI.getOrCreateStandaloneType(QualTy, D->getLocation());
@@ -165,7 +173,7 @@ public:
     // Collect debug info for all decls in this group.
     for (auto *I : D)
       if (!I->isFromASTFile()) {
-        DebugTypeVisitor DTV(*Builder->getModuleDebugInfo(), *Ctx);
+        DebugTypeVisitor DTV(*Builder->getModuleDebugInfo(), *Ctx, true);
         DTV.TraverseDecl(I);
       }
     return true;
@@ -179,6 +187,11 @@ public:
     if (Diags.hasErrorOccurred())
       return;
 
+    if (D->isFromASTFile())
+      return;
+
+    DebugTypeVisitor DTV(*Builder->getModuleDebugInfo(), *Ctx, false);
+    DTV.TraverseDecl(D);
     Builder->UpdateCompletedType(D);
   }
 

clang/test/Modules/Inputs/DebugCXX.h

@@ -50,3 +50,9 @@ namespace DebugCXX {
   typedef A<void> B;
   void foo(B) {}
 }
+
+// Virtual class with a forward declaration.
+class FwdVirtual;
+class FwdVirtual {
+  virtual ~FwdVirtual() {}
+};

clang/test/Modules/ModuleDebugInfo.cpp

@@ -7,13 +7,11 @@
 // RUN: rm -rf %t
 // RUN: %clang_cc1 -triple %itanium_abi_triple -x objective-c++ -std=c++11 -debug-info-kind=limited -fmodules -fmodule-format=obj -fimplicit-module-maps -DMODULES -fmodules-cache-path=%t %s -I %S/Inputs -I %t -emit-llvm -o %t.ll -mllvm -debug-only=pchcontainer &>%t-mod.ll
 // RUN: cat %t-mod.ll | FileCheck %s
-// RUN: cat %t-mod.ll | FileCheck --check-prefix=CHECK-NEG %s
 // RUN: cat %t-mod.ll | FileCheck --check-prefix=CHECK-DWO %s
 
 // PCH:
 // RUN: %clang_cc1 -triple %itanium_abi_triple -x c++ -std=c++11 -emit-pch -fmodule-format=obj -I %S/Inputs -o %t.pch %S/Inputs/DebugCXX.h -mllvm -debug-only=pchcontainer &>%t-pch.ll
 // RUN: cat %t-pch.ll | FileCheck %s
-// RUN: cat %t-pch.ll | FileCheck --check-prefix=CHECK-NEG %s
 
 #ifdef MODULES
 @import DebugCXX;
@@ -23,22 +21,32 @@
 // CHECK-SAME:                    isOptimized: false,
 // CHECK-SAME-NOT:                splitDebugFilename:
 // CHECK-DWO:                     dwoId:
+
 // CHECK: !DICompositeType(tag: DW_TAG_enumeration_type, name: "Enum"
 // CHECK-SAME:             identifier: "_ZTSN8DebugCXX4EnumE")
 // CHECK: !DINamespace(name: "DebugCXX"
+
 // CHECK: !DICompositeType(tag: DW_TAG_structure_type, name: "Struct"
 // CHECK-SAME:             identifier: "_ZTSN8DebugCXX6StructE")
+
 // CHECK: !DICompositeType(tag: DW_TAG_class_type,
 // CHECK-SAME:             name: "Template<int, DebugCXX::traits<int> >"
 // CHECK-SAME:             identifier: "_ZTSN8DebugCXX8TemplateIiNS_6traitsIiEEEE")
+
+// CHECK: !DICompositeType(tag: DW_TAG_class_type, name: "A<void>"
+// CHECK-SAME:             identifier: "_ZTSN8DebugCXX1AIJvEEE")
+
 // CHECK: !DICompositeType(tag: DW_TAG_class_type,
 // CHECK-SAME:             name: "Template<float, DebugCXX::traits<float> >"
 // CHECK-SAME:             identifier: "_ZTSN8DebugCXX8TemplateIfNS_6traitsIfEEEE")
-// CHECK: !DICompositeType(tag: DW_TAG_class_type, name: "A<void>"
+
-// CHECK-SAME:             identifier: "_ZTSN8DebugCXX1AIJvEEE")
+// CHECK: !DICompositeType(tag: DW_TAG_class_type, name: "FwdVirtual"
+// CHECK-SAME:             elements:
+// CHECK-SAME:             identifier: "_ZTS10FwdVirtual")
+// CHECK: !DIDerivedType(tag: DW_TAG_member, name: "_vptr$FwdVirtual"
+
 // CHECK: !DIDerivedType(tag: DW_TAG_typedef, name: "FloatInstatiation"
 // no mangled name here yet.
+
 // CHECK: !DIDerivedType(tag: DW_TAG_typedef, name: "B",
 // no mangled name here yet.
-
-// CHECK-NEG-NOT: "_ZTSN8DebugCXX8TemplateIlNS_6traitsIlEEEE"