[DWARF5][clang]: Added support for DebugInfo generation for auto return type for C++ member functions.

Summary:
This patch will provide support for auto return type for the C++ member
functions.

This patch includes clang side implementation of this feature.

Patch by: Awanish Pandey <[email protected]>

Reviewers: dblaikie, aprantl, shafik, alok, SouraVX, jini.susan.george
Reviewed by: dblaikie

Differential Revision: https://reviews.llvm.org/D70524

Author: Awanish Pandey

clang/lib/CodeGen/CGDebugInfo.cpp

@@ -810,6 +810,10 @@ llvm::DIType *CGDebugInfo::CreateType(const BuiltinType *BT) {
   return DBuilder.createBasicType(BTName, Size, Encoding);
 }
 
+llvm::DIType *CGDebugInfo::CreateType(const AutoType *Ty) {
+  return DBuilder.createUnspecifiedType("auto");
+}
+
 llvm::DIType *CGDebugInfo::CreateType(const ComplexType *Ty) {
   // Bit size and offset of the type.
   llvm::dwarf::TypeKind Encoding = llvm::dwarf::DW_ATE_complex_float;
@@ -1457,26 +1461,31 @@ void CGDebugInfo::CollectRecordFields(
 
 llvm::DISubroutineType *
 CGDebugInfo::getOrCreateMethodType(const CXXMethodDecl *Method,
-                                   llvm::DIFile *Unit) {
+                                   llvm::DIFile *Unit, bool decl) {
   const FunctionProtoType *Func = Method->getType()->getAs<FunctionProtoType>();
   if (Method->isStatic())
     return cast_or_null<llvm::DISubroutineType>(
         getOrCreateType(QualType(Func, 0), Unit));
-  return getOrCreateInstanceMethodType(Method->getThisType(), Func, Unit);
+  return getOrCreateInstanceMethodType(Method->getThisType(), Func, Unit, decl);
 }
 
-llvm::DISubroutineType *CGDebugInfo::getOrCreateInstanceMethodType(
-    QualType ThisPtr, const FunctionProtoType *Func, llvm::DIFile *Unit) {
+llvm::DISubroutineType *
+CGDebugInfo::getOrCreateInstanceMethodType(QualType ThisPtr,
+                                           const FunctionProtoType *Func,
+                                           llvm::DIFile *Unit, bool decl) {
   // Add "this" pointer.
   llvm::DITypeRefArray Args(
       cast<llvm::DISubroutineType>(getOrCreateType(QualType(Func, 0), Unit))
           ->getTypeArray());
   assert(Args.size() && "Invalid number of arguments!");
 
   SmallVector<llvm::Metadata *, 16> Elts;
-
   // First element is always return type. For 'void' functions it is NULL.
-  Elts.push_back(Args[0]);
+  QualType temp = Func->getReturnType();
+  if (temp->getTypeClass() == Type::Auto && decl)
+    Elts.push_back(CreateType(cast<AutoType>(temp)));
+  else
+    Elts.push_back(Args[0]);
 
   // "this" pointer is always first argument.
   const CXXRecordDecl *RD = ThisPtr->getPointeeCXXRecordDecl();
@@ -1535,7 +1544,7 @@ llvm::DISubprogram *CGDebugInfo::CreateCXXMemberFunction(
       isa<CXXConstructorDecl>(Method) || isa<CXXDestructorDecl>(Method);
 
   StringRef MethodName = getFunctionName(Method);
-  llvm::DISubroutineType *MethodTy = getOrCreateMethodType(Method, Unit);
+  llvm::DISubroutineType *MethodTy = getOrCreateMethodType(Method, Unit, true);
 
   // Since a single ctor/dtor corresponds to multiple functions, it doesn't
   // make sense to give a single ctor/dtor a linkage name.
@@ -2754,7 +2763,7 @@ llvm::DIType *CGDebugInfo::CreateType(const MemberPointerType *Ty,
   return DBuilder.createMemberPointerType(
       getOrCreateInstanceMethodType(
           CXXMethodDecl::getThisType(FPT, Ty->getMostRecentCXXRecordDecl()),
-          FPT, U),
+          FPT, U, false),
       ClassType, Size, /*Align=*/0, Flags);
 }
 
@@ -3529,7 +3538,7 @@ llvm::DISubroutineType *CGDebugInfo::getOrCreateFunctionType(const Decl *D,
     return DBuilder.createSubroutineType(DBuilder.getOrCreateTypeArray(None));
 
   if (const auto *Method = dyn_cast<CXXMethodDecl>(D))
-    return getOrCreateMethodType(Method, F);
+    return getOrCreateMethodType(Method, F, false);
 
   const auto *FTy = FnType->getAs<FunctionType>();
   CallingConv CC = FTy ? FTy->getCallConv() : CallingConv::CC_C;

clang/lib/CodeGen/CGDebugInfo.h

@@ -165,6 +165,7 @@ class CGDebugInfo {
   /// ivars and property accessors.
   llvm::DIType *CreateType(const BuiltinType *Ty);
   llvm::DIType *CreateType(const ComplexType *Ty);
+  llvm::DIType *CreateType(const AutoType *Ty);
   llvm::DIType *CreateQualifiedType(QualType Ty, llvm::DIFile *Fg);
   llvm::DIType *CreateType(const TypedefType *Ty, llvm::DIFile *Fg);
   llvm::DIType *CreateType(const TemplateSpecializationType *Ty,
@@ -214,10 +215,10 @@ class CGDebugInfo {
   /// not updated to include implicit \c this pointer. Use this routine
   /// to get a method type which includes \c this pointer.
   llvm::DISubroutineType *getOrCreateMethodType(const CXXMethodDecl *Method,
-                                                llvm::DIFile *F);
+                                                llvm::DIFile *F, bool decl);
   llvm::DISubroutineType *
   getOrCreateInstanceMethodType(QualType ThisPtr, const FunctionProtoType *Func,
-                                llvm::DIFile *Unit);
+                                llvm::DIFile *Unit, bool decl);
   llvm::DISubroutineType *
   getOrCreateFunctionType(const Decl *D, QualType FnType, llvm::DIFile *F);
   /// \return debug info descriptor for vtable.

clang/test/CodeGenCXX/debug-info-auto-return.cpp

@@ -0,0 +1,22 @@
+//  Test for debug info for C++11 auto return member functions
+// RUN: %clang_cc1 -dwarf-version=5  -emit-llvm -triple x86_64-linux-gnu %s -o - \
+// RUN:   -O0 -disable-llvm-passes \
+// RUN:   -debug-info-kind=standalone \
+// RUN: | FileCheck %s
+
+// CHECK: !DISubprogram(name: "findMax",{{.*}}, type: ![[FUN_TYPE:[0-9]+]],{{.*}}
+
+// CHECK: ![[FUN_TYPE]] = !DISubroutineType(types: ![[TYPE_NODE:[0-9]+]])
+// CHECK-NEXT: ![[TYPE_NODE]] = !{![[DOUBLE_TYPE:[0-9]+]], {{.*}}
+// CHECK-NEXT: ![[DOUBLE_TYPE]] = !DIBasicType(name: "double", {{.*}})
+
+// CHECK: !DISubroutineType(types: ![[TYPE_DECL_NODE:[0-9]+]])
+// CHECK-NEXT: ![[TYPE_DECL_NODE]] = !{![[AUTO_TYPE:[0-9]+]], {{.*}}
+// CHECK-NEXT: ![[AUTO_TYPE]] = !DIBasicType(tag: DW_TAG_unspecified_type, name: "auto")
+struct myClass {
+  auto findMax();
+};
+
+auto myClass::findMax() {
+  return 0.0;
+}