DebugInfo: Add support for 'nodebug' attribute on typedefs and alias templates

Seems like a logical extension to me - and of interest because it might
help reduce the debug info size of libc++ by applying this attribute to
type traits that have a disproportionate debug info cost compared to the
benefit (& possibly harm/confusion) they cause users.

llvm-svn: 362856

clang/include/clang/Basic/Attr.td

@@ -1434,7 +1434,7 @@ def NoCommon : InheritableAttr {
 
 def NoDebug : InheritableAttr {
   let Spellings = [GCC<"nodebug">];
-  let Subjects = SubjectList<[FunctionLike, ObjCMethod, NonParmVar]>;
+  let Subjects = SubjectList<[TypedefName, FunctionLike, ObjCMethod, NonParmVar]>;
   let Documentation = [NoDebugDocs];
 }
 

clang/lib/CodeGen/CGDebugInfo.cpp

@@ -1091,15 +1091,18 @@ llvm::DIType *CGDebugInfo::CreateType(const TemplateSpecializationType *Ty,
   assert(Ty->isTypeAlias());
   llvm::DIType *Src = getOrCreateType(Ty->getAliasedType(), Unit);
 
+  auto *AliasDecl =
+      cast<TypeAliasTemplateDecl>(Ty->getTemplateName().getAsTemplateDecl())
+          ->getTemplatedDecl();
+
+  if (AliasDecl->hasAttr<NoDebugAttr>())
+    return Src;
+
   SmallString<128> NS;
   llvm::raw_svector_ostream OS(NS);
   Ty->getTemplateName().print(OS, getPrintingPolicy(), /*qualified*/ false);
   printTemplateArgumentList(OS, Ty->template_arguments(), getPrintingPolicy());
 
-  auto *AliasDecl =
-      cast<TypeAliasTemplateDecl>(Ty->getTemplateName().getAsTemplateDecl())
-          ->getTemplatedDecl();
-
   SourceLocation Loc = AliasDecl->getLocation();
   return DBuilder.createTypedef(Src, OS.str(), getOrCreateFile(Loc),
                                 getLineNumber(Loc),
@@ -1108,15 +1111,20 @@ llvm::DIType *CGDebugInfo::CreateType(const TemplateSpecializationType *Ty,
 
 llvm::DIType *CGDebugInfo::CreateType(const TypedefType *Ty,
                                       llvm::DIFile *Unit) {
+  llvm::DIType *Underlying =
+      getOrCreateType(Ty->getDecl()->getUnderlyingType(), Unit);
+
+  if (Ty->getDecl()->hasAttr<NoDebugAttr>())
+    return Underlying;
+
   // We don't set size information, but do specify where the typedef was
   // declared.
   SourceLocation Loc = Ty->getDecl()->getLocation();
 
   // Typedefs are derived from some other type.
-  return DBuilder.createTypedef(
-      getOrCreateType(Ty->getDecl()->getUnderlyingType(), Unit),
-      Ty->getDecl()->getName(), getOrCreateFile(Loc), getLineNumber(Loc),
-      getDeclContextDescriptor(Ty->getDecl()));
+  return DBuilder.createTypedef(Underlying, Ty->getDecl()->getName(),
+                                getOrCreateFile(Loc), getLineNumber(Loc),
+                                getDeclContextDescriptor(Ty->getDecl()));
 }
 
 static unsigned getDwarfCC(CallingConv CC) {

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

@@ -1,5 +1,5 @@
-// RUN: %clang_cc1 -DSETNODEBUG=0 -emit-llvm -debug-info-kind=limited %s -o - | FileCheck %s --check-prefix=YESINFO
-// RUN: %clang_cc1 -DSETNODEBUG=1 -emit-llvm -debug-info-kind=limited %s -o - | FileCheck %s --check-prefix=NOINFO
+// RUN: %clang_cc1 -DSETNODEBUG=0 -emit-llvm -std=c++14 -debug-info-kind=limited %s -o - | FileCheck %s --check-prefix=YESINFO
+// RUN: %clang_cc1 -DSETNODEBUG=1 -emit-llvm -std=c++14 -debug-info-kind=limited %s -o - | FileCheck %s --check-prefix=NOINFO
 
 #if SETNODEBUG
 #define NODEBUG __attribute__((nodebug))
@@ -53,3 +53,15 @@ void func4() {
 // NOINFO-NOT:  !DIGlobalVariable(name: "static_local"
 // YESINFO-DAG: !DILocalVariable(name: "normal_local"
 // NOINFO-NOT:  !DILocalVariable(name: "normal_local"
+
+template <typename T>
+using y NODEBUG = int;
+void func5() {
+  NODEBUG typedef int x;
+  x a;
+  y<int> b;
+}
+// YESINFO-DAG: !DIDerivedType(tag: DW_TAG_typedef, name: "x"
+// NOINFO-NOT:  !DIDerivedType(tag: DW_TAG_typedef, name: "x"
+// YESINFO-DAG: !DIDerivedType(tag: DW_TAG_typedef, name: "y<int>"
+// NOINFO-NOT:  !DIDerivedType(tag: DW_TAG_typedef, name: "y<int>"

clang/test/Misc/pragma-attribute-supported-attributes-list.test

@@ -72,7 +72,7 @@
 // CHECK-NEXT: NSConsumesSelf (SubjectMatchRule_objc_method)
 // CHECK-NEXT: Naked (SubjectMatchRule_function)
 // CHECK-NEXT: NoCommon (SubjectMatchRule_variable)
-// CHECK-NEXT: NoDebug (SubjectMatchRule_hasType_functionType, SubjectMatchRule_objc_method, SubjectMatchRule_variable_not_is_parameter)
+// CHECK-NEXT: NoDebug (SubjectMatchRule_type_alias, SubjectMatchRule_hasType_functionType, SubjectMatchRule_objc_method, SubjectMatchRule_variable_not_is_parameter)
 // CHECK-NEXT: NoDestroy (SubjectMatchRule_variable)
 // CHECK-NEXT: NoDuplicate (SubjectMatchRule_function)
 // CHECK-NEXT: NoEscape (SubjectMatchRule_variable_is_parameter)

clang/test/Sema/attr-nodebug.c

@@ -2,7 +2,7 @@
 
 int a __attribute__((nodebug));
 
-void b(int p __attribute__((nodebug))) { // expected-warning {{'nodebug' attribute only applies to functions, function pointers, Objective-C methods, and variables}}
+void b(int p __attribute__((nodebug))) { // expected-warning {{'nodebug' attribute only applies to typedefs, functions, function pointers, Objective-C methods, and variables}}
   int b __attribute__((nodebug));
 }