Implement a new -fstandalone-debug option. rdar://problem/15685848

It controls everything that -flimit-debug-info used to, plus the
vtable type optimization. The old -fno-limit-debug-info option is now an
alias to -fstandalone-debug and vice versa.

Standalone is the default on Darwin until dtrace is updated to work with
non-standalone debug info (rdar://problem/15758808).

Note: I kept the LimitedDebugInfo name in CodeGenOptions::DebugInfoKind
because NoStandaloneDebugInfo sounded even more confusing.

llvm-svn: 198655

clang/docs/tools/clang.pod

@@ -312,12 +312,19 @@ Currently equivalent to B<-O3>
 Generate debug information.  Note that Clang debug information works best at
 B<-O0>.
 
-=item B<-flimit-debug-info> B<-fno-limit-debug-info>
+=item B<-fstandalone-debug> B<-fno-standalone-debug>
 
-By default Clang does not emit type definitions for types that are not
-needed by the module and could be replaced with a forward
-declaration. By specifying B<-fno-limit-debug-info> this optimization
-can be turned off. Note that Clang will never emit type information
+Clang supports a number of optimizations to reduce the size of debug
+information in the binary. They work based on the assumption that the
+debug type information can be spread out over multiple compilation
+units.  For instance, Clang will not emit type definitions for types
+that are not needed by a module and could be replaced with a forward
+declaration.  Further, Clang will only emit type info for a dynamic
+C++ class in the module that contains the vtable for the class.
+
+The B<-fstandalone-debug> option turns off these optimizations.  This
+is useful when working with 3rd-party libraries that don't come with
+debug information.  Note that Clang will never emit type information
 for types that are not referenced at all by the program.
 
 =item B<-fexceptions>

clang/include/clang/Driver/Options.td

@@ -559,8 +559,6 @@ def finstrument_functions : Flag<["-"], "finstrument-functions">, Group<f_Group>
 def fkeep_inline_functions : Flag<["-"], "fkeep-inline-functions">, Group<clang_ignored_f_Group>;
 def flat__namespace : Flag<["-"], "flat_namespace">;
 def flax_vector_conversions : Flag<["-"], "flax-vector-conversions">, Group<f_Group>;
-def flimit_debug_info : Flag<["-"], "flimit-debug-info">, Group<f_Group>, Flags<[CC1Option]>,
-  HelpText<"Limit debug information produced to reduce size of debug binary">;
 def flimited_precision_EQ : Joined<["-"], "flimited-precision=">, Group<f_Group>;
 def flto : Flag<["-"], "flto">, Group<f_Group>;
 def fno_lto : Flag<["-"], "fno-lto">, Group<f_Group>;
@@ -654,8 +652,6 @@ def fno_inline : Flag<["-"], "fno-inline">, Group<f_clang_Group>, Flags<[CC1Opti
 def fno_keep_inline_functions : Flag<["-"], "fno-keep-inline-functions">, Group<clang_ignored_f_Group>;
 def fno_lax_vector_conversions : Flag<["-"], "fno-lax-vector-conversions">, Group<f_Group>,
   HelpText<"Disallow implicit conversions between vectors with a different number of elements or different element types">, Flags<[CC1Option]>;
-def fno_limit_debug_info : Flag<["-"], "fno-limit-debug-info">, Group<f_Group>, Flags<[CC1Option]>,
-  HelpText<"Do not limit debug information produced to reduce size of debug binary">;
 def fno_merge_all_constants : Flag<["-"], "fno-merge-all-constants">, Group<f_Group>,
     Flags<[CC1Option]>, HelpText<"Disallow merging of constants">;
 def fno_modules : Flag <["-"], "fno-modules">, Group<f_Group>,
@@ -783,6 +779,12 @@ def fno_signed_char : Flag<["-"], "fno-signed-char">, Flags<[CC1Option]>,
 def fsplit_stack : Flag<["-"], "fsplit-stack">, Group<f_Group>;
 def fstack_protector_all : Flag<["-"], "fstack-protector-all">, Group<f_Group>;
 def fstack_protector : Flag<["-"], "fstack-protector">, Group<f_Group>;
+def fstandalone_debug : Flag<["-"], "fstandalone-debug">, Group<f_Group>, Flags<[CC1Option]>,
+  HelpText<"Emit full debug info for all types used by the program">;
+def fno_standalone_debug : Flag<["-"], "fno-standalone-debug">, Group<f_Group>, Flags<[CC1Option]>,
+  HelpText<"Limit debug information produced to reduce size of debug binary">;
+def flimit_debug_info : Flag<["-"], "flimit-debug-info">, Alias<fno_standalone_debug>;
+def fno_limit_debug_info : Flag<["-"], "fno-limit-debug-info">, Alias<fstandalone_debug>;
 def fstrict_aliasing : Flag<["-"], "fstrict-aliasing">, Group<f_Group>;
 def fstrict_enums : Flag<["-"], "fstrict-enums">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Enable optimizations based on the strict definition of an enum's "

clang/include/clang/Frontend/CodeGenOptions.h

@@ -50,12 +50,20 @@ public:
   };
 
   enum DebugInfoKind {
-    NoDebugInfo,          // Don't generate debug info.
-    DebugLineTablesOnly,  // Emit only debug info necessary for generating
-                          // line number tables (-gline-tables-only).
-    LimitedDebugInfo,     // Limit generated debug info to reduce size
-                          // (-flimit-debug-info).
-    FullDebugInfo         // Generate complete debug info.
+    NoDebugInfo,          /// Don't generate debug info.
+
+    DebugLineTablesOnly,  /// Emit only debug info necessary for generating
+                          /// line number tables (-gline-tables-only).
+
+    LimitedDebugInfo,     /// Limit generated debug info to reduce size
+                          /// (-fno-standalone-debug). This emits
+                          /// forward decls for types that could be
+                          /// replaced with forward decls in the source
+                          /// code. For dynamic C++ classes type info
+                          /// is only emitted int the module that
+                          /// contains the classe's vtable.
+
+    FullDebugInfo         /// Generate complete debug info.
   };
 
   enum TLSModel {

clang/lib/CodeGen/CGDebugInfo.cpp

@@ -1464,13 +1464,13 @@ llvm::DIType CGDebugInfo::CreateType(const RecordType *Ty) {
   // declaration. The completeType, completeRequiredType, and completeClassData
   // callbacks will handle promoting the declaration to a definition.
   if (T ||
+      // Under -flimit-debug-info:
       (DebugKind <= CodeGenOptions::LimitedDebugInfo &&
-       // Under -flimit-debug-info, emit only a declaration unless the type is
-       // required to be complete.
-       !RD->isCompleteDefinitionRequired() && CGM.getLangOpts().CPlusPlus) ||
-      // If the class is dynamic, only emit a declaration. A definition will be
-      // emitted whenever the vtable is emitted.
-      (CXXDecl && CXXDecl->hasDefinition() && CXXDecl->isDynamicClass())) {
+       // Emit only a forward declaration unless the type is required.
+       ((!RD->isCompleteDefinitionRequired() && CGM.getLangOpts().CPlusPlus) ||
+        // If the class is dynamic, only emit a declaration. A definition will be
+        // emitted whenever the vtable is emitted.
+        (CXXDecl && CXXDecl->hasDefinition() && CXXDecl->isDynamicClass())))) {
     llvm::DIDescriptor FDContext =
       getContextDescriptor(cast<Decl>(RD->getDeclContext()));
     if (!T)

clang/lib/Driver/Tools.cpp

@@ -2945,8 +2945,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   // Forward -f (flag) options which we can pass directly.
   Args.AddLastArg(CmdArgs, options::OPT_femit_all_decls);
   Args.AddLastArg(CmdArgs, options::OPT_fheinous_gnu_extensions);
-  Args.AddLastArg(CmdArgs, options::OPT_flimit_debug_info);
-  Args.AddLastArg(CmdArgs, options::OPT_fno_limit_debug_info);
+  Args.AddLastArg(CmdArgs, options::OPT_fstandalone_debug);
+  Args.AddLastArg(CmdArgs, options::OPT_fno_standalone_debug);
   Args.AddLastArg(CmdArgs, options::OPT_fno_operator_names);
   // AltiVec language extensions aren't relevant for assembling.
   if (!isa<PreprocessJobAction>(JA) || 

clang/lib/Frontend/CompilerInvocation.cpp

@@ -296,7 +296,8 @@ static void ParseCommentArgs(CommentOptions &Opts, ArgList &Args) {
 }
 
 static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
-                             DiagnosticsEngine &Diags) {
+                             DiagnosticsEngine &Diags,
+                             const TargetOptions &TargetOpts) {
   using namespace options;
   bool Success = true;
 
@@ -323,10 +324,16 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
     Opts.setDebugInfo(CodeGenOptions::DebugLineTablesOnly);
   } else if (Args.hasArg(OPT_g_Flag) || Args.hasArg(OPT_gdwarf_2) ||
              Args.hasArg(OPT_gdwarf_3) || Args.hasArg(OPT_gdwarf_4)) {
-    if (Args.hasFlag(OPT_flimit_debug_info, OPT_fno_limit_debug_info, true))
-      Opts.setDebugInfo(CodeGenOptions::LimitedDebugInfo);
-    else
+    bool Default = false;
+    // Until dtrace (via CTF) can deal with distributed debug info,
+    // Darwin defaults to standalone/full debug info.
+    if (llvm::Triple(TargetOpts.Triple).isOSDarwin())
+      Default = true;
+
+    if (Args.hasFlag(OPT_fstandalone_debug, OPT_fno_standalone_debug, Default))
       Opts.setDebugInfo(CodeGenOptions::FullDebugInfo);
+    else
+      Opts.setDebugInfo(CodeGenOptions::LimitedDebugInfo);
   }
   Opts.DebugColumnInfo = Args.hasArg(OPT_dwarf_column_info);
   Opts.SplitDwarfFile = Args.getLastArgValue(OPT_split_dwarf_file);
@@ -1662,8 +1669,9 @@ bool CompilerInvocation::CreateFromArgs(CompilerInvocation &Res,
   ParseFileSystemArgs(Res.getFileSystemOpts(), *Args);
   // FIXME: We shouldn't have to pass the DashX option around here
   InputKind DashX = ParseFrontendArgs(Res.getFrontendOpts(), *Args, Diags);
-  Success = ParseCodeGenArgs(Res.getCodeGenOpts(), *Args, DashX, Diags)
-            && Success;
+  ParseTargetArgs(Res.getTargetOpts(), *Args);
+  Success = ParseCodeGenArgs(Res.getCodeGenOpts(), *Args, DashX, Diags,
+                             Res.getTargetOpts()) && Success;
   ParseHeaderSearchArgs(Res.getHeaderSearchOpts(), *Args);
   if (DashX != IK_AST && DashX != IK_LLVM_IR) {
     ParseLangArgs(*Res.getLangOpts(), *Args, DashX, Diags);
@@ -1678,8 +1686,6 @@ bool CompilerInvocation::CreateFromArgs(CompilerInvocation &Res,
   ParsePreprocessorArgs(Res.getPreprocessorOpts(), *Args, FileMgr, Diags);
   ParsePreprocessorOutputArgs(Res.getPreprocessorOutputOpts(), *Args,
                               Res.getFrontendOpts().ProgramAction);
-  ParseTargetArgs(Res.getTargetOpts(), *Args);
-
   return Success;
 }
 

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

@@ -1,4 +1,4 @@
-// RUN: %clang -emit-llvm -g -S %s -o - | FileCheck %s
+// RUN: %clang -emit-llvm -fno-standalone-debug -g -S %s -o - | FileCheck %s
 
 namespace PR16214_1 {
 // CHECK-DAG: [ DW_TAG_structure_type ] [foo] [line [[@LINE+1]], {{.*}} [def]

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

@@ -1,4 +1,6 @@
-// RUN: %clang_cc1 -triple x86_64-unk-unk -fno-limit-debug-info -o - -emit-llvm -g %s | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-unk-unk -fstandalone-debug -o - -emit-llvm -g %s | FileCheck %s
+// On Darwin, this should be the default:
+// RUN: %clang_cc1 -triple x86_64-apple-darwin -o - -emit-llvm -g %s | FileCheck %s
 
 namespace rdar14101097_1 { // see also PR16214
 // Check that we emit debug info for the definition of a struct if the

clang/test/CodeGenCXX/debug-info-dup-fwd-decl.cpp

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -emit-llvm -g -triple x86_64-apple-darwin -fno-limit-debug-info %s -o - | FileCheck %s
+// RUN: %clang_cc1 -emit-llvm -g -triple x86_64-apple-darwin -fstandalone-debug %s -o - | FileCheck %s
 
 class Test
 {

clang/test/CodeGenCXX/debug-info-method2.cpp

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -flimit-debug-info -x c++ -g -S -emit-llvm < %s | FileCheck %s
+// RUN: %clang_cc1 -fno-standalone-debug -x c++ -g -S -emit-llvm < %s | FileCheck %s
 // rdar://10336845
 // Preserve type qualifiers in -flimit-debug-info mode.
 

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

@@ -1,6 +1,6 @@
-// RUN: %clang -g -S -emit-llvm %s -o - | FileCheck %s
-// RUN: %clang -g -gline-tables-only -S -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-GMLT %s
-// RUN: %clang -g -fno-limit-debug-info -S -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-NOLIMIT %s
+// RUN: %clang -g -fno-standalone-debug -S -emit-llvm %s -o - | FileCheck %s
+// RUN: %clang -g -gline-tables-only    -S -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-GMLT %s
+// RUN: %clang -g -fstandalone-debug    -S -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-NOLIMIT %s
 
 namespace A {
 #line 1 "foo.cpp"

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

@@ -1,5 +1,5 @@
 // REQUIRES: x86-registered-target
-// RUN: %clang_cc1 -triple x86_64-apple-darwin10  -g -fno-limit-debug-info -S -mllvm -generate-dwarf-pub-sections=Enable %s -o - | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10  -g -fstandalone-debug -S -mllvm -generate-dwarf-pub-sections=Enable %s -o - | FileCheck %s
 
 // FIXME: This testcase shouldn't rely on assembly emission.
 //CHECK: Lpubtypes_begin[[SECNUM:[0-9]:]]

clang/test/CodeGenCXX/debug-info-template-limit.cpp

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -emit-llvm -flimit-debug-info -cxx-abi itanium -g %s -o - | FileCheck %s
+// RUN: %clang_cc1 -emit-llvm -fno-standalone-debug -cxx-abi itanium -g %s -o - | FileCheck %s
 
 // Check that this pointer type is TC<int>
 // CHECK: ![[LINE:[0-9]+]] = {{.*}}"TC<int>", {{.*}} metadata !"_ZTS2TCIiE"} ; [ DW_TAG_class_type ]

clang/test/CodeGenCXX/debug-info-template-member.cpp

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -emit-llvm -g -triple x86_64-apple-darwin %s -o - | FileCheck %s
+// RUN: %clang_cc1 -emit-llvm -g -fno-standalone-debug -triple x86_64-apple-darwin %s -o - | FileCheck %s
 
 struct MyClass {
   template <int i> int add(int j) {

clang/test/CodeGenCXX/debug-info-vtable-optzn.cpp

@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -emit-llvm -g -triple x86_64-apple-darwin %s -o - | FileCheck %s
+//
+// This tests that the "emit debug info for a C++ class only in the
+// module that has its vtable" optimization is disabled by default on
+// Darwin.
+//
+// CHECK: [ DW_TAG_member ] [lost]
+class A
+{
+  virtual bool f() = 0;
+  int lost;
+};
+
+class B : public A
+{
+  B *g();
+};
+
+B *B::g() {
+  return this;
+}