Introduce -flimit-debug-info.

In this experimental mode try avoiding debug info emission for classes as much as possible. The goal is to reduce size of produced debuginfo without reducing quality of debug info in general. This is a work in progress.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@115188 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Driver/CC1Options.td

@@ -131,6 +131,8 @@ def dwarf_debug_flags : Separate<"-dwarf-debug-flags">,
 def g : Flag<"-g">, HelpText<"Generate source level debug information">;
 def fcatch_undefined_behavior : Flag<"-fcatch-undefined-behavior">,
     HelpText<"Generate runtime checks for undefined behavior.">;
+def flimit_debug_info : Flag<"-flimit-debug-info">,
+  HelpText<"Limit debug information produced to reduce size of debug binary">;
 def fno_common : Flag<"-fno-common">,
   HelpText<"Compile common globals like normal definitions">;
 def no_implicit_float : Flag<"-no-implicit-float">,

include/clang/Driver/Options.td

@@ -288,6 +288,8 @@ 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>, 
+  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 fmacro_backtrace_limit_EQ : Joined<"-fmacro-backtrace-limit=">, 

include/clang/Frontend/CodeGenOptions.h

@@ -40,6 +40,7 @@ public:
                                   /// aliases to base ctors when possible.
   unsigned DataSections      : 1; /// Set when -fdata-sections is enabled
   unsigned DebugInfo         : 1; /// Should generate debug info (-g).
+  unsigned LimitDebugInfo    : 1; /// Limit generated debug info to reduce size.
   unsigned DisableFPElim     : 1; /// Set when -fomit-frame-pointer is enabled.
   unsigned DisableLLVMOpts   : 1; /// Don't run any optimizations, for use in
                                   /// getting .bc files that correspond to the
@@ -109,6 +110,7 @@ public:
     CXXCtorDtorAliases = 0;
     DataSections = 0;
     DebugInfo = 0;
+    LimitDebugInfo = 0;
     DisableFPElim = 0;
     DisableLLVMOpts = 0;
     DisableRedZone = 0;

lib/CodeGen/CGDebugInfo.cpp

@@ -413,12 +413,44 @@ llvm::DIType CGDebugInfo::CreateType(const PointerType *Ty,
                                Ty->getPointeeType(), Unit);
 }
 
+/// CreatePointeeType - Create PointTee type. If Pointee is a record
+/// then emit record's fwd if debug info size reduction is enabled.
+llvm::DIType CGDebugInfo::CreatePointeeType(QualType PointeeTy,
+                                            llvm::DIFile Unit) {
+  if (!CGM.getCodeGenOpts().LimitDebugInfo)
+    return getOrCreateType(PointeeTy, Unit);
+  
+  if (const RecordType *RTy = dyn_cast<RecordType>(PointeeTy)) {
+    RecordDecl *RD = RTy->getDecl();
+    unsigned RTag;
+    if (RD->isStruct())
+      RTag = llvm::dwarf::DW_TAG_structure_type;
+    else if (RD->isUnion())
+      RTag = llvm::dwarf::DW_TAG_union_type;
+    else {
+      assert(RD->isClass() && "Unknown RecordType!");
+      RTag = llvm::dwarf::DW_TAG_class_type;
+    }
+
+    llvm::DIFile DefUnit = getOrCreateFile(RD->getLocation());
+    unsigned Line = getLineNumber(RD->getLocation());
+    llvm::DIDescriptor FDContext =
+      getContextDescriptor(dyn_cast<Decl>(RD->getDeclContext()), Unit);
+  
+    return
+      DebugFactory.CreateCompositeType(RTag, FDContext, RD->getName(),
+                                       DefUnit, Line, 0, 0, 0,
+                                       llvm::DIType::FlagFwdDecl,
+                                       llvm::DIType(), llvm::DIArray());
+  }
+  return getOrCreateType(PointeeTy, Unit);
+
+}
+
 llvm::DIType CGDebugInfo::CreatePointerLikeType(unsigned Tag,
                                                 const Type *Ty, 
                                                 QualType PointeeTy,
                                                 llvm::DIFile Unit) {
-  llvm::DIType EltTy = getOrCreateType(PointeeTy, Unit);
-
   // Bit size, align and offset of the type.
   
   // Size is always the size of a pointer. We can't use getTypeSize here
@@ -427,10 +459,10 @@ llvm::DIType CGDebugInfo::CreatePointerLikeType(unsigned Tag,
     CGM.getContext().Target.getPointerWidth(PointeeTy.getAddressSpace());
   uint64_t Align = CGM.getContext().getTypeAlign(Ty);
 
-  return
-    DebugFactory.CreateDerivedType(Tag, Unit, "", Unit,
-                                   0, Size, Align, 0, 0, EltTy);
-  
+  return DebugFactory.CreateDerivedType(Tag, Unit, "", Unit,
+                                        0, Size, Align, 0, 0, 
+                                        CreatePointeeType(PointeeTy, Unit));
+
 }
 
 llvm::DIType CGDebugInfo::CreateType(const BlockPointerType *Ty,
@@ -877,6 +909,14 @@ CollectVTableInfo(const CXXRecordDecl *RD, llvm::DIFile Unit,
   EltTys.push_back(VPTR);
 }
 
+/// getOrCreateRecordType - Emit record type's standalone debug info. 
+llvm::DIType CGDebugInfo::getOrCreateRecordType(QualType RTy, 
+                                                SourceLocation Loc) {
+  llvm::DIType T =  getOrCreateType(RTy, getOrCreateFile(Loc));
+  DebugFactory.RecordType(T);
+  return T;
+}
+
 /// CreateType - get structure or union type.
 llvm::DIType CGDebugInfo::CreateType(const RecordType *Ty,
                                      llvm::DIFile Unit) {

lib/CodeGen/CGDebugInfo.h

@@ -98,7 +98,7 @@ class CGDebugInfo {
   llvm::DIType getOrCreateVTablePtrType(llvm::DIFile F);
   llvm::DINameSpace getOrCreateNameSpace(const NamespaceDecl *N, 
                                          llvm::DIDescriptor Unit);
-
+  llvm::DIType CreatePointeeType(QualType PointeeTy, llvm::DIFile F);
   llvm::DIType CreatePointerLikeType(unsigned Tag,
                                      const Type *Ty, QualType PointeeTy,
                                      llvm::DIFile F);
@@ -189,6 +189,8 @@ public:
   void EmitGlobalVariable(const ValueDecl *VD, llvm::ConstantInt *Init, 
                           CGBuilderTy &Builder);
 
+  /// getOrCreateRecordType - Emit record type's standalone debug info. 
+  llvm::DIType getOrCreateRecordType(QualType Ty, SourceLocation L);
 private:
   /// EmitDeclare - Emit call to llvm.dbg.declare for a variable declaration.
   void EmitDeclare(const VarDecl *decl, unsigned Tag, llvm::Value *AI,

lib/CodeGen/CGExprCXX.cpp

@@ -11,9 +11,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "clang/Frontend/CodeGenOptions.h"
 #include "CodeGenFunction.h"
 #include "CGCXXABI.h"
 #include "CGObjCRuntime.h"
+#include "CGDebugInfo.h"
 #include "llvm/Intrinsics.h"
 using namespace clang;
 using namespace CodeGen;
@@ -87,6 +89,15 @@ RValue CodeGenFunction::EmitCXXMemberCallExpr(const CXXMemberCallExpr *CE,
   const MemberExpr *ME = cast<MemberExpr>(CE->getCallee()->IgnoreParens());
   const CXXMethodDecl *MD = cast<CXXMethodDecl>(ME->getMemberDecl());
 
+  CGDebugInfo *DI = getDebugInfo();
+  if (DI && CGM.getCodeGenOpts().LimitDebugInfo) {
+    QualType PQTy = ME->getBase()->IgnoreParenImpCasts()->getType();
+    if (const PointerType * PTy = dyn_cast<PointerType>(PQTy)) {
+      DI->getOrCreateRecordType(PTy->getPointeeType(), 
+                                MD->getParent()->getLocation());
+    }
+  }
+
   if (MD->isStatic()) {
     // The method is static, emit it as we would a regular call.
     llvm::Value *Callee = CGM.GetAddrOfFunction(MD);

lib/Driver/Tools.cpp

@@ -1165,6 +1165,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   Args.AddLastArg(CmdArgs, options::OPT_fcatch_undefined_behavior);
   Args.AddLastArg(CmdArgs, options::OPT_femit_all_decls);
   Args.AddLastArg(CmdArgs, options::OPT_fheinous_gnu_extensions);
+  Args.AddLastArg(CmdArgs, options::OPT_flimit_debug_info);
 
   // -flax-vector-conversions is default.
   if (!Args.hasFlag(options::OPT_flax_vector_conversions,

lib/Frontend/CompilerInvocation.cpp

@@ -859,6 +859,7 @@ static void ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args,
     : CodeGenOptions::OnlyAlwaysInlining;
 
   Opts.DebugInfo = Args.hasArg(OPT_g);
+  Opts.LimitDebugInfo = Args.hasArg(OPT_flimit_debug_info);
   Opts.DisableLLVMOpts = Args.hasArg(OPT_disable_llvm_optzns);
   Opts.DisableRedZone = Args.hasArg(OPT_disable_red_zone);
   Opts.DwarfDebugFlags = Args.getLastArgValue(OPT_dwarf_debug_flags);