This patch adds a new Clang compiler flag "-gline-tables-only".

It reduces the amount of emitted debug information:
1) DIEs in .debug_info have types DW_TAG_compile_unit, DW_TAG_subprogram,
DW_TAG_inlined_subroutine (for opt builds) and DW_TAG_lexical_block only.
2) .debug_str contains only function names.
3) No debug data for types/namespaces/variables is emitted.
4) The data in .debug_line is enough to produce valid stack traces with
function names and line numbers.

Reviewed by Eric Christopher.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@156160 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 43 insertions, 17 deletions

diff --git a/lib/CodeGen/CGDebugInfo.cpp b/lib/CodeGen/CGDebugInfo.cpp
index af6e340b9d..b3fc0a45ce 100644
--- a/lib/CodeGen/CGDebugInfo.cpp
+++ b/lib/CodeGen/CGDebugInfo.cpp
@@ -1176,6 +1176,7 @@ CollectVTableInfo(const CXXRecordDecl *RD, llvm::DIFile Unit,
 /// getOrCreateRecordType - Emit record type's standalone debug info. 
 llvm::DIType CGDebugInfo::getOrCreateRecordType(QualType RTy, 
                                                 SourceLocation Loc) {
+  assert(CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo);
   llvm::DIType T = getOrCreateType(RTy, getOrCreateFile(Loc));
   return T;
 }
@@ -1184,6 +1185,7 @@ llvm::DIType CGDebugInfo::getOrCreateRecordType(QualType RTy,
 /// debug info.
 llvm::DIType CGDebugInfo::getOrCreateInterfaceType(QualType D,
 						   SourceLocation Loc) {
+  assert(CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo);
   llvm::DIType T = getOrCreateType(D, getOrCreateFile(Loc));
   DBuilder.retainType(T);
   return T;
@@ -2012,18 +2014,21 @@ void CGDebugInfo::EmitFunctionStart(GlobalDecl GD, QualType FnType,
       LinkageName = CGM.getMangledName(GD);
       Flags |= llvm::DIDescriptor::FlagPrototyped;
     }
-    if (LinkageName == Name)
+    if (LinkageName == Name ||
+        CGM.getCodeGenOpts().DebugInfo <= CodeGenOptions::DebugLineTablesOnly)
       LinkageName = StringRef();
 
-    if (const NamespaceDecl *NSDecl =
-        dyn_cast_or_null<NamespaceDecl>(FD->getDeclContext()))
-      FDContext = getOrCreateNameSpace(NSDecl);
-    else if (const RecordDecl *RDecl =
-             dyn_cast_or_null<RecordDecl>(FD->getDeclContext()))
-      FDContext = getContextDescriptor(cast<Decl>(RDecl->getDeclContext()));
+    if (CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo) {
+      if (const NamespaceDecl *NSDecl =
+          dyn_cast_or_null<NamespaceDecl>(FD->getDeclContext()))
+        FDContext = getOrCreateNameSpace(NSDecl);
+      else if (const RecordDecl *RDecl =
+               dyn_cast_or_null<RecordDecl>(FD->getDeclContext()))
+        FDContext = getContextDescriptor(cast<Decl>(RDecl->getDeclContext()));
 
-    // Collect template parameters.
-    TParamsArray = CollectFunctionTemplateParams(FD, Unit);
+      // Collect template parameters.
+      TParamsArray = CollectFunctionTemplateParams(FD, Unit);
+    }
   } else if (const ObjCMethodDecl *OMD = dyn_cast<ObjCMethodDecl>(D)) {
     Name = getObjCMethodName(OMD);
     Flags |= llvm::DIDescriptor::FlagPrototyped;
@@ -2039,14 +2044,27 @@ void CGDebugInfo::EmitFunctionStart(GlobalDecl GD, QualType FnType,
   if (D->isImplicit())
     Flags |= llvm::DIDescriptor::FlagArtificial;
 
-  llvm::DISubprogram SPDecl = getFunctionDeclaration(D);
-  llvm::DISubprogram SP =
-    DBuilder.createFunction(FDContext, Name, LinkageName, Unit,
-                            LineNo, getOrCreateFunctionType(D, FnType, Unit),
-                            Fn->hasInternalLinkage(), true/*definition*/,
-                            getLineNumber(CurLoc),
-                            Flags, CGM.getLangOpts().Optimize, Fn,
-                            TParamsArray, SPDecl);
+  llvm::DIType DIFnType;
+  llvm::DISubprogram SPDecl;
+  if (CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo) {
+    DIFnType = getOrCreateFunctionType(D, FnType, Unit);
+    SPDecl = getFunctionDeclaration(D);
+  } else {
+    // Create fake but valid subroutine type. Otherwise
+    // llvm::DISubprogram::Verify() would return false, and
+    // subprogram DIE will miss DW_AT_decl_file and
+    // DW_AT_decl_line fields.
+    SmallVector<llvm::Value*, 16> Elts;
+    llvm::DIArray EltTypeArray = DBuilder.getOrCreateArray(Elts);
+    DIFnType = DBuilder.createSubroutineType(Unit, EltTypeArray);
+  }
+  llvm::DISubprogram SP;
+  SP = DBuilder.createFunction(FDContext, Name, LinkageName, Unit,
+                               LineNo, DIFnType,
+                               Fn->hasInternalLinkage(), true/*definition*/,
+                               getLineNumber(CurLoc), Flags,
+                               CGM.getLangOpts().Optimize,
+                               Fn, TParamsArray, SPDecl);
 
   // Push function on region stack.
   llvm::MDNode *SPN = SP;
@@ -2204,6 +2222,7 @@ llvm::DIType CGDebugInfo::EmitTypeForVarWithBlocksAttr(const ValueDecl *VD,
 void CGDebugInfo::EmitDeclare(const VarDecl *VD, unsigned Tag,
                               llvm::Value *Storage, 
                               unsigned ArgNo, CGBuilderTy &Builder) {
+  assert(CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo);
   assert(!LexicalBlockStack.empty() && "Region stack mismatch, stack empty!");
 
   llvm::DIFile Unit = getOrCreateFile(VD->getLocation());
@@ -2320,12 +2339,14 @@ void CGDebugInfo::EmitDeclare(const VarDecl *VD, unsigned Tag,
 void CGDebugInfo::EmitDeclareOfAutoVariable(const VarDecl *VD,
                                             llvm::Value *Storage,
                                             CGBuilderTy &Builder) {
+  assert(CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo);
   EmitDeclare(VD, llvm::dwarf::DW_TAG_auto_variable, Storage, 0, Builder);
 }
 
 void CGDebugInfo::EmitDeclareOfBlockDeclRefVariable(
   const VarDecl *VD, llvm::Value *Storage, CGBuilderTy &Builder,
   const CGBlockInfo &blockInfo) {
+  assert(CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo);
   assert(!LexicalBlockStack.empty() && "Region stack mismatch, stack empty!");
   
   if (Builder.GetInsertBlock() == 0)
@@ -2386,6 +2407,7 @@ void CGDebugInfo::EmitDeclareOfBlockDeclRefVariable(
 void CGDebugInfo::EmitDeclareOfArgVariable(const VarDecl *VD, llvm::Value *AI,
                                            unsigned ArgNo,
                                            CGBuilderTy &Builder) {
+  assert(CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo);
   EmitDeclare(VD, llvm::dwarf::DW_TAG_arg_variable, AI, ArgNo, Builder);
 }
 
@@ -2402,6 +2424,7 @@ namespace {
 void CGDebugInfo::EmitDeclareOfBlockLiteralArgVariable(const CGBlockInfo &block,
                                                        llvm::Value *addr,
                                                        CGBuilderTy &Builder) {
+  assert(CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo);
   ASTContext &C = CGM.getContext();
   const BlockDecl *blockDecl = block.getBlockDecl();
 
@@ -2546,6 +2569,7 @@ void CGDebugInfo::EmitDeclareOfBlockLiteralArgVariable(const CGBlockInfo &block,
 /// EmitGlobalVariable - Emit information about a global variable.
 void CGDebugInfo::EmitGlobalVariable(llvm::GlobalVariable *Var,
                                      const VarDecl *D) {
+  assert(CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo);
   // Create global variable debug descriptor.
   llvm::DIFile Unit = getOrCreateFile(D->getLocation());
   unsigned LineNo = getLineNumber(D->getLocation());
@@ -2581,6 +2605,7 @@ void CGDebugInfo::EmitGlobalVariable(llvm::GlobalVariable *Var,
 /// EmitGlobalVariable - Emit information about an objective-c interface.
 void CGDebugInfo::EmitGlobalVariable(llvm::GlobalVariable *Var,
                                      ObjCInterfaceDecl *ID) {
+  assert(CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo);
   // Create global variable debug descriptor.
   llvm::DIFile Unit = getOrCreateFile(ID->getLocation());
   unsigned LineNo = getLineNumber(ID->getLocation());
@@ -2608,6 +2633,7 @@ void CGDebugInfo::EmitGlobalVariable(llvm::GlobalVariable *Var,
 /// EmitGlobalVariable - Emit global variable's debug info.
 void CGDebugInfo::EmitGlobalVariable(const ValueDecl *VD, 
                                      llvm::Constant *Init) {
+  assert(CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo);
   // Create the descriptor for the variable.
   llvm::DIFile Unit = getOrCreateFile(VD->getLocation());
   StringRef Name = VD->getName();