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
diff --git a/lib/CodeGen/CGBlocks.cpp b/lib/CodeGen/CGBlocks.cpp
index 1a1fe65..dad8e7e 100644
--- a/lib/CodeGen/CGBlocks.cpp
+++ b/lib/CodeGen/CGBlocks.cpp
@@ -1134,15 +1134,17 @@
       const VarDecl *variable = ci->getVariable();
       DI->EmitLocation(Builder, variable->getLocation());
 
-      const CGBlockInfo::Capture &capture = blockInfo.getCapture(variable);
-      if (capture.isConstant()) {
-        DI->EmitDeclareOfAutoVariable(variable, LocalDeclMap[variable],
-                                      Builder);
-        continue;
-      }
+      if (CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo) {
+        const CGBlockInfo::Capture &capture = blockInfo.getCapture(variable);
+        if (capture.isConstant()) {
+          DI->EmitDeclareOfAutoVariable(variable, LocalDeclMap[variable],
+                                        Builder);
+          continue;
+        }
 
-      DI->EmitDeclareOfBlockDeclRefVariable(variable, BlockPointer,
-                                            Builder, blockInfo);
+        DI->EmitDeclareOfBlockDeclRefVariable(variable, BlockPointer,
+                                              Builder, blockInfo);
+      }
     }
   }
 
diff --git a/lib/CodeGen/CGDebugInfo.cpp b/lib/CodeGen/CGDebugInfo.cpp
index af6e340..b3fc0a4 100644
--- a/lib/CodeGen/CGDebugInfo.cpp
+++ b/lib/CodeGen/CGDebugInfo.cpp
@@ -1176,6 +1176,7 @@
 /// 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 @@
 /// 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 @@
       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 @@
   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 @@
 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::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::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 @@
 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 @@
 /// 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 @@
 /// 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 @@
 /// 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();
diff --git a/lib/CodeGen/CGDecl.cpp b/lib/CodeGen/CGDecl.cpp
index 6447779..4d4b579 100644
--- a/lib/CodeGen/CGDecl.cpp
+++ b/lib/CodeGen/CGDecl.cpp
@@ -326,7 +326,8 @@
 
   // Emit global variable debug descriptor for static vars.
   CGDebugInfo *DI = getDebugInfo();
-  if (DI) {
+  if (DI &&
+      CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo) {
     DI->setLocation(D.getLocation());
     DI->EmitGlobalVariable(var, &D);
   }
@@ -897,11 +898,14 @@
   // Emit debug info for local var declaration.
   if (HaveInsertPoint())
     if (CGDebugInfo *DI = getDebugInfo()) {
-      DI->setLocation(D.getLocation());
-      if (Target.useGlobalsForAutomaticVariables()) {
-        DI->EmitGlobalVariable(static_cast<llvm::GlobalVariable *>(DeclPtr), &D);
-      } else
-        DI->EmitDeclareOfAutoVariable(&D, DeclPtr, Builder);
+      if (CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo) {
+        DI->setLocation(D.getLocation());
+        if (Target.useGlobalsForAutomaticVariables()) {
+          DI->EmitGlobalVariable(static_cast<llvm::GlobalVariable *>(DeclPtr),
+                                 &D);
+        } else
+          DI->EmitDeclareOfAutoVariable(&D, DeclPtr, Builder);
+      }
     }
 
   if (D.hasAttr<AnnotateAttr>())
@@ -1477,8 +1481,11 @@
       LocalDeclMap[&D] = Arg;
 
       if (CGDebugInfo *DI = getDebugInfo()) {
-        DI->setLocation(D.getLocation());
-        DI->EmitDeclareOfBlockLiteralArgVariable(*BlockInfo, Arg, Builder);
+        if (CGM.getCodeGenOpts().DebugInfo >=
+            CodeGenOptions::LimitedDebugInfo) {
+          DI->setLocation(D.getLocation());
+          DI->EmitDeclareOfBlockLiteralArgVariable(*BlockInfo, Arg, Builder);
+        }
       }
 
       return;
@@ -1556,8 +1563,11 @@
   DMEntry = DeclPtr;
 
   // Emit debug info for param declaration.
-  if (CGDebugInfo *DI = getDebugInfo())
-    DI->EmitDeclareOfArgVariable(&D, DeclPtr, ArgNo, Builder);
+  if (CGDebugInfo *DI = getDebugInfo()) {
+    if (CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo) {
+      DI->EmitDeclareOfArgVariable(&D, DeclPtr, ArgNo, Builder);
+    }
+  }
 
   if (D.hasAttr<AnnotateAttr>())
       EmitVarAnnotations(&D, DeclPtr);
diff --git a/lib/CodeGen/CodeGenFunction.cpp b/lib/CodeGen/CodeGenFunction.cpp
index fd78739..dfb04b4 100644
--- a/lib/CodeGen/CodeGenFunction.cpp
+++ b/lib/CodeGen/CodeGenFunction.cpp
@@ -1087,7 +1087,8 @@
                                               llvm::Constant *Init) {
   assert (Init && "Invalid DeclRefExpr initializer!");
   if (CGDebugInfo *Dbg = getDebugInfo())
-    Dbg->EmitGlobalVariable(E->getDecl(), Init);
+    if (CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo)
+      Dbg->EmitGlobalVariable(E->getDecl(), Init);
 }
 
 CodeGenFunction::PeepholeProtection
diff --git a/lib/CodeGen/CodeGenModule.cpp b/lib/CodeGen/CodeGenModule.cpp
index 660cc8b..775f500 100644
--- a/lib/CodeGen/CodeGenModule.cpp
+++ b/lib/CodeGen/CodeGenModule.cpp
@@ -1606,7 +1606,8 @@
 
   // Emit global variable debug information.
   if (CGDebugInfo *DI = getModuleDebugInfo())
-    DI->EmitGlobalVariable(GV, D);
+    if (getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo)
+      DI->EmitGlobalVariable(GV, D);
 }
 
 llvm::GlobalValue::LinkageTypes