Revert "PR14569: Omit debug info for thunks"

This reverts commit r189320.

Alexey Samsonov and Dmitry Vyukov presented some arguments for keeping
these around - though it still seems like those tasks could be solved by
a tool just using the symbol table. In a very small number of cases,
thunks may be inlined & debug info might be able to save profilers &
similar tools from misclassifying those cases as part of the caller.

The extra changes here plumb through the VarDecl for various cases to
CodeGenFunction - this provides better fidelity through a few APIs but
generally just causes the CGF::StartFunction to fallback to using the
name of the IR function as the name in the debug info.

The changes to debug-info-global-ctor-dtor.cpp seem like goodness. The
two names that go missing (in favor of only emitting those names as
linkage names) are names that can be demangled - emitting them only as
the linkage name should encourage tools to do just that.

Again, thanks to Dinesh Dwivedi for investigation/work on this issue.

llvm-svn: 189421

clang/lib/CodeGen/CGCXXABI.cpp

@@ -227,7 +227,7 @@ void CGCXXABI::registerGlobalDtor(CodeGenFunction &CGF,
     CGM.ErrorUnsupported(&D, "non-trivial TLS destruction");
 
   // The default behavior is to use atexit.
-  CGF.registerGlobalDtorWithAtExit(dtor, addr);
+  CGF.registerGlobalDtorWithAtExit(D, dtor, addr);
 }
 
 /// Returns the adjustment, in bytes, required for the given

clang/lib/CodeGen/CGDebugInfo.cpp

@@ -2450,7 +2450,7 @@ void CGDebugInfo::EmitFunctionStart(GlobalDecl GD, QualType FnType,
   llvm::DIArray TParamsArray;
   if (!HasDecl) {
     // Use llvm function name.
-    Name = Fn->getName();
+    LinkageName = Fn->getName();
   } else if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
     // If there is a DISubprogram for this function available then use it.
     llvm::DenseMap<const FunctionDecl *, llvm::WeakVH>::iterator

clang/lib/CodeGen/CGDeclCXX.cpp

@@ -100,9 +100,9 @@ static void EmitDeclDestroy(CodeGenFunction &CGF, const VarDecl &D,
 
   // Otherwise, the standard logic requires a helper function.
   } else {
-    function = CodeGenFunction(CGM).generateDestroyHelper(addr, type,
-                                                  CGF.getDestroyer(dtorKind),
-                                                  CGF.needsEHCleanup(dtorKind));
+    function = CodeGenFunction(CGM)
+        .generateDestroyHelper(addr, type, CGF.getDestroyer(dtorKind),
+                               CGF.needsEHCleanup(dtorKind), &D);
     argument = llvm::Constant::getNullValue(CGF.Int8PtrTy);
   }
 
@@ -161,7 +161,7 @@ CreateGlobalInitOrDestructFunction(CodeGenModule &CGM,
 
 /// Create a stub function, suitable for being passed to atexit,
 /// which passes the given address to the given destructor function.
-static llvm::Constant *createAtExitStub(CodeGenModule &CGM,
+static llvm::Constant *createAtExitStub(CodeGenModule &CGM, const VarDecl &VD,
                                         llvm::Constant *dtor,
                                         llvm::Constant *addr) {
   // Get the destructor function type, void(*)(void).
@@ -172,9 +172,9 @@ static llvm::Constant *createAtExitStub(CodeGenModule &CGM,
 
   CodeGenFunction CGF(CGM);
 
-  CGF.StartFunction(GlobalDecl(), CGM.getContext().VoidTy, fn,
-                    CGM.getTypes().arrangeNullaryFunction(),
-                    FunctionArgList(), SourceLocation());
+  CGF.StartFunction(&VD, CGM.getContext().VoidTy, fn,
+                    CGM.getTypes().arrangeNullaryFunction(), FunctionArgList(),
+                    SourceLocation());
 
   llvm::CallInst *call = CGF.Builder.CreateCall(dtor, addr);
  
@@ -189,10 +189,11 @@ static llvm::Constant *createAtExitStub(CodeGenModule &CGM,
 }
 
 /// Register a global destructor using the C atexit runtime function.
-void CodeGenFunction::registerGlobalDtorWithAtExit(llvm::Constant *dtor,
+void CodeGenFunction::registerGlobalDtorWithAtExit(const VarDecl &VD,
+                                                   llvm::Constant *dtor,
                                                    llvm::Constant *addr) {
   // Create a function which calls the destructor.
-  llvm::Constant *dtorStub = createAtExitStub(CGM, dtor, addr);
+  llvm::Constant *dtorStub = createAtExitStub(CGM, VD, dtor, addr);
 
   // extern "C" int atexit(void (*f)(void));
   llvm::FunctionType *atexitTy =
@@ -485,11 +486,9 @@ void CodeGenFunction::GenerateCXXGlobalDtorsFunc(llvm::Function *Fn,
 
 /// generateDestroyHelper - Generates a helper function which, when
 /// invoked, destroys the given object.
-llvm::Function * 
-CodeGenFunction::generateDestroyHelper(llvm::Constant *addr,
-                                       QualType type,
-                                       Destroyer *destroyer,
-                                       bool useEHCleanupForArray) {
+llvm::Function *CodeGenFunction::generateDestroyHelper(
+    llvm::Constant *addr, QualType type, Destroyer *destroyer,
+    bool useEHCleanupForArray, const VarDecl *VD) {
   FunctionArgList args;
   ImplicitParamDecl dst(0, SourceLocation(), 0, getContext().VoidPtrTy);
   args.push_back(&dst);
@@ -502,8 +501,7 @@ CodeGenFunction::generateDestroyHelper(llvm::Constant *addr,
   llvm::Function *fn = 
     CreateGlobalInitOrDestructFunction(CGM, FTy, "__cxx_global_array_dtor");
 
-  StartFunction(GlobalDecl(), getContext().VoidTy, fn, FI, args,
-                SourceLocation());
+  StartFunction(VD, getContext().VoidTy, fn, FI, args, SourceLocation());
 
   emitDestroy(addr, type, destroyer, useEHCleanupForArray);
   

clang/lib/CodeGen/CGExpr.cpp

@@ -261,7 +261,8 @@ pushTemporaryCleanup(CodeGenFunction &CGF, const MaterializeTemporaryExpr *M,
     if (E->getType()->isArrayType()) {
       CleanupFn = CodeGenFunction(CGF.CGM).generateDestroyHelper(
           cast<llvm::Constant>(ReferenceTemporary), E->getType(),
-          CodeGenFunction::destroyCXXObject, CGF.getLangOpts().Exceptions);
+          CodeGenFunction::destroyCXXObject, CGF.getLangOpts().Exceptions,
+          dyn_cast_or_null<VarDecl>(M->getExtendingDecl()));
       CleanupArg = llvm::Constant::getNullValue(CGF.Int8PtrTy);
     } else {
       CleanupFn =

clang/lib/CodeGen/CGVTables.cpp

@@ -292,7 +292,6 @@ void CodeGenFunction::GenerateVarArgsThunk(
 void CodeGenFunction::GenerateThunk(llvm::Function *Fn,
                                     const CGFunctionInfo &FnInfo,
                                     GlobalDecl GD, const ThunkInfo &Thunk) {
-  DebugInfo = NULL; // debug info for thunks is not required or desired
   const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
   const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
   QualType ThisType = MD->getThisType(getContext());

clang/lib/CodeGen/CodeGenFunction.h

@@ -1021,10 +1021,10 @@ public:
                                    bool useEHCleanupForArray);
   void emitDestroy(llvm::Value *addr, QualType type, Destroyer *destroyer,
                    bool useEHCleanupForArray);
-  llvm::Function *generateDestroyHelper(llvm::Constant *addr,
-                                        QualType type,
+  llvm::Function *generateDestroyHelper(llvm::Constant *addr, QualType type,
                                         Destroyer *destroyer,
-                                        bool useEHCleanupForArray);
+                                        bool useEHCleanupForArray,
+                                        const VarDecl *VD);
   void emitArrayDestroy(llvm::Value *begin, llvm::Value *end,
                         QualType type, Destroyer *destroyer,
                         bool checkZeroLength, bool useEHCleanup);
@@ -2305,7 +2305,8 @@ public:
 
   /// Call atexit() with a function that passes the given argument to
   /// the given function.
-  void registerGlobalDtorWithAtExit(llvm::Constant *fn, llvm::Constant *addr);
+  void registerGlobalDtorWithAtExit(const VarDecl &D, llvm::Constant *fn,
+                                    llvm::Constant *addr);
 
   /// Emit code in this function to perform a guarded variable
   /// initialization.  Guarded initializations are used when it's not

clang/lib/CodeGen/ItaniumCXXABI.cpp

@@ -1310,7 +1310,7 @@ void ItaniumCXXABI::registerGlobalDtor(CodeGenFunction &CGF,
     return CGM.AddCXXDtorEntry(dtor, addr);
   }
 
-  CGF.registerGlobalDtorWithAtExit(dtor, addr);
+  CGF.registerGlobalDtorWithAtExit(D, dtor, addr);
 }
 
 /// Get the appropriate linkage for the wrapper function. This is essentially

clang/test/CodeGenCXX/debug-info-global-ctor-dtor.cpp

@@ -22,6 +22,6 @@ void foo() {
 // CHECK-NOKEXT: [ DW_TAG_subprogram ] [line 13] [local] [def] [__cxx_global_array_dtor]
 // CHECK-NOKEXT: [ DW_TAG_subprogram ] [line 13] [local] [def] [__dtor_]
 // CHECK-NOKEXT: [ DW_TAG_subprogram ] [line 16] [local] [def] [__dtor__ZZ3foovE4stat]
-// CHECK-NOKEXT: [ DW_TAG_subprogram ] [line {{.*}}] [local] [def] [_GLOBAL__I_a]
+// CHECK-NOKEXT: [ DW_TAG_subprogram ] [line {{.*}}] [local] [def]{{$}}
 
-// CHECK-KEXT: [ DW_TAG_subprogram ] [line {{.*}}] [local] [def] [_GLOBAL__D_a]
+// CHECK-KEXT: [ DW_TAG_subprogram ] [line {{.*}}] [local] [def]{{$}}

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

@@ -14,4 +14,4 @@ struct C : A, B {
 
 void C::f() { }
 
-// CHECK-NOT: [ DW_TAG_subprogram ] [line 15] [def] [_ZThn{{4|8}}_N1C1fEv]
+// CHECK: metadata !"_ZThn{{4|8}}_N1C1fEv", i32 15, {{.*}} ; [ DW_TAG_subprogram ] [line 15] [def]{{$}}