Remove all uses of DIFlagBlockByrefStruct from Clang

[aprantl]

Summary

This patch removes the last reason why DIFlagBlockByrefStruct from Clang by directly implementing the drilling into the member type done in DwarfDebug::DbgVariable::getType() into the frontend.

[aprantl]

( D51763 is not *really* a dependency, but it's closely related. )

[JDevlieghere]

Thanks Adrian, LGTM!

lib/CodeGen/CGDebugInfo.h

 private:
   /// Emit call to llvm.dbg.declare for a variable declaration.
   /// Returns a pointer to the DILocalVariable associated with the
   /// llvm.dbg.declare, or nullptr otherwise.
   llvm::DILocalVariable *EmitDeclare(const VarDecl *decl, llvm::Value *AI,
                                      llvm::Optional<unsigned> ArgNo,
                                      CGBuilderTy &Builder);
 
+  struct BlockByRefType {
+    /// The wrapper struct used inside the __block_literal struct.
+    llvm::DIType *BlockByRefWrapper;
+    /// The type as it appears in the source code.
+    llvm::DIType *WrappedType;
+  };
+
   /// Build up structure info for the byref.  See \a BuildByRefType.
-  llvm::DIType *EmitTypeForVarWithBlocksAttr(const VarDecl *VD,
+  BlockByRefType EmitTypeForVarWithBlocksAttr(const VarDecl *VD,
                                               uint64_t *OffSet);
 
   /// Get context info for the DeclContext of \p Decl.
   llvm::DIScope *getDeclContextDescriptor(const Decl *D);
   /// Get context info for a given DeclContext \p Decl.
   llvm::DIScope *getContextDescriptor(const Decl *Context,
                                       llvm::DIScope *Default);
 
   llvm::DIScope *getCurrentContextDescriptor(const Decl *Decl);

lib/CodeGen/CGDebugInfo.cpp

while (LexicalBlockStack.size() != RCount) {
     LexicalBlockStack.pop_back();
   }
   FnBeginRegionCount.pop_back();
 
   if (Fn && Fn->getSubprogram())
     DBuilder.finalizeSubprogram(Fn->getSubprogram());
 }
 
-llvm::DIType *CGDebugInfo::EmitTypeForVarWithBlocksAttr(const VarDecl *VD,
-                                                        uint64_t *XOffset) {
-
+CGDebugInfo::BlockByRefType
+CGDebugInfo::EmitTypeForVarWithBlocksAttr(const VarDecl *VD,
   SmallVector<llvm::Metadata *, 5> EltTys;
   QualType FType;
   uint64_t FieldSize, FieldOffset;
   uint32_t FieldAlign;
 
   llvm::DIFile *Unit = getOrCreateFile(VD->getLocation());
   QualType Type = VD->getType();
 
if (NumPaddingBytes.isPositive()) {
       llvm::APInt pad(32, NumPaddingBytes.getQuantity());
       FType = CGM.getContext().getConstantArrayType(CGM.getContext().CharTy,
                                                     pad, ArrayType::Normal, 0);
       EltTys.push_back(CreateMemberType(Unit, FType, "", &FieldOffset));
     }
   }
 
   FType = Type;
-  llvm::DIType *FieldTy = getOrCreateType(FType, Unit);
+  llvm::DIType *WrappedTy = getOrCreateType(FType, Unit);
   FieldSize = CGM.getContext().getTypeSize(FType);
   FieldAlign = CGM.getContext().toBits(Align);
 
   *XOffset = FieldOffset;
-  FieldTy = DBuilder.createMemberType(Unit, VD->getName(), Unit, 0, FieldSize,
-                                      FieldAlign, FieldOffset,
-                                      llvm::DINode::FlagZero, FieldTy);
+  llvm::DIType *FieldTy = DBuilder.createMemberType(
+      Unit, VD->getName(), Unit, 0, FieldSize, FieldAlign, FieldOffset,
+      llvm::DINode::FlagZero, WrappedTy);
   EltTys.push_back(FieldTy);
   FieldOffset += FieldSize;
 
   llvm::DINodeArray Elements = DBuilder.getOrCreateArray(EltTys);
-
-  llvm::DINode::DIFlags Flags = llvm::DINode::FlagBlockByrefStruct;
-
-  return DBuilder.createStructType(Unit, "", Unit, 0, FieldOffset, 0, Flags,
-                                   nullptr, Elements);
+  return {DBuilder.createStructType(Unit, "", Unit, 0, FieldOffset, 0,
+                                    llvm::DINode::FlagZero, nullptr, Elements),
+          WrappedTy};
 }
 
 llvm::DILocalVariable *CGDebugInfo::EmitDeclare(const VarDecl *VD,
                                                 llvm::Value *Storage,
                                                 llvm::Optional<unsigned> ArgNo,
                                                 CGBuilderTy &Builder) {
   assert(DebugKind >= codegenoptions::LimitedDebugInfo);
   assert(!LexicalBlockStack.empty() && "Region stack mismatch, stack empty!");
   if (VD->hasAttr<NoDebugAttr>())
     return nullptr;
 
   bool Unwritten =
       VD->isImplicit() || (isa<Decl>(VD->getDeclContext()) &&
                            cast<Decl>(VD->getDeclContext())->isImplicit());
   llvm::DIFile *Unit = nullptr;
   if (!Unwritten)
     Unit = getOrCreateFile(VD->getLocation());
   llvm::DIType *Ty;
   uint64_t XOffset = 0;
   if (VD->hasAttr<BlocksAttr>())
-    Ty = EmitTypeForVarWithBlocksAttr(VD, &XOffset);
+    Ty = EmitTypeForVarWithBlocksAttr(VD, &XOffset).WrappedType;
   else
     Ty = getOrCreateType(VD->getType(), Unit);
 
   // If there is no debug info for this type then do not emit debug info
   // for this variable.
   if (!Ty)
     return nullptr;
 
if (VD->hasAttr<NoDebugAttr>())
     return;
 
   bool isByRef = VD->hasAttr<BlocksAttr>();
 
   uint64_t XOffset = 0;
   llvm::DIFile *Unit = getOrCreateFile(VD->getLocation());
   llvm::DIType *Ty;
   if (isByRef)
-    Ty = EmitTypeForVarWithBlocksAttr(VD, &XOffset);
+    Ty = EmitTypeForVarWithBlocksAttr(VD, &XOffset).WrappedType;
   else
     Ty = getOrCreateType(VD->getType(), Unit);
 
   // Self is passed along as an implicit non-arg variable in a
   // block. Mark it as the object pointer.
   if (const auto *IPD = dyn_cast<ImplicitParamDecl>(VD))
     if (IPD->getParameterKind() == ImplicitParamDecl::ObjCSelf)
       Ty = CreateSelfType(VD->getType(), Ty);
for (const BlockLayoutChunk &Chunk : chunks) {
 
     const VarDecl *variable = capture->getVariable();
     StringRef name = variable->getName();
 
     llvm::DIType *fieldType;
     if (capture->isByRef()) {
       TypeInfo PtrInfo = C.getTypeInfo(C.VoidPtrTy);
       auto Align = PtrInfo.AlignIsRequired ? PtrInfo.Align : 0;
-
-      // FIXME: this creates a second copy of this type!
+      // FIXME: This recomputes the layout of the BlockByRefWrapper.
       uint64_t xoffset;
-      fieldType = EmitTypeForVarWithBlocksAttr(variable, &xoffset);
+      fieldType =
+          EmitTypeForVarWithBlocksAttr(variable, &xoffset).BlockByRefWrapper;
       fieldType = DBuilder.createPointerType(fieldType, PtrInfo.Width);
       fieldType = DBuilder.createMemberType(tunit, name, tunit, line,
                                             PtrInfo.Width, Align, offsetInBits,
                                             llvm::DINode::FlagZero, fieldType);
     } else {
       auto Align = getDeclAlignIfRequired(variable, CGM.getContext());
       fieldType = createFieldType(name, variable->getType(), loc, AS_public,
                                   offsetInBits, Align, tunit, tunit);

test/CodeGenObjC/block-byref-debuginfo.m

 // RUN: %clang_cc1 -fblocks -fobjc-arc -fobjc-runtime-has-weak -debug-info-kind=limited -triple x86_64-apple-darwin -emit-llvm %s -o - | FileCheck %s
 
-// rdar://problem/14386148
+// CHECK: !DILocalVariable(name: "foo", {{.*}}type: ![[FOOTY:[0-9]+]])
+// CHECK: ![[FOOTY]] = {{.*}}!DICompositeType({{.*}}, name: "Foo"
+
+// CHECK-NOT: DIFlagBlockByrefStruct
+// CHECK: !DICompositeType(tag: DW_TAG_structure_type, name: "__block_literal_1",
+// CHECK-SAME:             size: 320, elements: ![[BL_ELTS:[0-9]+]])
+// CHECK: ![[BL_ELTS]] = !{{.*}}![[WFOO:[0-9]+]]}
+
 // Test that the foo is aligned at an 8 byte boundary in the DWARF
 // expression (256) that locates it inside of the byref descriptor:
-// CHECK: !DIDerivedType(tag: DW_TAG_member, name: "foo",
-// CHECK-NOT:            line:
-// CHECK-SAME:           offset: 256
+// CHECK: ![[WFOO]] = !DIDerivedType(tag: DW_TAG_member, name: "foo",
+// CHECK-SAME:                       baseType: ![[PTR:[0-9]+]]
+// CHECK-SAME:                       offset: 256)
+
+// CHECK: ![[PTR]] = !DIDerivedType(tag: DW_TAG_pointer_type,
+// CHECK-SAME:                      baseType: ![[WRAPPER:[0-9]+]]
+// CHECK: ![[WRAPPER]] = !DICompositeType(tag: DW_TAG_structure_type, scope:
+// CHECK:                                 elements: ![[WR_ELTS:[0-9]+]])
+// CHECK: ![[WR_ELTS]] = !{{.*}}![[WFOO:[0-9]+]]}
+// CHECK: ![[WFOO]] = !DIDerivedType(tag: DW_TAG_member, name: "foo",
+// CHECK-SAME:                       baseType: ![[FOOTY]]
+
+// CHECK: !DILocalVariable(name: "foo", {{.*}}type: ![[FOOTY]])
+
 
 struct Foo {
   unsigned char *data;
 };
 int func() {
   __attribute__((__blocks__(byref))) struct Foo foo;
+  ^{ foo.data = 0; }();
   return 0;
 }