Debug Info: Retreive the layout information of exploded values from the

explosion schema rather than from the debug type information and retire
a bunch of heuristics that are no longer necessary.

To enable this, this commit also includes a bugfix to debug info for
opaque data structures with the correct size and alignment information.

<rdar://problem/21470869+22707597>

lib/IRGen/IRGenDebugInfo.cpp

@@ -885,74 +885,6 @@ llvm::DIFile *IRGenDebugInfo::getFile(llvm::DIScope *Scope) {
   return cast<llvm::DIFile>(Scope);
 }
 
-/// Return the storage size of an explosion value.
-static uint64_t getSizeFromExplosionValue(const clang::TargetInfo &TI,
-                                          llvm::Value *V) {
-  llvm::Type *Ty = V->getType();
-  if (unsigned PrimitiveSize = Ty->getPrimitiveSizeInBits())
-    return PrimitiveSize;
-  else if (Ty->isPointerTy())
-    return TI.getPointerWidth(0);
-  else
-    llvm_unreachable("unhandled type of explosion value");
-}
-
-/// A generator that recursively returns the size of each element of a
-/// composite type.
-class ElementSizes {
-  const TrackingDIRefMap &DIRefMap;
-  llvm::SmallPtrSetImpl<const llvm::DIType *> &IndirectEnums;
-  llvm::SmallVector<const llvm::DIType *, 12> Stack;
-public:
-  ElementSizes(const llvm::DIType *DITy, const TrackingDIRefMap &DIRefMap,
-               llvm::SmallPtrSetImpl<const llvm::DIType *> &IndirectEnums)
-    : DIRefMap(DIRefMap), IndirectEnums(IndirectEnums), Stack(1, DITy) {}
-
-  struct SizeAlign {
-    uint64_t SizeInBits, AlignInBits;
-  };
-
-  struct SizeAlign getNext() {
-    if (Stack.empty())
-      return {0, 0};
-
-    auto *Cur = Stack.pop_back_val();
-    if (isa<llvm::DICompositeType>(Cur) &&
-        Cur->getTag() != llvm::dwarf::DW_TAG_subroutine_type) {
-      auto *CTy = cast<llvm::DICompositeType>(Cur);
-      auto Elts = CTy->getElements();
-      unsigned N = Cur->getTag() == llvm::dwarf::DW_TAG_union_type
-        ? std::min(1U, Elts.size()) // For unions, pick any one.
-        : Elts.size();
-
-      if (N) {
-        // Push all elements in reverse order.
-        // FIXME: With a little more state we don't need to actually
-        // store them on the Stack.
-        for (unsigned I = N; I > 0; --I)
-          Stack.push_back(cast<llvm::DIType>(Elts[I - 1]));
-        return getNext();
-      }
-    }
-    switch (Cur->getTag()) {
-    case llvm::dwarf::DW_TAG_member:
-      // FIXME: Correctly handle the explosion value for enum types
-      // with indirect members.
-      if (IndirectEnums.count(Cur))
-        return {0, 0};
-      [[clang::fallthrough]];
-    case llvm::dwarf::DW_TAG_typedef: {
-      // Replace top of stack.
-      auto *DTy = cast<llvm::DIDerivedType>(Cur);
-      Stack.push_back(DTy->getBaseType().resolve(DIRefMap));
-      return getNext();
-    }
-    default:
-      return {Cur->getSizeInBits(), Cur->getAlignInBits()};
-    }
-  }
-};
-
 static Size
 getStorageSize(const llvm::DataLayout &DL, ArrayRef<llvm::Value *> Storage) {
   unsigned size = 0;
@@ -1012,13 +944,16 @@ void IRGenDebugInfo::emitVariableDeclaration(
                                   Optimized, Flags);
 
   // Insert a debug intrinsic into the current block.
-  unsigned OffsetInBits = 0;
   auto *BB = Builder.GetInsertBlock();
   bool IsPiece = Storage.size() > 1;
   uint64_t SizeOfByte = CI.getTargetInfo().getCharWidth();
   unsigned VarSizeInBits = getSizeInBits(Var, DIRefMap);
-  ElementSizes EltSizes(DITy, DIRefMap, IndirectEnumCases);
+
-  auto Dim = EltSizes.getNext();
+  // Running variables for the current/previous piece.
+  unsigned SizeInBits = 0;
+  unsigned AlignInBits = SizeOfByte;
+  unsigned OffsetInBits = 0;
+
   for (llvm::Value *Piece : Storage) {
     SmallVector<uint64_t, 3> Operands;
     if (Indirection)
@@ -1030,32 +965,22 @@ void IRGenDebugInfo::emitVariableDeclaration(
       Piece = llvm::ConstantInt::get(llvm::Type::getInt64Ty(M.getContext()), 0);
 
     if (IsPiece) {
-      // Try to get the size from the type if possible.
+      // Advance the offset and align it for the next piece.
-      auto StorageSize = getSizeFromExplosionValue(CI.getTargetInfo(), Piece);
+      OffsetInBits += llvm::alignTo(SizeInBits, AlignInBits);
-      assert((Dim.SizeInBits != 0 || StorageSize != 0) &&
+      SizeInBits = IGM.DataLayout.getTypeSizeInBits(Piece->getType());
-            "zero-sized variable with nonzero storage size");
+      AlignInBits = IGM.DataLayout.getABITypeAlignment(Piece->getType());
+      if (!AlignInBits)
+        AlignInBits = SizeOfByte;
 
-      // FIXME: Occasionally we miss out that the Storage is actually a
+      // Sanity checks.
-      // refcount wrapper. Silently skip these for now.
+      assert(SizeInBits && "zero-sized piece");
-      if (OffsetInBits+Dim.SizeInBits > VarSizeInBits)
+      assert(SizeInBits < VarSizeInBits && "piece covers entire var");
-        break;
+      assert(OffsetInBits+SizeInBits <= VarSizeInBits && "pars > totum");
-      if (OffsetInBits == 0 && Dim.SizeInBits == VarSizeInBits)
-        break;
-      if (Dim.SizeInBits == 0)
-        break;
 
-      assert(Dim.SizeInBits < VarSizeInBits
+      // Add the piece DWARF expression.
-             && "piece covers entire var");
-      assert(OffsetInBits+Dim.SizeInBits <= VarSizeInBits && "pars > totum");
       Operands.push_back(llvm::dwarf::DW_OP_bit_piece);
       Operands.push_back(OffsetInBits);
-      Operands.push_back(Dim.SizeInBits);
+      Operands.push_back(SizeInBits);
-
-      auto Size = Dim.SizeInBits;
-      Dim = EltSizes.getNext();
-      OffsetInBits +=
-        llvm::alignTo(Size, Dim.AlignInBits ? Dim.AlignInBits
-                      : SizeOfByte);
     }
     emitDbgIntrinsic(BB, Piece, Var, DBuilder.createExpression(Operands), Line,
                      Loc.Column, Scope, DS);
@@ -1334,14 +1259,46 @@ llvm::DIType *IRGenDebugInfo::createPointerSizedStruct(
   unsigned PtrAlign = CI.getTargetInfo().getPointerAlign(0);
   auto PtrTy = DBuilder.createPointerType(PointeeTy, PtrSize, PtrAlign);
   llvm::Metadata *Elements[] = {
-    DBuilder.createMemberType(Scope, "pointer", File, 0,
+    DBuilder.createMemberType(Scope, "ptr", File, 0,
                               PtrSize, PtrAlign, 0, Flags, PtrTy)
   };
   return DBuilder.createStructType(
       Scope, Name, File, Line, PtrSize, PtrAlign, Flags,
-      nullptr, // DerivedFrom
+      /* DerivedFrom */ nullptr, DBuilder.getOrCreateArray(Elements),
-      DBuilder.getOrCreateArray(Elements), llvm::dwarf::DW_LANG_Swift,
+      llvm::dwarf::DW_LANG_Swift, nullptr, MangledName);
-      nullptr, MangledName);
+}
+
+/// Create a 2*pointer-sized struct with a mangled name and a single
+/// member of PointeeTy.
+llvm::DIType *IRGenDebugInfo::createDoublePointerSizedStruct(
+    llvm::DIScope *Scope, StringRef Name, llvm::DIType *PointeeTy,
+    llvm::DIFile *File, unsigned Line, unsigned Flags, StringRef MangledName) {
+  unsigned PtrSize = CI.getTargetInfo().getPointerWidth(0);
+  unsigned PtrAlign = CI.getTargetInfo().getPointerAlign(0);
+  llvm::Metadata *Elements[] = {
+      DBuilder.createMemberType(
+          Scope, "ptr", File, 0, PtrSize, PtrAlign, 0, Flags,
+          DBuilder.createPointerType(PointeeTy, PtrSize, PtrAlign)),
+      DBuilder.createMemberType(
+          Scope, "_", File, 0, PtrSize, PtrAlign, 0, Flags,
+          DBuilder.createPointerType(nullptr, PtrSize, PtrAlign))};
+  return DBuilder.createStructType(
+      Scope, Name, File, Line, 2*PtrSize, PtrAlign, Flags,
+      /* DerivedFrom */ nullptr, DBuilder.getOrCreateArray(Elements),
+      llvm::dwarf::DW_LANG_Swift, nullptr, MangledName);
+}
+
+/// Create an opaque struct with a mangled name.
+llvm::DIType *
+IRGenDebugInfo::createOpaqueStruct(llvm::DIScope *Scope, StringRef Name,
+                                   llvm::DIFile *File, unsigned Line,
+                                   unsigned SizeInBits, unsigned AlignInBits,
+                                   unsigned Flags, StringRef MangledName) {
+  return DBuilder.createStructType(
+      Scope, Name, File, Line, SizeInBits, AlignInBits, Flags,
+      /* DerivedFrom */ nullptr,
+      DBuilder.getOrCreateArray(ArrayRef<llvm::Metadata *>()),
+      llvm::dwarf::DW_LANG_Swift, nullptr, MangledName);
 }
 
 /// Construct a DIType from a DebugTypeInfo object.
@@ -1497,6 +1454,7 @@ llvm::DIType *IRGenDebugInfo::createType(DebugTypeInfo DbgTy,
         }
       Scope = getOrCreateModule(ModuleName, TheCU, ModuleName, ModulePath);
     }
+    assert(SizeInBits == CI.getTargetInfo().getPointerWidth(0));
     return createPointerSizedStruct(Scope, Decl->getNameStr(),
                                     getOrCreateFile(L.Filename), L.Line, Flags,
                                     MangledName);
@@ -1508,9 +1466,9 @@ llvm::DIType *IRGenDebugInfo::createType(DebugTypeInfo DbgTy,
     // FIXME: (LLVM branch) This should probably be a DW_TAG_interface_type.
     auto L = getDebugLoc(SM, Decl);
     auto File = getOrCreateFile(L.Filename);
-    return createPointerSizedStruct(Scope,
+    return createOpaqueStruct(Scope, Decl ? Decl->getNameStr() : MangledName,
-                                    Decl ? Decl->getNameStr() : MangledName,
+                              File, L.Line, SizeInBits, AlignInBits, Flags,
-                                    File, L.Line, Flags, MangledName);
+                              MangledName);
   }
 
   case TypeKind::ProtocolComposition: {
@@ -1520,15 +1478,16 @@ llvm::DIType *IRGenDebugInfo::createType(DebugTypeInfo DbgTy,
 
     // FIXME: emit types
     // auto ProtocolCompositionTy = BaseTy->castTo<ProtocolCompositionType>();
-    return createPointerSizedStruct(Scope,
+    return createOpaqueStruct(Scope, Decl ? Decl->getNameStr() : MangledName,
-                                    Decl ? Decl->getNameStr() : MangledName,
+                              File, L.Line, SizeInBits, AlignInBits, Flags,
-                                    File, L.Line, Flags, MangledName);
+                              MangledName);
   }
 
   case TypeKind::UnboundGeneric: {
     auto *UnboundTy = BaseTy->castTo<UnboundGenericType>();
     auto *Decl = UnboundTy->getDecl();
     auto L = getDebugLoc(SM, Decl);
+    assert(SizeInBits == CI.getTargetInfo().getPointerWidth(0));
     return createPointerSizedStruct(Scope,
                                     Decl ? Decl->getNameStr() : MangledName,
                                     File, L.Line, Flags, MangledName);
@@ -1538,9 +1497,9 @@ llvm::DIType *IRGenDebugInfo::createType(DebugTypeInfo DbgTy,
     auto *StructTy = BaseTy->castTo<BoundGenericStructType>();
     auto *Decl = StructTy->getDecl();
     auto L = getDebugLoc(SM, Decl);
-    return createPointerSizedStruct(Scope,
+    return createOpaqueStruct(Scope, Decl ? Decl->getNameStr() : MangledName,
-                                    Decl ? Decl->getNameStr() : MangledName,
+                              File, L.Line, SizeInBits, AlignInBits, Flags,
-                                    File, L.Line, Flags, MangledName);
+                              MangledName);
   }
 
   case TypeKind::BoundGenericClass: {
@@ -1549,6 +1508,7 @@ llvm::DIType *IRGenDebugInfo::createType(DebugTypeInfo DbgTy,
     auto L = getDebugLoc(SM, Decl);
     // TODO: We may want to peek at Decl->isObjC() and set this
     // attribute accordingly.
+    assert(SizeInBits == CI.getTargetInfo().getPointerWidth(0));
     return createPointerSizedStruct(Scope,
                                     Decl ? Decl->getNameStr() : MangledName,
                                     File, L.Line, Flags, MangledName);
@@ -1640,18 +1600,17 @@ llvm::DIType *IRGenDebugInfo::createType(DebugTypeInfo DbgTy,
   case TypeKind::Function:
   case TypeKind::PolymorphicFunction:
   case TypeKind::GenericFunction: {
-    auto FwdDecl = llvm::TempDINode(
+    auto FwdDecl = llvm::TempDINode(DBuilder.createReplaceableCompositeType(
-      DBuilder.createReplaceableCompositeType(
         llvm::dwarf::DW_TAG_subroutine_type, MangledName, Scope, File, 0,
-          llvm::dwarf::DW_LANG_Swift, SizeInBits, AlignInBits, Flags,
+        llvm::dwarf::DW_LANG_Swift, SizeInBits, AlignInBits, Flags,
-          MangledName));
+        MangledName));
-     
+
     auto TH = llvm::TrackingMDNodeRef(FwdDecl.get());
     DITypeCache[DbgTy.getType()] = TH;
 
-    CanSILFunctionType FunctionTy;
+    CanSILFunctionType FunTy;
     if (auto *SILFnTy = dyn_cast<SILFunctionType>(BaseTy))
-      FunctionTy = CanSILFunctionType(SILFnTy);
+      FunTy = CanSILFunctionType(SILFnTy);
     // FIXME: Handling of generic parameters in SIL type lowering is in flux.
     // DebugInfo doesn't appear to care about the generic context, so just
     // throw it away before lowering.
@@ -1659,20 +1618,31 @@ llvm::DIType *IRGenDebugInfo::createType(DebugTypeInfo DbgTy,
              isa<PolymorphicFunctionType>(BaseTy)) {
       auto *fTy = cast<AnyFunctionType>(BaseTy);
       auto *nongenericTy = FunctionType::get(fTy->getInput(), fTy->getResult(),
-                                            fTy->getExtInfo());
+                                             fTy->getExtInfo());
 
-      FunctionTy = IGM.SILMod->Types.getLoweredType(nongenericTy)
+      FunTy = IGM.SILMod->Types.getLoweredType(nongenericTy)
-                       .castTo<SILFunctionType>();
+                  .castTo<SILFunctionType>();
     } else
-      FunctionTy =
+      FunTy =
           IGM.SILMod->Types.getLoweredType(BaseTy).castTo<SILFunctionType>();
-    auto Params = createParameterTypes(FunctionTy, DbgTy.getDeclContext());
+    auto Params = createParameterTypes(FunTy, DbgTy.getDeclContext());
 
-    // Functions are actually stored as a Pointer or a FunctionPairTy:
-    // { i8*, %swift.refcounted* }
     auto FnTy = DBuilder.createSubroutineType(Params, Flags);
-    auto DITy = createPointerSizedStruct(Scope, MangledName, FnTy,
+    llvm::DIType *DITy;
-                                         MainFile, 0, Flags, MangledName);
+    if (FunTy->getRepresentation() == SILFunctionType::Representation::Thick) {
+      if (SizeInBits == 2 * CI.getTargetInfo().getPointerWidth(0))
+        // This is a FunctionPairTy: { i8*, %swift.refcounted* }.
+        DITy = createDoublePointerSizedStruct(Scope, MangledName, FnTy,
+                                              MainFile, 0, Flags, MangledName);
+      else
+        // This is a generic function as noted above.
+        DITy = createOpaqueStruct(Scope, MangledName, MainFile, 0, SizeInBits,
+                                  AlignInBits, Flags, MangledName);
+    } else {
+      assert(SizeInBits == CI.getTargetInfo().getPointerWidth(0));
+      DITy = createPointerSizedStruct(Scope, MangledName, FnTy, MainFile, 0,
+                                      Flags, MangledName);
+    }
     DBuilder.replaceTemporary(std::move(FwdDecl), DITy);
     return DITy;
   }

lib/IRGen/IRGenDebugInfo.h

@@ -264,6 +264,13 @@ private:
                                          llvm::DIType *PointeeTy,
                                          llvm::DIFile *File, unsigned Line,
                                          unsigned Flags, StringRef MangledName);
+  llvm::DIType *createDoublePointerSizedStruct(
+      llvm::DIScope *Scope, StringRef Name, llvm::DIType *PointeeTy,
+      llvm::DIFile *File, unsigned Line, unsigned Flags, StringRef MangledName);
+  llvm::DIType *createOpaqueStruct(llvm::DIScope *Scope, StringRef Name,
+                                   llvm::DIFile *File, unsigned Line,
+                                   unsigned SizeInBits, unsigned AlignInBits,
+                                   unsigned Flags, StringRef MangledName);
   uint64_t getSizeOfBasicType(DebugTypeInfo DbgTy);
   TypeAliasDecl *getMetadataType();
 };

test/DebugInfo/fnptr.swift

@@ -13,7 +13,7 @@ func main() -> Int64 {
     // CHECK-DAG: !DILocalVariable(name: "bar_function_pointer",{{.*}} line: [[@LINE+1]],{{.*}} type: !"[[BARPT:[^,]+]]"
     var bar_function_pointer = bar
     // CHECK-DAG: !DICompositeType(tag: DW_TAG_structure_type, name: "[[BARPT]]",{{.*}} elements: ![[BARMEMBERS:[0-9]+]]
-    // CHECK-DAG: ![[BARMEMBERS]] = !{![[BARMEMBER:.*]]}
+    // CHECK-DAG: ![[BARMEMBERS]] = !{![[BARMEMBER:.*]], {{.*}}}
     // CHECK-DAG: ![[BARMEMBER]] = !DIDerivedType(tag: DW_TAG_member,{{.*}} baseType: ![[BARPTR:[0-9]+]]
     // CHECK-DAG: ![[BARPTR]] = !DIDerivedType(tag: DW_TAG_pointer_type,{{.*}} baseType: ![[BART:[0-9]+]]
     // CHECK-DAG: ![[BART]] = !DISubroutineType(types: ![[BARARGS:[0-9]+]])
@@ -22,7 +22,7 @@ func main() -> Int64 {
 
     // CHECK-DAG: !DILocalVariable(name: "baz_function_pointer",{{.*}} type: !"[[BAZPT:[^,]+]]"
     // CHECK-DAG: !DICompositeType(tag: DW_TAG_structure_type, name: "[[BAZPT]]",{{.*}} elements: ![[BAZMEMBERS:[0-9]+]]
-    // CHECK-DAG: ![[BAZMEMBERS]] = !{![[BAZMEMBER:.*]]}
+    // CHECK-DAG: ![[BAZMEMBERS]] = !{![[BAZMEMBER:.*]], {{.*}}}
     // CHECK-DAG: ![[BAZMEMBER]] = !DIDerivedType(tag: DW_TAG_member,{{.*}} baseType: ![[BAZPTR:[0-9]+]]
     // CHECK-DAG: ![[BAZPTR]] = !DIDerivedType(tag: DW_TAG_pointer_type,{{.*}} baseType: ![[BAZT:[0-9]+]]
     // CHECK-DAG: ![[BAZT]] = !DISubroutineType(types: ![[BAZARGS:.*]])
@@ -32,7 +32,7 @@ func main() -> Int64 {
 
     // CHECK-DAG: !DILocalVariable(name: "barz_function_pointer",{{.*}} type: !"[[BARZPT:[^,]+]]"
     // CHECK-DAG: !DICompositeType(tag: DW_TAG_structure_type, name: "[[BARZPT]]",{{.*}} elements: ![[BARZMEMBERS:[0-9]+]]
-    // CHECK-DAG: ![[BARZMEMBERS]] = !{![[BARZMEMBER:.*]]}
+    // CHECK-DAG: ![[BARZMEMBERS]] = !{![[BARZMEMBER:.*]], {{.*}}}
     // CHECK-DAG: ![[BARZMEMBER]] = !DIDerivedType(tag: DW_TAG_member,{{.*}} baseType: ![[BARZPTR:[0-9]+]]
     // CHECK-DAG: ![[BARZPTR]] = !DIDerivedType(tag: DW_TAG_pointer_type,{{.*}} baseType: ![[BARZT:[0-9]+]]
     // CHECK-DAG: ![[BARZT]] = !DISubroutineType(types: ![[BARZARGS:.*]])