Merge pull request #9455 from swiftlang/revert-9425-remove-spare-bits-debug

Revert "[DebugInfo] Remove spare bits mask from LLVM IR and DWARF"

Author: jckarter

lldb/source/Plugins/LanguageRuntime/Swift/ReflectionContext.cpp

@@ -45,6 +45,13 @@ struct DescriptorFinderForwarder : public swift::reflection::DescriptorFinder {
     return nullptr;
   }
 
+  std::unique_ptr<swift::reflection::MultiPayloadEnumDescriptorBase>
+  getMultiPayloadEnumDescriptor(const swift::reflection::TypeRef *TR) override {
+    if (!m_descriptor_finders.empty() && shouldConsultDescriptorFinder())
+      return m_descriptor_finders.back()->getMultiPayloadEnumDescriptor(TR);
+    return nullptr;
+  }
+
   void PushExternalDescriptorFinder(
       swift::reflection::DescriptorFinder *descriptor_finder) {
     m_descriptor_finders.push_back(descriptor_finder);

lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserSwift.h

@@ -89,6 +89,10 @@ class DWARFASTParserSwift : public lldb_private::plugin::dwarf::DWARFASTParser,
   std::unique_ptr<swift::reflection::BuiltinTypeDescriptorBase>
   getBuiltinTypeDescriptor(const swift::reflection::TypeRef *TR) override;
 
+  /// Returns a builtin descriptor constructed from DWARF info.
+  std::unique_ptr<swift::reflection::MultiPayloadEnumDescriptorBase>
+  getMultiPayloadEnumDescriptor(const swift::reflection::TypeRef *TR) override;
+
 private:
   /// Returns the canonical demangle tree of a die's type.
   NodePointer GetCanonicalDemangleTree(DWARFDIE &die);

lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserSwiftDescriptorFinder.cpp

@@ -280,6 +280,53 @@ class DWARFFieldDescriptorImpl : public swift::reflection::FieldDescriptorBase {
     return payload_fields;
   }
 };
+
+class DWARFMultiPayloadEnumDescriptorImpl
+    : public swift::reflection::MultiPayloadEnumDescriptorBase {
+  ConstString m_mangled_name;
+  DIERef m_die_ref;
+  std::vector<uint8_t> m_spare_bits_mask;
+  uint64_t m_byte_offset;
+
+public:
+  ~DWARFMultiPayloadEnumDescriptorImpl() override = default;
+
+  DWARFMultiPayloadEnumDescriptorImpl(ConstString mangled_name, DIERef die_ref,
+                                      std::vector<uint8_t> &&spare_bits_mask,
+                                      uint64_t byte_offset)
+      : swift::reflection::MultiPayloadEnumDescriptorBase(),
+        m_mangled_name(mangled_name), m_die_ref(die_ref),
+        m_spare_bits_mask(std::move(spare_bits_mask)),
+        m_byte_offset(byte_offset) {}
+
+  llvm::StringRef getMangledTypeName() override {
+    return m_mangled_name.GetStringRef();
+  }
+
+  uint32_t getContentsSizeInWords() const override {
+    return m_spare_bits_mask.size() / 4;
+  }
+
+  size_t getSizeInBytes() const override { return m_spare_bits_mask.size(); }
+
+  uint32_t getFlags() const override { return usesPayloadSpareBits(); }
+
+  bool usesPayloadSpareBits() const override {
+    return !m_spare_bits_mask.empty();
+  }
+
+  uint32_t getPayloadSpareBitMaskByteOffset() const override {
+    return m_byte_offset;
+  }
+
+  uint32_t getPayloadSpareBitMaskByteCount() const override {
+    return getSizeInBytes();
+  }
+
+  const uint8_t *getPayloadSpareBits() const override {
+    return m_spare_bits_mask.data();
+  }
+};
 } // namespace
 
 /// Constructs a builtin type descriptor from DWARF information.
@@ -327,6 +374,85 @@ DWARFASTParserSwift::getBuiltinTypeDescriptor(
       type.GetMangledTypeName());
 }
 
+std::unique_ptr<swift::reflection::MultiPayloadEnumDescriptorBase>
+DWARFASTParserSwift::getMultiPayloadEnumDescriptor(
+    const swift::reflection::TypeRef *TR) {
+  assert(ModuleList::GetGlobalModuleListProperties()
+                 .GetSwiftEnableFullDwarfDebugging() !=
+             lldb_private::AutoBool::False &&
+         "Full DWARF debugging for Swift is disabled!");
+
+  auto pair = getTypeAndDie(m_swift_typesystem, TR);
+  if (!pair)
+    return nullptr;
+
+  auto [type, die] = *pair;
+  if (!die)
+    return nullptr;
+
+  auto kind = getFieldDescriptorKindForDie(type);
+  if (!kind)
+    return nullptr;
+
+  auto child_die = die.GetFirstChild();
+  auto bit_offset =
+      child_die.GetAttributeValueAsUnsigned(llvm::dwarf::DW_AT_bit_offset, 0);
+
+  auto byte_offset = (bit_offset + 7) / 8;
+
+  const auto &attributes = child_die.GetAttributes();
+  auto spare_bits_mask_idx =
+      attributes.FindAttributeIndex(llvm::dwarf::DW_AT_APPLE_spare_bits_mask);
+  if (spare_bits_mask_idx == UINT32_MAX)
+    return nullptr;
+
+  DWARFFormValue form_value;
+  attributes.ExtractFormValueAtIndex(spare_bits_mask_idx, form_value);
+
+  if (!form_value.IsValid()) {
+    if (auto *log = GetLog(LLDBLog::Types)) {
+      std::stringstream ss;
+      TR->dump(ss);
+      LLDB_LOG(log,
+               "Could not produce MultiPayloadEnumTypeInfo for typeref: {0}",
+               ss.str());
+    }
+    return nullptr;
+  }
+  // If there's a block data, this is a number bigger than 64 bits already
+  // encoded as an array.
+  if (form_value.BlockData()) {
+    uint64_t block_length = form_value.Unsigned();
+    std::vector<uint8_t> bytes(form_value.BlockData(),
+                             form_value.BlockData() + block_length);
+    return std::make_unique<DWARFMultiPayloadEnumDescriptorImpl>(
+        type.GetMangledTypeName(), *die.GetDIERef(),
+        std::move(bytes), byte_offset);
+  }
+
+  // If there is no block data, the spare bits mask is encoded as a single 64
+  // bit number. Convert this to a byte array with only the amount of bytes
+  // necessary to cover the whole number (see
+  // MultiPayloadEnumDescriptorBuilder::layout on GenReflection.cpp for a
+  // similar calculation when emitting this into metadata).
+  llvm::APInt bits(64, form_value.Unsigned());
+  auto bitsInMask = bits.getActiveBits(); 
+  uint32_t bytesInMask = (bitsInMask + 7) / 8;
+  auto wordsInMask = (bytesInMask + 3) / 4;
+  bits = bits.zextOrTrunc(wordsInMask * 32);
+
+  std::vector<uint8_t> bytes;
+  for (size_t i = 0; i < bytesInMask; ++i) {
+    uint8_t byte = bits.extractBitsAsZExtValue(8, 0);
+    bytes.push_back(byte);
+    bits.lshrInPlace(8);
+  }
+
+  return std::make_unique<DWARFMultiPayloadEnumDescriptorImpl>(
+      type.GetMangledTypeName(), *die.GetDIERef(), std::move(bytes),
+      byte_offset);
+}
+
 namespace {
 DWARFDIE FindSuperClassDIE(DWARFDIE &die) {
   const auto inheritance_die_it =

llvm/include/llvm/BinaryFormat/Dwarf.def

@@ -636,6 +636,7 @@ HANDLE_DW_AT(0x3fee, APPLE_objc_direct, 0, APPLE)
 HANDLE_DW_AT(0x3fef, APPLE_sdk, 0, APPLE)
 HANDLE_DW_AT(0x3ff0, APPLE_origin, 0, APPLE)
 HANDLE_DW_AT(0x3ff1, APPLE_num_extra_inhabitants, 0, APPLE)
+HANDLE_DW_AT(0x3ff2, APPLE_spare_bits_mask, 0, APPLE)
 
 // Attribute form encodings.
 HANDLE_DW_FORM(0x01, addr, 2, DWARF)

llvm/include/llvm/IR/DIBuilder.h

@@ -533,12 +533,17 @@ namespace llvm {
     /// \param Discriminator Discriminant member
     /// \param Elements     Variant elements.
     /// \param UniqueIdentifier A unique identifier for the union.
+    /// \param OffsetInBits The offset of the variant payload in the variant
+    /// type.
+    /// \param SpareBitMask A mask of spare bits of the payload, spare bits are
+    /// bits that aren't used in any of the variant's cases.
     DICompositeType *
     createVariantPart(DIScope *Scope, StringRef Name, DIFile *File,
                       unsigned LineNumber, uint64_t SizeInBits,
                       uint32_t AlignInBits, DINode::DIFlags Flags,
                       DIDerivedType *Discriminator, DINodeArray Elements,
-                      StringRef UniqueIdentifier = "");
+                      StringRef UniqueIdentifier = "",
+                      uint64_t OffsetInBits = 0, APInt SpareBitsMask = APInt());
 
     /// Create debugging information for template
     /// type parameter.

llvm/include/llvm/IR/DebugInfoMetadata.h

@@ -1172,15 +1172,16 @@ class DICompositeType : public DIType {
   friend class MDNode;
 
   unsigned RuntimeLang;
+  llvm::APInt SpareBitsMask;
 
   DICompositeType(LLVMContext &C, StorageType Storage, unsigned Tag,
                   unsigned Line, unsigned RuntimeLang, uint64_t SizeInBits,
                   uint32_t AlignInBits, uint64_t OffsetInBits,
-                  uint32_t NumExtraInhabitants, DIFlags Flags,
-                  ArrayRef<Metadata *> Ops)
+                  uint32_t NumExtraInhabitants, APInt SpareBitsMask,
+                  DIFlags Flags, ArrayRef<Metadata *> Ops)
       : DIType(C, DICompositeTypeKind, Storage, Tag, Line, SizeInBits,
                AlignInBits, OffsetInBits, NumExtraInhabitants, Flags, Ops),
-        RuntimeLang(RuntimeLang) {}
+        RuntimeLang(RuntimeLang), SpareBitsMask(SpareBitsMask) {}
   ~DICompositeType() = default;
 
   /// Change fields in place.
@@ -1198,20 +1199,20 @@ class DICompositeType : public DIType {
   getImpl(LLVMContext &Context, unsigned Tag, StringRef Name, Metadata *File,
           unsigned Line, DIScope *Scope, DIType *BaseType, uint64_t SizeInBits,
           uint32_t AlignInBits, uint64_t OffsetInBits, DIType *SpecificationOf,
-          uint32_t NumExtraInhabitants, DIFlags Flags, DINodeArray Elements,
-          unsigned RuntimeLang, DIType *VTableHolder,
+          uint32_t NumExtraInhabitants, APInt SpareBitsMask, DIFlags Flags,
+          DINodeArray Elements, unsigned RuntimeLang, DIType *VTableHolder,
           DITemplateParameterArray TemplateParams, StringRef Identifier,
           DIDerivedType *Discriminator, Metadata *DataLocation,
           Metadata *Associated, Metadata *Allocated, Metadata *Rank,
           DINodeArray Annotations, StorageType Storage,
           bool ShouldCreate = true) {
-    return getImpl(Context, Tag, getCanonicalMDString(Context, Name), File,
-                   Line, Scope, BaseType, SizeInBits, AlignInBits, OffsetInBits,
-                   Flags, Elements.get(), RuntimeLang, VTableHolder,
-                   TemplateParams.get(),
-                   getCanonicalMDString(Context, Identifier), Discriminator,
-                   DataLocation, Associated, Allocated, Rank, Annotations.get(),
-                   SpecificationOf, NumExtraInhabitants, Storage, ShouldCreate);
+    return getImpl(
+        Context, Tag, getCanonicalMDString(Context, Name), File, Line, Scope,
+        BaseType, SizeInBits, AlignInBits, OffsetInBits, Flags, Elements.get(),
+        RuntimeLang, VTableHolder, TemplateParams.get(),
+        getCanonicalMDString(Context, Identifier), Discriminator, DataLocation,
+        Associated, Allocated, Rank, Annotations.get(), SpecificationOf,
+        NumExtraInhabitants, SpareBitsMask, Storage, ShouldCreate);
   }
   static DICompositeType *
   getImpl(LLVMContext &Context, unsigned Tag, MDString *Name, Metadata *File,
@@ -1222,8 +1223,8 @@ class DICompositeType : public DIType {
           MDString *Identifier, Metadata *Discriminator, Metadata *DataLocation,
           Metadata *Associated, Metadata *Allocated, Metadata *Rank,
           Metadata *Annotations, Metadata *SpecificationOf,
-          uint32_t NumExtraInhabitants, StorageType Storage,
-          bool ShouldCreate = true);
+          uint32_t NumExtraInhabitants, APInt SpareBitsMask,
+          StorageType Storage, bool ShouldCreate = true);
 
   TempDICompositeType cloneImpl() const {
     return getTemporary(
@@ -1233,7 +1234,7 @@ class DICompositeType : public DIType {
         getTemplateParams(), getIdentifier(), getDiscriminator(),
         getRawDataLocation(), getRawAssociated(), getRawAllocated(),
         getRawRank(), getAnnotations(), getSpecificationOf(),
-        getNumExtraInhabitants());
+        getNumExtraInhabitants(), getSpareBitsMask());
   }
 
 public:
@@ -1248,11 +1249,11 @@ class DICompositeType : public DIType {
        Metadata *DataLocation = nullptr, Metadata *Associated = nullptr,
        Metadata *Allocated = nullptr, Metadata *Rank = nullptr,
        DINodeArray Annotations = nullptr, DIType *SpecificationOf = nullptr,
-       uint32_t NumExtraInhabitants = 0),
+       uint32_t NumExtraInhabitants = 0, APInt SpareBitsMask = APInt()),
       (Tag, Name, File, Line, Scope, BaseType, SizeInBits, AlignInBits,
-       OffsetInBits, SpecificationOf, NumExtraInhabitants, Flags, Elements,
-       RuntimeLang, VTableHolder, TemplateParams, Identifier, Discriminator,
-       DataLocation, Associated, Allocated, Rank, Annotations))
+       OffsetInBits, SpecificationOf, NumExtraInhabitants, SpareBitsMask, Flags,
+       Elements, RuntimeLang, VTableHolder, TemplateParams, Identifier,
+       Discriminator, DataLocation, Associated, Allocated, Rank, Annotations))
   DEFINE_MDNODE_GET(
       DICompositeType,
       (unsigned Tag, MDString *Name, Metadata *File, unsigned Line,
@@ -1263,11 +1264,12 @@ class DICompositeType : public DIType {
        Metadata *Discriminator = nullptr, Metadata *DataLocation = nullptr,
        Metadata *Associated = nullptr, Metadata *Allocated = nullptr,
        Metadata *Rank = nullptr, Metadata *Annotations = nullptr,
-       Metadata *SpecificationOf = nullptr, uint32_t NumExtraInhabitants = 0),
+       Metadata *SpecificationOf = nullptr, uint32_t NumExtraInhabitants = 0,
+       APInt SpareBitsMask = APInt()),
       (Tag, Name, File, Line, Scope, BaseType, SizeInBits, AlignInBits,
        OffsetInBits, Flags, Elements, RuntimeLang, VTableHolder, TemplateParams,
        Identifier, Discriminator, DataLocation, Associated, Allocated, Rank,
-       Annotations, SpecificationOf, NumExtraInhabitants))
+       Annotations, SpecificationOf, NumExtraInhabitants, SpareBitsMask))
 
   TempDICompositeType clone() const { return cloneImpl(); }
 
@@ -1283,7 +1285,7 @@ class DICompositeType : public DIType {
              MDString *Name, Metadata *File, unsigned Line, Metadata *Scope,
              Metadata *BaseType, uint64_t SizeInBits, uint32_t AlignInBits,
              uint64_t OffsetInBits, Metadata *SpecificationOf,
-             uint32_t NumExtraInhabitants,  DIFlags Flags,
+             uint32_t NumExtraInhabitants, APInt SpareBitsMask, DIFlags Flags,
              Metadata *Elements, unsigned RuntimeLang, Metadata *VTableHolder,
              Metadata *TemplateParams, Metadata *Discriminator,
              Metadata *DataLocation, Metadata *Associated, Metadata *Allocated,
@@ -1305,8 +1307,8 @@ class DICompositeType : public DIType {
                MDString *Name, Metadata *File, unsigned Line, Metadata *Scope,
                Metadata *BaseType, uint64_t SizeInBits, uint32_t AlignInBits,
                uint64_t OffsetInBits, Metadata *SpecificationOf,
-               uint32_t NumExtraInhabitants, DIFlags Flags, Metadata *Elements,
-               unsigned RuntimeLang, Metadata *VTableHolder,
+               uint32_t NumExtraInhabitants, APInt SpareBitsMask, DIFlags Flags,
+               Metadata *Elements, unsigned RuntimeLang, Metadata *VTableHolder,
                Metadata *TemplateParams, Metadata *Discriminator,
                Metadata *DataLocation, Metadata *Associated,
                Metadata *Allocated, Metadata *Rank, Metadata *Annotations);
@@ -1323,6 +1325,7 @@ class DICompositeType : public DIType {
   }
   StringRef getIdentifier() const { return getStringOperand(7); }
   unsigned getRuntimeLang() const { return RuntimeLang; }
+  const APInt &getSpareBitsMask() const { return SpareBitsMask; }
 
   Metadata *getRawBaseType() const { return getOperand(3); }
   Metadata *getRawElements() const { return getOperand(4); }

llvm/lib/AsmParser/LLParser.cpp

@@ -5433,7 +5433,8 @@ bool LLParser::parseDICompositeType(MDNode *&Result, bool IsDistinct) {
   OPTIONAL(rank, MDSignedOrMDField, );                                         \
   OPTIONAL(annotations, MDField, );                                            \
   OPTIONAL(num_extra_inhabitants, MDUnsignedField, (0, UINT32_MAX));           \
-  OPTIONAL(specification_of, MDField, ); 
+  OPTIONAL(specification_of, MDField, );                                       \
+  OPTIONAL(spare_bits_mask, MDAPSIntField, );                                  
   PARSE_MD_FIELDS();
 #undef VISIT_MD_FIELDS
 
@@ -5449,10 +5450,11 @@ bool LLParser::parseDICompositeType(MDNode *&Result, bool IsDistinct) {
     if (auto *CT = DICompositeType::buildODRType(
             Context, *identifier.Val, tag.Val, name.Val, file.Val, line.Val,
             scope.Val, baseType.Val, size.Val, align.Val, offset.Val,
-            specification_of.Val, num_extra_inhabitants.Val, flags.Val,
-            elements.Val, runtimeLang.Val, vtableHolder.Val, templateParams.Val,
-            discriminator.Val, dataLocation.Val, associated.Val, allocated.Val,
-            Rank, annotations.Val)) {
+            specification_of.Val, num_extra_inhabitants.Val,
+            spare_bits_mask.Val, flags.Val, elements.Val, runtimeLang.Val,
+            vtableHolder.Val, templateParams.Val, discriminator.Val,
+            dataLocation.Val, associated.Val, allocated.Val, Rank,
+            annotations.Val)) {
       Result = CT;
       return false;
     }
@@ -5465,7 +5467,8 @@ bool LLParser::parseDICompositeType(MDNode *&Result, bool IsDistinct) {
        size.Val, align.Val, offset.Val, flags.Val, elements.Val,
        runtimeLang.Val, vtableHolder.Val, templateParams.Val, identifier.Val,
        discriminator.Val, dataLocation.Val, associated.Val, allocated.Val, Rank,
-       annotations.Val, specification_of.Val, num_extra_inhabitants.Val));
+       annotations.Val, specification_of.Val, num_extra_inhabitants.Val,
+       spare_bits_mask.Val));
   return false;
 }