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

We are able to calculate the spare bits mask from other information.
Remove this from the LLVM  IR representation and DWARF.

(cherry picked from commit a1bc710)

Author: augusto2112

llvm/include/llvm/BinaryFormat/Dwarf.def

@@ -636,7 +636,6 @@ 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

@@ -533,17 +533,12 @@ 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 = "",
-                      uint64_t OffsetInBits = 0, APInt SpareBitsMask = APInt());
+                      StringRef UniqueIdentifier = "");
 
     /// Create debugging information for template
     /// type parameter.

llvm/include/llvm/IR/DebugInfoMetadata.h

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

@@ -5442,8 +5442,7 @@ 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(spare_bits_mask, MDAPSIntField, );                                  
+  OPTIONAL(specification_of, MDField, ); 
   PARSE_MD_FIELDS();
 #undef VISIT_MD_FIELDS
 
@@ -5459,11 +5458,10 @@ 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,
-            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)) {
+            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)) {
       Result = CT;
       return false;
     }
@@ -5476,8 +5474,7 @@ 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,
-       spare_bits_mask.Val));
+       annotations.Val, specification_of.Val, num_extra_inhabitants.Val));
   return false;
 }
 

llvm/lib/Bitcode/Reader/MetadataLoader.cpp

@@ -1600,13 +1600,10 @@ Error MetadataLoader::MetadataLoaderImpl::parseOneMetadata(
     break;
   }
   case bitc::METADATA_COMPOSITE_TYPE: {
-    // The last field is a variable sized APInt, so the metadata loader can't
-    // reliably check the end for this record.
     if (Record.size() < 16)
       return error("Invalid record");
 
     IsDistinct = Record[0] & 1;
-    bool IsBigInt = (Record[0] >> 3) & 1;
     // If we have a UUID and this is not a forward declaration, lookup the
     // mapping.
     IsDistinct = Record[0] & 0x1;
@@ -1688,28 +1685,13 @@ Error MetadataLoader::MetadataLoaderImpl::parseOneMetadata(
       }
     }
     DICompositeType *CT = nullptr;
-    APInt SpareBitsMask;
-    // SpareBitsMask is an optional field so the metadata loader has to check if
-    // it was emitted before accessing it.
-    if (Record.size() > 24) {
-      if (IsBigInt) {
-        const uint64_t BitWidth = Record[24];
-        const size_t NumWords = Record.size() - 3;
-        SpareBitsMask =
-            readWideAPInt(ArrayRef(&Record[25], NumWords), BitWidth);
-      } else {
-        const uint64_t IntValue = Record[24];
-        SpareBitsMask = APInt(64, IntValue);
-      }
-    }
-
     if (Identifier)
       CT = DICompositeType::buildODRType(
           Context, *Identifier, Tag, Name, File, Line, Scope, BaseType,
           SizeInBits, AlignInBits, OffsetInBits, SpecificationOf,
-          NumExtraInhabitants, SpareBitsMask, Flags, Elements, RuntimeLang,
-          VTableHolder, TemplateParams, Discriminator, DataLocation, Associated,
-          Allocated, Rank, Annotations);
+          NumExtraInhabitants, Flags, Elements, RuntimeLang, VTableHolder,
+          TemplateParams, Discriminator, DataLocation, Associated, Allocated,
+          Rank, Annotations);
 
     // Create a node if we didn't get a lazy ODR type.
     if (!CT)
@@ -1719,7 +1701,7 @@ Error MetadataLoader::MetadataLoaderImpl::parseOneMetadata(
                             Elements, RuntimeLang, VTableHolder, TemplateParams,
                             Identifier, Discriminator, DataLocation, Associated,
                             Allocated, Rank, Annotations, SpecificationOf,
-                            NumExtraInhabitants, SpareBitsMask));
+                            NumExtraInhabitants));
     if (!IsNotUsedInTypeRef && Identifier)
       MetadataList.addTypeRef(*Identifier, *cast<DICompositeType>(CT));
 

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -1923,14 +1923,9 @@ void ModuleBitcodeWriter::writeDICompositeType(
     const DICompositeType *N, SmallVectorImpl<uint64_t> &Record,
     unsigned Abbrev) {
 
-  APInt SpareBitsMask = N->getSpareBitsMask();
-  unsigned IsWideAPInt = 0;;
-  if (!SpareBitsMask.isZero() && SpareBitsMask.getBitWidth() > 64) 
-    IsWideAPInt = 1 << 3;
 
   const unsigned IsNotUsedInOldTypeRef = 0x2;
-  Record.push_back(IsWideAPInt | IsNotUsedInOldTypeRef |
-                   (unsigned)N->isDistinct());
+  Record.push_back(IsNotUsedInOldTypeRef | (unsigned)N->isDistinct());
   Record.push_back(N->getTag());
   Record.push_back(VE.getMetadataOrNullID(N->getRawName()));
   Record.push_back(VE.getMetadataOrNullID(N->getFile()));
@@ -1955,17 +1950,6 @@ void ModuleBitcodeWriter::writeDICompositeType(
   Record.push_back(N->getNumExtraInhabitants());
   Record.push_back(VE.getMetadataOrNullID(N->getRawSpecificationOf()));
 
-
-  if (!SpareBitsMask.isZero()) {
-    if (IsWideAPInt) {
-      Record.push_back(SpareBitsMask.getBitWidth());
-      emitWideAPInt(Record, SpareBitsMask);
-    } else {
-        uint64_t V = SpareBitsMask.getZExtValue();
-        Record.push_back(V);
-    }
-  }
-
   Stream.EmitRecord(bitc::METADATA_COMPOSITE_TYPE, Record, Abbrev);
   Record.clear();
 }

llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp

@@ -1104,14 +1104,7 @@ void DwarfUnit::constructTypeDIE(DIE &Buffer, const DICompositeType *CTy) {
       addUInt(Buffer, dwarf::DW_AT_APPLE_num_extra_inhabitants,
             std::nullopt, NumExtraInhabitants);
 
-  } else if (Tag == dwarf::DW_TAG_variant_part) {
-    auto SpareBitsMask = CTy->getSpareBitsMask();
-    if (!SpareBitsMask.isZero())
-      addConstantValue(Buffer, SpareBitsMask, false,
-                       dwarf::DW_AT_APPLE_spare_bits_mask);
-    if (auto OffsetInBits = CTy->getOffsetInBits()) 
-      addUInt(Buffer, dwarf::DW_AT_bit_offset, std::nullopt, OffsetInBits);
-  }
+  } 
 }
 
 void DwarfUnit::constructTemplateTypeParameterDIE(

llvm/lib/IR/AsmWriter.cpp

@@ -2218,8 +2218,6 @@ static void writeDICompositeType(raw_ostream &Out, const DICompositeType *N,
   Printer.printInt("align", N->getAlignInBits());
   Printer.printInt("offset", N->getOffsetInBits());
   Printer.printInt("num_extra_inhabitants", N->getNumExtraInhabitants());
-  if (!N->getSpareBitsMask().isZero())
-    Printer.printAPInt("spare_bits_mask", N->getSpareBitsMask(), true, false);
   Printer.printDIFlags("flags", N->getFlags());
   Printer.printMetadata("elements", N->getRawElements());
   Printer.printDwarfEnum("runtimeLang", N->getRuntimeLang(),

llvm/lib/IR/DIBuilder.cpp

@@ -545,17 +545,17 @@ DICompositeType *DIBuilder::createUnionType(
   return R;
 }
 
-DICompositeType *DIBuilder::createVariantPart(
-    DIScope *Scope, StringRef Name, DIFile *File, unsigned LineNumber,
-    uint64_t SizeInBits, uint32_t AlignInBits, DINode::DIFlags Flags,
-    DIDerivedType *Discriminator, DINodeArray Elements,
-    StringRef UniqueIdentifier, uint64_t OffsetInBits, APInt SpareBitsMask) {
+DICompositeType *
+DIBuilder::createVariantPart(DIScope *Scope, StringRef Name, DIFile *File,
+                             unsigned LineNumber, uint64_t SizeInBits,
+                             uint32_t AlignInBits, DINode::DIFlags Flags,
+                             DIDerivedType *Discriminator, DINodeArray Elements,
+                             StringRef UniqueIdentifier) {
   auto *R = DICompositeType::get(
       VMContext, dwarf::DW_TAG_variant_part, Name, File, LineNumber,
-      getNonCompileUnitScope(Scope), nullptr, SizeInBits, AlignInBits,
-      OffsetInBits, Flags, Elements, 0, nullptr, nullptr, UniqueIdentifier,
-      nullptr, 0, Discriminator, nullptr, nullptr, nullptr, {}, {},
-      SpareBitsMask);
+      getNonCompileUnitScope(Scope), nullptr, SizeInBits, AlignInBits, 0, Flags,
+      Elements, 0, nullptr, nullptr, UniqueIdentifier, nullptr, 0,
+      Discriminator, nullptr, nullptr, nullptr, {}, {});
   trackIfUnresolved(R);
   return R;
 }