Clean up DWARFFormValue by reducing duplicated code and removing DWARFFormValue::getFixedFormSizes()

In preparation for a follow on patch that improves DWARF parsing speed, clean up DWARFFormValue so that we have can get the fixed byte size of a form value given a DWARFUnit or given the version, address byte size and dwarf32/64.

This patch cleans up code so that everyone is using one of the new DWARFFormValue functions:

static Optional<uint8_t> DWARFFormValue::getFixedByteSize(dwarf::Form Form, const DWARFUnit *U = nullptr);
static Optional<uint8_t> DWARFFormValue::getFixedByteSize(dwarf::Form Form, uint16_t Version, uint8_t AddrSize, bool Dwarf32);

This patch changes DWARFFormValue::skipValue() to rely on the output of DWARFFormValue::getFixedByteSize(...) instead of duplicating the code in each function. This will reduce the number of changes we need to make to DWARF to fewer places in DWARFFormValue when we add support for new form.

This patch also starts to support DWARF64 so that we can get correct byte sizes for forms that vary according the DWARF 32/64.

To reduce the code duplication a new FormSizeHelper pure virtual class was created that can be created as a FormSizeHelperDWARFUnit when you have a DWARFUnit, or FormSizeHelperManual where you manually specify the DWARF version, address byte size and DWARF32/DWARF64. There is now a single implementation of a function that gets the fixed byte size (instead of two where one took a DWARFUnit and one took the DWARF version, address byte size and DWARFFormat enum) and one function to skip the form values.

https://reviews.llvm.org/D26526




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@286597 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/DebugInfo/DWARF/DWARFFormValue.h

@@ -81,17 +81,79 @@ public:
   Optional<uint64_t> getAsAddress() const;
   Optional<uint64_t> getAsSectionOffset() const;
   Optional<ArrayRef<uint8_t>> getAsBlock() const;
+  /// Get the fixed byte size for a given form.
+  ///
+  /// If the form always has a fixed valid byte size that doesn't depend on a
+  /// DWARFUnit, then an Optional with a value will be returned. If the form
+  /// can vary in size depending on the DWARFUnit (DWARF version, address byte
+  /// size, or DWARF 32/64) and the DWARFUnit is valid, then an Optional with a
+  /// valid value is returned. If the form is always encoded using a variable
+  /// length storage format (ULEB or SLEB numbers or blocks) or the size
+  /// depends on a DWARFUnit and the DWARFUnit is NULL, then None will be
+  /// returned.
+  /// \param Form The DWARF form to get the fixed byte size for
+  /// \param U The DWARFUnit that can be used to help determine the byte size.
+  ///
+  /// \returns Optional<uint8_t> value with the fixed byte size or None if
+  /// \p Form doesn't have a fixed byte size or a DWARFUnit wasn't supplied
+  /// and was needed to calculate the byte size.
+  static Optional<uint8_t> getFixedByteSize(dwarf::Form Form,
+                                            const DWARFUnit *U = nullptr);
+  /// Get the fixed byte size for a given form.
+  ///
+  /// If the form has a fixed byte size given a valid DWARF version and address
+  /// byte size, then an Optional with a valid value is returned. If the form
+  /// is always encoded using a variable length storage format (ULEB or SLEB
+  /// numbers or blocks) then None will be returned.
+  ///
+  /// \param Form DWARF form to get the fixed byte size for
+  /// \param Version DWARF version number.
+  /// \param AddrSize size of an address in bytes.
+  /// \param Format enum value from llvm::dwarf::DwarfFormat.
+  /// \returns Optional<uint8_t> value with the fixed byte size or None if
+  /// \p Form doesn't have a fixed byte size.
+  static Optional<uint8_t> getFixedByteSize(dwarf::Form Form, uint16_t Version,
+                                            uint8_t AddrSize,
+                                            llvm::dwarf::DwarfFormat Format);
 
+  /// Skip a form in \p debug_info_data at offset specified by \p offset_ptr.
+  ///
+  /// Skips the bytes for this form in the debug info and updates the offset.
+  ///
+  /// \param debug_info_data the .debug_info data to use to skip the value.
+  /// \param offset_ptr a reference to the offset that will be updated.
+  /// \param U the DWARFUnit to use when skipping the form in case the form
+  /// size differs according to data in the DWARFUnit.
+  /// \returns true on success, false if the form was not skipped.
   bool skipValue(DataExtractor debug_info_data, uint32_t *offset_ptr,
                  const DWARFUnit *U) const;
+  /// Skip a form in \p debug_info_data at offset specified by \p offset_ptr.
+  ///
+  /// Skips the bytes for this form in the debug info and updates the offset.
+  ///
+  /// \param form the DW_FORM enumeration that indicates the form to skip.
+  /// \param debug_info_data the .debug_info data to use to skip the value.
+  /// \param offset_ptr a reference to the offset that will be updated.
+  /// \param U the DWARFUnit to use when skipping the form in case the form
+  /// size differs according to data in the DWARFUnit.
+  /// \returns true on success, false if the form was not skipped.
   static bool skipValue(dwarf::Form form, DataExtractor debug_info_data,
-                        uint32_t *offset_ptr, const DWARFUnit *u);
+                        uint32_t *offset_ptr, const DWARFUnit *U);
+  /// Skip a form in \p debug_info_data at offset specified by \p offset_ptr.
+  ///
+  /// Skips the bytes for this form in the debug info and updates the offset.
+  ///
+  /// \param form the DW_FORM enumeration that indicates the form to skip.
+  /// \param debug_info_data the .debug_info data to use to skip the value.
+  /// \param offset_ptr a reference to the offset that will be updated.
+  /// \param Version DWARF version number.
+  /// \param AddrSize size of an address in bytes.
+  /// \param Format enum value from llvm::dwarf::DwarfFormat.
+  /// \returns true on success, false if the form was not skipped.
   static bool skipValue(dwarf::Form form, DataExtractor debug_info_data,
                         uint32_t *offset_ptr, uint16_t Version,
-                        uint8_t AddrSize);
+                        uint8_t AddrSize, llvm::dwarf::DwarfFormat Format);
 
-  static ArrayRef<uint8_t> getFixedFormSizes(uint8_t AddrSize,
-                                             uint16_t Version);
 private:
   void dumpString(raw_ostream &OS) const;
 };

include/llvm/DebugInfo/DWARF/DWARFUnit.h

@@ -191,13 +191,25 @@ public:
   uint32_t getNextUnitOffset() const { return Offset + Length + 4; }
   uint32_t getLength() const { return Length; }
   uint16_t getVersion() const { return Version; }
+  dwarf::DwarfFormat getFormat() const {
+    return dwarf::DwarfFormat::DWARF32; // FIXME: Support DWARF64.
+  }
   const DWARFAbbreviationDeclarationSet *getAbbreviations() const {
     return Abbrevs;
   }
   uint8_t getAddressByteSize() const { return AddrSize; }
   uint8_t getRefAddrByteSize() const {
-    // FIXME: Support DWARF64.
-    return (Version == 2) ? AddrSize : 4;
+    if (Version == 2)
+      return AddrSize;
+    return getDwarfOffsetByteSize();
+  }
+  uint8_t getDwarfOffsetByteSize() const {
+    switch (getFormat()) {
+    case dwarf::DwarfFormat::DWARF32:
+      return 4;
+    case dwarf::DwarfFormat::DWARF64:
+      return 8;
+    }
   }
   uint64_t getBaseAddress() const { return BaseAddr; }
 

include/llvm/Support/Dwarf.h

@@ -433,6 +433,9 @@ private:
   };
 };
 
+/// Constants that define the DWARF format as 32 or 64 bit.
+enum DwarfFormat { DWARF32, DWARF64 };
+
 } // End of namespace dwarf
 
 } // End of namespace llvm

lib/DebugInfo/DWARF/DWARFDebugInfoEntry.cpp

@@ -202,18 +202,13 @@ bool DWARFDebugInfoEntryMinimal::extractFast(const DWARFUnit *U,
     *OffsetPtr = Offset;
     return false;
   }
-  ArrayRef<uint8_t> FixedFormSizes = DWARFFormValue::getFixedFormSizes(
-      U->getAddressByteSize(), U->getVersion());
-  assert(FixedFormSizes.size() > 0);
 
   // Skip all data in the .debug_info for the attributes
   for (const auto &AttrSpec : AbbrevDecl->attributes()) {
     auto Form = AttrSpec.Form;
 
-    uint8_t FixedFormSize =
-        (Form < FixedFormSizes.size()) ? FixedFormSizes[Form] : 0;
-    if (FixedFormSize)
-      *OffsetPtr += FixedFormSize;
+    if (Optional<uint8_t> FixedSize = DWARFFormValue::getFixedByteSize(Form, U))
+      *OffsetPtr += *FixedSize;
     else if (!DWARFFormValue::skipValue(Form, DebugInfoData, OffsetPtr, U)) {
       // Restore the original offset.
       *OffsetPtr = Offset;

lib/DebugInfo/DWARF/DWARFFormValue.cpp

@@ -23,60 +23,6 @@ using namespace llvm;
 using namespace dwarf;
 using namespace syntax;
 
-namespace {
-uint8_t getRefAddrSize(uint8_t AddrSize, uint16_t Version) {
-  // FIXME: Support DWARF64.
-  return (Version == 2) ? AddrSize : 4;
-}
-
-template <uint8_t AddrSize, uint8_t RefAddrSize>
-ArrayRef<uint8_t> makeFixedFormSizesArrayRef() {
-  static const uint8_t sizes[] = {
-    0,           // 0x00 unused
-    AddrSize,    // 0x01 DW_FORM_addr
-    0,           // 0x02 unused
-    0,           // 0x03 DW_FORM_block2
-    0,           // 0x04 DW_FORM_block4
-    2,           // 0x05 DW_FORM_data2
-    4,           // 0x06 DW_FORM_data4
-    8,           // 0x07 DW_FORM_data8
-    0,           // 0x08 DW_FORM_string
-    0,           // 0x09 DW_FORM_block
-    0,           // 0x0a DW_FORM_block1
-    1,           // 0x0b DW_FORM_data1
-    1,           // 0x0c DW_FORM_flag
-    0,           // 0x0d DW_FORM_sdata
-    4,           // 0x0e DW_FORM_strp
-    0,           // 0x0f DW_FORM_udata
-    RefAddrSize, // 0x10 DW_FORM_ref_addr
-    1,           // 0x11 DW_FORM_ref1
-    2,           // 0x12 DW_FORM_ref2
-    4,           // 0x13 DW_FORM_ref4
-    8,           // 0x14 DW_FORM_ref8
-    0,           // 0x15 DW_FORM_ref_udata
-    0,           // 0x16 DW_FORM_indirect
-    4,           // 0x17 DW_FORM_sec_offset
-    0,           // 0x18 DW_FORM_exprloc
-    0,           // 0x19 DW_FORM_flag_present
-  };
-  return makeArrayRef(sizes);
-}
-}
-
-ArrayRef<uint8_t> DWARFFormValue::getFixedFormSizes(uint8_t AddrSize,
-                                                    uint16_t Version) {
-  uint8_t RefAddrSize = getRefAddrSize(AddrSize, Version);
-  if (AddrSize == 4 && RefAddrSize == 4)
-    return makeFixedFormSizesArrayRef<4, 4>();
-  if (AddrSize == 4 && RefAddrSize == 8)
-    return makeFixedFormSizesArrayRef<4, 8>();
-  if (AddrSize == 8 && RefAddrSize == 4)
-    return makeFixedFormSizesArrayRef<8, 4>();
-  if (AddrSize == 8 && RefAddrSize == 8)
-    return makeFixedFormSizesArrayRef<8, 8>();
-  return None;
-}
-
 static const DWARFFormValue::FormClass DWARF4FormClasses[] = {
   DWARFFormValue::FC_Unknown,       // 0x0
   DWARFFormValue::FC_Address,       // 0x01 DW_FORM_addr
@@ -108,6 +54,214 @@ static const DWARFFormValue::FormClass DWARF4FormClasses[] = {
   DWARFFormValue::FC_Flag,          // 0x19 DW_FORM_flag_present
 };
 
+namespace {
+
+/// A helper class that can be used in DWARFFormValue.cpp functions that need
+/// to know the byte size of DW_FORM values that vary in size depending on the
+/// DWARF version, address byte size, or DWARF32 or DWARF64.
+class FormSizeHelper {
+  uint16_t Version;
+  uint8_t AddrSize;
+  llvm::dwarf::DwarfFormat Format;
+
+public:
+  FormSizeHelper(uint16_t V, uint8_t A, llvm::dwarf::DwarfFormat F)
+  : Version(V), AddrSize(A), Format(F) {}
+  uint8_t getAddressByteSize() const { return AddrSize; }
+  uint8_t getRefAddrByteSize() const {
+    if (Version == 2)
+      return AddrSize;
+    return getDwarfOffsetByteSize();
+  }
+  uint8_t getDwarfOffsetByteSize() const {
+    switch (Format) {
+      case dwarf::DwarfFormat::DWARF32:
+        return 4;
+      case dwarf::DwarfFormat::DWARF64:
+        return 8;
+    }
+    llvm_unreachable("Invalid Format value");
+  }
+};
+
+} // end anonymous namespace
+
+template <class T>
+static Optional<uint8_t> getFixedByteSize(dwarf::Form Form, const T *U) {
+  switch (Form) {
+    case DW_FORM_addr:
+      if (U)
+        return U->getAddressByteSize();
+      return None;
+
+    case DW_FORM_block:          // ULEB128 length L followed by L bytes.
+    case DW_FORM_block1:         // 1 byte length L followed by L bytes.
+    case DW_FORM_block2:         // 2 byte length L followed by L bytes.
+    case DW_FORM_block4:         // 4 byte length L followed by L bytes.
+    case DW_FORM_string:         // C-string with null terminator.
+    case DW_FORM_sdata:          // SLEB128.
+    case DW_FORM_udata:          // ULEB128.
+    case DW_FORM_ref_udata:      // ULEB128.
+    case DW_FORM_indirect:       // ULEB128.
+    case DW_FORM_exprloc:        // ULEB128 length L followed by L bytes.
+    case DW_FORM_strx:           // ULEB128.
+    case DW_FORM_addrx:          // ULEB128.
+    case DW_FORM_loclistx:       // ULEB128.
+    case DW_FORM_rnglistx:       // ULEB128.
+    case DW_FORM_GNU_addr_index: // ULEB128.
+    case DW_FORM_GNU_str_index:  // ULEB128.
+      return None;
+
+    case DW_FORM_ref_addr:
+      if (U)
+        return U->getRefAddrByteSize();
+      return None;
+
+    case DW_FORM_flag:
+    case DW_FORM_data1:
+    case DW_FORM_ref1:
+      return 1;
+
+    case DW_FORM_data2:
+    case DW_FORM_ref2:
+      return 2;
+
+    case DW_FORM_data4:
+    case DW_FORM_ref4:
+    case DW_FORM_strp:
+      return 4;
+
+    case DW_FORM_GNU_ref_alt:
+    case DW_FORM_GNU_strp_alt:
+    case DW_FORM_line_strp:
+    case DW_FORM_sec_offset:
+    case DW_FORM_strp_sup:
+    case DW_FORM_ref_sup:
+      if (U)
+        return U->getDwarfOffsetByteSize();
+      return None;
+
+    case DW_FORM_data8:
+    case DW_FORM_ref8:
+    case DW_FORM_ref_sig8:
+      return 8;
+
+    case DW_FORM_flag_present:
+      return 0;
+
+    case DW_FORM_data16:
+      return 16;
+
+    case DW_FORM_implicit_const:
+      // The implicit value is stored in the abbreviation as a ULEB128, any
+      // there no data in debug info.
+      return 0;
+
+    default:
+      llvm_unreachable("Handle this form in this switch statement");
+  }
+  return None;
+}
+
+template <class T>
+static bool skipFormValue(dwarf::Form Form, const DataExtractor &DebugInfoData,
+                          uint32_t *OffsetPtr, const T *U) {
+  bool Indirect = false;
+  do {
+    switch (Form) {
+        // Blocks if inlined data that have a length field and the data bytes
+        // inlined in the .debug_info.
+      case DW_FORM_exprloc:
+      case DW_FORM_block: {
+        uint64_t size = DebugInfoData.getULEB128(OffsetPtr);
+        *OffsetPtr += size;
+        return true;
+      }
+      case DW_FORM_block1: {
+        uint8_t size = DebugInfoData.getU8(OffsetPtr);
+        *OffsetPtr += size;
+        return true;
+      }
+      case DW_FORM_block2: {
+        uint16_t size = DebugInfoData.getU16(OffsetPtr);
+        *OffsetPtr += size;
+        return true;
+      }
+      case DW_FORM_block4: {
+        uint32_t size = DebugInfoData.getU32(OffsetPtr);
+        *OffsetPtr += size;
+        return true;
+      }
+
+        // Inlined NULL terminated C-strings.
+      case DW_FORM_string:
+        DebugInfoData.getCStr(OffsetPtr);
+        return true;
+
+      case DW_FORM_addr:
+      case DW_FORM_ref_addr:
+      case DW_FORM_flag_present:
+      case DW_FORM_data1:
+      case DW_FORM_data2:
+      case DW_FORM_data4:
+      case DW_FORM_data8:
+      case DW_FORM_flag:
+      case DW_FORM_ref1:
+      case DW_FORM_ref2:
+      case DW_FORM_ref4:
+      case DW_FORM_ref8:
+      case DW_FORM_ref_sig8:
+      case DW_FORM_sec_offset:
+      case DW_FORM_strp:
+      case DW_FORM_GNU_ref_alt:
+      case DW_FORM_GNU_strp_alt:
+        if (Optional<uint8_t> FixedSize = ::getFixedByteSize(Form, U)) {
+          *OffsetPtr += *FixedSize;
+          return true;
+        }
+        return false;
+
+        // signed or unsigned LEB 128 values.
+      case DW_FORM_sdata:
+        DebugInfoData.getSLEB128(OffsetPtr);
+        return true;
+
+      case DW_FORM_udata:
+      case DW_FORM_ref_udata:
+      case DW_FORM_strx:
+      case DW_FORM_addrx:
+      case DW_FORM_loclistx:
+      case DW_FORM_rnglistx:
+      case DW_FORM_GNU_addr_index:
+      case DW_FORM_GNU_str_index:
+        DebugInfoData.getULEB128(OffsetPtr);
+        return true;
+        
+      case DW_FORM_indirect:
+        Indirect = true;
+        Form = static_cast<dwarf::Form>(DebugInfoData.getULEB128(OffsetPtr));
+        break;
+        
+      default:
+        return false;
+    }
+  } while (Indirect);
+  return true;
+}
+
+Optional<uint8_t> DWARFFormValue::getFixedByteSize(dwarf::Form Form,
+                                                   const DWARFUnit *U) {
+  return ::getFixedByteSize(Form, U);
+}
+
+Optional<uint8_t>
+DWARFFormValue::getFixedByteSize(dwarf::Form Form, uint16_t Version,
+                                 uint8_t AddrSize,
+                                 llvm::dwarf::DwarfFormat Format) {
+  FormSizeHelper FSH(Version, AddrSize, Format);
+  return ::getFixedByteSize(Form, &FSH);
+}
+
 bool DWARFFormValue::isFormClass(DWARFFormValue::FormClass FC) const {
   // First, check DWARF4 form classes.
   if (Form < makeArrayRef(DWARF4FormClasses).size() &&
@@ -155,8 +309,7 @@ bool DWARFFormValue::extractValue(const DataExtractor &data,
               : U->getRefAddrByteSize();
       RelocAddrMap::const_iterator AI = U->getRelocMap()->find(*offset_ptr);
       if (AI != U->getRelocMap()->end()) {
-        const std::pair<uint8_t, int64_t> &R = AI->second;
-        Value.uval = data.getUnsigned(offset_ptr, AddrSize) + R.second;
+        Value.uval = data.getUnsigned(offset_ptr, AddrSize) + AI->second.second;
       } else
         Value.uval = data.getUnsigned(offset_ptr, AddrSize);
       break;
@@ -188,7 +341,8 @@ bool DWARFFormValue::extractValue(const DataExtractor &data,
       Value.uval = data.getU16(offset_ptr);
       break;
     case DW_FORM_data4:
-    case DW_FORM_ref4: {
+    case DW_FORM_ref4:
+    case DW_FORM_strp: {
       Value.uval = data.getU32(offset_ptr);
       if (!U)
         break;
@@ -216,15 +370,16 @@ bool DWARFFormValue::extractValue(const DataExtractor &data,
       indirect = true;
       break;
     case DW_FORM_sec_offset:
-    case DW_FORM_strp:
     case DW_FORM_GNU_ref_alt:
-    case DW_FORM_GNU_strp_alt: {
-      // FIXME: This is 64-bit for DWARF64.
-      Value.uval = data.getU32(offset_ptr);
+    case DW_FORM_GNU_strp_alt:
+    case DW_FORM_line_strp:
+    case DW_FORM_strp_sup:
+    case DW_FORM_ref_sup: {
       if (!U)
-        break;
-      RelocAddrMap::const_iterator AI =
-          U->getRelocMap()->find(*offset_ptr - 4);
+        return false;
+      RelocAddrMap::const_iterator AI = U->getRelocMap()->find(*offset_ptr);
+      uint8_t Size = U->getDwarfOffsetByteSize();
+      Value.uval = data.getUnsigned(offset_ptr, Size);
       if (AI != U->getRelocMap()->end())
         Value.uval += AI->second.second;
       break;
@@ -256,120 +411,22 @@ bool DWARFFormValue::extractValue(const DataExtractor &data,
   return true;
 }
 
-bool
-DWARFFormValue::skipValue(DataExtractor debug_info_data, uint32_t* offset_ptr,
-                          const DWARFUnit *U) const {
-  return DWARFFormValue::skipValue(Form, debug_info_data, offset_ptr, U);
+bool DWARFFormValue::skipValue(DataExtractor DebugInfoData,
+                               uint32_t *offset_ptr, const DWARFUnit *U) const {
+  return DWARFFormValue::skipValue(Form, DebugInfoData, offset_ptr, U);
 }
 
-bool
-DWARFFormValue::skipValue(dwarf::Form form, DataExtractor debug_info_data,
-                          uint32_t *offset_ptr, const DWARFUnit *cu) {
-  return skipValue(form, debug_info_data, offset_ptr, cu->getVersion(),
-                   cu->getAddressByteSize());
+bool DWARFFormValue::skipValue(dwarf::Form form, DataExtractor DebugInfoData,
+                               uint32_t *offset_ptr, const DWARFUnit *U) {
+  return skipFormValue(form, DebugInfoData, offset_ptr, U);
 }
-bool 
-DWARFFormValue::skipValue(dwarf::Form form, DataExtractor debug_info_data,
-                          uint32_t *offset_ptr, uint16_t Version,
-                          uint8_t AddrSize) {
-  bool indirect = false;
-  do {
-    switch (form) {
-    // Blocks if inlined data that have a length field and the data bytes
-    // inlined in the .debug_info
-    case DW_FORM_exprloc:
-    case DW_FORM_block: {
-      uint64_t size = debug_info_data.getULEB128(offset_ptr);
-      *offset_ptr += size;
-      return true;
-    }
-    case DW_FORM_block1: {
-      uint8_t size = debug_info_data.getU8(offset_ptr);
-      *offset_ptr += size;
-      return true;
-    }
-    case DW_FORM_block2: {
-      uint16_t size = debug_info_data.getU16(offset_ptr);
-      *offset_ptr += size;
-      return true;
-    }
-    case DW_FORM_block4: {
-      uint32_t size = debug_info_data.getU32(offset_ptr);
-      *offset_ptr += size;
-      return true;
-    }
-
-    // Inlined NULL terminated C-strings
-    case DW_FORM_string:
-      debug_info_data.getCStr(offset_ptr);
-      return true;
-
-    // Compile unit address sized values
-    case DW_FORM_addr:
-      *offset_ptr += AddrSize;
-      return true;
-    case DW_FORM_ref_addr:
-      *offset_ptr += getRefAddrSize(AddrSize, Version);
-      return true;
-
-    // 0 byte values - implied from the form.
-    case DW_FORM_flag_present:
-      return true;
-
-    // 1 byte values
-    case DW_FORM_data1:
-    case DW_FORM_flag:
-    case DW_FORM_ref1:
-      *offset_ptr += 1;
-      return true;
-
-    // 2 byte values
-    case DW_FORM_data2:
-    case DW_FORM_ref2:
-      *offset_ptr += 2;
-      return true;
-
-    // 4 byte values
-    case DW_FORM_data4:
-    case DW_FORM_ref4:
-      *offset_ptr += 4;
-      return true;
-
-    // 8 byte values
-    case DW_FORM_data8:
-    case DW_FORM_ref8:
-    case DW_FORM_ref_sig8:
-      *offset_ptr += 8;
-      return true;
-
-    // signed or unsigned LEB 128 values
-    //  case DW_FORM_APPLE_db_str:
-    case DW_FORM_sdata:
-    case DW_FORM_udata:
-    case DW_FORM_ref_udata:
-    case DW_FORM_GNU_str_index:
-    case DW_FORM_GNU_addr_index:
-      debug_info_data.getULEB128(offset_ptr);
-      return true;
 
-    case DW_FORM_indirect:
-      indirect = true;
-      form = static_cast<dwarf::Form>(debug_info_data.getULEB128(offset_ptr));
-      break;
-
-    // FIXME: 4 for DWARF32, 8 for DWARF64.
-    case DW_FORM_sec_offset:
-    case DW_FORM_strp:
-    case DW_FORM_GNU_ref_alt:
-    case DW_FORM_GNU_strp_alt:
-      *offset_ptr += 4;
-      return true;
-
-    default:
-      return false;
-    }
-  } while (indirect);
-  return true;
+bool DWARFFormValue::skipValue(dwarf::Form form, DataExtractor DebugInfoData,
+                               uint32_t *offset_ptr, uint16_t Version,
+                               uint8_t AddrSize,
+                               llvm::dwarf::DwarfFormat Format) {
+  FormSizeHelper FSH(Version, AddrSize, Format);
+  return skipFormValue(form, DebugInfoData, offset_ptr, &FSH);
 }
 
 void
@@ -556,8 +613,9 @@ Optional<uint64_t> DWARFFormValue::getAsReference() const {
       return None;
     return Value.uval + U->getOffset();
   case DW_FORM_ref_addr:
+  case DW_FORM_ref_sig8:
+  case DW_FORM_GNU_ref_alt:
     return Value.uval;
-  // FIXME: Add proper support for DW_FORM_ref_sig8 and DW_FORM_GNU_ref_alt.
   default:
     return None;
   }

tools/llvm-dwp/llvm-dwp.cpp

@@ -133,7 +133,14 @@ static Expected<CompileUnitIdentifiers> getCUIdentifiers(StringRef Abbrev,
                                                          StringRef Str) {
   uint32_t Offset = 0;
   DataExtractor InfoData(Info, true, 0);
-  InfoData.getU32(&Offset); // Length
+  dwarf::DwarfFormat Format = dwarf::DwarfFormat::DWARF32;
+  uint64_t Length = InfoData.getU32(&Offset);
+  // If the length is 0xffffffff, then this indictes that this is a DWARF 64
+  // stream and the length is actually encoded into a 64 bit value that follows.
+  if (Length == 0xffffffffU) {
+    Format = dwarf::DwarfFormat::DWARF64;
+    Length = InfoData.getU64(&Offset);
+  }
   uint16_t Version = InfoData.getU16(&Offset);
   InfoData.getU32(&Offset); // Abbrev offset (should be zero)
   uint8_t AddrSize = InfoData.getU8(&Offset);
@@ -174,7 +181,8 @@ static Expected<CompileUnitIdentifiers> getCUIdentifiers(StringRef Abbrev,
       ID.Signature = InfoData.getU64(&Offset);
       break;
     default:
-      DWARFFormValue::skipValue(Form, InfoData, &Offset, Version, AddrSize);
+      DWARFFormValue::skipValue(Form, InfoData, &Offset, Version, AddrSize,
+                                Format);
     }
   }
   return ID;

unittests/DebugInfo/DWARF/DWARFFormValueTest.cpp

@@ -21,16 +21,47 @@ using namespace dwarf;
 namespace {
 
 TEST(DWARFFormValue, FixedFormSizes) {
-  // Size of DW_FORM_addr and DW_FORM_ref_addr are equal in DWARF2,
-  // DW_FORM_ref_addr is always 4 bytes in DWARF32 starting from DWARF3.
-  ArrayRef<uint8_t> sizes = DWARFFormValue::getFixedFormSizes(4, 2);
-  EXPECT_EQ(sizes[DW_FORM_addr], sizes[DW_FORM_ref_addr]);
-  sizes = DWARFFormValue::getFixedFormSizes(8, 2);
-  EXPECT_EQ(sizes[DW_FORM_addr], sizes[DW_FORM_ref_addr]);
-  sizes = DWARFFormValue::getFixedFormSizes(8, 3);
-  EXPECT_EQ(4, sizes[DW_FORM_ref_addr]);
-  // Check that we don't have fixed form sizes for weird address sizes.
-  EXPECT_EQ(0U, DWARFFormValue::getFixedFormSizes(16, 2).size());
+  Optional<uint8_t> RefSize;
+  Optional<uint8_t> AddrSize;
+  // Test 32 bit DWARF version 2 with 4 byte addresses.
+  RefSize = DWARFFormValue::getFixedByteSize(DW_FORM_ref_addr, 2, 4, DWARF32);
+  AddrSize = DWARFFormValue::getFixedByteSize(DW_FORM_ref_addr, 2, 4, DWARF32);
+  EXPECT_TRUE(RefSize.hasValue());
+  EXPECT_TRUE(AddrSize.hasValue());
+  EXPECT_EQ(*RefSize, *AddrSize);
+
+  // Test 32 bit DWARF version 2 with 8 byte addresses.
+  RefSize = DWARFFormValue::getFixedByteSize(DW_FORM_ref_addr, 2, 8, DWARF32);
+  AddrSize = DWARFFormValue::getFixedByteSize(DW_FORM_ref_addr, 2, 8, DWARF32);
+  EXPECT_TRUE(RefSize.hasValue());
+  EXPECT_TRUE(AddrSize.hasValue());
+  EXPECT_EQ(*RefSize, *AddrSize);
+
+  // DW_FORM_ref_addr is 4 bytes in DWARF 32 in DWARF version 3 and beyond.
+  RefSize = DWARFFormValue::getFixedByteSize(DW_FORM_ref_addr, 3, 4, DWARF32);
+  EXPECT_TRUE(RefSize.hasValue());
+  EXPECT_EQ(*RefSize, 4);
+
+  RefSize = DWARFFormValue::getFixedByteSize(DW_FORM_ref_addr, 4, 4, DWARF32);
+  EXPECT_TRUE(RefSize.hasValue());
+  EXPECT_EQ(*RefSize, 4);
+
+  RefSize = DWARFFormValue::getFixedByteSize(DW_FORM_ref_addr, 5, 4, DWARF32);
+  EXPECT_TRUE(RefSize.hasValue());
+  EXPECT_EQ(*RefSize, 4);
+
+  // DW_FORM_ref_addr is 8 bytes in DWARF 64 in DWARF version 3 and beyond.
+  RefSize = DWARFFormValue::getFixedByteSize(DW_FORM_ref_addr, 3, 8, DWARF64);
+  EXPECT_TRUE(RefSize.hasValue());
+  EXPECT_EQ(*RefSize, 8);
+
+  RefSize = DWARFFormValue::getFixedByteSize(DW_FORM_ref_addr, 4, 8, DWARF64);
+  EXPECT_TRUE(RefSize.hasValue());
+  EXPECT_EQ(*RefSize, 8);
+
+  RefSize = DWARFFormValue::getFixedByteSize(DW_FORM_ref_addr, 5, 8, DWARF64);
+  EXPECT_TRUE(RefSize.hasValue());
+  EXPECT_EQ(*RefSize, 8);
 }
 
 bool isFormClass(dwarf::Form Form, DWARFFormValue::FormClass FC) {