lldb/source/Plugins/SymbolFile/DWARF/DWARFFormValue.cpp - toolchain/llvm-project - Gitiles

 //===-- DWARFFormValue.cpp --------------------------------------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//

 #include <assert.h>

 #include "lldb/Core/dwarf.h"
 #include "lldb/Utility/Stream.h"

 #include "DWARFUnit.h"
 #include "DWARFFormValue.h"

 class DWARFUnit;

 using namespace lldb_private;

 static uint8_t g_form_sizes_addr4[] = {
     0, // 0x00 unused
     4, // 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
     0, // 0x10 DW_FORM_ref_addr (addr size for DWARF2 and earlier, 4 bytes for
        // DWARF32, 8 bytes for DWARF32 in DWARF 3 and later
     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
     0, // 0x1a
     0, // 0x1b
     0, // 0x1c
     0, // 0x1d
     0, // 0x1e
     0, // 0x1f
     8, // 0x20 DW_FORM_ref_sig8

 };

 static uint8_t g_form_sizes_addr8[] = {
     0, // 0x00 unused
     8, // 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
     0, // 0x10 DW_FORM_ref_addr (addr size for DWARF2 and earlier, 4 bytes for
        // DWARF32, 8 bytes for DWARF32 in DWARF 3 and later
     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
     0, // 0x1a
     0, // 0x1b
     0, // 0x1c
     0, // 0x1d
     0, // 0x1e
     0, // 0x1f
     8, // 0x20 DW_FORM_ref_sig8
 };

 // Difference with g_form_sizes_addr8:
 // DW_FORM_strp and DW_FORM_sec_offset are 8 instead of 4
 static uint8_t g_form_sizes_addr8_dwarf64[] = {
     0, // 0x00 unused
     8, // 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
     8, // 0x0e DW_FORM_strp
     0, // 0x0f DW_FORM_udata
     0, // 0x10 DW_FORM_ref_addr (addr size for DWARF2 and earlier, 4 bytes for
        // DWARF32, 8 bytes for DWARF32 in DWARF 3 and later
     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
     8, // 0x17 DW_FORM_sec_offset
     0, // 0x18 DW_FORM_exprloc
     0, // 0x19 DW_FORM_flag_present
     0, // 0x1a
     0, // 0x1b
     0, // 0x1c
     0, // 0x1d
     0, // 0x1e
     0, // 0x1f
     8, // 0x20 DW_FORM_ref_sig8
 };

 DWARFFormValue::FixedFormSizes
 DWARFFormValue::GetFixedFormSizesForAddressSize(uint8_t addr_size,
                                                 bool is_dwarf64) {
   if (!is_dwarf64) {
     switch (addr_size) {
     case 4:
       return FixedFormSizes(g_form_sizes_addr4, sizeof(g_form_sizes_addr4));
     case 8:
       return FixedFormSizes(g_form_sizes_addr8, sizeof(g_form_sizes_addr8));
     }
   } else {
     if (addr_size == 8)
       return FixedFormSizes(g_form_sizes_addr8_dwarf64,
                             sizeof(g_form_sizes_addr8_dwarf64));
     // is_dwarf64 && addr_size == 4 : no provider does this.
   }
   return FixedFormSizes();
 }

 DWARFFormValue::DWARFFormValue() : m_cu(NULL), m_form(0), m_value() {}

 DWARFFormValue::DWARFFormValue(const DWARFUnit *cu)
     : m_cu(cu), m_form(0), m_value() {}

 DWARFFormValue::DWARFFormValue(const DWARFUnit *cu, dw_form_t form)
     : m_cu(cu), m_form(form), m_value() {}

 void DWARFFormValue::Clear() {
   m_cu = nullptr;
   m_form = 0;
   memset(&m_value, 0, sizeof(m_value));
 }

 bool DWARFFormValue::ExtractValue(const DWARFDataExtractor &data,
                                   lldb::offset_t *offset_ptr) {
   if (m_form == DW_FORM_implicit_const)
     return true;

   bool indirect = false;
   bool is_block = false;
   m_value.data = NULL;
   uint8_t ref_addr_size;
   // Read the value for the form into value and follow and DW_FORM_indirect
   // instances we run into
   do {
     indirect = false;
     switch (m_form) {
     case DW_FORM_addr:
       assert(m_cu);
       m_value.value.uval =
           data.GetMaxU64(offset_ptr, DWARFUnit::GetAddressByteSize(m_cu));
       break;
     case DW_FORM_block1:
       m_value.value.uval = data.GetU8(offset_ptr);
       is_block = true;
       break;
     case DW_FORM_block2:
       m_value.value.uval = data.GetU16(offset_ptr);
       is_block = true;
       break;
     case DW_FORM_block4:
       m_value.value.uval = data.GetU32(offset_ptr);
       is_block = true;
       break;
     case DW_FORM_data16:
       m_value.value.uval = 16;
       is_block = true;
       break;
     case DW_FORM_exprloc:
     case DW_FORM_block:
       m_value.value.uval = data.GetULEB128(offset_ptr);
       is_block = true;
       break;
     case DW_FORM_string:
       m_value.value.cstr = data.GetCStr(offset_ptr);
       break;
     case DW_FORM_sdata:
       m_value.value.sval = data.GetSLEB128(offset_ptr);
       break;
     case DW_FORM_strp:
     case DW_FORM_line_strp:
     case DW_FORM_sec_offset:
       assert(m_cu);
       m_value.value.uval =
           data.GetMaxU64(offset_ptr, DWARFUnit::IsDWARF64(m_cu) ? 8 : 4);
       break;
     case DW_FORM_addrx1:
     case DW_FORM_strx1:
     case DW_FORM_ref1:
     case DW_FORM_data1:
     case DW_FORM_flag:
       m_value.value.uval = data.GetU8(offset_ptr);
       break;
     case DW_FORM_addrx2:
     case DW_FORM_strx2:
     case DW_FORM_ref2:
     case DW_FORM_data2:
       m_value.value.uval = data.GetU16(offset_ptr);
       break;
     case DW_FORM_addrx3:
     case DW_FORM_strx3:
       m_value.value.uval = data.GetMaxU64(offset_ptr, 3);
       break;
     case DW_FORM_addrx4:
     case DW_FORM_strx4:
     case DW_FORM_ref4:
     case DW_FORM_data4:
       m_value.value.uval = data.GetU32(offset_ptr);
       break;
     case DW_FORM_data8:
     case DW_FORM_ref8:
     case DW_FORM_ref_sig8:
       m_value.value.uval = data.GetU64(offset_ptr);
       break;
     case DW_FORM_addrx:
     case DW_FORM_rnglistx:
     case DW_FORM_strx:
     case DW_FORM_udata:
     case DW_FORM_ref_udata:
     case DW_FORM_GNU_str_index:
     case DW_FORM_GNU_addr_index:
       m_value.value.uval = data.GetULEB128(offset_ptr);
       break;
     case DW_FORM_ref_addr:
       assert(m_cu);
       if (m_cu->GetVersion() <= 2)
         ref_addr_size = m_cu->GetAddressByteSize();
       else
         ref_addr_size = m_cu->IsDWARF64() ? 8 : 4;
       m_value.value.uval = data.GetMaxU64(offset_ptr, ref_addr_size);
       break;
     case DW_FORM_indirect:
       m_form = data.GetULEB128(offset_ptr);
       indirect = true;
       break;
     case DW_FORM_flag_present:
       m_value.value.uval = 1;
       break;
     default:
       return false;
     }
   } while (indirect);

   if (is_block) {
     m_value.data = data.PeekData(*offset_ptr, m_value.value.uval);
     if (m_value.data != NULL) {
       *offset_ptr += m_value.value.uval;
     }
   }

   return true;
 }

 bool DWARFFormValue::SkipValue(const DWARFDataExtractor &debug_info_data,
                                lldb::offset_t *offset_ptr) const {
   return DWARFFormValue::SkipValue(m_form, debug_info_data, offset_ptr, m_cu);
 }

 bool DWARFFormValue::SkipValue(dw_form_t form,
                                const DWARFDataExtractor &debug_info_data,
                                lldb::offset_t *offset_ptr,
                                const DWARFUnit *cu) {
   uint8_t ref_addr_size;
   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: {
     dw_uleb128_t size = debug_info_data.GetULEB128(offset_ptr);
     *offset_ptr += size;
   }
     return true;
   case DW_FORM_block1: {
     dw_uleb128_t size = debug_info_data.GetU8(offset_ptr);
     *offset_ptr += size;
   }
     return true;
   case DW_FORM_block2: {
     dw_uleb128_t size = debug_info_data.GetU16(offset_ptr);
     *offset_ptr += size;
   }
     return true;
   case DW_FORM_block4: {
     dw_uleb128_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 += DWARFUnit::GetAddressByteSize(cu);
     return true;

   case DW_FORM_ref_addr:
     ref_addr_size = 4;
     assert(cu); // CU must be valid for DW_FORM_ref_addr objects or we will get
                 // this wrong
     if (cu->GetVersion() <= 2)
       ref_addr_size = cu->GetAddressByteSize();
     else
       ref_addr_size = cu->IsDWARF64() ? 8 : 4;
     *offset_ptr += ref_addr_size;
     return true;

   // 0 bytes values (implied from DW_FORM)
   case DW_FORM_flag_present:
   case DW_FORM_implicit_const:
     return true;

     // 1 byte values
     case DW_FORM_addrx1:
     case DW_FORM_data1:
     case DW_FORM_flag:
     case DW_FORM_ref1:
     case DW_FORM_strx1:
       *offset_ptr += 1;
       return true;

     // 2 byte values
     case DW_FORM_addrx2:
     case DW_FORM_data2:
     case DW_FORM_ref2:
     case DW_FORM_strx2:
       *offset_ptr += 2;
       return true;

     // 3 byte values
     case DW_FORM_addrx3:
     case DW_FORM_strx3:
       *offset_ptr += 3;
       return true;

     // 32 bit for DWARF 32, 64 for DWARF 64
     case DW_FORM_sec_offset:
     case DW_FORM_strp:
       assert(cu);
       *offset_ptr += (cu->IsDWARF64() ? 8 : 4);
       return true;

     // 4 byte values
     case DW_FORM_addrx4:
     case DW_FORM_data4:
     case DW_FORM_ref4:
     case DW_FORM_strx4:
       *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_addrx:
     case DW_FORM_rnglistx:
     case DW_FORM_sdata:
     case DW_FORM_udata:
     case DW_FORM_ref_udata:
     case DW_FORM_GNU_addr_index:
     case DW_FORM_GNU_str_index:
     case DW_FORM_strx:
       debug_info_data.Skip_LEB128(offset_ptr);
       return true;

   case DW_FORM_indirect: {
     dw_form_t indirect_form = debug_info_data.GetULEB128(offset_ptr);
     return DWARFFormValue::SkipValue(indirect_form, debug_info_data, offset_ptr,
                                      cu);
   }

   default:
     break;
   }
   return false;
 }

 void DWARFFormValue::Dump(Stream &s) const {
   uint64_t uvalue = Unsigned();
   bool cu_relative_offset = false;

   switch (m_form) {
   case DW_FORM_addr:
     s.Address(uvalue, sizeof(uint64_t));
     break;
   case DW_FORM_flag:
   case DW_FORM_data1:
     s.PutHex8(uvalue);
     break;
   case DW_FORM_data2:
     s.PutHex16(uvalue);
     break;
   case DW_FORM_sec_offset:
   case DW_FORM_data4:
     s.PutHex32(uvalue);
     break;
   case DW_FORM_ref_sig8:
   case DW_FORM_data8:
     s.PutHex64(uvalue);
     break;
   case DW_FORM_string:
     s.QuotedCString(AsCString());
     break;
   case DW_FORM_exprloc:
   case DW_FORM_block:
   case DW_FORM_block1:
   case DW_FORM_block2:
   case DW_FORM_block4:
     if (uvalue > 0) {
       switch (m_form) {
       case DW_FORM_exprloc:
       case DW_FORM_block:
         s.Printf("<0x%" PRIx64 "> ", uvalue);
         break;
       case DW_FORM_block1:
         s.Printf("<0x%2.2x> ", (uint8_t)uvalue);
         break;
       case DW_FORM_block2:
         s.Printf("<0x%4.4x> ", (uint16_t)uvalue);
         break;
       case DW_FORM_block4:
         s.Printf("<0x%8.8x> ", (uint32_t)uvalue);
         break;
       default:
         break;
       }

       const uint8_t *data_ptr = m_value.data;
       if (data_ptr) {
         const uint8_t *end_data_ptr =
             data_ptr + uvalue; // uvalue contains size of block
         while (data_ptr < end_data_ptr) {
           s.Printf("%2.2x ", *data_ptr);
           ++data_ptr;
         }
       } else
         s.PutCString("NULL");
     }
     break;

   case DW_FORM_sdata:
     s.PutSLEB128(uvalue);
     break;
   case DW_FORM_udata:
     s.PutULEB128(uvalue);
     break;
   case DW_FORM_strp: {
     const char *dbg_str = AsCString();
     if (dbg_str) {
       s.QuotedCString(dbg_str);
     } else {
       s.PutHex32(uvalue);
     }
   } break;

   case DW_FORM_ref_addr: {
     assert(m_cu); // CU must be valid for DW_FORM_ref_addr objects or we will
                   // get this wrong
     if (m_cu->GetVersion() <= 2)
       s.Address(uvalue, sizeof(uint64_t) * 2);
     else
       s.Address(uvalue, 4 * 2); // 4 for DWARF32, 8 for DWARF64, but we don't
                                 // support DWARF64 yet
     break;
   }
   case DW_FORM_ref1:
     cu_relative_offset = true;
     break;
   case DW_FORM_ref2:
     cu_relative_offset = true;
     break;
   case DW_FORM_ref4:
     cu_relative_offset = true;
     break;
   case DW_FORM_ref8:
     cu_relative_offset = true;
     break;
   case DW_FORM_ref_udata:
     cu_relative_offset = true;
     break;

   // All DW_FORM_indirect attributes should be resolved prior to calling this
   // function
   case DW_FORM_indirect:
     s.PutCString("DW_FORM_indirect");
     break;
   case DW_FORM_flag_present:
     break;
   default:
     s.Printf("DW_FORM(0x%4.4x)", m_form);
     break;
   }

   if (cu_relative_offset) {
     assert(m_cu); // CU must be valid for DW_FORM_ref forms that are compile
                   // unit relative or we will get this wrong
     s.Printf("{0x%8.8" PRIx64 "}", uvalue + m_cu->GetOffset());
   }
 }

 const char *DWARFFormValue::AsCString() const {
   SymbolFileDWARF *symbol_file = m_cu->GetSymbolFileDWARF();

   if (m_form == DW_FORM_string) {
     return m_value.value.cstr;
   } else if (m_form == DW_FORM_strp) {
     if (!symbol_file)
       return nullptr;

     return symbol_file->get_debug_str_data().PeekCStr(m_value.value.uval);
   } else if (m_form == DW_FORM_GNU_str_index) {
     if (!symbol_file)
       return nullptr;

     uint32_t index_size = m_cu->IsDWARF64() ? 8 : 4;
     lldb::offset_t offset = m_value.value.uval * index_size;
     dw_offset_t str_offset =
         symbol_file->get_debug_str_offsets_data().GetMaxU64(&offset,
                                                             index_size);
     return symbol_file->get_debug_str_data().PeekCStr(str_offset);
   }

   if (m_form == DW_FORM_strx || m_form == DW_FORM_strx1 ||
       m_form == DW_FORM_strx2 || m_form == DW_FORM_strx3 ||
       m_form == DW_FORM_strx4) {

     // The same code as above.
     if (!symbol_file)
       return nullptr;

     uint32_t indexSize = m_cu->IsDWARF64() ? 8 : 4;
     lldb::offset_t offset =
         m_cu->GetStrOffsetsBase() + m_value.value.uval * indexSize;
     dw_offset_t strOffset =
         symbol_file->get_debug_str_offsets_data().GetMaxU64(&offset, indexSize);
     return symbol_file->get_debug_str_data().PeekCStr(strOffset);
   }

   if (m_form == DW_FORM_line_strp)
     return symbol_file->get_debug_line_str_data().PeekCStr(m_value.value.uval);

   return nullptr;
 }

 dw_addr_t DWARFFormValue::Address() const {
   SymbolFileDWARF *symbol_file = m_cu->GetSymbolFileDWARF();

   if (m_form == DW_FORM_addr)
     return Unsigned();

   assert(m_cu);
   assert(m_form == DW_FORM_GNU_addr_index || m_form == DW_FORM_addrx ||
          m_form == DW_FORM_addrx1 || m_form == DW_FORM_addrx2 ||
          m_form == DW_FORM_addrx3 || m_form == DW_FORM_addrx4);

   if (!symbol_file)
     return 0;

   uint32_t index_size = m_cu->GetAddressByteSize();
   dw_offset_t addr_base = m_cu->GetAddrBase();
   lldb::offset_t offset = addr_base + m_value.value.uval * index_size;
   return symbol_file->get_debug_addr_data().GetMaxU64(&offset, index_size);
 }

 uint64_t DWARFFormValue::Reference() const {
   uint64_t value = m_value.value.uval;
   switch (m_form) {
   case DW_FORM_ref1:
   case DW_FORM_ref2:
   case DW_FORM_ref4:
   case DW_FORM_ref8:
   case DW_FORM_ref_udata:
     assert(m_cu); // CU must be valid for DW_FORM_ref forms that are compile
                   // unit relative or we will get this wrong
     return value + m_cu->GetOffset();

   case DW_FORM_ref_addr:
   case DW_FORM_ref_sig8:
   case DW_FORM_GNU_ref_alt:
     return value;

   default:
     return DW_INVALID_OFFSET;
   }
 }

 uint64_t DWARFFormValue::Reference(dw_offset_t base_offset) const {
   uint64_t value = m_value.value.uval;
   switch (m_form) {
   case DW_FORM_ref1:
   case DW_FORM_ref2:
   case DW_FORM_ref4:
   case DW_FORM_ref8:
   case DW_FORM_ref_udata:
     return value + base_offset;

   case DW_FORM_ref_addr:
   case DW_FORM_ref_sig8:
   case DW_FORM_GNU_ref_alt:
     return value;

   default:
     return DW_INVALID_OFFSET;
   }
 }

 const uint8_t *DWARFFormValue::BlockData() const { return m_value.data; }

 bool DWARFFormValue::IsBlockForm(const dw_form_t form) {
   switch (form) {
   case DW_FORM_exprloc:
   case DW_FORM_block:
   case DW_FORM_block1:
   case DW_FORM_block2:
   case DW_FORM_block4:
     return true;
   }
   return false;
 }

 bool DWARFFormValue::IsDataForm(const dw_form_t form) {
   switch (form) {
   case DW_FORM_sdata:
   case DW_FORM_udata:
   case DW_FORM_data1:
   case DW_FORM_data2:
   case DW_FORM_data4:
   case DW_FORM_data8:
     return true;
   }
   return false;
 }

 int DWARFFormValue::Compare(const DWARFFormValue &a_value,
                             const DWARFFormValue &b_value) {
   dw_form_t a_form = a_value.Form();
   dw_form_t b_form = b_value.Form();
   if (a_form < b_form)
     return -1;
   if (a_form > b_form)
     return 1;
   switch (a_form) {
   case DW_FORM_addr:
   case DW_FORM_flag:
   case DW_FORM_data1:
   case DW_FORM_data2:
   case DW_FORM_data4:
   case DW_FORM_data8:
   case DW_FORM_udata:
   case DW_FORM_ref_addr:
   case DW_FORM_sec_offset:
   case DW_FORM_flag_present:
   case DW_FORM_ref_sig8:
   case DW_FORM_GNU_addr_index: {
     uint64_t a = a_value.Unsigned();
     uint64_t b = b_value.Unsigned();
     if (a < b)
       return -1;
     if (a > b)
       return 1;
     return 0;
   }

   case DW_FORM_sdata: {
     int64_t a = a_value.Signed();
     int64_t b = b_value.Signed();
     if (a < b)
       return -1;
     if (a > b)
       return 1;
     return 0;
   }

   case DW_FORM_string:
   case DW_FORM_strp:
   case DW_FORM_GNU_str_index: {
     const char *a_string = a_value.AsCString();
     const char *b_string = b_value.AsCString();
     if (a_string == b_string)
       return 0;
     else if (a_string && b_string)
       return strcmp(a_string, b_string);
     else if (a_string == NULL)
       return -1; // A string is NULL, and B is valid
     else
       return 1; // A string valid, and B is NULL
   }

   case DW_FORM_block:
   case DW_FORM_block1:
   case DW_FORM_block2:
   case DW_FORM_block4:
   case DW_FORM_exprloc: {
     uint64_t a_len = a_value.Unsigned();
     uint64_t b_len = b_value.Unsigned();
     if (a_len < b_len)
       return -1;
     if (a_len > b_len)
       return 1;
     // The block lengths are the same
     return memcmp(a_value.BlockData(), b_value.BlockData(), a_value.Unsigned());
   } break;

   case DW_FORM_ref1:
   case DW_FORM_ref2:
   case DW_FORM_ref4:
   case DW_FORM_ref8:
   case DW_FORM_ref_udata: {
     uint64_t a = a_value.Reference();
     uint64_t b = b_value.Reference();
     if (a < b)
       return -1;
     if (a > b)
       return 1;
     return 0;
   }

   case DW_FORM_indirect:
     llvm_unreachable(
         "This shouldn't happen after the form has been extracted...");

   default:
     llvm_unreachable("Unhandled DW_FORM");
   }
   return -1;
 }

 bool DWARFFormValue::FormIsSupported(dw_form_t form) {
   switch (form) {
     case DW_FORM_addr:
     case DW_FORM_addrx:
     case DW_FORM_rnglistx:
     case DW_FORM_block2:
     case DW_FORM_block4:
     case DW_FORM_data2:
     case DW_FORM_data4:
     case DW_FORM_data8:
     case DW_FORM_string:
     case DW_FORM_block:
     case DW_FORM_block1:
     case DW_FORM_data1:
     case DW_FORM_flag:
     case DW_FORM_sdata:
     case DW_FORM_strp:
     case DW_FORM_strx:
     case DW_FORM_strx1:
     case DW_FORM_strx2:
     case DW_FORM_strx3:
     case DW_FORM_strx4:
     case DW_FORM_udata:
     case DW_FORM_ref_addr:
     case DW_FORM_ref1:
     case DW_FORM_ref2:
     case DW_FORM_ref4:
     case DW_FORM_ref8:
     case DW_FORM_ref_udata:
     case DW_FORM_indirect:
     case DW_FORM_sec_offset:
     case DW_FORM_exprloc:
     case DW_FORM_flag_present:
     case DW_FORM_ref_sig8:
     case DW_FORM_GNU_str_index:
     case DW_FORM_GNU_addr_index:
     case DW_FORM_implicit_const:
       return true;
     default:
       break;
   }
   return false;
 }
	//===-- DWARFFormValue.cpp --------------------------------------- C++ --===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//

	#include <assert.h>

	#include "lldb/Core/dwarf.h"
	#include "lldb/Utility/Stream.h"

	#include "DWARFUnit.h"
	#include "DWARFFormValue.h"

	class DWARFUnit;

	using namespace lldb_private;

	static uint8_t g_form_sizes_addr4[] = {
	0, // 0x00 unused
	4, // 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
	0, // 0x10 DW_FORM_ref_addr (addr size for DWARF2 and earlier, 4 bytes for
	// DWARF32, 8 bytes for DWARF32 in DWARF 3 and later
	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
	0, // 0x1a
	0, // 0x1b
	0, // 0x1c
	0, // 0x1d
	0, // 0x1e
	0, // 0x1f
	8, // 0x20 DW_FORM_ref_sig8

	};

	static uint8_t g_form_sizes_addr8[] = {
	0, // 0x00 unused
	8, // 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
	0, // 0x10 DW_FORM_ref_addr (addr size for DWARF2 and earlier, 4 bytes for
	// DWARF32, 8 bytes for DWARF32 in DWARF 3 and later
	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
	0, // 0x1a
	0, // 0x1b
	0, // 0x1c
	0, // 0x1d
	0, // 0x1e
	0, // 0x1f
	8, // 0x20 DW_FORM_ref_sig8
	};

	// Difference with g_form_sizes_addr8:
	// DW_FORM_strp and DW_FORM_sec_offset are 8 instead of 4
	static uint8_t g_form_sizes_addr8_dwarf64[] = {
	0, // 0x00 unused
	8, // 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
	8, // 0x0e DW_FORM_strp
	0, // 0x0f DW_FORM_udata
	0, // 0x10 DW_FORM_ref_addr (addr size for DWARF2 and earlier, 4 bytes for
	// DWARF32, 8 bytes for DWARF32 in DWARF 3 and later
	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
	8, // 0x17 DW_FORM_sec_offset
	0, // 0x18 DW_FORM_exprloc
	0, // 0x19 DW_FORM_flag_present
	0, // 0x1a
	0, // 0x1b
	0, // 0x1c
	0, // 0x1d
	0, // 0x1e
	0, // 0x1f
	8, // 0x20 DW_FORM_ref_sig8
	};

	DWARFFormValue::FixedFormSizes
	DWARFFormValue::GetFixedFormSizesForAddressSize(uint8_t addr_size,
	bool is_dwarf64) {
	if (!is_dwarf64) {
	switch (addr_size) {
	case 4:
	return FixedFormSizes(g_form_sizes_addr4, sizeof(g_form_sizes_addr4));
	case 8:
	return FixedFormSizes(g_form_sizes_addr8, sizeof(g_form_sizes_addr8));
	}
	} else {
	if (addr_size == 8)
	return FixedFormSizes(g_form_sizes_addr8_dwarf64,
	sizeof(g_form_sizes_addr8_dwarf64));
	// is_dwarf64 && addr_size == 4 : no provider does this.
	}
	return FixedFormSizes();
	}

	DWARFFormValue::DWARFFormValue() : m_cu(NULL), m_form(0), m_value() {}

	DWARFFormValue::DWARFFormValue(const DWARFUnit *cu)
	: m_cu(cu), m_form(0), m_value() {}

	DWARFFormValue::DWARFFormValue(const DWARFUnit *cu, dw_form_t form)
	: m_cu(cu), m_form(form), m_value() {}

	void DWARFFormValue::Clear() {
	m_cu = nullptr;
	m_form = 0;
	memset(&m_value, 0, sizeof(m_value));
	}

	bool DWARFFormValue::ExtractValue(const DWARFDataExtractor &data,
	lldb::offset_t *offset_ptr) {
	if (m_form == DW_FORM_implicit_const)
	return true;

	bool indirect = false;
	bool is_block = false;
	m_value.data = NULL;
	uint8_t ref_addr_size;
	// Read the value for the form into value and follow and DW_FORM_indirect
	// instances we run into
	do {
	indirect = false;
	switch (m_form) {
	case DW_FORM_addr:
	assert(m_cu);
	m_value.value.uval =
	data.GetMaxU64(offset_ptr, DWARFUnit::GetAddressByteSize(m_cu));
	break;
	case DW_FORM_block1:
	m_value.value.uval = data.GetU8(offset_ptr);
	is_block = true;
	break;
	case DW_FORM_block2:
	m_value.value.uval = data.GetU16(offset_ptr);
	is_block = true;
	break;
	case DW_FORM_block4:
	m_value.value.uval = data.GetU32(offset_ptr);
	is_block = true;
	break;
	case DW_FORM_data16:
	m_value.value.uval = 16;
	is_block = true;
	break;
	case DW_FORM_exprloc:
	case DW_FORM_block:
	m_value.value.uval = data.GetULEB128(offset_ptr);
	is_block = true;
	break;
	case DW_FORM_string:
	m_value.value.cstr = data.GetCStr(offset_ptr);
	break;
	case DW_FORM_sdata:
	m_value.value.sval = data.GetSLEB128(offset_ptr);
	break;
	case DW_FORM_strp:
	case DW_FORM_line_strp:
	case DW_FORM_sec_offset:
	assert(m_cu);
	m_value.value.uval =
	data.GetMaxU64(offset_ptr, DWARFUnit::IsDWARF64(m_cu) ? 8 : 4);
	break;
	case DW_FORM_addrx1:
	case DW_FORM_strx1:
	case DW_FORM_ref1:
	case DW_FORM_data1:
	case DW_FORM_flag:
	m_value.value.uval = data.GetU8(offset_ptr);
	break;
	case DW_FORM_addrx2:
	case DW_FORM_strx2:
	case DW_FORM_ref2:
	case DW_FORM_data2:
	m_value.value.uval = data.GetU16(offset_ptr);
	break;
	case DW_FORM_addrx3:
	case DW_FORM_strx3:
	m_value.value.uval = data.GetMaxU64(offset_ptr, 3);
	break;
	case DW_FORM_addrx4:
	case DW_FORM_strx4:
	case DW_FORM_ref4:
	case DW_FORM_data4:
	m_value.value.uval = data.GetU32(offset_ptr);
	break;
	case DW_FORM_data8:
	case DW_FORM_ref8:
	case DW_FORM_ref_sig8:
	m_value.value.uval = data.GetU64(offset_ptr);
	break;
	case DW_FORM_addrx:
	case DW_FORM_rnglistx:
	case DW_FORM_strx:
	case DW_FORM_udata:
	case DW_FORM_ref_udata:
	case DW_FORM_GNU_str_index:
	case DW_FORM_GNU_addr_index:
	m_value.value.uval = data.GetULEB128(offset_ptr);
	break;
	case DW_FORM_ref_addr:
	assert(m_cu);
	if (m_cu->GetVersion() <= 2)
	ref_addr_size = m_cu->GetAddressByteSize();
	else
	ref_addr_size = m_cu->IsDWARF64() ? 8 : 4;
	m_value.value.uval = data.GetMaxU64(offset_ptr, ref_addr_size);
	break;
	case DW_FORM_indirect:
	m_form = data.GetULEB128(offset_ptr);
	indirect = true;
	break;
	case DW_FORM_flag_present:
	m_value.value.uval = 1;
	break;
	default:
	return false;
	}
	} while (indirect);

	if (is_block) {
	m_value.data = data.PeekData(*offset_ptr, m_value.value.uval);
	if (m_value.data != NULL) {
	*offset_ptr += m_value.value.uval;
	}
	}

	return true;
	}

	bool DWARFFormValue::SkipValue(const DWARFDataExtractor &debug_info_data,
	lldb::offset_t *offset_ptr) const {
	return DWARFFormValue::SkipValue(m_form, debug_info_data, offset_ptr, m_cu);
	}

	bool DWARFFormValue::SkipValue(dw_form_t form,
	const DWARFDataExtractor &debug_info_data,
	lldb::offset_t *offset_ptr,
	const DWARFUnit *cu) {
	uint8_t ref_addr_size;
	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: {
	dw_uleb128_t size = debug_info_data.GetULEB128(offset_ptr);
	*offset_ptr += size;
	}
	return true;
	case DW_FORM_block1: {
	dw_uleb128_t size = debug_info_data.GetU8(offset_ptr);
	*offset_ptr += size;
	}
	return true;
	case DW_FORM_block2: {
	dw_uleb128_t size = debug_info_data.GetU16(offset_ptr);
	*offset_ptr += size;
	}
	return true;
	case DW_FORM_block4: {
	dw_uleb128_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 += DWARFUnit::GetAddressByteSize(cu);
	return true;

	case DW_FORM_ref_addr:
	ref_addr_size = 4;
	assert(cu); // CU must be valid for DW_FORM_ref_addr objects or we will get
	// this wrong
	if (cu->GetVersion() <= 2)
	ref_addr_size = cu->GetAddressByteSize();
	else
	ref_addr_size = cu->IsDWARF64() ? 8 : 4;
	*offset_ptr += ref_addr_size;
	return true;

	// 0 bytes values (implied from DW_FORM)
	case DW_FORM_flag_present:
	case DW_FORM_implicit_const:
	return true;

	// 1 byte values
	case DW_FORM_addrx1:
	case DW_FORM_data1:
	case DW_FORM_flag:
	case DW_FORM_ref1:
	case DW_FORM_strx1:
	*offset_ptr += 1;
	return true;

	// 2 byte values
	case DW_FORM_addrx2:
	case DW_FORM_data2:
	case DW_FORM_ref2:
	case DW_FORM_strx2:
	*offset_ptr += 2;
	return true;

	// 3 byte values
	case DW_FORM_addrx3:
	case DW_FORM_strx3:
	*offset_ptr += 3;
	return true;

	// 32 bit for DWARF 32, 64 for DWARF 64
	case DW_FORM_sec_offset:
	case DW_FORM_strp:
	assert(cu);
	*offset_ptr += (cu->IsDWARF64() ? 8 : 4);
	return true;

	// 4 byte values
	case DW_FORM_addrx4:
	case DW_FORM_data4:
	case DW_FORM_ref4:
	case DW_FORM_strx4:
	*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_addrx:
	case DW_FORM_rnglistx:
	case DW_FORM_sdata:
	case DW_FORM_udata:
	case DW_FORM_ref_udata:
	case DW_FORM_GNU_addr_index:
	case DW_FORM_GNU_str_index:
	case DW_FORM_strx:
	debug_info_data.Skip_LEB128(offset_ptr);
	return true;

	case DW_FORM_indirect: {
	dw_form_t indirect_form = debug_info_data.GetULEB128(offset_ptr);
	return DWARFFormValue::SkipValue(indirect_form, debug_info_data, offset_ptr,
	cu);
	}

	default:
	break;
	}
	return false;
	}

	void DWARFFormValue::Dump(Stream &s) const {
	uint64_t uvalue = Unsigned();
	bool cu_relative_offset = false;

	switch (m_form) {
	case DW_FORM_addr:
	s.Address(uvalue, sizeof(uint64_t));
	break;
	case DW_FORM_flag:
	case DW_FORM_data1:
	s.PutHex8(uvalue);
	break;
	case DW_FORM_data2:
	s.PutHex16(uvalue);
	break;
	case DW_FORM_sec_offset:
	case DW_FORM_data4:
	s.PutHex32(uvalue);
	break;
	case DW_FORM_ref_sig8:
	case DW_FORM_data8:
	s.PutHex64(uvalue);
	break;
	case DW_FORM_string:
	s.QuotedCString(AsCString());
	break;
	case DW_FORM_exprloc:
	case DW_FORM_block:
	case DW_FORM_block1:
	case DW_FORM_block2:
	case DW_FORM_block4:
	if (uvalue > 0) {
	switch (m_form) {
	case DW_FORM_exprloc:
	case DW_FORM_block:
	s.Printf("<0x%" PRIx64 "> ", uvalue);
	break;
	case DW_FORM_block1:
	s.Printf("<0x%2.2x> ", (uint8_t)uvalue);
	break;
	case DW_FORM_block2:
	s.Printf("<0x%4.4x> ", (uint16_t)uvalue);
	break;
	case DW_FORM_block4:
	s.Printf("<0x%8.8x> ", (uint32_t)uvalue);
	break;
	default:
	break;
	}

	const uint8_t *data_ptr = m_value.data;
	if (data_ptr) {
	const uint8_t *end_data_ptr =
	data_ptr + uvalue; // uvalue contains size of block
	while (data_ptr < end_data_ptr) {
	s.Printf("%2.2x ", *data_ptr);
	++data_ptr;
	}
	} else
	s.PutCString("NULL");
	}
	break;

	case DW_FORM_sdata:
	s.PutSLEB128(uvalue);
	break;
	case DW_FORM_udata:
	s.PutULEB128(uvalue);
	break;
	case DW_FORM_strp: {
	const char *dbg_str = AsCString();
	if (dbg_str) {
	s.QuotedCString(dbg_str);
	} else {
	s.PutHex32(uvalue);
	}
	} break;

	case DW_FORM_ref_addr: {
	assert(m_cu); // CU must be valid for DW_FORM_ref_addr objects or we will
	// get this wrong
	if (m_cu->GetVersion() <= 2)
	s.Address(uvalue, sizeof(uint64_t) * 2);
	else
	s.Address(uvalue, 4 * 2); // 4 for DWARF32, 8 for DWARF64, but we don't
	// support DWARF64 yet
	break;
	}
	case DW_FORM_ref1:
	cu_relative_offset = true;
	break;
	case DW_FORM_ref2:
	cu_relative_offset = true;
	break;
	case DW_FORM_ref4:
	cu_relative_offset = true;
	break;
	case DW_FORM_ref8:
	cu_relative_offset = true;
	break;
	case DW_FORM_ref_udata:
	cu_relative_offset = true;
	break;

	// All DW_FORM_indirect attributes should be resolved prior to calling this
	// function
	case DW_FORM_indirect:
	s.PutCString("DW_FORM_indirect");
	break;
	case DW_FORM_flag_present:
	break;
	default:
	s.Printf("DW_FORM(0x%4.4x)", m_form);
	break;
	}

	if (cu_relative_offset) {
	assert(m_cu); // CU must be valid for DW_FORM_ref forms that are compile
	// unit relative or we will get this wrong
	s.Printf("{0x%8.8" PRIx64 "}", uvalue + m_cu->GetOffset());
	}
	}

	const char *DWARFFormValue::AsCString() const {
	SymbolFileDWARF *symbol_file = m_cu->GetSymbolFileDWARF();

	if (m_form == DW_FORM_string) {
	return m_value.value.cstr;
	} else if (m_form == DW_FORM_strp) {
	if (!symbol_file)
	return nullptr;

	return symbol_file->get_debug_str_data().PeekCStr(m_value.value.uval);
	} else if (m_form == DW_FORM_GNU_str_index) {
	if (!symbol_file)
	return nullptr;

	uint32_t index_size = m_cu->IsDWARF64() ? 8 : 4;
	lldb::offset_t offset = m_value.value.uval * index_size;
	dw_offset_t str_offset =
	symbol_file->get_debug_str_offsets_data().GetMaxU64(&offset,
	index_size);
	return symbol_file->get_debug_str_data().PeekCStr(str_offset);
	}

	if (m_form == DW_FORM_strx \|\| m_form == DW_FORM_strx1 \|\|
	m_form == DW_FORM_strx2 \|\| m_form == DW_FORM_strx3 \|\|
	m_form == DW_FORM_strx4) {

	// The same code as above.
	if (!symbol_file)
	return nullptr;

	uint32_t indexSize = m_cu->IsDWARF64() ? 8 : 4;
	lldb::offset_t offset =
	m_cu->GetStrOffsetsBase() + m_value.value.uval * indexSize;
	dw_offset_t strOffset =
	symbol_file->get_debug_str_offsets_data().GetMaxU64(&offset, indexSize);
	return symbol_file->get_debug_str_data().PeekCStr(strOffset);
	}

	if (m_form == DW_FORM_line_strp)
	return symbol_file->get_debug_line_str_data().PeekCStr(m_value.value.uval);

	return nullptr;
	}

	dw_addr_t DWARFFormValue::Address() const {
	SymbolFileDWARF *symbol_file = m_cu->GetSymbolFileDWARF();

	if (m_form == DW_FORM_addr)
	return Unsigned();

	assert(m_cu);
	assert(m_form == DW_FORM_GNU_addr_index \|\| m_form == DW_FORM_addrx \|\|
	m_form == DW_FORM_addrx1 \|\| m_form == DW_FORM_addrx2 \|\|
	m_form == DW_FORM_addrx3 \|\| m_form == DW_FORM_addrx4);

	if (!symbol_file)
	return 0;

	uint32_t index_size = m_cu->GetAddressByteSize();
	dw_offset_t addr_base = m_cu->GetAddrBase();
	lldb::offset_t offset = addr_base + m_value.value.uval * index_size;
	return symbol_file->get_debug_addr_data().GetMaxU64(&offset, index_size);
	}

	uint64_t DWARFFormValue::Reference() const {
	uint64_t value = m_value.value.uval;
	switch (m_form) {
	case DW_FORM_ref1:
	case DW_FORM_ref2:
	case DW_FORM_ref4:
	case DW_FORM_ref8:
	case DW_FORM_ref_udata:
	assert(m_cu); // CU must be valid for DW_FORM_ref forms that are compile
	// unit relative or we will get this wrong
	return value + m_cu->GetOffset();

	case DW_FORM_ref_addr:
	case DW_FORM_ref_sig8:
	case DW_FORM_GNU_ref_alt:
	return value;

	default:
	return DW_INVALID_OFFSET;
	}
	}

	uint64_t DWARFFormValue::Reference(dw_offset_t base_offset) const {
	uint64_t value = m_value.value.uval;
	switch (m_form) {
	case DW_FORM_ref1:
	case DW_FORM_ref2:
	case DW_FORM_ref4:
	case DW_FORM_ref8:
	case DW_FORM_ref_udata:
	return value + base_offset;

	case DW_FORM_ref_addr:
	case DW_FORM_ref_sig8:
	case DW_FORM_GNU_ref_alt:
	return value;

	default:
	return DW_INVALID_OFFSET;
	}
	}

	const uint8_t *DWARFFormValue::BlockData() const { return m_value.data; }

	bool DWARFFormValue::IsBlockForm(const dw_form_t form) {
	switch (form) {
	case DW_FORM_exprloc:
	case DW_FORM_block:
	case DW_FORM_block1:
	case DW_FORM_block2:
	case DW_FORM_block4:
	return true;
	}
	return false;
	}

	bool DWARFFormValue::IsDataForm(const dw_form_t form) {
	switch (form) {
	case DW_FORM_sdata:
	case DW_FORM_udata:
	case DW_FORM_data1:
	case DW_FORM_data2:
	case DW_FORM_data4:
	case DW_FORM_data8:
	return true;
	}
	return false;
	}

	int DWARFFormValue::Compare(const DWARFFormValue &a_value,
	const DWARFFormValue &b_value) {
	dw_form_t a_form = a_value.Form();
	dw_form_t b_form = b_value.Form();
	if (a_form < b_form)
	return -1;
	if (a_form > b_form)
	return 1;
	switch (a_form) {
	case DW_FORM_addr:
	case DW_FORM_flag:
	case DW_FORM_data1:
	case DW_FORM_data2:
	case DW_FORM_data4:
	case DW_FORM_data8:
	case DW_FORM_udata:
	case DW_FORM_ref_addr:
	case DW_FORM_sec_offset:
	case DW_FORM_flag_present:
	case DW_FORM_ref_sig8:
	case DW_FORM_GNU_addr_index: {
	uint64_t a = a_value.Unsigned();
	uint64_t b = b_value.Unsigned();
	if (a < b)
	return -1;
	if (a > b)
	return 1;
	return 0;
	}

	case DW_FORM_sdata: {
	int64_t a = a_value.Signed();
	int64_t b = b_value.Signed();
	if (a < b)
	return -1;
	if (a > b)
	return 1;
	return 0;
	}

	case DW_FORM_string:
	case DW_FORM_strp:
	case DW_FORM_GNU_str_index: {
	const char *a_string = a_value.AsCString();
	const char *b_string = b_value.AsCString();
	if (a_string == b_string)
	return 0;
	else if (a_string && b_string)
	return strcmp(a_string, b_string);
	else if (a_string == NULL)
	return -1; // A string is NULL, and B is valid
	else
	return 1; // A string valid, and B is NULL
	}

	case DW_FORM_block:
	case DW_FORM_block1:
	case DW_FORM_block2:
	case DW_FORM_block4:
	case DW_FORM_exprloc: {
	uint64_t a_len = a_value.Unsigned();
	uint64_t b_len = b_value.Unsigned();
	if (a_len < b_len)
	return -1;
	if (a_len > b_len)
	return 1;
	// The block lengths are the same
	return memcmp(a_value.BlockData(), b_value.BlockData(), a_value.Unsigned());
	} break;

	case DW_FORM_ref1:
	case DW_FORM_ref2:
	case DW_FORM_ref4:
	case DW_FORM_ref8:
	case DW_FORM_ref_udata: {
	uint64_t a = a_value.Reference();
	uint64_t b = b_value.Reference();
	if (a < b)
	return -1;
	if (a > b)
	return 1;
	return 0;
	}

	case DW_FORM_indirect:
	llvm_unreachable(
	"This shouldn't happen after the form has been extracted...");

	default:
	llvm_unreachable("Unhandled DW_FORM");
	}
	return -1;
	}

	bool DWARFFormValue::FormIsSupported(dw_form_t form) {
	switch (form) {
	case DW_FORM_addr:
	case DW_FORM_addrx:
	case DW_FORM_rnglistx:
	case DW_FORM_block2:
	case DW_FORM_block4:
	case DW_FORM_data2:
	case DW_FORM_data4:
	case DW_FORM_data8:
	case DW_FORM_string:
	case DW_FORM_block:
	case DW_FORM_block1:
	case DW_FORM_data1:
	case DW_FORM_flag:
	case DW_FORM_sdata:
	case DW_FORM_strp:
	case DW_FORM_strx:
	case DW_FORM_strx1:
	case DW_FORM_strx2:
	case DW_FORM_strx3:
	case DW_FORM_strx4:
	case DW_FORM_udata:
	case DW_FORM_ref_addr:
	case DW_FORM_ref1:
	case DW_FORM_ref2:
	case DW_FORM_ref4:
	case DW_FORM_ref8:
	case DW_FORM_ref_udata:
	case DW_FORM_indirect:
	case DW_FORM_sec_offset:
	case DW_FORM_exprloc:
	case DW_FORM_flag_present:
	case DW_FORM_ref_sig8:
	case DW_FORM_GNU_str_index:
	case DW_FORM_GNU_addr_index:
	case DW_FORM_implicit_const:
	return true;
	default:
	break;
	}
	return false;
	}