Cleanup fixed form sizes.

[clayborg]

Summary

The fix form sizes use to have two arrays: one for 4 byte addresses and in for 8 byte addresses. The table had an issue where DW_FORM_flag_present wasn't being represented as a fixed size form because its actual size _is_ zero and zero was used to indicate the form isn't fixed in size. Any code that needed to quickly access the DWARF had to get a FixedFormSizes instance using the address byte size.

This fix cleans things up by adding a DWARFFormValue::GetFixedSize() both as a static method and as a member function on DWARFFormValue. It correctly can indicate if a form size is zero. This cleanup is a precursor to a follow up patch where I hope to speed up DWARF parsing.

I verified performance doesn't regress by loading hundreds of DWARF files and setting a breakpoint by file and line and by name in files that do not have DWARF indexes. Performance remained consistent between the two approaches.

[clayborg]

Removed unused function added to DWARFFormValue

[JDevlieghere]

Looks like a good change. Small comment inline but otherwise LGTM.

source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp

3170–3174

if (auto data_length = form_value.GetFixedSize()) 
    ...

3188

Same as previous comment.

source/Plugins/SymbolFile/DWARF/DWARFBaseDIE.cpp

 }
 
 bool DWARFBaseDIE::Supports_DW_AT_APPLE_objc_complete_type() const {
   return IsValid() && GetDWARF()->Supports_DW_AT_APPLE_objc_complete_type(m_cu);
 }
 
 size_t DWARFBaseDIE::GetAttributes(DWARFAttributes &attributes,
                                uint32_t depth) const {
-  if (IsValid()) {
-    return m_die->GetAttributes(m_cu, m_cu->GetFixedFormSizes(), attributes,
-                                depth);
-  }
+  if (IsValid())
+    return m_die->GetAttributes(m_cu, attributes, depth);
   if (depth == 0)
     attributes.Clear();
   return 0;
 }
 
 bool operator==(const DWARFBaseDIE &lhs, const DWARFBaseDIE &rhs) {
   return lhs.GetDIE() == rhs.GetDIE() && lhs.GetCU() == rhs.GetCU();
 }

source/Plugins/SymbolFile/DWARF/DWARFDebugInfoEntry.h

public:
   void BuildAddressRangeTable(const DWARFUnit *cu,
                               DWARFDebugAranges *debug_aranges) const;
 
   void BuildFunctionAddressRangeTable(const DWARFUnit *cu,
                                       DWARFDebugAranges *debug_aranges) const;
 
   bool FastExtract(const lldb_private::DWARFDataExtractor &debug_info_data,
                    const DWARFUnit *cu,
-                   const DWARFFormValue::FixedFormSizes &fixed_form_sizes,
                    lldb::offset_t *offset_ptr);
 
   bool Extract(const DWARFUnit *cu, lldb::offset_t *offset_ptr);
 
   bool LookupAddress(const dw_addr_t address, const DWARFUnit *cu,
                      DWARFDebugInfoEntry **function_die,
                      DWARFDebugInfoEntry **block_die);
 
   size_t GetAttributes(const DWARFUnit *cu,
-                       DWARFFormValue::FixedFormSizes fixed_form_sizes,
                        DWARFAttributes &attrs,
                        uint32_t curr_depth = 0)
       const; // "curr_depth" for internal use only, don't set this yourself!!!
 
   dw_offset_t
   GetAttributeValue(const DWARFUnit *cu, const dw_attr_t attr,
                     DWARFFormValue &formValue,
                     dw_offset_t *end_attr_offset_ptr = nullptr,

source/Plugins/SymbolFile/DWARF/DWARFDebugInfoEntry.cpp

 #include "SymbolFileDWARFDwo.h"
 
 using namespace lldb_private;
 using namespace std;
 extern int g_verbose;
 
 bool DWARFDebugInfoEntry::FastExtract(
     const DWARFDataExtractor &debug_info_data, const DWARFUnit *cu,
-    const DWARFFormValue::FixedFormSizes &fixed_form_sizes,
     lldb::offset_t *offset_ptr) {
   m_offset = *offset_ptr;
   m_parent_idx = 0;
   m_sibling_idx = 0;
   const uint64_t abbr_idx = debug_info_data.GetULEB128(offset_ptr);
   lldbassert(abbr_idx <= UINT16_MAX);
   m_abbr_idx = abbr_idx;
 
if (m_abbr_idx) {
     m_has_children = abbrevDecl->HasChildren();
     // Skip all data in the .debug_info for the attributes
     const uint32_t numAttributes = abbrevDecl->NumAttributes();
     uint32_t i;
     dw_form_t form;
     for (i = 0; i < numAttributes; ++i) {
       form = abbrevDecl->GetFormByIndexUnchecked(i);
 
-      const uint8_t fixed_skip_size = fixed_form_sizes.GetSize(form);
+      llvm::Optional<uint8_t> fixed_skip_size = DWARFFormValue::GetFixedSize(form, cu);
       if (fixed_skip_size)
-        offset += fixed_skip_size;
+        offset += *fixed_skip_size;
       else {
         bool form_is_indirect = false;
         do {
           form_is_indirect = false;
           uint32_t form_size = 0;
           switch (form) {
           // Blocks if inlined data that have a length field and the data bytes
           // inlined in the .debug_info
void DWARFDebugInfoEntry::DumpAttribute(
   s.PutCString(" )\n");
 }
 
 // Get all attribute values for a given DIE, including following any
 // specification or abstract origin attributes and including those in the
 // results. Any duplicate attributes will have the first instance take
 // precedence (this can happen for declaration attributes).
 size_t DWARFDebugInfoEntry::GetAttributes(
-    const DWARFUnit *cu, DWARFFormValue::FixedFormSizes fixed_form_sizes,
-    DWARFAttributes &attributes, uint32_t curr_depth) const {
+    const DWARFUnit *cu, DWARFAttributes &attributes,
+    uint32_t curr_depth) const {
   const DWARFAbbreviationDeclaration *abbrevDecl = nullptr;
   lldb::offset_t offset = 0;
   if (cu)
     abbrevDecl = GetAbbreviationDeclarationPtr(cu, offset);
 
   if (abbrevDecl) {
     const DWARFDataExtractor &debug_info_data = cu->GetData();
 
-    if (fixed_form_sizes.Empty())
-      fixed_form_sizes = DWARFFormValue::GetFixedFormSizesForAddressSize(
-          cu->GetAddressByteSize());
-
     const uint32_t num_attributes = abbrevDecl->NumAttributes();
     for (uint32_t i = 0; i < num_attributes; ++i) {
       DWARFFormValue form_value(cu);
       dw_attr_t attr;
       abbrevDecl->GetAttrAndFormValueByIndex(i, attr, form_value);
       const dw_form_t form = form_value.Form();
 
       // If we are tracking down DW_AT_specification or DW_AT_abstract_origin
for (uint32_t i = 0; i < num_attributes; ++i) {
 
       if ((attr == DW_AT_specification) || (attr == DW_AT_abstract_origin)) {
         if (form_value.ExtractValue(debug_info_data, &offset)) {
           DWARFDIE spec_die = form_value.Reference();
           if (spec_die)
             spec_die.GetAttributes(attributes, curr_depth + 1);
         }
       } else {
-        const uint8_t fixed_skip_size = fixed_form_sizes.GetSize(form);
+        llvm::Optional<uint8_t> fixed_skip_size = DWARFFormValue::GetFixedSize(form, cu);
         if (fixed_skip_size)
-          offset += fixed_skip_size;
+          offset += *fixed_skip_size;
         else
           DWARFFormValue::SkipValue(form, debug_info_data, &offset, cu);
       }
     }
   } else {
     attributes.Clear();
   }
   return attributes.Size();
bool DWARFDebugInfoEntry::MatchesDWARFDeclContext(
   DWARFDeclContext this_dwarf_decl_ctx;
   GetDWARFDeclContext(cu, this_dwarf_decl_ctx);
   return this_dwarf_decl_ctx == dwarf_decl_ctx;
 }
 
 DWARFDIE
 DWARFDebugInfoEntry::GetParentDeclContextDIE(DWARFUnit *cu) const {
   DWARFAttributes attributes;
-  GetAttributes(cu, DWARFFormValue::FixedFormSizes(), attributes);
+  GetAttributes(cu, attributes);
   return GetParentDeclContextDIE(cu, attributes);
 }
 
 DWARFDIE
 DWARFDebugInfoEntry::GetParentDeclContextDIE(
     DWARFUnit *cu, const DWARFAttributes &attributes) const {
   DWARFDIE die(cu, const_cast<DWARFDebugInfoEntry *>(this));
 
while (die) {
     die = die.GetParent();
   }
   return DWARFDIE();
 }
 
 const char *DWARFDebugInfoEntry::GetQualifiedName(DWARFUnit *cu,
                                                   std::string &storage) const {
   DWARFAttributes attributes;
-  GetAttributes(cu, DWARFFormValue::FixedFormSizes(), attributes);
+  GetAttributes(cu, attributes);
   return GetQualifiedName(cu, attributes, storage);
 }
 
 const char *
 DWARFDebugInfoEntry::GetQualifiedName(DWARFUnit *cu,
                                       const DWARFAttributes &attributes,
                                       std::string &storage) const {
 

source/Plugins/SymbolFile/DWARF/DWARFFormValue.h

 //===-- DWARFFormValue.h ----------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef SymbolFileDWARF_DWARFFormValue_h_
 #define SymbolFileDWARF_DWARFFormValue_h_
 
 #include "DWARFDataExtractor.h"
 #include <stddef.h>
+#include "llvm/ADT/Optional.h"
 
 class DWARFUnit;
 class SymbolFileDWARF;
 class DWARFDIE;
 
 class DWARFFormValue {
 public:
   typedef struct ValueTypeTag {
     ValueTypeTag() : value(), data(nullptr) { value.uval = 0; }
 
     union {
       uint64_t uval;
       int64_t sval;
       const char *cstr;
     } value;
     const uint8_t *data;
   } ValueType;
 
-  class FixedFormSizes {
-  public:
-    FixedFormSizes() : m_fix_sizes(nullptr), m_size(0) {}
-
-    FixedFormSizes(const uint8_t *fix_sizes, size_t size)
-        : m_fix_sizes(fix_sizes), m_size(size) {}
-
-    uint8_t GetSize(uint32_t index) const {
-      return index < m_size ? m_fix_sizes[index] : 0;
-    }
-
-    bool Empty() const { return m_size == 0; }
-
-  private:
-    const uint8_t *m_fix_sizes;
-    size_t m_size;
-  };
-
   enum {
     eValueTypeInvalid = 0,
     eValueTypeUnsigned,
     eValueTypeSigned,
     eValueTypeCStr,
     eValueTypeBlock
   };
 
   DWARFFormValue() = default;
   DWARFFormValue(const DWARFUnit *unit) : m_unit(unit) {}
   DWARFFormValue(const DWARFUnit *unit, dw_form_t form)
       : m_unit(unit), m_form(form) {}
   void SetUnit(const DWARFUnit *unit) { m_unit = unit; }
   dw_form_t Form() const { return m_form; }
   dw_form_t& FormRef() { return m_form; }
   void SetForm(dw_form_t form) { m_form = form; }
   const ValueType &Value() const { return m_value; }
   ValueType &ValueRef() { return m_value; }
   void SetValue(const ValueType &val) { m_value = val; }
 
   void Dump(lldb_private::Stream &s) const;
   bool ExtractValue(const lldb_private::DWARFDataExtractor &data,
                     lldb::offset_t *offset_ptr);
   const uint8_t *BlockData() const;
+  static llvm::Optional<uint8_t> GetAddressSize(const DWARFUnit *u);
+  static llvm::Optional<uint8_t> GetFixedSize(dw_form_t form,
+                                              const DWARFUnit *u);
+  llvm::Optional<uint8_t> GetFixedSize() const;
   DWARFDIE Reference() const;
   uint64_t Reference(dw_offset_t offset) const;
   bool Boolean() const { return m_value.value.uval != 0; }
   uint64_t Unsigned() const { return m_value.value.uval; }
   void SetUnsigned(uint64_t uval) { m_value.value.uval = uval; }
   int64_t Signed() const { return m_value.value.sval; }
   void SetSigned(int64_t sval) { m_value.value.sval = sval; }
   const char *AsCString() const;
   dw_addr_t Address() const;
   bool IsValid() const { return m_form != 0; }
   bool SkipValue(const lldb_private::DWARFDataExtractor &debug_info_data,
                  lldb::offset_t *offset_ptr) const;
   static bool SkipValue(const dw_form_t form,
                         const lldb_private::DWARFDataExtractor &debug_info_data,
                         lldb::offset_t *offset_ptr, const DWARFUnit *unit);
   static bool IsBlockForm(const dw_form_t form);
   static bool IsDataForm(const dw_form_t form);
-  static FixedFormSizes GetFixedFormSizesForAddressSize(uint8_t addr_size);
   static int Compare(const DWARFFormValue &a, const DWARFFormValue &b);
   void Clear();
   static bool FormIsSupported(dw_form_t form);
 
 protected:
   // Compile unit where m_value was located.
   // It may be different from compile unit where m_value refers to.
   const DWARFUnit *m_unit = nullptr; // Unit for this form
   dw_form_t m_form = 0;              // Form for this value
   ValueType m_value;            // Contains all data for the form
 };
 
 #endif // SymbolFileDWARF_DWARFFormValue_h_

source/Plugins/SymbolFile/DWARF/DWARFFormValue.cpp

 #include "DWARFDebugInfo.h"
 #include "DWARFFormValue.h"
 #include "DWARFUnit.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
-};
-
-DWARFFormValue::FixedFormSizes
-DWARFFormValue::GetFixedFormSizesForAddressSize(uint8_t addr_size) {
-  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));
-  }
-  return FixedFormSizes();
-}
-
 void DWARFFormValue::Clear() {
   m_unit = nullptr;
   m_form = 0;
   m_value = ValueTypeTag();
 }
 
 bool DWARFFormValue::ExtractValue(const DWARFDataExtractor &data,
                                   lldb::offset_t *offset_ptr) {
if (is_block) {
     if (m_value.data != nullptr) {
       *offset_ptr += m_value.value.uval;
     }
   }
 
   return true;
 }
 
+struct FormSize {
+  uint8_t valid:1, size:7;
+};
+static FormSize g_form_sizes[] = {
+  {0,0}, // 0x00 unused
+  {0,0}, // 0x01 DW_FORM_addr
+  {0,0}, // 0x02 unused
+  {0,0}, // 0x03 DW_FORM_block2
+  {0,0}, // 0x04 DW_FORM_block4
+  {1,2}, // 0x05 DW_FORM_data2
+  {1,4}, // 0x06 DW_FORM_data4
+  {1,8}, // 0x07 DW_FORM_data8
+  {0,0}, // 0x08 DW_FORM_string
+  {0,0}, // 0x09 DW_FORM_block
+  {0,0}, // 0x0a DW_FORM_block1
+  {1,1}, // 0x0b DW_FORM_data1
+  {1,1}, // 0x0c DW_FORM_flag
+  {0,0}, // 0x0d DW_FORM_sdata
+  {1,4}, // 0x0e DW_FORM_strp
+  {0,0}, // 0x0f DW_FORM_udata
+  {0,0}, // 0x10 DW_FORM_ref_addr (addr size for DWARF2 and earlier, 4 bytes for
+         // DWARF32, 8 bytes for DWARF32 in DWARF 3 and later
+  {1,1}, // 0x11 DW_FORM_ref1
+  {1,2}, // 0x12 DW_FORM_ref2
+  {1,4}, // 0x13 DW_FORM_ref4
+  {1,8}, // 0x14 DW_FORM_ref8
+  {0,0}, // 0x15 DW_FORM_ref_udata
+  {0,0}, // 0x16 DW_FORM_indirect
+  {1,4}, // 0x17 DW_FORM_sec_offset
+  {0,0}, // 0x18 DW_FORM_exprloc
+  {1,0}, // 0x19 DW_FORM_flag_present
+  {0,0}, // 0x1a
+  {0,0}, // 0x1b
+  {0,0}, // 0x1c
+  {0,0}, // 0x1d
+  {0,0}, // 0x1e
+  {0,0}, // 0x1f
+  {1,8}, // 0x20 DW_FORM_ref_sig8
+};
+
+llvm::Optional<uint8_t>
+DWARFFormValue::GetFixedSize(dw_form_t form, const DWARFUnit *u) {
+  if (form <= DW_FORM_ref_sig8 && g_form_sizes[form].valid)
+    return g_form_sizes[form].size;
+  if (form == DW_FORM_addr && u)
+    return u->GetAddressByteSize();
+  return llvm::None;
+}
+
+llvm::Optional<uint8_t> DWARFFormValue::GetAddressSize(const DWARFUnit *u) {
+  if (u)
+    return u->GetAddressByteSize();
+  return llvm::None;
+}
+
+llvm::Optional<uint8_t> DWARFFormValue::GetFixedSize() const {
+  return GetFixedSize(m_form, m_unit);
+}
+
 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_unit);
 }
 
 bool DWARFFormValue::SkipValue(dw_form_t form,
                                const DWARFDataExtractor &debug_info_data,
                                lldb::offset_t *offset_ptr,

source/Plugins/SymbolFile/DWARF/DWARFUnit.h

public:
   virtual void BuildAddressRangeTable(DWARFDebugAranges *debug_aranges) = 0;
 
   lldb::ByteOrder GetByteOrder() const;
 
   lldb_private::TypeSystem *GetTypeSystem();
 
   const DWARFDebugAranges &GetFunctionAranges();
 
-  DWARFFormValue::FixedFormSizes GetFixedFormSizes();
-
   void SetBaseAddress(dw_addr_t base_addr);
 
   DWARFBaseDIE GetUnitDIEOnly() { return DWARFDIE(this, GetUnitDIEPtrOnly()); }
 
   DWARFDIE DIE() { return DWARFDIE(this, DIEPtr()); }
 
   DWARFDIE GetDIE(dw_offset_t die_offset);
 

source/Plugins/SymbolFile/DWARF/DWARFUnit.cpp

void DWARFUnit::ExtractUnitDIEIfNeeded() {
 
   // Set the offset to that of the first DIE and calculate the start of the
   // next compilation unit header.
   lldb::offset_t offset = GetFirstDIEOffset();
 
   // We are in our compile unit, parse starting at the offset we were told to
   // parse
   const DWARFDataExtractor &data = GetData();
-  DWARFFormValue::FixedFormSizes fixed_form_sizes =
-      DWARFFormValue::GetFixedFormSizesForAddressSize(GetAddressByteSize());
   if (offset < GetNextUnitOffset() &&
-      m_first_die.FastExtract(data, this, fixed_form_sizes, &offset)) {
+      m_first_die.FastExtract(data, this, &offset)) {
     AddUnitDIE(m_first_die);
     return;
   }
 }
 
 // Parses a compile unit and indexes its DIEs if it hasn't already been done.
 // It will leave this compile unit extracted forever.
 void DWARFUnit::ExtractDIEsIfNeeded() {
void DWARFUnit::ExtractDIEsRWLocked() {
   uint32_t depth = 0;
   // We are in our compile unit, parse starting at the offset we were told to
   // parse
   const DWARFDataExtractor &data = GetData();
   std::vector<uint32_t> die_index_stack;
   die_index_stack.reserve(32);
   die_index_stack.push_back(0);
   bool prev_die_had_children = false;
-  DWARFFormValue::FixedFormSizes fixed_form_sizes =
-      DWARFFormValue::GetFixedFormSizesForAddressSize(GetAddressByteSize());
-  while (offset < next_cu_offset &&
-         die.FastExtract(data, this, fixed_form_sizes, &offset)) {
+  while (offset < next_cu_offset && die.FastExtract(data, this, &offset)) {
     const bool null_die = die.IsNULL();
     if (depth == 0) {
       assert(m_die_array.empty() && "Compile unit DIE already added");
 
       // The average bytes per DIE entry has been seen to be around 14-20 so
       // lets pre-reserve half of that since we are now stripping the NULL
       // tags.
 

 
 TypeSystem *DWARFUnit::GetTypeSystem() {
   if (m_dwarf)
     return m_dwarf->GetTypeSystemForLanguage(GetLanguageType());
   else
     return nullptr;
 }
 
-DWARFFormValue::FixedFormSizes DWARFUnit::GetFixedFormSizes() {
-  return DWARFFormValue::GetFixedFormSizesForAddressSize(GetAddressByteSize());
-}
-
 void DWARFUnit::SetBaseAddress(dw_addr_t base_addr) { m_base_addr = base_addr; }
 
 // Compare function DWARFDebugAranges::Range structures
 static bool CompareDIEOffset(const DWARFDebugInfoEntry &die,
                              const dw_offset_t die_offset) {
   return die.GetOffset() < die_offset;
 }
 

source/Plugins/SymbolFile/DWARF/ManualDWARFIndex.h

struct IndexSet {
     NameToDIE types;
     NameToDIE namespaces;
   };
   void Index();
   void IndexUnit(DWARFUnit &unit, IndexSet &set);
 
   static void
   IndexUnitImpl(DWARFUnit &unit, const lldb::LanguageType cu_language,
-                const DWARFFormValue::FixedFormSizes &fixed_form_sizes,
                 const dw_offset_t cu_offset, IndexSet &set);
 
   /// Non-null value means we haven't built the index yet.
   DWARFDebugInfo *m_debug_info;
   /// Which dwarf units should we skip while building the index.
   llvm::DenseSet<dw_offset_t> m_units_to_avoid;
 
   IndexSet m_set;
 };
 } // namespace lldb_private
 
 #endif // LLDB_MANUALDWARFINDEX_H

source/Plugins/SymbolFile/DWARF/ManualDWARFIndex.cpp

void ManualDWARFIndex::IndexUnit(DWARFUnit &unit, IndexSet &set) {
 
   if (log) {
     m_module.LogMessage(
         log, "ManualDWARFIndex::IndexUnit for unit at .debug_info[0x%8.8x]",
         unit.GetOffset());
   }
 
   const LanguageType cu_language = unit.GetLanguageType();
-  DWARFFormValue::FixedFormSizes fixed_form_sizes = unit.GetFixedFormSizes();
 
-  IndexUnitImpl(unit, cu_language, fixed_form_sizes, unit.GetOffset(), set);
+  IndexUnitImpl(unit, cu_language, unit.GetOffset(), set);
 
   SymbolFileDWARFDwo *dwo_symbol_file = unit.GetDwoSymbolFile();
   if (dwo_symbol_file && dwo_symbol_file->GetCompileUnit()) {
     IndexUnitImpl(*dwo_symbol_file->GetCompileUnit(), cu_language,
-                  fixed_form_sizes, unit.GetOffset(), set);
+                  unit.GetOffset(), set);
   }
 }
 
 void ManualDWARFIndex::IndexUnitImpl(
     DWARFUnit &unit, const LanguageType cu_language,
-    const DWARFFormValue::FixedFormSizes &fixed_form_sizes,
     const dw_offset_t cu_offset, IndexSet &set) {
   for (const DWARFDebugInfoEntry &die : unit.dies()) {
     const dw_tag_t tag = die.Tag();
 
     switch (tag) {
     case DW_TAG_array_type:
     case DW_TAG_base_type:
     case DW_TAG_class_type:
for (const DWARFDebugInfoEntry &die : unit.dies()) {
     const char *mangled_cstr = nullptr;
     bool is_declaration = false;
     // bool is_artificial = false;
     bool has_address = false;
     bool has_location_or_const_value = false;
     bool is_global_or_static_variable = false;
 
     DWARFFormValue specification_die_form;
-    const size_t num_attributes =
-        die.GetAttributes(&unit, fixed_form_sizes, attributes);
+    const size_t num_attributes = die.GetAttributes(&unit, attributes);
     if (num_attributes > 0) {
       for (uint32_t i = 0; i < num_attributes; ++i) {
         dw_attr_t attr = attributes.AttributeAtIndex(i);
         DWARFFormValue form_value;
         switch (attr) {
         case DW_AT_name:
           if (attributes.ExtractFormValueAtIndex(i, form_value))
             name = form_value.AsCString();

source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp

if (num_attributes > 0) {
                 // Retrieve the value as a block expression.
                 uint32_t block_offset =
                     form_value.BlockData() - debug_info_data.GetDataStart();
                 uint32_t block_length = form_value.Unsigned();
                 location.CopyOpcodeData(module, debug_info_data, block_offset,
                                         block_length);
               } else if (DWARFFormValue::IsDataForm(form_value.Form())) {
                 // Retrieve the value as a data expression.
-                DWARFFormValue::FixedFormSizes fixed_form_sizes =
-                    DWARFFormValue::GetFixedFormSizesForAddressSize(
-                        attributes.CompileUnitAtIndex(i)->GetAddressByteSize());
                 uint32_t data_offset = attributes.DIEOffsetAtIndex(i);
-                uint32_t data_length =
-                    fixed_form_sizes.GetSize(form_value.Form());
-                if (data_length == 0) {
+                auto data_length = form_value.GetFixedSize();
+                if (data_length)
+                  location.CopyOpcodeData(module, debug_info_data, data_offset,
+                                          *data_length);
+                else {
                   const uint8_t *data_pointer = form_value.BlockData();
                   if (data_pointer) {
                     form_value.Unsigned();
                   } else if (DWARFFormValue::IsDataForm(form_value.Form())) {
                     // we need to get the byte size of the type later after we
                     // create the variable
                     const_value = form_value;
                   }
-                } else
-                  location.CopyOpcodeData(module, debug_info_data, data_offset,
-                                          data_length);
+                }
               } else {
                 // Retrieve the value as a string expression.
                 if (form_value.Form() == DW_FORM_strp) {
-                  DWARFFormValue::FixedFormSizes fixed_form_sizes =
-                      DWARFFormValue::GetFixedFormSizesForAddressSize(
-                          attributes.CompileUnitAtIndex(i)
-                              ->GetAddressByteSize());
                   uint32_t data_offset = attributes.DIEOffsetAtIndex(i);
-                  uint32_t data_length =
-                      fixed_form_sizes.GetSize(form_value.Form());
+                  auto data_length = form_value.GetFixedSize();
                   location.CopyOpcodeData(module, debug_info_data, data_offset,
-                                          data_length);
+                                          *data_length);
                 } else {
                   const char *str = form_value.AsCString();
                   uint32_t string_offset =
                       str - (const char *)debug_info_data.GetDataStart();
                   uint32_t string_length = strlen(str) + 1;
                   location.CopyOpcodeData(module, debug_info_data,
                                           string_offset, string_length);
                 }