include/llvm/DebugInfo/DWARF/DWARFAbbreviationDeclaration.h

   1 //===- DWARFAbbreviationDeclaration.h ---------------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_DEBUGINFO_DWARFABBREVIATIONDECLARATION_H
  10 #define LLVM_DEBUGINFO_DWARFABBREVIATIONDECLARATION_H
  11
  12 #include "llvm/ADT/Optional.h"
  13 #include "llvm/ADT/SmallVector.h"
  14 #include "llvm/ADT/iterator_range.h"
  15 #include "llvm/BinaryFormat/Dwarf.h"
  16 #include "llvm/Support/DataExtractor.h"
  17 #include <cassert>
  18 #include <cstddef>
  19 #include <cstdint>
  20
  21 namespace llvm {
  22
  23 class DWARFFormValue;
  24 class DWARFUnit;
  25 class raw_ostream;
  26
  27 class DWARFAbbreviationDeclaration {
  28 public:
  29   struct AttributeSpec {
  30     AttributeSpec(dwarf::Attribute A, dwarf::Form F, int64_t Value)
  31         : Attr(A), Form(F), Value(Value) {
  32       assert(isImplicitConst());
  33     }
  34     AttributeSpec(dwarf::Attribute A, dwarf::Form F, Optional<uint8_t> ByteSize)
  35         : Attr(A), Form(F) {
  36       assert(!isImplicitConst());
  37       this->ByteSize.HasByteSize = ByteSize.hasValue();
  38       if (this->ByteSize.HasByteSize)
  39         this->ByteSize.ByteSize = *ByteSize;
  40     }
  41
  42     dwarf::Attribute Attr;
  43     dwarf::Form Form;
  44
  45   private:
  46     /// The following field is used for ByteSize for non-implicit_const
  47     /// attributes and as value for implicit_const ones, indicated by
  48     /// Form == DW_FORM_implicit_const.
  49     /// The following cases are distinguished:
  50     /// * Form != DW_FORM_implicit_const and HasByteSize is true:
  51     ///     ByteSize contains the fixed size in bytes for the Form in this
  52     ///     object.
  53     /// * Form != DW_FORM_implicit_const and HasByteSize is false:
  54     ///     byte size of Form either varies according to the DWARFUnit
  55     ///     that it is contained in or the value size varies and must be
  56     ///     decoded from the debug information in order to determine its size.
  57     /// * Form == DW_FORM_implicit_const:
  58     ///     Value contains value for the implicit_const attribute.
  59     struct ByteSizeStorage {
  60       bool HasByteSize;
  61       uint8_t ByteSize;
  62     };
  63     union {
  64       ByteSizeStorage ByteSize;
  65       int64_t Value;
  66     };
  67
  68   public:
  69     bool isImplicitConst() const {
  70       return Form == dwarf::DW_FORM_implicit_const;
  71     }
  72
  73     int64_t getImplicitConstValue() const {
  74       assert(isImplicitConst());
  75       return Value;
  76     }
  77
  78     /// Get the fixed byte size of this Form if possible. This function might
  79     /// use the DWARFUnit to calculate the size of the Form, like for
  80     /// DW_AT_address and DW_AT_ref_addr, so this isn't just an accessor for
  81     /// the ByteSize member.
  82     Optional<int64_t> getByteSize(const DWARFUnit &U) const;
  83   };
  84   using AttributeSpecVector = SmallVector<AttributeSpec, 8>;
  85
  86   DWARFAbbreviationDeclaration();
  87
  88   uint32_t getCode() const { return Code; }
  89   uint8_t getCodeByteSize() const { return CodeByteSize; }
  90   dwarf::Tag getTag() const { return Tag; }
  91   bool hasChildren() const { return HasChildren; }
  92
  93   using attr_iterator_range =
  94       iterator_range<AttributeSpecVector::const_iterator>;
  95
  96   attr_iterator_range attributes() const {
  97     return attr_iterator_range(AttributeSpecs.begin(), AttributeSpecs.end());
  98   }
  99
 100   dwarf::Form getFormByIndex(uint32_t idx) const {
 101     assert(idx < AttributeSpecs.size());
 102     return AttributeSpecs[idx].Form;
 103   }
 104
 105   size_t getNumAttributes() const {
 106     return AttributeSpecs.size();
 107   }
 108
 109   dwarf::Attribute getAttrByIndex(uint32_t idx) const {
 110     assert(idx < AttributeSpecs.size());
 111     return AttributeSpecs[idx].Attr;
 112   }
 113
 114   /// Get the index of the specified attribute.
 115   ///
 116   /// Searches the this abbreviation declaration for the index of the specified
 117   /// attribute.
 118   ///
 119   /// \param attr DWARF attribute to search for.
 120   /// \returns Optional index of the attribute if found, None otherwise.
 121   Optional<uint32_t> findAttributeIndex(dwarf::Attribute attr) const;
 122
 123   /// Extract a DWARF form value from a DIE specified by DIE offset.
 124   ///
 125   /// Extract an attribute value for a DWARFUnit given the DIE offset and the
 126   /// attribute.
 127   ///
 128   /// \param DIEOffset the DIE offset that points to the ULEB128 abbreviation
 129   /// code in the .debug_info data.
 130   /// \param Attr DWARF attribute to search for.
 131   /// \param U the DWARFUnit the contains the DIE.
 132   /// \returns Optional DWARF form value if the attribute was extracted.
 133   Optional<DWARFFormValue> getAttributeValue(const uint64_t DIEOffset,
 134                                              const dwarf::Attribute Attr,
 135                                              const DWARFUnit &U) const;
 136
 137   bool extract(DataExtractor Data, uint64_t* OffsetPtr);
 138   void dump(raw_ostream &OS) const;
 139
 140   // Return an optional byte size of all attribute data in this abbreviation
 141   // if a constant byte size can be calculated given a DWARFUnit. This allows
 142   // DWARF parsing to be faster as many DWARF DIEs have a fixed byte size.
 143   Optional<size_t> getFixedAttributesByteSize(const DWARFUnit &U) const;
 144
 145 private:
 146   void clear();
 147
 148   /// A helper structure that can quickly determine the size in bytes of an
 149   /// abbreviation declaration.
 150   struct FixedSizeInfo {
 151     /// The fixed byte size for fixed size forms.
 152     uint16_t NumBytes = 0;
 153     /// Number of DW_FORM_address forms in this abbrevation declaration.
 154     uint8_t NumAddrs = 0;
 155     /// Number of DW_FORM_ref_addr forms in this abbrevation declaration.
 156     uint8_t NumRefAddrs = 0;
 157     /// Number of 4 byte in DWARF32 and 8 byte in DWARF64 forms.
 158     uint8_t NumDwarfOffsets = 0;
 159
 160     FixedSizeInfo() = default;
 161
 162     /// Calculate the fixed size in bytes given a DWARFUnit.
 163     ///
 164     /// \param U the DWARFUnit to use when determing the byte size.
 165     /// \returns the size in bytes for all attribute data in this abbreviation.
 166     /// The returned size does not include bytes for the  ULEB128 abbreviation
 167     /// code
 168     size_t getByteSize(const DWARFUnit &U) const;
 169   };
 170
 171   uint32_t Code;
 172   dwarf::Tag Tag;
 173   uint8_t CodeByteSize;
 174   bool HasChildren;
 175   AttributeSpecVector AttributeSpecs;
 176   /// If this abbreviation has a fixed byte size then FixedAttributeSize member
 177   /// variable below will have a value.
 178   Optional<FixedSizeInfo> FixedAttributeSize;
 179 };
 180
 181 } // end namespace llvm
 182
 183 #endif // LLVM_DEBUGINFO_DWARFABBREVIATIONDECLARATION_H