llvm/lib/DWARFLinker/DWARFLinkerDeclContext.cpp

   1 //===- DWARFLinkerDeclContext.cpp -----------------------------------------===//
   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 #include "llvm/DWARFLinker/DWARFLinkerDeclContext.h"
  10 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
  11 #include "llvm/DebugInfo/DWARF/DWARFDie.h"
  12 #include "llvm/DebugInfo/DWARF/DWARFUnit.h"
  13
  14 namespace llvm {
  15
  16 /// Set the last DIE/CU a context was seen in and, possibly invalidate the
  17 /// context if it is ambiguous.
  18 ///
  19 /// In the current implementation, we don't handle overloaded functions well,
  20 /// because the argument types are not taken into account when computing the
  21 /// DeclContext tree.
  22 ///
  23 /// Some of this is mitigated byt using mangled names that do contain the
  24 /// arguments types, but sometimes (e.g. with function templates) we don't have
  25 /// that. In that case, just do not unique anything that refers to the contexts
  26 /// we are not able to distinguish.
  27 ///
  28 /// If a context that is not a namespace appears twice in the same CU, we know
  29 /// it is ambiguous. Make it invalid.
  30 bool DeclContext::setLastSeenDIE(CompileUnit &U, const DWARFDie &Die) {
  31   if (LastSeenCompileUnitID == U.getUniqueID()) {
  32     DWARFUnit &OrigUnit = U.getOrigUnit();
  33     uint32_t FirstIdx = OrigUnit.getDIEIndex(LastSeenDIE);
  34     U.getInfo(FirstIdx).Ctxt = nullptr;
  35     return false;
  36   }
  37
  38   LastSeenCompileUnitID = U.getUniqueID();
  39   LastSeenDIE = Die;
  40   return true;
  41 }
  42
  43 PointerIntPair<DeclContext *, 1> DeclContextTree::getChildDeclContext(
  44     DeclContext &Context, const DWARFDie &DIE, CompileUnit &U,
  45     UniquingStringPool &StringPool, bool InClangModule) {
  46   unsigned Tag = DIE.getTag();
  47
  48   // FIXME: dsymutil-classic compat: We should bail out here if we
  49   // have a specification or an abstract_origin. We will get the
  50   // parent context wrong here.
  51
  52   switch (Tag) {
  53   default:
  54     // By default stop gathering child contexts.
  55     return PointerIntPair<DeclContext *, 1>(nullptr);
  56   case dwarf::DW_TAG_module:
  57     break;
  58   case dwarf::DW_TAG_compile_unit:
  59     return PointerIntPair<DeclContext *, 1>(&Context);
  60   case dwarf::DW_TAG_subprogram:
  61     // Do not unique anything inside CU local functions.
  62     if ((Context.getTag() == dwarf::DW_TAG_namespace ||
  63          Context.getTag() == dwarf::DW_TAG_compile_unit) &&
  64         !dwarf::toUnsigned(DIE.find(dwarf::DW_AT_external), 0))
  65       return PointerIntPair<DeclContext *, 1>(nullptr);
  66     LLVM_FALLTHROUGH;
  67   case dwarf::DW_TAG_member:
  68   case dwarf::DW_TAG_namespace:
  69   case dwarf::DW_TAG_structure_type:
  70   case dwarf::DW_TAG_class_type:
  71   case dwarf::DW_TAG_union_type:
  72   case dwarf::DW_TAG_enumeration_type:
  73   case dwarf::DW_TAG_typedef:
  74     // Artificial things might be ambiguous, because they might be created on
  75     // demand. For example implicitly defined constructors are ambiguous
  76     // because of the way we identify contexts, and they won't be generated
  77     // every time everywhere.
  78     if (dwarf::toUnsigned(DIE.find(dwarf::DW_AT_artificial), 0))
  79       return PointerIntPair<DeclContext *, 1>(nullptr);
  80     break;
  81   }
  82
  83   const char *Name = DIE.getName(DINameKind::LinkageName);
  84   const char *ShortName = DIE.getName(DINameKind::ShortName);
  85   StringRef NameRef;
  86   StringRef ShortNameRef;
  87   StringRef FileRef;
  88
  89   if (Name)
  90     NameRef = StringPool.internString(Name);
  91   else if (Tag == dwarf::DW_TAG_namespace)
  92     // FIXME: For dsymutil-classic compatibility. I think uniquing within
  93     // anonymous namespaces is wrong. There is no ODR guarantee there.
  94     NameRef = StringPool.internString("(anonymous namespace)");
  95
  96   if (ShortName && ShortName != Name)
  97     ShortNameRef = StringPool.internString(ShortName);
  98   else
  99     ShortNameRef = NameRef;
 100
 101   if (Tag != dwarf::DW_TAG_class_type && Tag != dwarf::DW_TAG_structure_type &&
 102       Tag != dwarf::DW_TAG_union_type &&
 103       Tag != dwarf::DW_TAG_enumeration_type && NameRef.empty())
 104     return PointerIntPair<DeclContext *, 1>(nullptr);
 105
 106   unsigned Line = 0;
 107   unsigned ByteSize = std::numeric_limits<uint32_t>::max();
 108
 109   if (!InClangModule) {
 110     // Gather some discriminating data about the DeclContext we will be
 111     // creating: File, line number and byte size. This shouldn't be necessary,
 112     // because the ODR is just about names, but given that we do some
 113     // approximations with overloaded functions and anonymous namespaces, use
 114     // these additional data points to make the process safer.
 115     //
 116     // This is disabled for clang modules, because forward declarations of
 117     // module-defined types do not have a file and line.
 118     ByteSize = dwarf::toUnsigned(DIE.find(dwarf::DW_AT_byte_size),
 119                                  std::numeric_limits<uint64_t>::max());
 120     if (Tag != dwarf::DW_TAG_namespace || !Name) {
 121       if (unsigned FileNum =
 122               dwarf::toUnsigned(DIE.find(dwarf::DW_AT_decl_file), 0)) {
 123         if (const auto *LT = U.getOrigUnit().getContext().getLineTableForUnit(
 124                 &U.getOrigUnit())) {
 125           // FIXME: dsymutil-classic compatibility. I'd rather not
 126           // unique anything in anonymous namespaces, but if we do, then
 127           // verify that the file and line correspond.
 128           if (!Name && Tag == dwarf::DW_TAG_namespace)
 129             FileNum = 1;
 130
 131           if (LT->hasFileAtIndex(FileNum)) {
 132             Line = dwarf::toUnsigned(DIE.find(dwarf::DW_AT_decl_line), 0);
 133             // Cache the resolved paths based on the index in the line table,
 134             // because calling realpath is expansive.
 135             StringRef ResolvedPath = U.getResolvedPath(FileNum);
 136             if (!ResolvedPath.empty()) {
 137               FileRef = ResolvedPath;
 138             } else {
 139               std::string File;
 140               bool FoundFileName = LT->getFileNameByIndex(
 141                   FileNum, U.getOrigUnit().getCompilationDir(),
 142                   DILineInfoSpecifier::FileLineInfoKind::AbsoluteFilePath,
 143                   File);
 144               (void)FoundFileName;
 145               assert(FoundFileName && "Must get file name from line table");
 146               // Second level of caching, this time based on the file's parent
 147               // path.
 148               FileRef = PathResolver.resolve(File, StringPool);
 149               U.setResolvedPath(FileNum, FileRef);
 150             }
 151           }
 152         }
 153       }
 154     }
 155   }
 156
 157   if (!Line && NameRef.empty())
 158     return PointerIntPair<DeclContext *, 1>(nullptr);
 159
 160   // We hash NameRef, which is the mangled name, in order to get most
 161   // overloaded functions resolve correctly.
 162   //
 163   // Strictly speaking, hashing the Tag is only necessary for a
 164   // DW_TAG_module, to prevent uniquing of a module and a namespace
 165   // with the same name.
 166   //
 167   // FIXME: dsymutil-classic won't unique the same type presented
 168   // once as a struct and once as a class. Using the Tag in the fully
 169   // qualified name hash to get the same effect.
 170   unsigned Hash = hash_combine(Context.getQualifiedNameHash(), Tag, NameRef);
 171
 172   // FIXME: dsymutil-classic compatibility: when we don't have a name,
 173   // use the filename.
 174   if (Tag == dwarf::DW_TAG_namespace && NameRef == "(anonymous namespace)")
 175     Hash = hash_combine(Hash, FileRef);
 176
 177   // Now look if this context already exists.
 178   DeclContext Key(Hash, Line, ByteSize, Tag, NameRef, FileRef, Context);
 179   auto ContextIter = Contexts.find(&Key);
 180
 181   if (ContextIter == Contexts.end()) {
 182     // The context wasn't found.
 183     bool Inserted;
 184     DeclContext *NewContext =
 185         new (Allocator) DeclContext(Hash, Line, ByteSize, Tag, NameRef, FileRef,
 186                                     Context, DIE, U.getUniqueID());
 187     std::tie(ContextIter, Inserted) = Contexts.insert(NewContext);
 188     assert(Inserted && "Failed to insert DeclContext");
 189     (void)Inserted;
 190   } else if (Tag != dwarf::DW_TAG_namespace &&
 191              !(*ContextIter)->setLastSeenDIE(U, DIE)) {
 192     // The context was found, but it is ambiguous with another context
 193     // in the same file. Mark it invalid.
 194     return PointerIntPair<DeclContext *, 1>(*ContextIter, /* Invalid= */ 1);
 195   }
 196
 197   assert(ContextIter != Contexts.end());
 198   // FIXME: dsymutil-classic compatibility. Union types aren't
 199   // uniques, but their children might be.
 200   if ((Tag == dwarf::DW_TAG_subprogram &&
 201        Context.getTag() != dwarf::DW_TAG_structure_type &&
 202        Context.getTag() != dwarf::DW_TAG_class_type) ||
 203       (Tag == dwarf::DW_TAG_union_type))
 204     return PointerIntPair<DeclContext *, 1>(*ContextIter, /* Invalid= */ 1);
 205
 206   return PointerIntPair<DeclContext *, 1>(*ContextIter);
 207 }
 208
 209 } // namespace llvm