llvm/lib/DWARFLinker/Classic/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/Classic/DWARFLinkerDeclContext.h"
  10 #include "llvm/DWARFLinker/Classic/DWARFLinkerCompileUnit.h"
  11 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
  12 #include "llvm/DebugInfo/DWARF/DWARFDie.h"
  13 #include "llvm/DebugInfo/DWARF/DWARFUnit.h"
  14
  15 namespace llvm {
  16
  17 using namespace dwarf_linker;
  18 using namespace dwarf_linker::classic;
  19
  20 /// Set the last DIE/CU a context was seen in and, possibly invalidate the
  21 /// context if it is ambiguous.
  22 ///
  23 /// In the current implementation, we don't handle overloaded functions well,
  24 /// because the argument types are not taken into account when computing the
  25 /// DeclContext tree.
  26 ///
  27 /// Some of this is mitigated byt using mangled names that do contain the
  28 /// arguments types, but sometimes (e.g. with function templates) we don't have
  29 /// that. In that case, just do not unique anything that refers to the contexts
  30 /// we are not able to distinguish.
  31 ///
  32 /// If a context that is not a namespace appears twice in the same CU, we know
  33 /// it is ambiguous. Make it invalid.
  34 bool DeclContext::setLastSeenDIE(CompileUnit &U, const DWARFDie &Die) {
  35   if (LastSeenCompileUnitID == U.getUniqueID()) {
  36     DWARFUnit &OrigUnit = U.getOrigUnit();
  37     uint32_t FirstIdx = OrigUnit.getDIEIndex(LastSeenDIE);
  38     U.getInfo(FirstIdx).Ctxt = nullptr;
  39     return false;
  40   }
  41
  42   LastSeenCompileUnitID = U.getUniqueID();
  43   LastSeenDIE = Die;
  44   return true;
  45 }
  46
  47 PointerIntPair<DeclContext *, 1>
  48 DeclContextTree::getChildDeclContext(DeclContext &Context, const DWARFDie &DIE,
  49                                      CompileUnit &U, bool InClangModule) {
  50   unsigned Tag = DIE.getTag();
  51
  52   // FIXME: dsymutil-classic compat: We should bail out here if we
  53   // have a specification or an abstract_origin. We will get the
  54   // parent context wrong here.
  55
  56   switch (Tag) {
  57   default:
  58     // By default stop gathering child contexts.
  59     return PointerIntPair<DeclContext *, 1>(nullptr);
  60   case dwarf::DW_TAG_module:
  61     break;
  62   case dwarf::DW_TAG_compile_unit:
  63     return PointerIntPair<DeclContext *, 1>(&Context);
  64   case dwarf::DW_TAG_subprogram:
  65     // Do not unique anything inside CU local functions.
  66     if ((Context.getTag() == dwarf::DW_TAG_namespace ||
  67          Context.getTag() == dwarf::DW_TAG_compile_unit) &&
  68         !dwarf::toUnsigned(DIE.find(dwarf::DW_AT_external), 0))
  69       return PointerIntPair<DeclContext *, 1>(nullptr);
  70     [[fallthrough]];
  71   case dwarf::DW_TAG_member:
  72   case dwarf::DW_TAG_namespace:
  73   case dwarf::DW_TAG_structure_type:
  74   case dwarf::DW_TAG_class_type:
  75   case dwarf::DW_TAG_union_type:
  76   case dwarf::DW_TAG_enumeration_type:
  77   case dwarf::DW_TAG_typedef:
  78     // Artificial things might be ambiguous, because they might be created on
  79     // demand. For example implicitly defined constructors are ambiguous
  80     // because of the way we identify contexts, and they won't be generated
  81     // every time everywhere.
  82     if (dwarf::toUnsigned(DIE.find(dwarf::DW_AT_artificial), 0))
  83       return PointerIntPair<DeclContext *, 1>(nullptr);
  84     break;
  85   }
  86
  87   StringRef NameRef;
  88   StringRef FileRef;
  89
  90   if (const char *LinkageName = DIE.getLinkageName())
  91     NameRef = StringPool.internString(LinkageName);
  92   else if (const char *ShortName = DIE.getShortName())
  93     NameRef = StringPool.internString(ShortName);
  94
  95   bool IsAnonymousNamespace = NameRef.empty() && Tag == dwarf::DW_TAG_namespace;
  96   if (IsAnonymousNamespace) {
  97     // FIXME: For dsymutil-classic compatibility. I think uniquing within
  98     // anonymous namespaces is wrong. There is no ODR guarantee there.
  99     NameRef = "(anonymous namespace)";
 100   }
 101
 102   if (Tag != dwarf::DW_TAG_class_type && Tag != dwarf::DW_TAG_structure_type &&
 103       Tag != dwarf::DW_TAG_union_type &&
 104       Tag != dwarf::DW_TAG_enumeration_type && NameRef.empty())
 105     return PointerIntPair<DeclContext *, 1>(nullptr);
 106
 107   unsigned Line = 0;
 108   unsigned ByteSize = std::numeric_limits<uint32_t>::max();
 109
 110   if (!InClangModule) {
 111     // Gather some discriminating data about the DeclContext we will be
 112     // creating: File, line number and byte size. This shouldn't be necessary,
 113     // because the ODR is just about names, but given that we do some
 114     // approximations with overloaded functions and anonymous namespaces, use
 115     // these additional data points to make the process safer.
 116     //
 117     // This is disabled for clang modules, because forward declarations of
 118     // module-defined types do not have a file and line.
 119     ByteSize = dwarf::toUnsigned(DIE.find(dwarf::DW_AT_byte_size),
 120                                  std::numeric_limits<uint64_t>::max());
 121     if (Tag != dwarf::DW_TAG_namespace || IsAnonymousNamespace) {
 122       if (unsigned FileNum =
 123               dwarf::toUnsigned(DIE.find(dwarf::DW_AT_decl_file), 0)) {
 124         if (const auto *LT = U.getOrigUnit().getContext().getLineTableForUnit(
 125                 &U.getOrigUnit())) {
 126           // FIXME: dsymutil-classic compatibility. I'd rather not
 127           // unique anything in anonymous namespaces, but if we do, then
 128           // verify that the file and line correspond.
 129           if (IsAnonymousNamespace)
 130             FileNum = 1;
 131
 132           if (LT->hasFileAtIndex(FileNum)) {
 133             Line = dwarf::toUnsigned(DIE.find(dwarf::DW_AT_decl_line), 0);
 134             // Cache the resolved paths based on the index in the line table,
 135             // because calling realpath is expensive.
 136             FileRef = getResolvedPath(U, FileNum, *LT);
 137           }
 138         }
 139       }
 140     }
 141   }
 142
 143   if (!Line && NameRef.empty())
 144     return PointerIntPair<DeclContext *, 1>(nullptr);
 145
 146   // We hash NameRef, which is the mangled name, in order to get most
 147   // overloaded functions resolve correctly.
 148   //
 149   // Strictly speaking, hashing the Tag is only necessary for a
 150   // DW_TAG_module, to prevent uniquing of a module and a namespace
 151   // with the same name.
 152   //
 153   // FIXME: dsymutil-classic won't unique the same type presented
 154   // once as a struct and once as a class. Using the Tag in the fully
 155   // qualified name hash to get the same effect.
 156   unsigned Hash = hash_combine(Context.getQualifiedNameHash(), Tag, NameRef);
 157
 158   // FIXME: dsymutil-classic compatibility: when we don't have a name,
 159   // use the filename.
 160   if (IsAnonymousNamespace)
 161     Hash = hash_combine(Hash, FileRef);
 162
 163   // Now look if this context already exists.
 164   DeclContext Key(Hash, Line, ByteSize, Tag, NameRef, FileRef, Context);
 165   auto ContextIter = Contexts.find(&Key);
 166
 167   if (ContextIter == Contexts.end()) {
 168     // The context wasn't found.
 169     bool Inserted;
 170     DeclContext *NewContext =
 171         new (Allocator) DeclContext(Hash, Line, ByteSize, Tag, NameRef, FileRef,
 172                                     Context, DIE, U.getUniqueID());
 173     std::tie(ContextIter, Inserted) = Contexts.insert(NewContext);
 174     assert(Inserted && "Failed to insert DeclContext");
 175     (void)Inserted;
 176   } else if (Tag != dwarf::DW_TAG_namespace &&
 177              !(*ContextIter)->setLastSeenDIE(U, DIE)) {
 178     // The context was found, but it is ambiguous with another context
 179     // in the same file. Mark it invalid.
 180     return PointerIntPair<DeclContext *, 1>(*ContextIter, /* IntVal= */ 1);
 181   }
 182
 183   assert(ContextIter != Contexts.end());
 184   // FIXME: dsymutil-classic compatibility. Union types aren't
 185   // uniques, but their children might be.
 186   if ((Tag == dwarf::DW_TAG_subprogram &&
 187        Context.getTag() != dwarf::DW_TAG_structure_type &&
 188        Context.getTag() != dwarf::DW_TAG_class_type) ||
 189       (Tag == dwarf::DW_TAG_union_type))
 190     return PointerIntPair<DeclContext *, 1>(*ContextIter, /* IntVal= */ 1);
 191
 192   return PointerIntPair<DeclContext *, 1>(*ContextIter);
 193 }
 194
 195 StringRef
 196 DeclContextTree::getResolvedPath(CompileUnit &CU, unsigned FileNum,
 197                                  const DWARFDebugLine::LineTable &LineTable) {
 198   std::pair<unsigned, unsigned> Key = {CU.getUniqueID(), FileNum};
 199
 200   ResolvedPathsMap::const_iterator It = ResolvedPaths.find(Key);
 201   if (It == ResolvedPaths.end()) {
 202     std::string FileName;
 203     bool FoundFileName = LineTable.getFileNameByIndex(
 204         FileNum, CU.getOrigUnit().getCompilationDir(),
 205         DILineInfoSpecifier::FileLineInfoKind::AbsoluteFilePath, FileName);
 206     (void)FoundFileName;
 207     assert(FoundFileName && "Must get file name from line table");
 208
 209     // Second level of caching, this time based on the file's parent
 210     // path.
 211     StringRef ResolvedPath = PathResolver.resolve(FileName, StringPool);
 212
 213     It = ResolvedPaths.insert(std::make_pair(Key, ResolvedPath)).first;
 214   }
 215
 216   return It->second;
 217 }
 218
 219 } // namespace llvm