3 files changed, 106 insertions, 6 deletions

diff --git a/llvm/lib/Object/ModuleSymbolTable.cpp b/llvm/lib/Object/ModuleSymbolTable.cpp
index 90488007ff5..21709b5c223 100644
--- a/llvm/lib/Object/ModuleSymbolTable.cpp
+++ b/llvm/lib/Object/ModuleSymbolTable.cpp
@@ -50,20 +50,95 @@ void ModuleSymbolTable::addModule(Module *M) {
   for (GlobalAlias &GA : M->aliases())
     SymTab.push_back(&GA);
 
-  CollectAsmSymbols(Triple(M->getTargetTriple()), M->getModuleInlineAsm(),
-                    [this](StringRef Name, BasicSymbolRef::Flags Flags) {
-                      SymTab.push_back(new (AsmSymbols.Allocate())
-                                           AsmSymbol(Name, Flags));
-                    });
+  CollectAsmSymbols(*M, [this](StringRef Name, BasicSymbolRef::Flags Flags) {
+    SymTab.push_back(new (AsmSymbols.Allocate()) AsmSymbol(Name, Flags));
+  });
+}
+
+// Ensure ELF .symver aliases get the same binding as the defined symbol
+// they alias with.
+static void handleSymverAliases(const Module &M, RecordStreamer &Streamer) {
+  if (Streamer.symverAliases().empty())
+    return;
+
+  // The name in the assembler will be mangled, but the name in the IR
+  // might not, so we first compute a mapping from mangled name to GV.
+  Mangler Mang;
+  SmallString<64> MangledName;
+  StringMap<const GlobalValue *> MangledNameMap;
+  auto GetMangledName = [&](const GlobalValue &GV) {
+    if (!GV.hasName())
+      return;
+
+    MangledName.clear();
+    MangledName.reserve(GV.getName().size() + 1);
+    Mang.getNameWithPrefix(MangledName, &GV, /*CannotUsePrivateLabel=*/false);
+    MangledNameMap[MangledName] = &GV;
+  };
+  for (const Function &F : M)
+    GetMangledName(F);
+  for (const GlobalVariable &GV : M.globals())
+    GetMangledName(GV);
+  for (const GlobalAlias &GA : M.aliases())
+    GetMangledName(GA);
+
+  // Walk all the recorded .symver aliases, and set up the binding
+  // for each alias.
+  for (auto &Symver : Streamer.symverAliases()) {
+    const MCSymbol *Aliasee = Symver.first;
+    MCSymbolAttr Attr = MCSA_Invalid;
+
+    // First check if the aliasee binding was recorded in the asm.
+    RecordStreamer::State state = Streamer.getSymbolState(Aliasee);
+    switch (state) {
+    case RecordStreamer::Global:
+    case RecordStreamer::DefinedGlobal:
+      Attr = MCSA_Global;
+      break;
+    case RecordStreamer::UndefinedWeak:
+    case RecordStreamer::DefinedWeak:
+      Attr = MCSA_Weak;
+      break;
+    default:
+      break;
+    }
+
+    // If we don't have a symbol attribute from assembly, then check if
+    // the aliasee was defined in the IR.
+    if (Attr == MCSA_Invalid) {
+      const auto *GV = M.getNamedValue(Aliasee->getName());
+      if (!GV) {
+        auto MI = MangledNameMap.find(Aliasee->getName());
+        if (MI != MangledNameMap.end())
+          GV = MI->second;
+        else
+          continue;
+      }
+      if (GV->hasExternalLinkage())
+        Attr = MCSA_Global;
+      else if (GV->hasLocalLinkage())
+        Attr = MCSA_Local;
+      else if (GV->isWeakForLinker())
+        Attr = MCSA_Weak;
+    }
+    if (Attr == MCSA_Invalid)
+      continue;
+
+    // Set the detected binding on each alias with this aliasee.
+    for (auto &Alias : Symver.second)
+      Streamer.EmitSymbolAttribute(Alias, Attr);
+  }
 }
 
 void ModuleSymbolTable::CollectAsmSymbols(
-    const Triple &TT, StringRef InlineAsm,
+    const Module &M,
     function_ref<void(StringRef, BasicSymbolRef::Flags)> AsmSymbol) {
+  StringRef InlineAsm = M.getModuleInlineAsm();
   if (InlineAsm.empty())
     return;
 
   std::string Err;
+  const Triple TT(M.getTargetTriple());
   const Target *T = TargetRegistry::lookupTarget(TT.str(), Err);
   assert(T && T->hasMCAsmParser());
 
@@ -106,6 +181,8 @@ void ModuleSymbolTable::CollectAsmSymbols(
   if (Parser->Run(false))
     return;
 
+  handleSymverAliases(M, Streamer);
+
   for (auto &KV : Streamer) {
     StringRef Key = KV.first();
     RecordStreamer::State Value = KV.second;
diff --git a/llvm/lib/Object/RecordStreamer.cpp b/llvm/lib/Object/RecordStreamer.cpp
index da99b3fea00..8be6d0b60cf 100644
--- a/llvm/lib/Object/RecordStreamer.cpp
+++ b/llvm/lib/Object/RecordStreamer.cpp
@@ -110,3 +110,8 @@ void RecordStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                                       unsigned ByteAlignment) {
   markDefined(*Symbol);
 }
+
+void RecordStreamer::emitELFSymverDirective(MCSymbol *Alias,
+                                            const MCSymbol *Aliasee) {
+  SymverAliasMap[Aliasee].push_back(Alias);
+}
diff --git a/llvm/lib/Object/RecordStreamer.h b/llvm/lib/Object/RecordStreamer.h
index c795dbb2e43..c3bd5b09a9b 100644
--- a/llvm/lib/Object/RecordStreamer.h
+++ b/llvm/lib/Object/RecordStreamer.h
@@ -20,6 +20,10 @@ public:
 
 private:
   StringMap<State> Symbols;
+  // Map of aliases created by .symver directives, saved so we can update
+  // their symbol binding after parsing complete. This maps from each
+  // aliasee to its list of aliases.
+  DenseMap<const MCSymbol *, std::vector<MCSymbol *>> SymverAliasMap;
   void markDefined(const MCSymbol &Symbol);
   void markGlobal(const MCSymbol &Symbol, MCSymbolAttr Attribute);
   void markUsed(const MCSymbol &Symbol);
@@ -38,6 +42,20 @@ public:
                     unsigned ByteAlignment) override;
   void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                         unsigned ByteAlignment) override;
+  /// Record .symver aliases for later processing.
+  void emitELFSymverDirective(MCSymbol *Alias,
+                              const MCSymbol *Aliasee) override;
+  /// Return the map of .symver aliasee to associated aliases.
+  DenseMap<const MCSymbol *, std::vector<MCSymbol *>> &symverAliases() {
+    return SymverAliasMap;
+  }
+  /// Get the state recorded for the given symbol.
+  State getSymbolState(const MCSymbol *Sym) {
+    auto SI = Symbols.find(Sym->getName());
+    if (SI == Symbols.end())
+      return NeverSeen;
+    return SI->second;
+  }
 };
 }
 #endif