Index: llvm/trunk/test/tools/dsymutil/X86/alias.test
===================================================================
--- llvm/trunk/test/tools/dsymutil/X86/alias.test
+++ llvm/trunk/test/tools/dsymutil/X86/alias.test
@@ -0,0 +1,19 @@
+# RUN: llvm-dsymutil -f -oso-prepend-path=%p/../Inputs/alias \
+# RUN: %p/../Inputs/alias/foobar -o - 2>&1 | llvm-dwarfdump - | FileCheck %s
+# CHECK-NOT: could not find object file symbol for symbol
+# CHECK: DW_AT_name ("foo.c")
+# CHECK: DW_AT_name ("bar.c")
+
+# Source:
+#   $ cat foo.c
+#   int foo = 1;
+#   $ cat bar.c
+#   extern int bar;
+#   int main() {
+#     return bar;
+#   }
+
+# Compile with:
+#   $ clang -g -O0 bar.c -c -o bar.o
+#   $ clang -g -O0 foo.c -c -o foo.o
+#   $ ld -arch x86_64 -macosx_version_min 10.13.0 foo.o bar.o -lSystem -alias _foo _bar -o foobar
Index: llvm/trunk/tools/dsymutil/MachODebugMapParser.cpp
===================================================================
--- llvm/trunk/tools/dsymutil/MachODebugMapParser.cpp
+++ llvm/trunk/tools/dsymutil/MachODebugMapParser.cpp
@@ -70,6 +70,7 @@
                             sys::TimePoint<std::chrono::seconds> Timestamp);
   void resetParserState();
   uint64_t getMainBinarySymbolAddress(StringRef Name);
+  std::vector<StringRef> getMainBinarySymbolNames(uint64_t Value);
   void loadMainBinarySymbols(const MachOObjectFile &MainBinary);
   void loadCurrentObjectFileSymbols(const object::MachOObjectFile &Obj);
   void handleStabSymbolTableEntry(uint32_t StringIndex, uint8_t Type,
@@ -382,9 +383,21 @@
   }
 
   auto ObjectSymIt = CurrentObjectAddresses.find(Name);
+
+  // If the name of a (non-static) symbol is not in the current object, we
+  // check all its aliases from the main binary.
+  if (ObjectSymIt == CurrentObjectAddresses.end() && Type != MachO::N_STSYM) {
+    for (const auto &Alias : getMainBinarySymbolNames(Value)) {
+      ObjectSymIt = CurrentObjectAddresses.find(Alias);
+      if (ObjectSymIt != CurrentObjectAddresses.end())
+        break;
+    }
+  }
+
   if (ObjectSymIt == CurrentObjectAddresses.end())
     return Warning("could not find object file symbol for symbol " +
                    Twine(Name));
+
   if (!CurrentDebugMapObject->addSymbol(Name, ObjectSymIt->getValue(), Value,
                                         Size))
     return Warning(Twine("failed to insert symbol '") + Name +
@@ -429,6 +442,17 @@
   return Sym->second;
 }
 
+/// Get all symbol names in the main binary for the given value.
+std::vector<StringRef>
+MachODebugMapParser::getMainBinarySymbolNames(uint64_t Value) {
+  std::vector<StringRef> Names;
+  for (const auto &Entry : MainBinarySymbolAddresses) {
+    if (Entry.second == Value)
+      Names.push_back(Entry.first());
+  }
+  return Names;
+}
+
 /// Load the interesting main binary symbols' addresses into
 /// MainBinarySymbolAddresses.
 void MachODebugMapParser::loadMainBinarySymbols(