Index: lld/trunk/include/lld/ReaderWriter/MachOLinkingContext.h
===================================================================
--- lld/trunk/include/lld/ReaderWriter/MachOLinkingContext.h
+++ lld/trunk/include/lld/ReaderWriter/MachOLinkingContext.h
@@ -84,7 +84,8 @@
   /// Initializes the context to sane default values given the specified output
   /// file type, arch, os, and minimum os version.  This should be called before
   /// other setXXX() methods.
-  void configure(HeaderFileType type, Arch arch, OS os, uint32_t minOSVersion);
+  void configure(HeaderFileType type, Arch arch, OS os, uint32_t minOSVersion,
+                 bool exportDynamicSymbols);
 
   void addPasses(PassManager &pm) override;
   bool validateImpl(raw_ostream &diagnostics) override;
Index: lld/trunk/lib/Driver/DarwinLdDriver.cpp
===================================================================
--- lld/trunk/lib/Driver/DarwinLdDriver.cpp
+++ lld/trunk/lib/Driver/DarwinLdDriver.cpp
@@ -385,9 +385,16 @@
     // No min-os version on command line, check environment variables
   }
 
+  // Handle export_dynamic
+  // FIXME: Should we warn when this applies to something other than a static
+  // executable or dylib?  Those are the only cases where this has an effect.
+  // Note, this has to come before ctx.configure() so that we get the correct
+  // value for _globalsAreDeadStripRoots.
+  bool exportDynamicSymbols = parsedArgs.hasArg(OPT_export_dynamic);
+
   // Now that there's enough information parsed in, let the linking context
   // set up default values.
-  ctx.configure(fileType, arch, os, minOSVersion);
+  ctx.configure(fileType, arch, os, minOSVersion, exportDynamicSymbols);
 
   // Handle -e xxx
   if (llvm::opt::Arg *entry = parsedArgs.getLastArg(OPT_entry))
Index: lld/trunk/lib/Driver/DarwinLdOptions.td
===================================================================
--- lld/trunk/lib/Driver/DarwinLdOptions.td
+++ lld/trunk/lib/Driver/DarwinLdOptions.td
@@ -84,6 +84,9 @@
      HelpText<"Specifies the maximum stack size for the main thread in a program. "
               "Must be a page-size multiple. (default=8Mb)">,
      Group<grp_main>;
+def export_dynamic : Flag<["-"], "export_dynamic">,
+     HelpText<"Preserves all global symbols in main executables during LTO">,
+     Group<grp_main>;
 
 // dylib executable options
 def grp_dylib : OptionGroup<"opts">, HelpText<"DYLIB EXECUTABLE OPTIONS">;
Index: lld/trunk/lib/ReaderWriter/MachO/MachOLinkingContext.cpp
===================================================================
--- lld/trunk/lib/ReaderWriter/MachO/MachOLinkingContext.cpp
+++ lld/trunk/lib/ReaderWriter/MachO/MachOLinkingContext.cpp
@@ -155,7 +155,8 @@
 MachOLinkingContext::~MachOLinkingContext() {}
 
 void MachOLinkingContext::configure(HeaderFileType type, Arch arch, OS os,
-                                    uint32_t minOSVersion) {
+                                    uint32_t minOSVersion,
+                                    bool exportDynamicSymbols) {
   _outputMachOType = type;
   _arch = arch;
   _os = os;
@@ -218,9 +219,10 @@
        case OS::unknown:
        break;
     }
+    setGlobalsAreDeadStripRoots(exportDynamicSymbols);
     break;
   case llvm::MachO::MH_DYLIB:
-    setGlobalsAreDeadStripRoots(true);
+    setGlobalsAreDeadStripRoots(exportDynamicSymbols);
     break;
   case llvm::MachO::MH_BUNDLE:
     break;
Index: lld/trunk/test/mach-o/dead-strip-globals.yaml
===================================================================
--- lld/trunk/test/mach-o/dead-strip-globals.yaml
+++ lld/trunk/test/mach-o/dead-strip-globals.yaml
@@ -0,0 +1,27 @@
+# RUN: lld -flavor darwin -arch x86_64 -dead_strip -export_dynamic %s -dylib %p/Inputs/libSystem.yaml -o %t.dylib -print_atoms | FileCheck -check-prefix=CHECK1 %s
+# RUN: lld -flavor darwin -arch x86_64 -export_dynamic -dead_strip %s -dylib %p/Inputs/libSystem.yaml -o %t.dylib -print_atoms | FileCheck -check-prefix=CHECK1 %s
+# RUN: lld -flavor darwin -arch x86_64 -dead_strip %s -dylib %p/Inputs/libSystem.yaml -o %t2.dylib -print_atoms | FileCheck -check-prefix=CHECK2 %s
+
+#
+# Test that -export_dynamic -dead-strip from removing globals.
+#
+
+---
+defined-atoms:
+  - name:            def
+    scope:           global
+    dead-strip:      never
+  - name:            dead
+    scope:           global
+shared-library-atoms:
+  - name:            dyld_stub_binder
+    load-name:       /usr/lib/libSystem.B.dylib
+    type:            unknown
+...
+
+# CHECK1:       name: def
+# CHECK1:       name: dead
+
+# CHECK2:       name: def
+# CHECK2-NOT:   name: dead
+
Index: lld/trunk/unittests/DriverTests/DarwinLdDriverTest.cpp
===================================================================
--- lld/trunk/unittests/DriverTests/DarwinLdDriverTest.cpp
+++ lld/trunk/unittests/DriverTests/DarwinLdDriverTest.cpp
@@ -84,9 +84,34 @@
 TEST_F(DarwinLdParserTest, DeadStripRootsDylib) {
   EXPECT_TRUE(parse("ld", "-arch", "x86_64", "-dylib", "-dead_strip", "foo.o",
                     nullptr));
+  EXPECT_FALSE(_ctx.globalsAreDeadStripRoots());
+}
+
+TEST_F(DarwinLdParserTest, DeadStripRootsRelocatable) {
+  EXPECT_TRUE(parse("ld", "-arch", "x86_64", "-r", "-dead_strip", "foo.o",
+                    nullptr));
+  EXPECT_FALSE(_ctx.globalsAreDeadStripRoots());
+}
+
+TEST_F(DarwinLdParserTest, DeadStripRootsExportDynamicExe) {
+  EXPECT_TRUE(parse("ld", "-arch", "x86_64", "-dead_strip",
+                    "-export_dynamic", "foo.o", nullptr));
   EXPECT_TRUE(_ctx.globalsAreDeadStripRoots());
 }
 
+TEST_F(DarwinLdParserTest, DeadStripRootsExportDynamicDylib) {
+  EXPECT_TRUE(parse("ld", "-arch", "x86_64", "-dylib", "-dead_strip",
+                    "-export_dynamic", "foo.o",
+                    nullptr));
+  EXPECT_TRUE(_ctx.globalsAreDeadStripRoots());
+}
+
+TEST_F(DarwinLdParserTest, DeadStripRootsExportDynamicRelocatable) {
+  EXPECT_TRUE(parse("ld", "-arch", "x86_64", "-r", "-dead_strip",
+                    "-export_dynamic", "foo.o", nullptr));
+  EXPECT_FALSE(_ctx.globalsAreDeadStripRoots());
+}
+
 TEST_F(DarwinLdParserTest, Arch) {
   EXPECT_TRUE(parse("ld", "-arch", "x86_64", "foo.o", nullptr));
   EXPECT_EQ(MachOLinkingContext::arch_x86_64, _ctx.arch());