Index: lib/Transforms/Instrumentation/AddressSanitizer.cpp
===================================================================
--- lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -89,6 +89,7 @@
 static const char *const kAsanModuleDtorName = "asan.module_dtor";
 static const uint64_t kAsanCtorAndDtorPriority = 1;
 static const char *const kAsanReportErrorTemplate = "__asan_report_";
+static const char *const kAsanApplyToGlobalsName = "__asan_apply_to_globals";
 static const char *const kAsanRegisterGlobalsName = "__asan_register_globals";
 static const char *const kAsanUnregisterGlobalsName =
     "__asan_unregister_globals";
@@ -546,6 +547,7 @@
   Function *AsanUnpoisonGlobals;
   Function *AsanRegisterGlobals;
   Function *AsanUnregisterGlobals;
+  Function *AsanApplyToGlobals;
 };
 
 // Stack poisoning does not play well with exception handling.
@@ -1298,6 +1300,13 @@
       M.getOrInsertFunction(kAsanUnregisterGlobalsName, IRB.getVoidTy(),
                             IntptrTy, IntptrTy, nullptr));
   AsanUnregisterGlobals->setLinkage(Function::ExternalLinkage);
+
+  if (TargetTriple.isOSBinFormatMachO()) {
+    AsanApplyToGlobals = checkSanitizerInterfaceFunction(
+        M.getOrInsertFunction(kAsanApplyToGlobalsName,
+        IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
+    AsanApplyToGlobals->setLinkage(Function::ExternalLinkage);
+  }
 }
 
 // This function replaces all global variables with new variables that have
@@ -1406,17 +1415,58 @@
     DEBUG(dbgs() << "NEW GLOBAL: " << *NewGlobal << "\n");
   }
 
-  ArrayType *ArrayOfGlobalStructTy = ArrayType::get(GlobalStructTy, n);
-  GlobalVariable *AllGlobals = new GlobalVariable(
-      M, ArrayOfGlobalStructTy, false, GlobalVariable::InternalLinkage,
-      ConstantArray::get(ArrayOfGlobalStructTy, Initializers), "");
+
+  GlobalVariable *AllGlobals = nullptr;
+
+  // On Mach-O platforms, we emit the global metadata in a way that allows the
+  // linker to properly strip dead globals.
+  if (TargetTriple.isOSBinFormatMachO()) {
+    // We use AllGlobals as a dummy symbol which lets us look up the header
+    // of the library that contains it later.
+    AllGlobals = new GlobalVariable(
+        M, IntptrTy, false, GlobalVariable::InternalLinkage,
+        ConstantInt::get(IntptrTy, 0), "");
+    
+    // We also emit a structure which binds the liveness of the global
+    // variable to the metadata struct.
+    StructType *LivenessTy = StructType::get(IntptrTy, IntptrTy, nullptr);
+
+    for (size_t i = 0; i < n; i++) {
+      GlobalVariable *Metadata = new GlobalVariable(
+          M, GlobalStructTy, false, GlobalVariable::InternalLinkage,
+          Initializers[i], "");
+      Metadata->setSection("__DATA,__asan_globals,regular");
+      Metadata->setAlignment(1); // don't leave padding in between
+
+      auto LivenessBinder = ConstantStruct::get(LivenessTy,
+          Initializers[i]->getAggregateElement(0u),
+          ConstantExpr::getPointerCast(Metadata, IntptrTy),
+          nullptr);
+      GlobalVariable *Liveness = new GlobalVariable(
+          M, LivenessTy, false, GlobalVariable::InternalLinkage,
+          LivenessBinder, "");
+      Liveness->setSection("__DATA,__asan_liveness,regular,live_support");
+    }
+  } else {
+    ArrayType *ArrayOfGlobalStructTy = ArrayType::get(GlobalStructTy, n);
+    AllGlobals = new GlobalVariable(
+        M, ArrayOfGlobalStructTy, false, GlobalVariable::InternalLinkage,
+        ConstantArray::get(ArrayOfGlobalStructTy, Initializers), "");
+  }
 
   // Create calls for poisoning before initializers run and unpoisoning after.
   if (HasDynamicallyInitializedGlobals)
     createInitializerPoisonCalls(M, ModuleName);
-  IRB.CreateCall(AsanRegisterGlobals,
-                 {IRB.CreatePointerCast(AllGlobals, IntptrTy),
-                  ConstantInt::get(IntptrTy, n)});
+
+  if (TargetTriple.isOSBinFormatMachO()) {
+    IRB.CreateCall(AsanApplyToGlobals,
+                   {IRB.CreatePointerCast(AsanRegisterGlobals, IntptrTy),
+                    IRB.CreatePointerCast(AllGlobals, IntptrTy)});
+  } else {
+    IRB.CreateCall(AsanRegisterGlobals,
+                   {IRB.CreatePointerCast(AllGlobals, IntptrTy),
+                    ConstantInt::get(IntptrTy, n)});
+  }
 
   // We also need to unregister globals at the end, e.g. when a shared library
   // gets closed.
@@ -1425,9 +1475,17 @@
                        GlobalValue::InternalLinkage, kAsanModuleDtorName, &M);
   BasicBlock *AsanDtorBB = BasicBlock::Create(*C, "", AsanDtorFunction);
   IRBuilder<> IRB_Dtor(ReturnInst::Create(*C, AsanDtorBB));
-  IRB_Dtor.CreateCall(AsanUnregisterGlobals,
-                      {IRB.CreatePointerCast(AllGlobals, IntptrTy),
-                       ConstantInt::get(IntptrTy, n)});
+
+  if (TargetTriple.isOSBinFormatMachO()) {
+    IRB_Dtor.CreateCall(AsanApplyToGlobals,
+                        {IRB.CreatePointerCast(AsanUnregisterGlobals, IntptrTy),
+                         IRB.CreatePointerCast(AllGlobals, IntptrTy)});
+  } else {
+    IRB_Dtor.CreateCall(AsanUnregisterGlobals,
+                        {IRB.CreatePointerCast(AllGlobals, IntptrTy),
+                         ConstantInt::get(IntptrTy, n)});
+  }
+
   appendToGlobalDtors(M, AsanDtorFunction, kAsanCtorAndDtorPriority);
 
   DEBUG(dbgs() << M);
Index: lib/asan/asan_globals.cc
===================================================================
--- lib/asan/asan_globals.cc
+++ lib/asan/asan_globals.cc
@@ -26,6 +26,12 @@
 #include "sanitizer_common/sanitizer_placement_new.h"
 #include "sanitizer_common/sanitizer_stackdepot.h"
 
+#if SANITIZER_MAC
+#include <mach-o/getsect.h>
+#include <dlfcn.h>
+#endif
+
+
 namespace __asan {
 
 typedef __asan_global Global;
@@ -212,6 +218,35 @@
 // ---------------------- Interface ---------------- {{{1
 using namespace __asan;  // NOLINT
 
+
+#if SANITIZER_MAC
+// Apply __asan_(un)register_globals to globals found listed in the
+// __DATA,__asan_globals section.
+void __asan_apply_to_globals(global_func func, void *canary) {
+  // Find the Mach-O header for the image containing the canary
+  Dl_info info;
+  int err = dladdr(canary, &info);
+  if (err == 0) return;
+
+#if __LP64__
+  const struct mach_header_64 *mh = (struct mach_header_64 *)info.dli_fbase;
+#else
+  const struct mach_header *mh = (struct mach_header *)info.dli_fbase;
+#endif
+
+  // Look up the __asan_globals section in that image and register its globals
+  unsigned long size = 0;
+  __asan_global *globals = (__asan_global *)getsectiondata(
+      mh,
+      "__DATA", "__asan_globals",
+      &size);
+
+  if (!globals) return;
+  if (size % sizeof(__asan_global) != 0) return;
+  func(globals, size / sizeof(__asan_global));
+}
+#endif
+
 // Register an array of globals.
 void __asan_register_globals(__asan_global *globals, uptr n) {
   if (!flags()->report_globals) return;
Index: lib/asan/asan_interface_internal.h
===================================================================
--- lib/asan/asan_interface_internal.h
+++ lib/asan/asan_interface_internal.h
@@ -56,6 +56,13 @@
                                               // or NULL if it is unknown.
   };
 
+  // This function can be called by instrumented code on Mach-O platforms.
+#if SANITIZER_MAC
+  typedef void (*global_func)(__asan_global *, uptr);
+  SANITIZER_INTERFACE_ATTRIBUTE
+  void __asan_apply_to_globals(global_func foo, void *canary);
+#endif
+
   // These two functions should be called by the instrumented code.
   // 'globals' is an array of structures describing 'n' globals.
   SANITIZER_INTERFACE_ATTRIBUTE