Index: lld/MachO/Config.h
===================================================================
--- lld/MachO/Config.h
+++ lld/MachO/Config.h
@@ -126,6 +126,7 @@
   llvm::StringRef outputFile;
   llvm::StringRef ltoObjPath;
   llvm::StringRef thinLTOJobs;
+  uint32_t ltoo = 2;
   bool deadStripDylibs = false;
   bool demangle = false;
   bool deadStrip = false;
Index: lld/MachO/Driver.cpp
===================================================================
--- lld/MachO/Driver.cpp
+++ lld/MachO/Driver.cpp
@@ -1068,6 +1068,9 @@
   config->ltoNewPassManager =
       args.hasFlag(OPT_no_lto_legacy_pass_manager, OPT_lto_legacy_pass_manager,
                    LLVM_ENABLE_NEW_PASS_MANAGER);
+  config->ltoo = args::getInteger(args, OPT_lto_O, 2);
+  if (config->ltoo > 3)
+    error("--lto-O: invalid optimization level: " + Twine(config->ltoo));
   config->runtimePaths = args::getStrings(args, OPT_rpath);
   config->allLoad = args.hasArg(OPT_all_load);
   config->forceLoadObjC = args.hasArg(OPT_ObjC);
Index: lld/MachO/LTO.cpp
===================================================================
--- lld/MachO/LTO.cpp
+++ lld/MachO/LTO.cpp
@@ -13,6 +13,7 @@
 #include "Symbols.h"
 #include "Target.h"
 
+#include "lld/Common/Args.h"
 #include "lld/Common/ErrorHandler.h"
 #include "lld/Common/Strings.h"
 #include "lld/Common/TargetOptionsCommandFlags.h"
@@ -40,6 +41,8 @@
   };
   c.TimeTraceEnabled = config->timeTraceEnabled;
   c.TimeTraceGranularity = config->timeTraceGranularity;
+  c.OptLevel = config->ltoo;
+  c.CGOptLevel = args::getCGOptLevel(config->ltoo);
   if (config->saveTemps)
     checkError(c.addSaveTemps(config->outputFile.str() + ".",
                               /*UseInputModulePath=*/true));
Index: lld/MachO/Options.td
===================================================================
--- lld/MachO/Options.td
+++ lld/MachO/Options.td
@@ -64,6 +64,10 @@
     HelpText<"Set level for identical code folding (default: none)">,
     MetaVarName<"[none,safe,all]">,
     Group<grp_lld>;
+def lto_O: Joined<["--"], "lto-O">,
+    HelpText<"Set optimization level for LTO (default: 2)">,
+    MetaVarName<"<opt-level>">,
+    Group<grp_lld>;
 
 // This is a complete Options.td compiled from Apple's ld(1) manpage
 // dated 2018-03-07 and cross checked with ld64 source code in repo
Index: lld/test/MachO/lto-opt-level.ll
===================================================================
--- /dev/null
+++ lld/test/MachO/lto-opt-level.ll
@@ -0,0 +1,28 @@
+; REQUIRES: x86
+
+; RUN: rm -rf %t; mkdir %t
+; RUN: llvm-as  %s -o %t/test.o
+
+; RUN: %lld %t/test.o --lto-O0 -o %t/test
+; RUN: llvm-nm -pa %t/test | FileCheck %s --check-prefixes=CHECK-O0
+
+; RUN: %lld %t/test.o --lto-O2 -o %t/test
+; RUN: llvm-nm -pa %t/test | FileCheck %s --check-prefixes=CHECK-O2
+
+; RUN: %lld %t/test.o -o %t/test
+; RUN: llvm-nm -pa %t/test | FileCheck %s --check-prefixes=CHECK-O2
+
+; CHECK-O0: foo
+; CHECK-O2-NOT: foo
+
+target triple = "x86_64-apple-macosx10.15.0"
+target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+
+define internal void @foo() {
+  ret void
+}
+
+define void @main() {
+  call void @foo()
+  ret void
+}