Index: llvm/trunk/cmake/config-ix.cmake
===================================================================
--- llvm/trunk/cmake/config-ix.cmake
+++ llvm/trunk/cmake/config-ix.cmake
@@ -532,6 +532,10 @@
 		"PATH to binutils/include containing plugin-api.h for gold plugin.")
 endif()
 
+if(APPLE)
+  find_program(LD64_EXECUTABLE NAMES ld DOC "The ld64 linker")
+endif()
+
 include(FindOCaml)
 include(AddOCaml)
 if(WIN32)
Index: llvm/trunk/test/CMakeLists.txt
===================================================================
--- llvm/trunk/test/CMakeLists.txt
+++ llvm/trunk/test/CMakeLists.txt
@@ -70,6 +70,10 @@
   set(LLVM_TEST_DEPENDS ${LLVM_TEST_DEPENDS} llvm-go)
 endif()
 
+if(APPLE)
+  set(LLVM_TEST_DEPENDS ${LLVM_TEST_DEPENDS} LTO)
+endif()
+
 if(TARGET ocaml_llvm)
   set(LLVM_TEST_DEPENDS ${LLVM_TEST_DEPENDS}
           ocaml_llvm
Index: llvm/trunk/test/Makefile
===================================================================
--- llvm/trunk/test/Makefile
+++ llvm/trunk/test/Makefile
@@ -129,6 +129,7 @@
 	@$(ECHOPATH) s=@EXEEXT@=$(EXEEXT)=g >> lit.tmp
 	@$(ECHOPATH) s=@PYTHON_EXECUTABLE@=$(PYTHON)=g >> lit.tmp
 	@$(ECHOPATH) s=@GOLD_EXECUTABLE@=ld=g >> lit.tmp
+	@$(ECHOPATH) s=@LD64_EXECUTABLE@=ld=g >> lit.tmp
 	@$(ECHOPATH) s=@OCAMLFIND@=$(OCAMLFIND)=g >> lit.tmp
 	@$(ECHOPATH) s!@OCAMLFLAGS@!$(addprefix -cclib ,$(LDFLAGS))!g >> lit.tmp
 	@$(ECHOPATH) s=@HAVE_OCAMLOPT@=$(HAVE_OCAMLOPT)=g >> lit.tmp
Index: llvm/trunk/test/lit.cfg
===================================================================
--- llvm/trunk/test/lit.cfg
+++ llvm/trunk/test/lit.cfg
@@ -188,6 +188,7 @@
 
 # Add site-specific substitutions.
 config.substitutions.append( ('%gold', config.gold_executable) )
+config.substitutions.append( ('%ld64', config.ld64_executable) )
 config.substitutions.append( ('%go', config.go_executable) )
 config.substitutions.append( ('%llvmshlibdir', config.llvm_shlib_dir) )
 config.substitutions.append( ('%shlibext', config.llvm_shlib_ext) )
@@ -369,6 +370,22 @@
 if have_ld_plugin_support():
     config.available_features.add('ld_plugin')
 
+def have_ld64_plugin_support():
+    if config.ld64_executable == '':
+        return False
+
+    ld_cmd = subprocess.Popen([config.ld64_executable, '-v'], stderr = subprocess.PIPE)
+    ld_out = ld_cmd.stderr.read().decode()
+    ld_cmd.wait()
+
+    if 'ld64' not in ld_out or 'LTO' not in ld_out:
+        return False
+
+    return True
+
+if have_ld64_plugin_support():
+    config.available_features.add('ld64_plugin')
+
 # Ask llvm-config about assertion mode.
 try:
     llvm_config_cmd = subprocess.Popen(
Index: llvm/trunk/test/lit.site.cfg.in
===================================================================
--- llvm/trunk/test/lit.site.cfg.in
+++ llvm/trunk/test/lit.site.cfg.in
@@ -14,6 +14,7 @@
 config.lit_tools_dir = "@LLVM_LIT_TOOLS_DIR@"
 config.python_executable = "@PYTHON_EXECUTABLE@"
 config.gold_executable = "@GOLD_EXECUTABLE@"
+config.ld64_executable = "@LD64_EXECUTABLE@"
 config.ocamlfind_executable = "@OCAMLFIND@"
 config.have_ocamlopt = "@HAVE_OCAMLOPT@"
 config.have_ocaml_ounit = "@HAVE_OCAML_OUNIT@"
Index: llvm/trunk/test/tools/lto/lit.local.cfg
===================================================================
--- llvm/trunk/test/tools/lto/lit.local.cfg
+++ llvm/trunk/test/tools/lto/lit.local.cfg
@@ -0,0 +1,2 @@
+if not 'ld64_plugin' in config.available_features:
+   config.unsupported = True
Index: llvm/trunk/test/tools/lto/opt-level.ll
===================================================================
--- llvm/trunk/test/tools/lto/opt-level.ll
+++ llvm/trunk/test/tools/lto/opt-level.ll
@@ -0,0 +1,20 @@
+; RUN: llvm-as %s -o %t.o
+; RUN: env DYLD_LIBRARY_PATH=%llvmshlibdir %ld64 -arch x86_64 -dylib -mllvm -O0 -o %t.dylib %t.o
+; RUN: llvm-nm -no-llvm-bc %t.dylib | FileCheck --check-prefix=CHECK-O0 %s
+; RUN: env DYLD_LIBRARY_PATH=%llvmshlibdir %ld64 -arch x86_64 -dylib -mllvm -O2 -o %t.dylib %t.o
+; RUN: llvm-nm -no-llvm-bc %t.dylib | FileCheck --check-prefix=CHECK-O2 %s
+
+target triple = "x86_64-apple-macosx10.8.0"
+
+; CHECK-O0: t _f1
+; CHECK-O2-NOT: _f1
+define internal void @f1() {
+  ret void
+}
+
+; CHECK-O0: T _f2
+; CHECK-O2: T _f2
+define void @f2() {
+  call void @f1()
+  ret void
+}