Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -270,27 +270,16 @@
 append_list_if(COMPILER_RT_HAS_WD4722_FLAG /wd4722 SANITIZER_COMMON_CFLAGS)
 append_list_if(COMPILER_RT_HAS_WD4800_FLAG /wd4800 SANITIZER_COMMON_CFLAGS)
 if(APPLE)
-  macro(find_darwin_sdk_dir var sdk_name)
-    # Let's first try the internal SDK, otherwise use the public SDK.
-    execute_process(
-      COMMAND xcodebuild -version -sdk ${sdk_name}.internal Path
-      OUTPUT_VARIABLE ${var}
-      OUTPUT_STRIP_TRAILING_WHITESPACE
-      ERROR_FILE /dev/null
-    )
-    if(${var} STREQUAL "")
-      execute_process(
-        COMMAND xcodebuild -version -sdk ${sdk_name} Path
-        OUTPUT_VARIABLE ${var}
-        OUTPUT_STRIP_TRAILING_WHITESPACE
-        ERROR_FILE /dev/null
-      )
-    endif()
-  endmacro()
+  include(CompilerRTDarwinUtils)
+
+  option(COMPILER_RT_ENABLE_IOS "Enable building for iOS - Experimental" Off)
 
   find_darwin_sdk_dir(OSX_SDK_DIR macosx)
   find_darwin_sdk_dir(IOSSIM_SDK_DIR iphonesimulator)
+  find_darwin_sdk_dir(IOS_SDK_DIR iphoneos)
 
+  # Note: In order to target x86_64h on OS X the minimum deployment target must
+  # be 10.8 or higher.
   set(SANITIZER_COMMON_SUPPORTED_OS osx)
   string(REGEX MATCH "-mmacosx-version-min=([.0-9]+)"
          MACOSX_VERSION_MIN_FLAG "${CMAKE_CXX_FLAGS}")
@@ -300,32 +289,78 @@
     set(SANITIZER_MIN_OSX_VERSION ${CMAKE_OSX_DEPLOYMENT_TARGET})
   else()
     set(SANITIZER_MIN_OSX_VERSION 10.9)
-    if(IOSSIM_SDK_DIR)
-      list(APPEND SANITIZER_COMMON_SUPPORTED_OS iossim)
-    endif()
   endif()
   if(SANITIZER_MIN_OSX_VERSION VERSION_LESS "10.7")
     message(FATAL_ERROR "Too old OS X version: ${SANITIZER_MIN_OSX_VERSION}")
   endif()
 
-  set(CMAKE_OSX_DEPLOYMENT_TARGET "") # We evaluate target OS X version above.
-  set(DARWIN_osx_CFLAGS -mmacosx-version-min=${SANITIZER_MIN_OSX_VERSION}
-    -stdlib=libc++)
-  set(DARWIN_iossim_CFLAGS
+  set(CMAKE_OSX_DEPLOYMENT_TARGET "") # We're setting the flag manually for each target OS
+  
+  set(DARWIN_COMMON_CFLAGS -stdlib=libc++)
+  set(DARWIN_COMMON_LINKFLAGS
     -stdlib=libc++
-    -mios-simulator-version-min=7.0 -isysroot ${IOSSIM_SDK_DIR})
-  set(DARWIN_osx_LINKFLAGS -mmacosx-version-min=${SANITIZER_MIN_OSX_VERSION}
-    -stdlib=libc++ -lc++ -lc++abi)
-  set(DARWIN_iossim_LINKFLAGS
-    -stdlib=libc++ -lc++ -lc++abi
-    -Wl,-ios_simulator_version_min,7.0.0
-    -mios-simulator-version-min=7.0
-    -isysroot ${IOSSIM_SDK_DIR})
+    -lc++
+    -lc++abi)
+  
+  set(DARWIN_osx_CFLAGS
+    ${DARWIN_COMMON_CFLAGS}
+    -mmacosx-version-min=${SANITIZER_MIN_OSX_VERSION})
+  set(DARWIN_osx_LINKFLAGS
+    ${DARWIN_COMMON_LINKFLAGS}
+    -mmacosx-version-min=${SANITIZER_MIN_OSX_VERSION})
 
   if(OSX_SDK_DIR)
     list(APPEND DARWIN_osx_CFLAGS -isysroot ${OSX_SDK_DIR})
     list(APPEND DARWIN_osx_LINKFLAGS -isysroot ${OSX_SDK_DIR})
   endif()
+
+  # Figure out which arches to use for each OS
+  darwin_get_toolchain_supported_archs(toolchain_arches)
+  message(STATUS "Toolchain supported arches: ${toolchain_arches}")
+  
+  if(NOT MACOSX_VERSION_MIN_FLAG)
+    darwin_test_archs(osx
+      SANITIZER_COMMON_DARWIN_osx_ARCHES
+      ${toolchain_arches})
+    message(STATUS "OSX supported arches: ${SANITIZER_COMMON_DARWIN_osx_ARCHES}")
+
+    if(IOSSIM_SDK_DIR)
+      set(DARWIN_iossim_CFLAGS
+        ${DARWIN_COMMON_CFLAGS}
+        -mios-simulator-version-min=7.0
+        -isysroot ${IOSSIM_SDK_DIR})
+      set(DARWIN_iossim_LINKFLAGS
+        ${DARWIN_COMMON_LINKFLAGS}
+        -Wl,-ios_simulator_version_min,7.0.0
+        -mios-simulator-version-min=7.0
+        -isysroot ${IOSSIM_SDK_DIR})
+
+      list(APPEND SANITIZER_COMMON_SUPPORTED_OS iossim)
+      darwin_test_archs(iossim
+        SANITIZER_COMMON_DARWIN_iossim_ARCHES
+        ${toolchain_arches})
+      message(STATUS "iOS Simulator supported arches: ${SANITIZER_COMMON_DARWIN_iossim_ARCHES}")
+    endif()
+
+    if(IOS_SDK_DIR AND COMPILER_RT_ENABLE_IOS)
+      set(DARWIN_ios_CFLAGS
+        ${DARWIN_COMMON_CFLAGS}
+        -miphoneos-version-min=7.0
+        -isysroot ${IOS_SDK_DIR})
+      set(DARWIN_ios_LINKFLAGS
+        ${DARWIN_COMMON_LINKFLAGS}
+        -Wl,-ios_version_min,7.0.0
+        -miphoneos-version-min=7.0
+        -isysroot ${IOS_SDK_DIR})
+
+      list(APPEND SANITIZER_COMMON_SUPPORTED_OS ios)
+      darwin_test_archs(ios
+        SANITIZER_COMMON_DARWIN_ios_ARCHES
+        ${toolchain_arches})
+      message(STATUS "iOS supported arches: ${SANITIZER_COMMON_DARWIN_ios_ARCHES}")
+    endif()
+  endif()
+
 endif()
 
 if(APPLE AND SANITIZER_MIN_OSX_VERSION VERSION_LESS "10.9")