Index: test/asan/CMakeLists.txt
===================================================================
--- test/asan/CMakeLists.txt
+++ test/asan/CMakeLists.txt
@@ -51,10 +51,7 @@
     set(ASAN_TEST_TARGET_ARCH ${arch})
   endif()
 
-  set(ASAN_TEST_IOS "0")
-  pythonize_bool(ASAN_TEST_IOS)
-  set(ASAN_TEST_IOSSIM "0")
-  pythonize_bool(ASAN_TEST_IOSSIM)
+  set(ASAN_TEST_APPLE_PLATFORM "osx")
 
   string(TOLOWER "-${arch}-${OS_NAME}" ASAN_TEST_CONFIG_SUFFIX)
   get_bits_for_arch(${arch} ASAN_TEST_BITS)
@@ -93,16 +90,13 @@
   set(EXCLUDE_FROM_ALL ON)
 
   set(ASAN_TEST_TARGET_CC ${COMPILER_RT_TEST_COMPILER})
-  set(ASAN_TEST_IOS "1")
-  pythonize_bool(ASAN_TEST_IOS)
   set(ASAN_TEST_DYNAMIC True)
 
   foreach(arch ${DARWIN_iossim_ARCHS})
-    set(ASAN_TEST_IOSSIM "1")
-    pythonize_bool(ASAN_TEST_IOSSIM)
+    set(ASAN_TEST_APPLE_PLATFORM "iossim")
     set(ASAN_TEST_TARGET_ARCH ${arch})
     set(ASAN_TEST_TARGET_CFLAGS "-arch ${arch} -isysroot ${DARWIN_iossim_SYSROOT} ${COMPILER_RT_TEST_COMPILER_CFLAGS}")
-    set(ASAN_TEST_CONFIG_SUFFIX "-${arch}-iossim")
+    set(ASAN_TEST_CONFIG_SUFFIX "-${arch}-${ASAN_TEST_APPLE_PLATFORM}")
     get_bits_for_arch(${arch} ASAN_TEST_BITS)
     string(TOUPPER ${arch} ARCH_UPPER_CASE)
     set(CONFIG_NAME "IOSSim${ARCH_UPPER_CASE}Config")
@@ -116,11 +110,10 @@
   endforeach()
 
   foreach (arch ${DARWIN_ios_ARCHS})
-    set(ASAN_TEST_IOSSIM "0")
-    pythonize_bool(ASAN_TEST_IOSSIM)
+    set(ASAN_TEST_APPLE_PLATFORM "ios")
     set(ASAN_TEST_TARGET_ARCH ${arch})
     set(ASAN_TEST_TARGET_CFLAGS "-arch ${arch} -isysroot ${DARWIN_ios_SYSROOT} ${COMPILER_RT_TEST_COMPILER_CFLAGS}")
-    set(ASAN_TEST_CONFIG_SUFFIX "-${arch}-ios")
+    set(ASAN_TEST_CONFIG_SUFFIX "-${arch}-${ASAN_TEST_APPLE_PLATFORM}")
     get_bits_for_arch(${arch} ASAN_TEST_BITS)
     string(TOUPPER ${arch} ARCH_UPPER_CASE)
     set(CONFIG_NAME "IOS${ARCH_UPPER_CASE}Config")
Index: test/asan/lit.cfg
===================================================================
--- test/asan/lit.cfg
+++ test/asan/lit.cfg
@@ -214,5 +214,5 @@
 if config.host_os == 'Darwin':
   if config.target_arch in ["x86_64", "x86_64h"]:
     config.parallelism_group = "darwin-64bit-sanitizer"
-  elif config.ios and not config.iossim:
+  elif config.apple_platform != "osx" and not config.apple_platform.endswith("sim"):
     config.parallelism_group = "darwin-ios-device-sanitizer"
Index: test/asan/lit.site.cfg.in
===================================================================
--- test/asan/lit.site.cfg.in
+++ test/asan/lit.site.cfg.in
@@ -5,8 +5,7 @@
 config.target_cflags = "@ASAN_TEST_TARGET_CFLAGS@"
 config.clang = "@ASAN_TEST_TARGET_CC@"
 config.bits = "@ASAN_TEST_BITS@"
-config.ios = @ASAN_TEST_IOS_PYBOOL@
-config.iossim = @ASAN_TEST_IOSSIM_PYBOOL@
+config.apple_platform = "@ASAN_TEST_APPLE_PLATFORM@"
 config.asan_dynamic = @ASAN_TEST_DYNAMIC@
 config.target_arch = "@ASAN_TEST_TARGET_ARCH@"
 
Index: test/fuzzer/CMakeLists.txt
===================================================================
--- test/fuzzer/CMakeLists.txt
+++ test/fuzzer/CMakeLists.txt
@@ -10,8 +10,6 @@
 set(EXCLUDE_FROM_ALL ON)
 
 add_custom_target(check-fuzzer)
-set(LIBFUZZER_TEST_IOS "0")
-pythonize_bool(LIBFUZZER_TEST_IOS)
 
 if(COMPILER_RT_INCLUDE_TESTS)
   # libFuzzer unit tests.
@@ -40,6 +38,8 @@
     set(LIBFUZZER_TEST_COMPILER ${COMPILER_RT_TEST_COMPILER})
     get_test_cc_for_arch(${arch} LIBFUZZER_TEST_COMPILER LIBFUZZER_TEST_FLAGS)
 
+    set(LIBFUZZER_TEST_APPLE_PLATFORM "osx")
+
     set(LIBFUZZER_TEST_STDLIB ${stdlib})
 
     string(TOUPPER ${arch} ARCH_UPPER_CASE)
@@ -78,11 +78,10 @@
   set(EXCLUDE_FROM_ALL ON)
 
   foreach(arch ${DARWIN_ios_ARCHS})
-    set(LIBFUZZER_TEST_IOS "1")
-    pythonize_bool(LIBFUZZER_TEST_IOS)
+    set(LIBFUZZER_TEST_APPLE_PLATFORM "ios")
     set(LIBFUZZER_TEST_TARGET_ARCH ${arch})
     set(LIBFUZZER_TEST_FLAGS "-arch ${arch} -isysroot ${DARWIN_ios_SYSROOT} ${COMPILER_RT_TEST_COMPILER_CFLAGS}")
-    set(LIBFUZZER_TEST_CONFIG_SUFFIX "-${arch}-ios")
+    set(LIBFUZZER_TEST_CONFIG_SUFFIX "-${arch}-${LIBFUZZER_TEST_APPLE_PLATFORM}")
     string(TOUPPER ${arch} ARCH_UPPER_CASE)
     set(CONFIG_NAME "IOS${ARCH_UPPER_CASE}Config")
     configure_lit_site_cfg(
Index: test/fuzzer/lit.cfg
===================================================================
--- test/fuzzer/lit.cfg
+++ test/fuzzer/lit.cfg
@@ -96,5 +96,5 @@
 if config.host_os == 'Darwin':
   if config.target_arch in ["x86_64", "x86_64h"]:
     config.parallelism_group = "darwin-64bit-sanitizer"
-  elif config.ios and not config.iossim:
+  elif config.apple_platform != "osx" and not config.apple_platform.endswith("sim"):
     config.parallelism_group = "darwin-ios-device-sanitizer"
Index: test/fuzzer/lit.site.cfg.in
===================================================================
--- test/fuzzer/lit.site.cfg.in
+++ test/fuzzer/lit.site.cfg.in
@@ -6,7 +6,7 @@
 config.target_flags = "@LIBFUZZER_TEST_FLAGS@"
 config.c_compiler = "@LIBFUZZER_TEST_COMPILER@"
 config.stdlib = "@LIBFUZZER_TEST_STDLIB@"
-config.ios = @LIBFUZZER_TEST_IOS_PYBOOL@
+config.apple_platform = "@LIBFUZZER_TEST_APPLE_PLATFORM@"
 config.name_suffix = "@LIBFUZZER_TEST_CONFIG_SUFFIX@"
 
 config.osx_sysroot_flag = "@OSX_SYSROOT_FLAG@"
Index: test/lit.common.cfg
===================================================================
--- test/lit.common.cfg
+++ test/lit.common.cfg
@@ -7,6 +7,7 @@
 import platform
 import re
 import subprocess
+import json
 
 import lit.formats
 import lit.util
@@ -104,17 +105,31 @@
   config.substitutions.append( ('%run', config.emulator) )
   config.substitutions.append( ('%env ', "env ") )
   config.compile_wrapper = ""
-elif config.ios:
+elif config.host_os == 'Darwin' and config.apple_platform != "osx":
+  ios_or_iossim = "iossim" if config.apple_platform.endswith("sim") else "ios"
+
   config.available_features.add('ios')
-  device_id_env = "SANITIZER_IOSSIM_TEST_DEVICE_IDENTIFIER" if config.iossim else "SANITIZER_IOS_TEST_DEVICE_IDENTIFIER"
-  if device_id_env in os.environ: config.environment[device_id_env] = os.environ[device_id_env]
+  if ios_or_iossim == "iossim":
+    config.available_features.add('iossim')
+  if config.apple_platform != "ios":
+    config.available_features.add(config.apple_platform)
+
   ios_commands_dir = os.path.join(config.compiler_rt_src_root, "test", "sanitizer_common", "ios_commands")
-  run_wrapper = os.path.join(ios_commands_dir, "iossim_run.py" if config.iossim else "ios_run.py")
+
+  device_id_env = "SANITIZER_" + ios_or_iossim.upper() + "_TEST_DEVICE_IDENTIFIER"
+  run_wrapper = os.path.join(ios_commands_dir, ios_or_iossim + "_run.py")
+  env_wrapper = os.path.join(ios_commands_dir, ios_or_iossim + "_env.py")
+  compile_wrapper = os.path.join(ios_commands_dir, ios_or_iossim + "_compile.py")
+  prepare_script = os.path.join(ios_commands_dir, ios_or_iossim + "_prepare.py")
+
+  if device_id_env in os.environ: config.environment[device_id_env] = os.environ[device_id_env]
   config.substitutions.append(('%run', run_wrapper))
-  env_wrapper = os.path.join(ios_commands_dir, "iossim_env.py" if config.iossim else "ios_env.py")
   config.substitutions.append(('%env ', env_wrapper + " "))
-  compile_wrapper = os.path.join(ios_commands_dir, "iossim_compile.py" if config.iossim else "ios_compile.py")
   config.compile_wrapper = compile_wrapper
+
+  prepare_output_json = subprocess.check_output([prepare_script, config.apple_platform, config.clang]).strip().split("\n")[-1]
+  prepare_output = json.loads(prepare_output_json)
+  config.environment.update(prepare_output["env"])
 elif config.android:
   config.available_features.add('android')
   compile_wrapper = os.path.join(config.compiler_rt_src_root, "test", "sanitizer_common", "android_commands", "android_compile.py") + " "
@@ -202,7 +217,7 @@
 
   config.substitutions.append( ("%macos_min_target_10_11", "-mmacosx-version-min=10.11") )
 
-  isIOS = getattr(config, 'ios', False)
+  isIOS = config.apple_platform != "osx"
   # rdar://problem/22207160
   config.substitutions.append( ("%darwin_min_target_with_full_runtime_arc_support",
       "-miphoneos-version-min=9.0" if isIOS else "-mmacosx-version-min=10.11") )
@@ -304,7 +319,7 @@
 # The current implementation of the tools in sanitizer_common/ios_comamnds
 # do not support parallel execution so force sequential execution of the
 # tests on iOS devices.
-if config.host_os == 'Darwin' and config.ios and not config.iossim:
+if config.host_os == 'Darwin' and config.apple_platform != "osx" and not config.apple_platform.endswith("sim"):
   lit_config.warning("iOS device test cases being run sequentially")
   lit_config.parallelism_groups["darwin-ios-device-sanitizer"] = 1
 
Index: test/lit.common.configured.in
===================================================================
--- test/lit.common.configured.in
+++ test/lit.common.configured.in
@@ -26,8 +26,7 @@
 set_default("compiler_rt_libdir", "@COMPILER_RT_RESOLVED_LIBRARY_OUTPUT_DIR@")
 set_default("emulator", "@COMPILER_RT_EMULATOR@")
 set_default("asan_shadow_scale", "@COMPILER_RT_ASAN_SHADOW_SCALE@")
-set_default("ios", False)
-set_default("iossim", False)
+set_default("apple_platform", None)
 set_default("sanitizer_can_use_cxxabi", @SANITIZER_CAN_USE_CXXABI_PYBOOL@)
 set_default("has_lld", @COMPILER_RT_HAS_LLD_PYBOOL@)
 set_default("can_symbolize", @CAN_SYMBOLIZE@)
Index: test/sanitizer_common/ios_commands/iossim_prepare.py
===================================================================
--- test/sanitizer_common/ios_commands/iossim_prepare.py
+++ test/sanitizer_common/ios_commands/iossim_prepare.py
@@ -0,0 +1,5 @@
+#!/usr/bin/python
+
+import os, sys, subprocess, json
+
+print(json.dumps({"env": {}}))
Index: test/tsan/CMakeLists.txt
===================================================================
--- test/tsan/CMakeLists.txt
+++ test/tsan/CMakeLists.txt
@@ -24,10 +24,7 @@
 endif()
 
 foreach(arch ${TSAN_TEST_ARCH})
-  set(TSAN_TEST_IOS "0")
-  pythonize_bool(TSAN_TEST_IOS)
-  set(TSAN_TEST_IOSSIM "0")
-  pythonize_bool(TSAN_TEST_IOSSIM)
+  set(TSAN_TEST_APPLE_PLATFORM "osx")
 
   set(TSAN_TEST_TARGET_ARCH ${arch})
   string(TOLOWER "-${arch}" TSAN_TEST_CONFIG_SUFFIX)
@@ -51,15 +48,12 @@
   set(EXCLUDE_FROM_ALL ON)
 
   set(TSAN_TEST_TARGET_CC ${COMPILER_RT_TEST_COMPILER})
-  set(TSAN_TEST_IOS "1")
-  pythonize_bool(TSAN_TEST_IOS)
 
+  set(TSAN_TEST_APPLE_PLATFORM "iossim")
   set(arch "x86_64")
-  set(TSAN_TEST_IOSSIM "1")
-  pythonize_bool(TSAN_TEST_IOSSIM)
   set(TSAN_TEST_TARGET_ARCH ${arch})
   set(TSAN_TEST_TARGET_CFLAGS "-arch ${arch} -isysroot ${DARWIN_iossim_SYSROOT} ${COMPILER_RT_TEST_COMPILER_CFLAGS}")
-  set(TSAN_TEST_CONFIG_SUFFIX "-${arch}-iossim")
+  set(TSAN_TEST_CONFIG_SUFFIX "-${arch}-${TSAN_TEST_APPLE_PLATFORM}")
   string(TOUPPER ${arch} ARCH_UPPER_CASE)
   set(CONFIG_NAME "IOSSim${ARCH_UPPER_CASE}Config")
   configure_lit_site_cfg(
@@ -70,12 +64,11 @@
     ${CMAKE_CURRENT_BINARY_DIR}/${CONFIG_NAME}/
     DEPENDS ${TSAN_TEST_DEPS})
 
+  set(TSAN_TEST_APPLE_PLATFORM "ios")
   set(arch "arm64")
-  set(TSAN_TEST_IOSSIM "0")
-  pythonize_bool(TSAN_TEST_IOSSIM)
   set(TSAN_TEST_TARGET_ARCH ${arch})
   set(TSAN_TEST_TARGET_CFLAGS "-arch ${arch} -isysroot ${DARWIN_ios_SYSROOT} ${COMPILER_RT_TEST_COMPILER_CFLAGS}")
-  set(TSAN_TEST_CONFIG_SUFFIX "-${arch}-ios")
+  set(TSAN_TEST_CONFIG_SUFFIX "-${arch}-${TSAN_TEST_APPLE_PLATFORM}")
   string(TOUPPER ${arch} ARCH_UPPER_CASE)
   set(CONFIG_NAME "IOS${ARCH_UPPER_CASE}Config")
   configure_lit_site_cfg(
Index: test/tsan/lit.cfg
===================================================================
--- test/tsan/lit.cfg
+++ test/tsan/lit.cfg
@@ -88,5 +88,5 @@
 if config.host_os == 'Darwin':
   if config.target_arch in ["x86_64", "x86_64h"]:
     config.parallelism_group = "darwin-64bit-sanitizer"
-  elif config.ios and not config.iossim:
+  elif config.apple_platform != "osx" and not config.apple_platform.endswith("sim"):
     config.parallelism_group = "darwin-ios-device-sanitizer"
Index: test/tsan/lit.site.cfg.in
===================================================================
--- test/tsan/lit.site.cfg.in
+++ test/tsan/lit.site.cfg.in
@@ -3,8 +3,7 @@
 config.name_suffix = "@TSAN_TEST_CONFIG_SUFFIX@"
 config.tsan_lit_source_dir = "@TSAN_LIT_SOURCE_DIR@"
 config.has_libcxx = @TSAN_HAS_LIBCXX@
-config.ios = @TSAN_TEST_IOS_PYBOOL@
-config.iossim = @TSAN_TEST_IOSSIM_PYBOOL@
+config.apple_platform = "@TSAN_TEST_APPLE_PLATFORM@"
 config.target_cflags = "@TSAN_TEST_TARGET_CFLAGS@"
 config.target_arch = "@TSAN_TEST_TARGET_ARCH@"