Index: compiler-rt/trunk/cmake/Modules/BuiltinTests.cmake
===================================================================
--- compiler-rt/trunk/cmake/Modules/BuiltinTests.cmake
+++ compiler-rt/trunk/cmake/Modules/BuiltinTests.cmake
@@ -0,0 +1,60 @@
+
+# This function takes an OS and a list of architectures and identifies the
+# subset of the architectures list that the installed toolchain can target.
+function(try_compile_only output)
+  set(SIMPLE_C ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/src.c)
+  file(WRITE ${SIMPLE_C} "int foo(int x, int y) { return x + y; }\n")
+  string(REGEX MATCHALL "<[A-Za-z0-9_]*>" substitutions
+         ${CMAKE_C_COMPILE_OBJECT})
+  string(REPLACE ";" " " extra_flags "${ARGN}")
+
+  set(test_compile_command "${CMAKE_C_COMPILE_OBJECT}")
+  foreach(substitution ${substitutions})
+    if(substitution STREQUAL "<CMAKE_C_COMPILER>")
+      string(REPLACE "<CMAKE_C_COMPILER>"
+             "${CMAKE_C_COMPILER}" test_compile_command ${test_compile_command})
+    elseif(substitution STREQUAL "<OBJECT>")
+      string(REPLACE "<OBJECT>"
+             "${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/test.o"
+             test_compile_command ${test_compile_command})
+    elseif(substitution STREQUAL "<SOURCE>")
+      string(REPLACE "<SOURCE>" "${SIMPLE_C}" test_compile_command
+             ${test_compile_command})
+    elseif(substitution STREQUAL "<FLAGS>")
+      string(REPLACE "<FLAGS>" "${CMAKE_C_FLAGS} ${extra_flags}"
+             test_compile_command ${test_compile_command})
+    else()
+      string(REPLACE "${substitution}" "" test_compile_command
+             ${test_compile_command})
+    endif()
+  endforeach()
+
+  string(REPLACE " " ";" test_compile_command "${test_compile_command}")
+
+  execute_process(
+    COMMAND ${test_compile_command}
+    RESULT_VARIABLE result
+    OUTPUT_VARIABLE TEST_OUTPUT
+    ERROR_VARIABLE TEST_ERROR
+  )
+  if(result EQUAL 0)
+    set(${output} True PARENT_SCOPE)
+  else()
+    file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
+        "Testing compiler for supporting " ${ARGN} ":\n"
+        "Command: ${test_compile_command}\n"
+        "${TEST_OUTPUT}\n${TEST_ERROR}\n${result}\n")
+    set(${output} False PARENT_SCOPE)
+  endif()
+endfunction()
+
+function(builtin_check_c_compiler_flag flag output)
+  message(STATUS "Performing Test ${output}")
+  try_compile_only(result ${flag})
+  set(${output} ${result} PARENT_SCOPE)
+  if(${result})
+    message(STATUS "Performing Test ${output} - Success")
+  else()
+    message(STATUS "Performing Test ${output} - Failed")
+  endif()
+endfunction()
Index: compiler-rt/trunk/cmake/Modules/CompilerRTDarwinUtils.cmake
===================================================================
--- compiler-rt/trunk/cmake/Modules/CompilerRTDarwinUtils.cmake
+++ compiler-rt/trunk/cmake/Modules/CompilerRTDarwinUtils.cmake
@@ -56,14 +56,16 @@
   endif()
 
   set(archs ${ARGN})
-  message(STATUS "Finding valid architectures for ${os}...")
-  set(SIMPLE_CPP ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/src.cpp)
-  file(WRITE ${SIMPLE_CPP} "#include <iostream>\nint main() { std::cout << std::endl; return 0; }\n")
-
-  set(os_linker_flags)
-  foreach(flag ${DARWIN_${os}_LINKFLAGS})
-    set(os_linker_flags "${os_linker_flags} ${flag}")
-  endforeach()
+  if(NOT TEST_COMPILE_ONLY)
+    message(STATUS "Finding valid architectures for ${os}...")
+    set(SIMPLE_CPP ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/src.cpp)
+    file(WRITE ${SIMPLE_CPP} "#include <iostream>\nint main() { std::cout << std::endl; return 0; }\n")
+  
+    set(os_linker_flags)
+    foreach(flag ${DARWIN_${os}_LINKFLAGS})
+      set(os_linker_flags "${os_linker_flags} ${flag}")
+    endforeach()
+  endif()
 
   # The simple program will build for x86_64h on the simulator because it is 
   # compatible with x86_64 libraries (mostly), but since x86_64h isn't actually
@@ -74,12 +76,16 @@
 
   set(working_archs)
   foreach(arch ${archs})
-    
+   
     set(arch_linker_flags "-arch ${arch} ${os_linker_flags}")
-    try_compile(CAN_TARGET_${os}_${arch} ${CMAKE_BINARY_DIR} ${SIMPLE_CPP}
-                COMPILE_DEFINITIONS "-v -arch ${arch}" ${DARWIN_${os}_CFLAGS}
-                CMAKE_FLAGS "-DCMAKE_EXE_LINKER_FLAGS=${arch_linker_flags}"
-                OUTPUT_VARIABLE TEST_OUTPUT)
+    if(TEST_COMPILE_ONLY)
+      try_compile_only(CAN_TARGET_${os}_${arch} -v -arch ${arch} ${DARWIN_${os}_CFLAGS})
+    else()
+      try_compile(CAN_TARGET_${os}_${arch} ${CMAKE_BINARY_DIR} ${SIMPLE_CPP}
+                  COMPILE_DEFINITIONS "-v -arch ${arch}" ${DARWIN_${os}_CFLAGS}
+                  CMAKE_FLAGS "-DCMAKE_EXE_LINKER_FLAGS=${arch_linker_flags}"
+                  OUTPUT_VARIABLE TEST_OUTPUT)
+    endif()
     if(${CAN_TARGET_${os}_${arch}})
       list(APPEND working_archs ${arch})
     else()
Index: compiler-rt/trunk/cmake/Modules/CompilerRTUtils.cmake
===================================================================
--- compiler-rt/trunk/cmake/Modules/CompilerRTUtils.cmake
+++ compiler-rt/trunk/cmake/Modules/CompilerRTUtils.cmake
@@ -114,6 +114,8 @@
   check_compile_definition("${def}" "${argstring}" HAS_${arch}_DEF)
   if(NOT HAS_${arch}_DEF)
     set(CAN_TARGET_${arch} FALSE)
+  elseif(TEST_COMPILE_ONLY)
+    try_compile_only(CAN_TARGET_${arch} ${TARGET_${arch}_CFLAGS})
   else()
     set(argstring "${CMAKE_EXE_LINKER_FLAGS} ${argstring}")
     try_compile(CAN_TARGET_${arch} ${CMAKE_BINARY_DIR} ${SIMPLE_SOURCE}