Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -57,8 +57,17 @@
          ${LLVM_INCLUDE_TESTS})
  option(COMPILER_RT_ENABLE_WERROR "Fail and stop if warning is triggered"
         ${LLVM_ENABLE_WERROR})
-  # Use just-built Clang to compile/link tests.
-  set(COMPILER_RT_TEST_COMPILER ${LLVM_RUNTIME_OUTPUT_INTDIR}/clang)
+  # Use just-built Clang to compile/link tests on all platforms, except for
+  # Windows where we need to use clang-cl instead.
+  if(NOT MSVC)
+    set(COMPILER_RT_TEST_COMPILER ${LLVM_RUNTIME_OUTPUT_INTDIR}/clang)
+    set(COMPILER_RT_TEST_COMPILER_EXE "-o")
+    set(COMPILER_RT_TEST_COMPILER_OUT "-o")
+  else()
+    set(COMPILER_RT_TEST_COMPILER ${LLVM_RUNTIME_OUTPUT_INTDIR}/clang-cl.exe)
+    set(COMPILER_RT_TEST_COMPILER_EXE "-Fe")
+    set(COMPILER_RT_TEST_COMPILER_OUT "-Fo")
+  endif()
 else()
   # Take output dir and install path from the user.
   set(COMPILER_RT_OUTPUT_DIR ${CMAKE_CURRENT_BINARY_DIR} CACHE PATH
Index: cmake/Modules/AddCompilerRT.cmake
===================================================================
--- cmake/Modules/AddCompilerRT.cmake
+++ cmake/Modules/AddCompilerRT.cmake
@@ -136,7 +136,8 @@
     list(APPEND TEST_DEPS clang)
   endif()
   add_custom_target(${test_name}
-    COMMAND ${COMPILER_RT_TEST_COMPILER} ${TEST_OBJECTS} -o "${output_bin}"
+    COMMAND ${COMPILER_RT_TEST_COMPILER} ${TEST_OBJECTS}
+            ${COMPILER_RT_TEST_COMPILER_EXE}"${output_bin}"
             ${TEST_LINK_FLAGS}
     DEPENDS ${TEST_DEPS})
   # Make the test suite depend on the binary.
Index: cmake/Modules/CompilerRTCompile.cmake
===================================================================
--- cmake/Modules/CompilerRTCompile.cmake
+++ cmake/Modules/CompilerRTCompile.cmake
@@ -23,7 +23,8 @@
   set(compile_flags ${global_flags} ${SOURCE_CFLAGS})
   add_custom_command(
     OUTPUT ${object_file}
-    COMMAND ${COMPILER_RT_TEST_COMPILER} ${compile_flags} -c -o "${object_file}"
+    COMMAND ${COMPILER_RT_TEST_COMPILER} ${compile_flags} -c
+            ${COMPILER_RT_TEST_COMPILER_OUT}"${object_file}"
             ${source_rpath}
     MAIN_DEPENDENCY ${source}
     DEPENDS ${SOURCE_DEPS})