diff --git a/llvm/CMakeLists.txt b/llvm/CMakeLists.txt
--- a/llvm/CMakeLists.txt
+++ b/llvm/CMakeLists.txt
@@ -514,6 +514,19 @@
   set(LLVM_LIT_TOOLS_DIR "" CACHE PATH "Path to GnuWin32 tools")
 endif()
 
+set(LLVM_INTEGRATED_CRT_ALLOC "" CACHE PATH "Replace the Windows CRT allocator with any of {rpmalloc|mimalloc|snmalloc}. Only works with /MT enabled.")
+if(LLVM_INTEGRATED_CRT_ALLOC)
+  if(NOT WIN32)
+    message(FATAL_ERROR "LLVM_INTEGRATED_CRT_ALLOC is only supported on Windows.")
+  endif()
+  if(LLVM_USE_SANITIZER)
+    message(FATAL_ERROR "LLVM_INTEGRATED_CRT_ALLOC cannot be used along with LLVM_USE_SANITIZER!")
+  endif()
+  if(CMAKE_BUILD_TYPE AND uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG")
+    message(FATAL_ERROR "The Debug target isn't supported along with LLVM_INTEGRATED_CRT_ALLOC!")
+  endif()
+endif()
+
 # Define options to control the inclusion and default build behavior for
 # components which may not strictly be necessary (tools, examples, and tests).
 #
@@ -567,19 +580,6 @@
 option (LLVM_VERSION_PRINTER_SHOW_HOST_TARGET_INFO
   "Show target and host info when tools are invoked with --version." ON)
 
-option(LLVM_INTEGRATED_CRT_ALLOC "Replace the Windows CRT allocator with any of {rpmalloc|mimalloc|snmalloc}. Only works with /MT enabled." OFF)
-if(LLVM_INTEGRATED_CRT_ALLOC)
-  if(NOT WIN32)
-    message(FATAL_ERROR "LLVM_INTEGRATED_CRT_ALLOC is only supported on Windows.")
-  endif()
-  if(LLVM_USE_SANITIZER)
-    message(FATAL_ERROR "LLVM_INTEGRATED_CRT_ALLOC cannot be used along with LLVM_USE_SANITIZER!")
-  endif()
-  if(CMAKE_BUILD_TYPE AND uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG")
-    message(FATAL_ERROR "The Debug target isn't supported along with LLVM_INTEGRATED_CRT_ALLOC!")
-  endif()
-endif()
-
 # You can configure which libraries from LLVM you want to include in the
 # shared library by setting LLVM_DYLIB_COMPONENTS to a semi-colon delimited
 # list of LLVM components. All component names handled by llvm-config are valid.