diff --git a/llvm/cmake/modules/HandleLLVMOptions.cmake b/llvm/cmake/modules/HandleLLVMOptions.cmake
index 45b4d3278cb3..30d0cd774f49 100644
--- a/llvm/cmake/modules/HandleLLVMOptions.cmake
+++ b/llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -243,7 +243,7 @@ if( MSVC )
   if( MSVC11 )
     add_llvm_definitions(-D_VARIADIC_MAX=10)
   endif()
-  
+
   # Add definitions that make MSVC much less annoying.
   add_llvm_definitions(
     # For some reason MS wants to deprecate a bunch of standard functions...
@@ -253,7 +253,9 @@ if( MSVC )
     -D_CRT_NONSTDC_NO_WARNINGS
     -D_SCL_SECURE_NO_DEPRECATE
     -D_SCL_SECURE_NO_WARNINGS
+    )
 
+  set(msvc_warning_flags
     # Disabled warnings.
     -wd4146 # Suppress 'unary minus operator applied to unsigned type, result still unsigned'
     -wd4180 # Suppress 'qualifier applied to function type has no meaning; ignored'
@@ -272,7 +274,7 @@ if( MSVC )
     -wd4624 # Suppress ''derived class' : destructor could not be generated because a base class destructor is inaccessible'
     -wd4722 # Suppress 'function' : destructor never returns, potential memory leak
     -wd4800 # Suppress ''type' : forcing value to bool 'true' or 'false' (performance warning)'
-    
+
     # Promoted warnings.
     -w14062 # Promote 'enumerator in switch of enum is not handled' to level 1 warning.
 
@@ -282,14 +284,19 @@ if( MSVC )
 
   # Enable warnings
   if (LLVM_ENABLE_WARNINGS)
-    add_llvm_definitions( /W4 )
+    append("/W4" msvc_warning_flags)
     if (LLVM_ENABLE_PEDANTIC)
       # No MSVC equivalent available
     endif (LLVM_ENABLE_PEDANTIC)
   endif (LLVM_ENABLE_WARNINGS)
   if (LLVM_ENABLE_WERROR)
-    add_llvm_definitions( /WX )
+    append("/WX" msvc_warning_flags)
   endif (LLVM_ENABLE_WERROR)
+
+  foreach(flag ${msvc_warning_flags})
+    append("${flag}" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+  endforeach(flag)
+
 elseif( LLVM_COMPILER_IS_GCC_COMPATIBLE )
   if (LLVM_ENABLE_WARNINGS)
     append("-Wall -W -Wno-unused-parameter -Wwrite-strings" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)