Index: llvm/trunk/cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- llvm/trunk/cmake/modules/HandleLLVMOptions.cmake
+++ llvm/trunk/cmake/modules/HandleLLVMOptions.cmake
@@ -224,6 +224,10 @@
   append_if(SUPPORTS_FVISIBILITY_INLINES_HIDDEN_FLAG "-fvisibility-inlines-hidden" CMAKE_CXX_FLAGS)
 endif()
 
+if(CMAKE_SIZEOF_VOID_P EQUAL 8 AND MINGW)
+  add_definitions( -D_FILE_OFFSET_BITS=64 )
+endif()
+
 if( CMAKE_SIZEOF_VOID_P EQUAL 8 AND NOT WIN32 )
   # TODO: support other platforms and toolchains.
   if( LLVM_BUILD_32_BITS )