diff --git a/llvm/cmake/modules/HandleLLVMOptions.cmake b/llvm/cmake/modules/HandleLLVMOptions.cmake
index 964fa59c0bae..133e8ef3d8a1 100644
--- a/llvm/cmake/modules/HandleLLVMOptions.cmake
+++ b/llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -232,6 +232,13 @@ if(MSVC)
   set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} /STACK:10000000")
 elseif(MINGW) # FIXME: Also cygwin?
   set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,--stack,16777216")
+
+  # Pass -mbig-obj to mingw gas on Win64. COFF has a 2**16 section limit, and
+  # on Win64, every COMDAT function creates at least 3 sections: .text, .pdata,
+  # and .xdata.
+  if (CMAKE_SIZEOF_VOID_P EQUAL 8)
+    append("-Wa,-mbig-obj" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+  endif()
 endif()
 
 if( MSVC )