diff --git a/llvm/lib/Target/X86/X86.td b/llvm/lib/Target/X86/X86.td
--- a/llvm/lib/Target/X86/X86.td
+++ b/llvm/lib/Target/X86/X86.td
@@ -378,7 +378,8 @@
     : SubtargetFeature<
           "tagged-globals", "AllowTaggedGlobals", "true",
           "Use an instruction sequence for taking the address of a global "
-          "that allows a memory tag in the upper address bits.">;
+          "that allows a memory tag in the upper address bits. Currently "
+          "also requires -mrelax-relocations=no to work properly.">;
 
 //===----------------------------------------------------------------------===//
 // X86 Subtarget Tuning features