diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt
index b8db3ab94e1..5789754439a 100644
--- a/lib/Target/X86/README.txt
+++ b/lib/Target/X86/README.txt
@@ -702,3 +702,5 @@ L2:
 Smells like a register coallescing/reassociation issue.
 
 //===---------------------------------------------------------------------===//
+
+Use cpuid to auto-detect CPU features such as SSE, SSE2, and SSE3.