diff --git a/lib/Target/X86/X86InstrInfo.td b/lib/Target/X86/X86InstrInfo.td
index 4bb1a9550a9..657cec5149a 100644
--- a/lib/Target/X86/X86InstrInfo.td
+++ b/lib/Target/X86/X86InstrInfo.td
@@ -181,6 +181,13 @@ def REP_MOVSW : X86Inst<"rep movsw", 0xA5, RawFrm, NoArg>, REP, OpSize,
 def REP_MOVSD : X86Inst<"rep movsd", 0xA5, RawFrm, NoArg>, REP,
                 Imp<[ECX,EDI,ESI], [ECX,EDI,ESI]>;
 
+def REP_STOSB : X86Inst<"rep stosb", 0xAA, RawFrm, NoArg>, REP,
+                Imp<[ECX,EDI], [ECX,EDI]>;
+def REP_STOSW : X86Inst<"rep stosw", 0xAB, RawFrm, NoArg>, REP, OpSize,
+                Imp<[ECX,EDI], [ECX,EDI]>;
+def REP_STOSD : X86Inst<"rep stosd", 0xAB, RawFrm, NoArg>, REP,
+                Imp<[ECX,EDI], [ECX,EDI]>;
+
 //===----------------------------------------------------------------------===//
 //  Move Instructions...
 //