diff --git a/lib/Target/X86/X86InstrInfo.td b/lib/Target/X86/X86InstrInfo.td
index 88f3b09c8e5..86e102e1d1a 100644
--- a/lib/Target/X86/X86InstrInfo.td
+++ b/lib/Target/X86/X86InstrInfo.td
@@ -261,7 +261,7 @@ def extloadi32i16  : PatFrag<(ops node:$ptr), (i32 (extloadi16 node:$ptr))>;
 // ADJCALLSTACKDOWN/UP implicitly use/def ESP because they may be expanded into
 // a stack adjustment and the codegen must know that they may modify the stack
 // pointer before prolog-epilog rewriting occurs.
-// Pessimisively assume ADJCALLSTACKDOWN / ADJCALLSTACKUP will become sub / add
+// Pessimistically assume ADJCALLSTACKDOWN / ADJCALLSTACKUP will become sub / add
 // which can clobber EFLAGS.
 let Defs = [ESP, EFLAGS], Uses = [ESP] in {
 def ADJCALLSTACKDOWN : I<0, Pseudo, (outs), (ins i32imm:$amt), "#ADJCALLSTACKDOWN",