diff --git a/lib/Target/X86/X86CallingConv.td b/lib/Target/X86/X86CallingConv.td
index ea01d1ead1e..f548af75fdc 100644
--- a/lib/Target/X86/X86CallingConv.td
+++ b/lib/Target/X86/X86CallingConv.td
@@ -101,7 +101,7 @@ def CC_X86_64_C : CallingConv<[
   CCIfType<[f32, f64, v16i8, v8i16, v4i32, v2i64, v4f32, v2f64],
               CCAssignToReg<[XMM0, XMM1, XMM2, XMM3, XMM4, XMM5, XMM6, XMM7]>>,
 
-  // The first 8 MMX vector arguments are passed in MMX registers.
+  // The first 8 MMX vector arguments are passed in GPRs.
   CCIfType<[v8i8, v4i16, v2i32, v1i64],
               CCAssignToReg<[RDI, RSI, RDX, RCX, R8 , R9 ]>>,