diff --git a/llvm/include/llvm/Target/Target.td b/llvm/include/llvm/Target/Target.td
index 98b41254fc7c..3ca7567b783e 100644
--- a/llvm/include/llvm/Target/Target.td
+++ b/llvm/include/llvm/Target/Target.td
@@ -290,6 +290,11 @@ class Operand<ValueType ty> {
   // ParserMatchClass - The "match class" that operands of this type fit
   // in. Match classes are used to define the order in which instructions are
   // match, to ensure that which instructions gets matched is deterministic.
+  //
+  // The target specific parser must be able to classify an parsed operand 
+  // into a unique class, which does not partially overlap with any other 
+  // classes. It can match a subset of some other class, in which case 
+  // ParserMatchSuperClass should be set to the name of that class.
   string ParserMatchClass = "Imm";
 
   // ParserMatchSuperClass - The enclosing super class for this operand (if
diff --git a/llvm/lib/Target/X86/X86Instr64bit.td b/llvm/lib/Target/X86/X86Instr64bit.td
index a4decbb93a2d..34a77282c9c1 100644
--- a/llvm/lib/Target/X86/X86Instr64bit.td
+++ b/llvm/lib/Target/X86/X86Instr64bit.td
@@ -33,12 +33,14 @@ def i64i8imm   : Operand<i64>;
 def lea64mem : Operand<i64> {
   let PrintMethod = "printlea64mem";
   let MIOperandInfo = (ops GR64, i8imm, GR64_NOSP, i32imm);
+  let ParserMatchClass = "Mem";
 }
 
 def lea64_32mem : Operand<i32> {
   let PrintMethod = "printlea64_32mem";
   let AsmOperandLowerMethod = "lower_lea64_32mem";
   let MIOperandInfo = (ops GR32, i8imm, GR32_NOSP, i32imm);
+  let ParserMatchClass = "Mem";
 }
 
 //===----------------------------------------------------------------------===//
diff --git a/llvm/lib/Target/X86/X86InstrSSE.td b/llvm/lib/Target/X86/X86InstrSSE.td
index fefdba096ab1..99d193c23c09 100644
--- a/llvm/lib/Target/X86/X86InstrSSE.td
+++ b/llvm/lib/Target/X86/X86InstrSSE.td
@@ -87,10 +87,12 @@ def sse_load_f64 : ComplexPattern<v2f64, 5, "SelectScalarSSELoad", [],
 def ssmem : Operand<v4f32> {
   let PrintMethod = "printf32mem";
   let MIOperandInfo = (ops ptr_rc, i8imm, ptr_rc_nosp, i32imm, i8imm);
+  let ParserMatchClass = "Mem";
 }
 def sdmem : Operand<v2f64> {
   let PrintMethod = "printf64mem";
   let MIOperandInfo = (ops ptr_rc, i8imm, ptr_rc_nosp, i32imm, i8imm);
+  let ParserMatchClass = "Mem";
 }
 
 //===----------------------------------------------------------------------===//