diff --git a/test/MC/Disassembler/X86/simple-tests.txt b/test/MC/Disassembler/X86/simple-tests.txt
index f1bdf145d77..ab4efe85ec9 100644
--- a/test/MC/Disassembler/X86/simple-tests.txt
+++ b/test/MC/Disassembler/X86/simple-tests.txt
@@ -96,3 +96,6 @@
 
 # CHECK: vcvtsd2si %xmm0, %rax
 0xc4 0xe1 0xfb 0x2d 0xc0
+
+# CHECK: vmaskmovpd %xmm0, %xmm1, (%rax)
+0xc4 0xe2 0x71 0x2f 0x00
diff --git a/utils/TableGen/X86RecognizableInstr.cpp b/utils/TableGen/X86RecognizableInstr.cpp
index 2604d42090a..1b37aa8fe84 100644
--- a/utils/TableGen/X86RecognizableInstr.cpp
+++ b/utils/TableGen/X86RecognizableInstr.cpp
@@ -623,20 +623,43 @@ void RecognizableInstr::emitInstructionSpecifier(DisassemblerTables &tables) {
   case X86Local::MRMDestReg:
     // Operand 1 is a register operand in the R/M field.
     // Operand 2 is a register operand in the Reg/Opcode field.
+    // - In AVX, there is a register operand in the VEX.vvvv field here -
     // Operand 3 (optional) is an immediate.
-    assert(numPhysicalOperands >= 2 && numPhysicalOperands <= 3 &&
-           "Unexpected number of operands for MRMDestRegFrm");
+    if (HasVEX_4VPrefix)
+      assert(numPhysicalOperands >= 3 && numPhysicalOperands <= 4 &&
+             "Unexpected number of operands for MRMDestRegFrm with VEX_4V");
+    else
+      assert(numPhysicalOperands >= 2 && numPhysicalOperands <= 3 &&
+             "Unexpected number of operands for MRMDestRegFrm");
+  
     HANDLE_OPERAND(rmRegister)
+
+    if (HasVEX_4VPrefix)
+      // FIXME: In AVX, the register below becomes the one encoded
+      // in ModRMVEX and the one above the one in the VEX.VVVV field
+      HANDLE_OPERAND(vvvvRegister)
+          
     HANDLE_OPERAND(roRegister)
     HANDLE_OPTIONAL(immediate)
     break;
   case X86Local::MRMDestMem:
     // Operand 1 is a memory operand (possibly SIB-extended)
     // Operand 2 is a register operand in the Reg/Opcode field.
+    // - In AVX, there is a register operand in the VEX.vvvv field here -
     // Operand 3 (optional) is an immediate.
-    assert(numPhysicalOperands >= 2 && numPhysicalOperands <= 3 &&
-           "Unexpected number of operands for MRMDestMemFrm");
+    if (HasVEX_4VPrefix)
+      assert(numPhysicalOperands >= 3 && numPhysicalOperands <= 4 &&
+             "Unexpected number of operands for MRMDestMemFrm with VEX_4V");
+    else
+      assert(numPhysicalOperands >= 2 && numPhysicalOperands <= 3 &&
+             "Unexpected number of operands for MRMDestMemFrm");
     HANDLE_OPERAND(memory)
+
+    if (HasVEX_4VPrefix)
+      // FIXME: In AVX, the register below becomes the one encoded
+      // in ModRMVEX and the one above the one in the VEX.VVVV field
+      HANDLE_OPERAND(vvvvRegister)
+          
     HANDLE_OPERAND(roRegister)
     HANDLE_OPTIONAL(immediate)
     break;