diff --git a/utils/TableGen/X86RecognizableInstr.cpp b/utils/TableGen/X86RecognizableInstr.cpp
index aa4f37b6cdb..6718e0d8001 100644
--- a/utils/TableGen/X86RecognizableInstr.cpp
+++ b/utils/TableGen/X86RecognizableInstr.cpp
@@ -541,6 +541,14 @@ void RecognizableInstr::emitInstructionSpecifier() {
   // physicalOperandIndex should always be < numPhysicalOperands
   unsigned physicalOperandIndex = 0;
 
+  // Given the set of prefix bits, how many additional operands does the
+  // instruction have?
+  unsigned additionalOperands = 0;
+  if (HasVEX_4V || HasVEX_4VOp3)
+    ++additionalOperands;
+  if (HasEVEX_K)
+    ++additionalOperands;
+
   switch (Form) {
   default: llvm_unreachable("Unhandled form");
   case X86Local::RawFrmSrc:
@@ -575,15 +583,13 @@ void RecognizableInstr::emitInstructionSpecifier() {
     break;
   case X86Local::MRMDestReg:
     // Operand 1 is a register operand in the R/M field.
+    // - In AVX512 there may be a mask operand here -
     // 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.
-    if (HasVEX_4V)
-      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");
+    assert(numPhysicalOperands >= 2 + additionalOperands &&
+           numPhysicalOperands <= 3 + additionalOperands &&
+           "Unexpected number of operands for MRMDestRegFrm");
 
     HANDLE_OPERAND(rmRegister)
 
@@ -600,12 +606,10 @@ void RecognizableInstr::emitInstructionSpecifier() {
     // 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.
-    if (HasVEX_4V)
-      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");
+    assert(numPhysicalOperands >= 2 + additionalOperands &&
+           numPhysicalOperands <= 3 + additionalOperands &&
+           "Unexpected number of operands for MRMDestMemFrm with VEX_4V");
+
     HANDLE_OPERAND(memory)
 
     if (HasEVEX_K)
@@ -626,12 +630,9 @@ void RecognizableInstr::emitInstructionSpecifier() {
     // Operand 3 (optional) is an immediate.
     // Operand 4 (optional) is an immediate.
 
-    if (HasVEX_4V || HasVEX_4VOp3)
-      assert(numPhysicalOperands >= 3 && numPhysicalOperands <= 5 &&
-             "Unexpected number of operands for MRMSrcRegFrm with VEX_4V");
-    else
-      assert(numPhysicalOperands >= 2 && numPhysicalOperands <= 4 &&
-             "Unexpected number of operands for MRMSrcRegFrm");
+    assert(numPhysicalOperands >= 2 + additionalOperands &&
+           numPhysicalOperands <= 4 + additionalOperands &&
+           "Unexpected number of operands for MRMSrcRegFrm");
 
     HANDLE_OPERAND(roRegister)
 
@@ -662,12 +663,9 @@ void RecognizableInstr::emitInstructionSpecifier() {
     // - In AVX, there is a register operand in the VEX.vvvv field here -
     // Operand 3 (optional) is an immediate.
 
-    if (HasVEX_4V || HasVEX_4VOp3)
-      assert(numPhysicalOperands >= 3 && numPhysicalOperands <= 5 &&
-             "Unexpected number of operands for MRMSrcMemFrm with VEX_4V");
-    else
-      assert(numPhysicalOperands >= 2 && numPhysicalOperands <= 3 &&
-             "Unexpected number of operands for MRMSrcMemFrm");
+    assert(numPhysicalOperands >= 2 + additionalOperands &&
+           numPhysicalOperands <= 4 + additionalOperands &&
+           "Unexpected number of operands for MRMSrcMemFrm");
 
     HANDLE_OPERAND(roRegister)
 
@@ -700,15 +698,13 @@ void RecognizableInstr::emitInstructionSpecifier() {
   case X86Local::MRM5r:
   case X86Local::MRM6r:
   case X86Local::MRM7r:
-    {
-      // Operand 1 is a register operand in the R/M field.
-      // Operand 2 (optional) is an immediate or relocation.
-      // Operand 3 (optional) is an immediate.
-      unsigned kOp = (HasEVEX_K) ? 1:0;
-      unsigned Op4v = (HasVEX_4V) ? 1:0;
-      if (numPhysicalOperands > 3 + kOp + Op4v)
-        llvm_unreachable("Unexpected number of operands for MRMnr");
-    }
+    // Operand 1 is a register operand in the R/M field.
+    // Operand 2 (optional) is an immediate or relocation.
+    // Operand 3 (optional) is an immediate.
+    assert(numPhysicalOperands >= 0 + additionalOperands &&
+           numPhysicalOperands <= 3 + additionalOperands &&
+           "Unexpected number of operands for MRMnr");
+
     if (HasVEX_4V)
       HANDLE_OPERAND(vvvvRegister)
 
@@ -727,15 +723,12 @@ void RecognizableInstr::emitInstructionSpecifier() {
   case X86Local::MRM5m:
   case X86Local::MRM6m:
   case X86Local::MRM7m:
-    {
-      // Operand 1 is a memory operand (possibly SIB-extended)
-      // Operand 2 (optional) is an immediate or relocation.
-      unsigned kOp = (HasEVEX_K) ? 1:0;
-      unsigned Op4v = (HasVEX_4V) ? 1:0;
-      if (numPhysicalOperands < 1 + kOp + Op4v ||
-          numPhysicalOperands > 2 + kOp + Op4v)
-        llvm_unreachable("Unexpected number of operands for MRMnm");
-    }
+    // Operand 1 is a memory operand (possibly SIB-extended)
+    // Operand 2 (optional) is an immediate or relocation.
+    assert(numPhysicalOperands >= 1 + additionalOperands &&
+           numPhysicalOperands <= 2 + additionalOperands &&
+           "Unexpected number of operands for MRMnm");
+
     if (HasVEX_4V)
       HANDLE_OPERAND(vvvvRegister)
     if (HasEVEX_K)