[TableGen,X86] Add NDEBUG check to a variable initialization that's only used by asserts. NFC

llvm-svn: 261188

llvm/utils/TableGen/X86RecognizableInstr.cpp

@@ -561,6 +561,7 @@ void RecognizableInstr::emitInstructionSpecifier() {
   // physicalOperandIndex should always be < numPhysicalOperands
   unsigned physicalOperandIndex = 0;
 
+#ifndef NDEBUG
   // Given the set of prefix bits, how many additional operands does the
   // instruction have?
   unsigned additionalOperands = 0;
@@ -568,6 +569,7 @@ void RecognizableInstr::emitInstructionSpecifier() {
     ++additionalOperands;
   if (HasEVEX_K)
     ++additionalOperands;
+#endif
 
   switch (Form) {
   default: llvm_unreachable("Unhandled form");