[x86] Bypass the shuffle mask comment generation when not using verbose

asm. This can be somewhat expensive and there is no reason to do it
outside of tests or debugging sessions. I'm also likely to make it
significantly more expensive to support more styles of shuffles.

llvm-svn: 218362

llvm/lib/Target/X86/X86MCInstLower.cpp

@@ -1121,6 +1121,8 @@ void X86AsmPrinter::EmitInstruction(const MachineInstr *MI) {
   case X86::VPERMILPDrm:
   case X86::VPERMILPSYrm:
   case X86::VPERMILPDYrm: {
+    if (!OutStreamer.isVerboseAsm())
+      break;
     // All of these instructions accept a constant pool operand as their fifth.
     assert(MI->getNumOperands() > 5 &&
            "We should always have at least 5 operands!");