[x86] Fix unused variable warning in no-asserts build.

llvm-svn: 213989
diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
index 9fa171c..febf821 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -1000,6 +1000,7 @@
       const MachineConstantPoolEntry &MaskConstantEntry =
           Constants[MI->getOperand(5).getIndex()];
       Type *MaskTy = MaskConstantEntry.getType();
+      (void)MaskTy;
       if (!MaskConstantEntry.isMachineConstantPoolEntry())
         if (auto *C = dyn_cast<ConstantDataSequential>(
                 MaskConstantEntry.Val.ConstVal)) {