Lower the select instruction when the operands are of vector type.

src/IceTargetLoweringX8632.h

Index: src/IceTargetLoweringX8632.h
diff --git a/src/IceTargetLoweringX8632.h b/src/IceTargetLoweringX8632.h
index 4c0c24521bac4a4720d108dccedc4c98c1406237..fed7d31739a3ca48be8546ef4c701e6b32d719a4 100644
--- a/src/IceTargetLoweringX8632.h
+++ b/src/IceTargetLoweringX8632.h
@@ -300,6 +300,9 @@ protected:
   void _pand(Variable *Dest, Operand *Src0) {
     Context.insert(InstX8632Pand::create(Func, Dest, Src0));
   }
+  void _pandn(Variable *Dest, Operand *Src0) {
+    Context.insert(InstX8632Pandn::create(Func, Dest, Src0));
+  }
   void _pcmpeq(Variable *Dest, Operand *Src0) {
     Context.insert(InstX8632Pcmpeq::create(Func, Dest, Src0));
   }