[AMDGPU] Add isAsCheapAsAMove for v_pk_mov_b32

Author: shiltian

llvm/lib/Target/AMDGPU/VOP3PInstructions.td

@@ -1151,7 +1151,7 @@ let isCommutable = 1, isReMaterializable = 1 in {
     defm V_PK_ADD_F32 : VOP3PInst<"v_pk_add_f32", VOP3P_Profile<VOP_V2F32_V2F32_V2F32, VOP3_PACKED>, any_fadd>;
   } // End SubtargetPredicate = HasPackedFP32Ops
 
-  let SubtargetPredicate = HasPkMovB32 in
+  let SubtargetPredicate = HasPkMovB32, isAsCheapAsAMove = 1 in
   defm V_PK_MOV_B32 : VOP3PInst<"v_pk_mov_b32", VOP3P_Profile<VOP_V2I32_V2I32_V2I32, VOP3_PACKED>>;
 } // End isCommutable = 1, isReMaterializable = 1