I ran a buildworld test that counted calls to vm_radix_lookup() and cycles spent in those calls, for for the original code and the code as modified by this change:
original
52562.781u 1460.546s 59:21.00 1517.0% 73473+3095k 121089+33149io 110813pf+0w
vm.radix.lookup_cycles: 52110657646
vm.radix.lookup_calls: 348966056
cycles/call: 149.32872911283957
modified:
52573.985u 1451.071s 59:17.72 1518.5% 73480+3095k 121022+33727io 110845pf+0w
vm.radix.lookup_cycles: 47328173864
vm.radix.lookup_calls: 348964777
cycles/call: 135.6245013347006
(/ 135.6245013347006 149.32872911283957)
0.9082277880515314