The CMPconstload opcodes take a ValAndOff as their AuxInt, not just
an offset.

Originally introduced in CL 135379.

Change-Id: I244b2d56ef2e99d2975faa2e97f4291ec97c64b7
Reviewed-on: https://go-review.googlesource.com/135418
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ilya Tocar <ilya.tocar@intel.com>