fix bug in codegen when we modified move instruction instead of text.
fix bug in codegen when we modified move instruction instead
of text.

R=rsc
APPROVED=rsc
DELTA=3  (1 added, 2 deleted, 0 changed)
OCL=31575
CL=31575

firebitsbr/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,wesolows/golang,wesolows/golang,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang-old,wesolows/golang,wesolows/golang,wesolows/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang