Do not reuse temp registers originally allocated to a subroutine within

Do not reuse temp registers originally allocated to a subroutine within
the main body of the program logic, since if the subroutine is called
while the reused temp registers are in use, their values will get clobbered.
Candidate fix for ticket [3a77c9714e63330]

FossilOrigin-Name: 092d53315e50be42b51ef7b3069c82c32a129b6a