With the default "nor" constraint, current GCC will use the "o"
constraint for constants, after emitting the constant to memory. That
results in unparseable Systemtap probe notes such as "-4@.L1052".
Removing the "o" alternative and using "nr" instead avoids this.
(cherry picked from commit f1ac7455831546e5dca0ed98fe8af2686fae7ce6)
Florian Weimer