If the qualifying branch predicate is 1, the branch is taken and several other actions occur:
The current values of the Current Frame Marker (CFM), the EC application register and the current privilege level are saved in the Previous Function State application register.
The caller's stack frame is effectively saved and the callee is provided with a frame containing only the caller's output region.
The rotation rename base registers in the CFM are reset to 0.
A return link value is placed in BR b1.