Call Sequence

. Caller evaluates the actual parameters

. Caller stores return address and other values (control link) into callee's activation record

. Callee saves register values and other status information

. Callee initializes its local data and begins execution

The fields whose sizes are fixed early are placed in the middle. The decision of whether or not to use the control and access links is part of the design of the compiler, so these fields can be fixed at compiler construction time. If exactly the same amount of machine-status information is saved for each activation, then the same code can do the saving and restoring for all activations. The size of temporaries may not be known to the front end. Temporaries needed by the procedure may be reduced by careful code generation or optimization. This field is shown after that for the local data. The caller usually evaluates the parameters and communicates them to the activation record of the callee. In the runtime stack, the activation record of the caller is just below that for the callee. The fields for parameters and a potential return value are placed next to the activation record of the caller. The caller can then access these fields using offsets from the end of its own activation record. In particular, there is no reason for the caller to know about the local data or temporaries of the callee.