To debug micro-processor code it is desirable to provide trace functionality. A call trace involves providing the target of every call instruction and return instruction. This provides basic program flow data to the user for program analysis.
A branch trace involves providing the target of every branch instruction in addition to the calls and returns. This provides detail to the user for program analysis.
In addition to call and branch data, it is desirable to provide context switch and interrupt data for user. For a context switch, it is desirable to provide the context number.
The mechanism for obtaining this data on a standard microprocessor is to instrument the customer's code, libraries, etc. Problems with this approach include the fact that code is modified in order to capture the data necessary for the analysis.
Some micro-processors provide a trace feature that does not have a performance overhead. Such micro-processors require a dedicated trace interface on the micro-processor chip and a dedicated hardware tool connected to the micro-processor any time the trace function is to be used.