Processor having a trace access instruction to access on-chip trace memory

摘要

A computer system includes a memory for storing instructions executable by a processor and an on-chip trace memory having a plurality of locations for storing trace information that indicates execution flow in the processor. A trace access instruction provides for access to the on-chip trace memory on the processor. The trace access instruction can be a write instruction or a read instruction. Typically, both read and write to the trace memory is provided. The system also has the capability to trace on start or restart of an executable thread by providing to the processor an indication of which executable thread to trace via a debug port. That indicates to the processor to provide trace information when the executable thread starts. When execution of the executable thread starts, the processor places an identifier corresponding to the executable thread into the trace memory to indicate that subsequent entries placed into the trace memory are part of said executable thread. The processor may also provide an entry indicating when the thread stops executing.