Tracepoint enhancements

[Michael Snyder]

Jakob Engblom wrote:
>>> If by checkpoint you mean "some point inside the execution of a single
> program"
>>> this is also a nice fit with simulators (and I presume VmWare as well, if we
>> use
>>> its snapshotting ability for this).  I think this is a very good idea that
>> works
>>> very well with a smart remote target.
>> Yes, that's what I meant.  A "point in time" in the execution
>> history, something that could be represented eg. by a cycle count
>> or instruction count, rather than just by a PC.
> 
> I think that is a bad idea to assume there is only one time or one instruction
> count in the target. It could be a multicore target with lots of CPUs running
> around... so let the backend handle that in a symbolic way rather than assume
> anything about what it means. 

Right, OK.  But it was a mental assumption rather than an
implementation assumption.

I think the idea we're both getting at is that a checkpoint
represents a machine state.  If there are multiple machines,
that complicates the picture -- but basically gdb is saying
to the target "I want to be able to return to the state that
you are in *right now*".