Re: [reverse RFA] no singlestep-over-BP in reverse

[Michael Snyder <msnyder at vmware dot com>]

Daniel Jacobowitz wrote:
> On Mon, Sep 15, 2008 at 11:31:33AM -0700, Michael Snyder wrote:
> > When we're stopped at a breakpoint and we want to
> > continue in reverse, we're not actually going to
> > execute the instruction at the breakpoint -- we're
> > going to de-execute the previous instruction.
> >
> > Therefore there's no need to singlestep before
> > inserting breakpoints.  In fact it would be a bad
> > idea to do so, because if there is a breakpoint at
> > the previous instruction, we WANT to hit it.
> >
> > Note that this patch is to be applied to the reverse branch.
>
> If there is a breakpoint on the previous instruction, will you hit it
> before or after de-executing that instruction? 

Well, if trap insns are in place, that's what will be
executed (not the shadow insn).

> It seems like this
> logic should be somehow still necessary... but I can't put my finger
> on when.

Good point -- there is a test in the testsuite for consecutive
breakpoints.  I'll try to reversify that.