Re: var-tracking bugfix

[Paolo Bonzini <paolo dot bonzini at lu dot unisi dot ch>]

> > The next Blackfin patch will add a call to split_all_insns from the
> > reorg pass.  split_all_insns calls verify_flow_info, and in 4.3 this
> > often aborts when debugging information is generated.  The var-tracking
> > pass can change basic block boundaries in such a way that a control flow
> > insn is no longer the last insn in a basic block, since a var tracking
> > note can replace it.
> >
> > Fixed with this patch which just slightly changes the way these notes
> > are emitted.  Bootstrapped and regression tested on i686-linux; I've
> > also compiled a large number of files with -g before and after the
> > change, the output was identical.  Committed as 119116.
>
> Could you explain this a little more?  If I read it right, then the
> var tracking note can move from one basic block to another because of
> this patch.  Seems like that would be a problem, or at least a lurking
> time bomb.

I think Daniel is right.  I think the note should be moved to all 
successors in this case, or not emitted at all?

Or possibly, verify_flow_info could allow notes after the last insn in a 
basic block?

Paolo