Re: [PATCH] Update source location for PRE inserted stmt

[Diego Novillo <dnovillo at google dot com>]

On 2012-11-05 06:54 , Eric Botcazou wrote:
> > Those compiler generated statements do not have source origins, but
> > they need to have debug location information attached so that
> > information collected for them can be correlated with program
> > constructs (such as CFG). One of the natural way is to use the source
> > location associated with the program point where they are inserted.
>
> No, there is nothing natural (and this can even be wrong).  The statements
> must have the source location corresponding to the source construct they are
> generated for, which may be totally different from that of the insertion
> point.  Yes, that can generate jumpiness in GDB, but this is far better that
> breaking the coverage info by giving the same source location to instructions
> that have different coverage status.

But UNKNOWN_LOCATION is effectively wrong as well.  If other 
optimizations move the statements above the inserted instruction, then 
the new instruction ends up inheriting whatever location happens to be 
in the previous statement.

Fixing the location when the statement is inserted will reduce this 
randomness.  I'm not sure I understand why you think this will break 
coverage.  The examples given in this thread were helped by this 
location fixing.

Do you have any counterexample?  I may be missing something here.


Thanks.  Diego.