Re: [tree-ssa] Debugging information issue.

[Jan Hubicka <hubicka at ucw dot cz>]

> 
> 
> On Thu, 25 Mar 2004, Andrew MacLeod wrote:
> 
> >
> >
> > It has been brought up before, but I'm about to make it more of an
> > issue.
> >
> > We need a way to associate a variable for debugging purposes with a
> > different variable.
> >
> > A simplistic example is when we make a temporary variable T.5 which we
> > happen to know is really the value of variable 'a', it would be nice if
> > the debugger knew this too, and could report the value of T.5 when asked
> > for 'a'.
> >
> >
> > Its pretty trivial for me to mark 'a.1' as really being 'a' when I
> > create it, but I am not aware of a way to communicate that to the debug
> > generator.
> >
> > I was thinking we could put an optional debug_info decl node on decls.
> > When we go to generate debug info, we could simply use relevant part of
> > the debug_decl instead of the real decl when its present.
> >
> I suggested exactly that in a bug on debug info + tree-ssa, after
> mentioning it on IRC (Diego told me to throw it on the bug). The bug
> number eludes me at the moment.
> 
> It seems to be the right thing to do. It's effectively a multimap of
> aliases to the original variables, which is what we want.
> 
> For dwarf2, we can probably generate tree-level location lists with this
> info with a little work, or *something*.
> 
> Certainly, we shouldn't need more info that this to generate the debug
> info, AFAIK.

We ought to be able to work out proper debug info for scalarized
structures and arrays.  I guess that doing equivalent of current
REG_ATTRS for the tree-ssa temporaries and passing the info down to RTL
land would do the trick.

Honza
> --Dan