Re: [PATCH][debug] Handle references to skipped params in remap_ssa_name

[Jakub Jelinek <jakub at redhat dot com>]

On Tue, Jul 24, 2018 at 12:29:37PM +0200, Tom de Vries wrote:
> > I wonder if it makes sense to disambiguate things from the gcc side
> > by generating an empty location description for known optimized out
> > values (the standard seems to explicitely call that out as a way to
> > say "optimized out").

You can't emit the empty location descriptions in the middle of other
expressions though, and if you have e.g. an expression that uses
DW_OP_GNU_variable_size only conditionally, even if you know that
the corresponding DIE doesn't have location, the containing DWARF expression
could still be well defined if the condition guarding the
DW_OP_GNU_variable_size isn't true.
And, also, for DW_OP_GNU_variable_size DIE lookup should be performed,
say you have only a declaration in the TU, but definition somewhere else,
in that case the debugger should be using that other TU's definition
with hopefully location description.  Or if there is a global variable
interposed by some other TU, again, DW_OP_GNU_variable_size should follow
to whatever variable wins.

	Jakub