Designs for better debug info in GCC

[Robert Dewar]

Alexandre Oliva wrote:

> Yep.  Sometimes code just is optimized away.  Can't stop that without
> harming optimizations.

OK, so you are agreeing that good debuggability is impossible
with all the optimizations in place, so once again, let's have
an optimziation level that optimizes as far as possible without
harming debuggability.
> 
> If dwarf line number programs were smarter, we could perhaps encode
> multiple lines for the same instruction, along with conditions to tell
> when the instruction applies to such or such lines, and even more
> fancy stuff like that.  But line number programs don't let us express
> this in Dwarf3.

So, that's not an option.