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Re: Designs for better debug info in GCC
On Nov 24, 2007 4:00 PM, Alexandre Oliva <aoliva@redhat.com> wrote:
> On Nov 24, 2007, "Steven Bosscher" <stevenb.gcc@gmail.com> wrote:
>
> > And it has to handle this new case everywhere.
>
> I've already explained why this isn't true. It's not even close to
> being true. In fact, I've chosen this representation *precisely*
> because I reasoned it would lead to the least global impact. Of
> course you can refuse to believe that and point at the changes I had
> to make as alleged counter-proof, failing to notice how many other
> locations I haven't had to change and that just work because adjusting
> other instructions after transformations is precisely what all
> transformation passes already do.
It also makes some things easier - for example during inlining of a function
body we re-map all DECLs in the inlined copy. With an on-the-side
representation you have to ensure to make the same mapping explicitly,
with DEBUG_INSNs the mapping is automatically done during the copying
of the IL. A similar problem with using SSA_NAME definition points to
store information is using the renamer to rename a variable that already
has SSA_NAMES (which is IMHO bogus, as we do not detect the errorneous
case of overlapping life-ranges - but ignore that for now) - in this case you
need some magic to transfer the on-the-side debug information from the
old SSA_NAMEs to the new ones (where possible).
Just to mention a few problems we are running into ;)
Richard.