[Bug debug/54796] [4.8 Regression] Non-addressable stack parameter debug quality regression

["aoliva at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54796

--- Comment #4 from Alexandre Oliva <aoliva at gcc dot gnu.org> 2012-10-08 14:37:53 UTC ---
I'm a bit uncomfortable with this approach.  On the one hand, it's quite
simple, which is nice, but if all we get from it is the base term, we'll still
have trouble given multiple sp-based non-overlapping memory regions, won't we? 
The patch in revision 188871 and others in that batch were meant to let alias
analysis within vta figure out the relationship between argp, fp and sp and
disambiguate accesses.  I wonder why it didn't work in this case, with or
without the still-pending patch to canonicalize stack pointer tracking.  I'd
rather go with the latter (even if with additional changes) because it would
enable alias analysis, through more precise sp+offset tracking, to distinguish
not only between argp and sp-based variables, but also between automatic
varying-sized objects.  Assuming my understanding of your patch is correct in
that it adds information on whether some object is at an sp-relative offset but
without making the offset available to alias analysis.  Is that so?