[Bug preprocessor/53525] Performance regression due to enabling track-macro-expansion

["jimis at gmx dot net" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53525

--- Comment #7 from jimis <jimis at gmx dot net> 2012-05-30 06:01:23 UTC ---
Now time for the most intrusive and problematic patches. I tried moving all
virt_locs, expanded, expanded_virt_locs to obstacks for allocation. After many
failures to work with obstacks as they are I had to introduce two new
functions, obstack_{mark,release}(), that allow me to continue growing an older
object by pushing and popping a special marker.

Previous patches are included with the following, but I'm submitting it
separately because it's WIP. Even though it is now stable, there is a bad
memory leak that I don't know how to handle since I'm kind of lost in the
macro-expansion code. I'd appreciate suggestions, just search for LEAK or TODO
in my comments. :-p

Please ignore whitespace changes (that are highlighted by emacs so I fix them)
or stylistic changes in parts that I rewrote so many times that lost completely
their initial style.