[Bug tree-optimization/44563] GCC uses a lot of RAM when compiling a large numbers of functions

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44563

--- Comment #14 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
Yeah, this is the old problem that after each inline we recompute the size of
the whole function inlined into. This means walking the whole inline tree and
sum size of all non-inlined call sites. If you get very many functions inlined
into single caller, the nonlinearity kicks in. Here the main() function calls
65536 empty functions that takes time to process.

My plan is to turn the sizes/times to sreal and then update them incrementally
(subtract size of the call statement and account changes). With old fixed
point+capping this did not work well and I always ended up with too many of
misaccounting issues.

This is however more intrussive then what I would like to do in stage3. I did
not completed the sreal conversion because sreal class came bit too late in
this development cycle. Have unfinished patch for that but it is >100K and hits
interestin problems like gengtype not understanding sreal.h header.

I will perf it and check for micro-optimization possibilities.