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From: "amacleod at redhat dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/102943] [12 Regression] Jump threader
 compile-time hog with 521.wrf_r
Date: Thu, 10 Mar 2022 14:36:02 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102943

--- Comment #46 from Andrew Macleod <amacleod at redhat dot com> ---
(In reply to Richard Biener from comment #44)
> (In reply to Richard Biener from comment #43)
> > (In reply to Andrew Macleod from comment #42)
> > > (In reply to Richard Biener from comment #37)
> > > > I'm looking at range_def_chain::m_def_chain, it's use is well obfus=
cated by
> > > > inheritance but comments suggest that we have one such structure ei=
ther for
> > > > each edge in the CFG or for each basic-block.  In particular this
> > >=20
> > > There is one structure per ssa-name globally.
> > [...]=20
> > > so its just O(ssa-name) already.
> >=20
> > so you mean O(num-ssa-names^2) since if it exists for each SSA name then
> > we have m_def_chain (of length num-ssa-names) for each SSA name?  That's
> > what I originally feared, but I failed to find the array(?) that stores
> > the range_def_chains.
>=20
> That is, I wondered what's the lifetime of the gori_compute : gori_map :
> range_def_chain object(s), where they are allocated and/or freed and
> maintained.  I've seen m_bitmaps in range_def_chain which should be
> of longer lifetime (maybe) for example.


They all live and die as one with ranger.

A gimple ranger object has a single ranger_cache:
    ranger_cache m_cache;
Which is constructed when ranger is created, and the cache has a single
gori_computer object:
  gori_compute m_gori;

So they all have identical lifetimes.=