[Bug tree-optimization/23384] Clobber list should be flow sensitive

[Bug tree-optimization/23384] Clobber list should be flow sensitive

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23384

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |patrick at parcs dot ath.cx

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
*** Bug 59690 has been marked as a duplicate of this bug. ***

[Bug tree-optimization/23384] escaped set should be flow sensitive

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23384

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Clobber list should be flow |escaped set should be flow
                   |sensitive                   |sensitive

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Note implementing a flow-sensitive ESCAPED set is not really possible within
the current framework.  Note that all memory operations are not flow-sensitive,
so

int *global;

int kk(void)
{
  int j;
  j = 1;
  g ();
  j += 2;
  global = &j;
}

will still cause g() to clobber j as far as points-to analysis is concerned
(the write to 'global' is not flow-sensitive).

"Trivial" optimization can avoid refering to ESCAPED in the first basic-block
as long as nothing could have been possibly escaped yet.  But that's a hack.

[Bug tree-optimization/23384] escaped set should be flow sensitive

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23384

--- Comment #6 from Steven Bosscher <steven at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #5)

Would it be possible to compute ESCAPED per basic block as a local set,
compute transitive closure over the CFG, and use that information when
constructing the points-to graph?

[Bug tree-optimization/23384] escaped set should be flow sensitive

[rguenther at suse dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23384

--- Comment #7 from rguenther at suse dot de <rguenther at suse dot de> ---
On Tue, 7 Jan 2014, steven at gcc dot gnu.org wrote:

> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23384
> 
> --- Comment #6 from Steven Bosscher <steven at gcc dot gnu.org> ---
> (In reply to Richard Biener from comment #5)
> 
> Would it be possible to compute ESCAPED per basic block as a local set,
> compute transitive closure over the CFG, and use that information when
> constructing the points-to graph?

Well, ESCAPED is computed by solving the points-to graph ... also
"transitive closing" over the CFG isn't easily possible without
doing a full points-to graph solving.

I think more flow-sensitivity asks for a entirely different algorithm
(or - just a weird quick idea - marking constraints with a "flow"
version, and during solving only consider "older" edges/constraints
and only when that converged bump the "age" of the solving process.
that's probably equivalent to incrementally building / solving the
points-to graph for all SESE regions in a dominator order)

[Bug tree-optimization/23384] escaped set should be flow sensitive

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=23384

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jhaberman at gmail dot com

--- Comment #11 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
*** Bug 108217 has been marked as a duplicate of this bug. ***