[Bug tree-optimization/79958] Missed tree DSE

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79958

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2017-03-10
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
First thing I notice (but unrelated to this bug) is that domwalk walks
non-optimally when walking in postdom order (all the tricks to use a RPO
dom order only were implemented for dominator walks).

Here the issue is that the walk over immediate uses of VDEFs finds two
stmts, one in the EH region and one in the fallthru block.  For simplicity
(cost reasons) we do not look for uses in more than one block (yeah, the
code is _really_ simple...).