https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103551
Andrew Macleod <amacleod at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Assignee|unassigned at gcc dot gnu.org |amacleod at redhat dot
com
--- Comment #4 from Andrew Macleod <amacleod at redhat dot com> ---
Created attachment 51935
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51935&action=edit
proposed patch
It gets eliminated/folded by propagation in VRP2 because it shosws one edge as
being executable and the other not: (from *.169t.vect)
_35 = offset_13(D) + 65535;
if (_35 <= 6)
goto <bb 14>; [10.00%]
else
goto <bb 9>; [90.00%]
;; succ: 9 [90.0% (guessed)] count:94607391 (estimated locally)
(FALSE_VALUE,EXECUTABLE)
;; 14 [10.0% (guessed)] count:10511933 (estimated locally)
(TRUE_VALUE)
substitute_and_fold_dom_walker::before_dom_children keys off of:
if (gimple_code (stmt) == GIMPLE_COND)
{
if ((EDGE_SUCC (bb, 0)->flags & EDGE_EXECUTABLE)
^ (EDGE_SUCC (bb, 1)->flags & EDGE_EXECUTABLE))
And folds the IF away.
I see inconsistencies in the value of the executable flag. Im a little
confused, because this code using EDGE_EXECUTABLE is in
substitute_and_fold_dom_walker, and will fold away conditions like this, yet it
does not initialize the domwalker with REACHABLE_BLOCKS, so non of the edges
are set. The old VRP use to invoke set_all_edges_as_executable() itself,
ranger is currently only doing it when we run warn_array_bounds_p.
SO my questions are
1) are EDGE_EXECUTABLE flags allowed to be in garbage state outside the
propagation passes? I think the answer is yes?
2) If this code can always be triggered in substitute_and_fold, should it not
create the dom_walker class with REACHABLE_BLOCKS so that they are in a known
state before any pass triggers them?
3) if that is undesirable for some reason, then I could always set them in
ranger vrp set up, but (2) seems more rational to me.
I've attached a patch which does that... and seems to solve the problem. Is
this the direction to go?
