RFR(XS): 8027626: assert(Opcode() != Op_If || outcnt() == 2) failed: bad if #1

[Krystal Mok]

Hi guys,

Do you have a regression test case that can show the bug and show the fix
works?
I noticed the replay file in the bug report, but a runnable test case (not
just replaying) would give me a better sense. Thanks!

Best regards,
Kris

On Mon, Jan 5, 2015 at 1:33 PM, Roland Westrelin <
roland.westrelin at oracle.com> wrote:

> Hi Vladimir,
>
> Thanks for looking at this.
>
> > I think correct fix will be eager dead 12212 If node elimination when
> 12214 is replaced by 18733. Keep it connected to graph can cause problems
> in other places.
>
> IfFalseNode::Identity() is what optimizes 12212/12214 out. Should I make
> it an Ideal transformation so that I can call igvn->remove_dead_node() on
> the dead branch?
>
> Roland.
>
> >
> > Thanks,
> > Vladimir
> >
> > On 1/5/15 7:48 AM, Roland Westrelin wrote:
> >> http://cr.openjdk.java.net/~roland/8027626/webrev.00/
> >>
> >> The following subgraph is where the bug shows up:
> >>
> >> If (18732)
> >> |     \
> >> IfTrue IfFalse
> >> (18734) (18733)
> >> | |
> >> | If (12212)
> >> | |     \
> >> | IfFalse IfTrue
> >> | (12214)
> >> | |
> >> Region (12183)
> >>
> >> Condition to 12212 is always false so 12214 is replaced by 18733 and
> both branches of If 18732 are directly connected to Region 12183. 18733
> still has dead 12212 as output.
> >> 12183 doesn't have phis so when it's transformed, If 18732 is
> considered for removal. IfTrue 18734 doesn't have uses anymore so it goes
> away but IfFalse 18733 still has some (dead branch 12212 is not yet
> removed).
> >> An If in the dead branch 12212 is processed. Range check smearing
> follows dominator controls until 18733, tests whether the If is a range
> check and the assert fires because the If only has one projection.
> >>
> >> So we’re trying to optimize a dead branch. I fixed it by making the
> range check code more robust.
> >>
> >> Roland.
> >>
>
>
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