[11] RFR(S): 8203196: C1 emits incorrect code due to integer overflow in _tableswitch keys

[Lindenmaier, Goetz]

Hi Tobias,

> Thanks! I've already verified with the failing JCK tests but additional testing is
> always good.
Sure, I assumed you tried the jck test. 
Our testsuite is green now, too.  Thanks a lot for fixing.

Best regards,
  Goetz.


> Best regards,
> Tobias
> 
> 
> >> -----Original Message-----
> >> From: hotspot-compiler-dev <hotspot-compiler-dev-
> >> bounces at openjdk.java.net> On Behalf Of Tobias Hartmann
> >> Sent: Friday, May 18, 2018 12:03 PM
> >> To: hotspot compiler <hotspot-compiler-dev at openjdk.java.net>
> >> Subject: [11] RFR(S): 8203196: C1 emits incorrect code due to integer
> >> overflow in _tableswitch keys
> >>
> >> Hi,
> >>
> >> please review the following patch:
> >> https://bugs.openjdk.java.net/browse/JDK-8203196
> >> http://cr.openjdk.java.net/~thartmann/8203196/webrev.00/
> >>
> >> C1 incorrectly compiles a _tableswitch instruction due to an integer
> overflow
> >> of x->hi_key() in
> >> Canonicalizer::do_TableSwitch():
> >>   0 0 i5 2147483647
> >> . 2 0 6 tableswitch i5
> >>                    case 2147483647: B1
> >>                    default : B2
> >> canonicalized to:
> >> . 2 0 7 goto B2
> >>
> >> We compute hi_key = _lo_key + length() - 1 = INT_MAX + (2 - 1) - 1 =
> >> INT_MAX + 1 - 1 which may
> >> overflow depending on how the C++ compiler translates it (fails with
> >> fastdebug, works with
> >> slowdebug). I've added parentheses and an assert for sanity checking.
> >>
> >> This problem was introduced by the fix for JDK-8200303. Before, we
> would
> >> use an if instead of a
> >> switch [1].
> >>
> >> Thanks,
> >> Tobias
> >>
> >> [1] http://hg.openjdk.java.net/jdk/jdk/rev/d84f06a0cae1#l3.8