[8u/9] RFR (S): 8154831: CastII/ConvI2L for a range check is prematurely eliminated

[Vladimir Ivanov]

Thanks, Vladimir.

>>> Why CastIINode::cmp() returns uint?
>>
>> That's how Node::cmp() is declared:
>>
>>   virtual uint cmp( const Node &n ) const;
>
> Please files starter RFE to fix it. I looked and result us used as bool.

Done: https://bugs.openjdk.java.net/browse/JDK-8157372

Best regards,
Vladimir Ivanov


>>> On 5/19/16 10:45 AM, Vladimir Ivanov wrote:
>>>> http://cr.openjdk.java.net/~vlivanov/8154831/webrev.9.00/
>>>> http://cr.openjdk.java.net/~vlivanov/8154831/webrev.8u.00/
>>>> https://bugs.openjdk.java.net/browse/JDK-8154831
>>>>
>>>> CastII node prematurely goes away and causes a cascade of other
>>>> eliminations which severely corrupts the graph (the actual crash
>>>> happens
>>>> due to a memory edge coming from a non-dominating region).
>>>>
>>>> CastII is replaced with TOP due to a type conflict (ranges don't
>>>> intersect) between the actual type of the value being range checked and
>>>> the type CastII tries to assign.
>>>>
>>>> It happens on effectively dead path (range check always fails) which C2
>>>> can't eliminate due to a missing transformation for CmpU:
>>>>
>>>>    Bool [lt] (CmpU (ConI #-1) (… #int)) => (ConI #0)
>>>>
>>>> The fix is to add the missing case in CmpUNode::sub(). It enables dead
>>>> path elimination along with CastII.
>>>>
>>>> Also, fixed a couple of missing cases in 8u (not applicable in 9):
>>>>   * CastII nodes shouldn't be eliminated during CCP pass;
>>>>   * CastII comparion should take _range_check_dependency flag into
>>>> account.
>>>>
>>>> Testing:
>>>>   * JPRT (8u/9);
>>>>   * RBT for 9 (hs-tier0-comp - in progress);
>>>>   * replay of problematic compilation (8u).
>>>>
>>>> Thanks!
>>>>
>>>> Best regards,
>>>> Vladimir Ivanov