[14] RFR(M): 8233033: Results of execution differ for C2 and C1/Xint

[Christian Hagedorn]

Hi Vladimir

On 28.11.19 10:46, Vladimir Ivanov wrote:
>> This bug can also be reproduced with JDK 11. Should we target this fix 
>> to 14 or defer it to 15 (since it's a more complex one)?
> 
> Silently producing erroneous code is a more serious issue than a JVM 
> crash (either during compilation or while executing generated code). 
> Instead of just shutting down the process, it silently continues running 
> and can stay unnoticed for a long time. Also, it makes it hard estimate 
> the impact.
> 
> If we aren't confident in the stability of the fix, then it's worth 
> considering implementing a stop-the-gap solution first (detect 
> problematic code shape and either avoid the transformation or even bail 
> out the compilation) while continue working on a proper fix.
> 
> But we should try our best to fix the problematic behavior in a prompt 
> manner (in 14 and backported to 11).

Thanks for the explanation. That sounds reasonable.

> PS: please, update bug synopsis with a summary of the problem.

I added a more precise description and changed the bug summary from
"Results of execution differ for C2 and C1/Xint" into "C2 produces wrong 
result while unswitching a loop due to lost control dependencies"

Best regards,
Christian