RFR (M) 8042786: Proper fix for 8032566

Vladimir Kozlov vladimir.kozlov at oracle.com
Thu May 15 05:58:10 UTC 2014

Thank you, John

On 5/14/14 7:14 PM, John Rose wrote:
> On May 14, 2014, at 5:26 PM, Vladimir Kozlov <vladimir.kozlov at oracle.com> wrote:
>> http://cr.openjdk.java.net/~kvn/8042786/webrev/
>> https://bugs.openjdk.java.net/browse/JDK-8042786
>> 8032566 was fixed in jdk8 by disabling autobox elimination: -XX:-EliminateAutoBox.
>> This fix will undo that change and fix the problem. In jdk9 8032566 change was not applied before, I will push it first so that I could use the same 8042786 changeset for 8u backport.
> Nice change; reviewed.
> One comment:  Surely there are better ways to differentiate the lower-case versions of the identifiers "HI1" and "HIL" by relying on "1" vs "l".
> I suggest linking to prior "t1" as "t1_hi", "t1_lo".

Okay. It is t11_lo and t12_lo.

> This optimization might also be beneficial on some signed comparisons, notably (r1+r2)==0 where r1 and r2 are both [1..maxint].
> So I suggest doing a follow-up application to CmpI.

Agree, I will file RFE.

About subtraction of [minint, x] which is converted into addition of [-x, -minint]. The concern was because -minint == 
minint in 32-bit int. I think it is fine in 64-bit long arithmetic which I used to detect overflow.

What I missed is the overlap check (hi_r1 < lo_r2) for new type ranges. If they overlap we back to [minint, maxint] 
bottom type and can't do optimization.

I will fix it and repeat testing tomorrow and will send new webrev.

> — John


More information about the hotspot-compiler-dev mailing list