RFR (M) 8042786: Proper fix for 8032566

[John Rose]

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".

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.

— John