URGENT: RFR: [BACKOUT] fix for JDK-8166188

[Daniel D. Daugherty]

Greetings,

Sending this backout code review to the same aliases used for:

     JDK-8166188 G1 Needs pre barrier on dereference of weak JNI handles
     https://bugs.openjdk.java.net/browse/JDK-8166188

more as a heads up that JDK-8166188 might be getting backed out.

I only need reviews from Kim and Jesper.

Doing a contingent backout of Kim's fix for the above due to some
unexpected test failures with some JDK tests:

JDK-8175085 8166188 causes JDK test failures
https://bugs.openjdk.java.net/browse/JDK-8175085

JDK-8175086 [BACKOUT] fix for JDK-8166188
https://bugs.openjdk.java.net/browse/JDK-8175086


Webrev URL: http://cr.openjdk.java.net/~dcubed/8175086-webrev/0-jdk9-hs/


I used "hg backout 3bc68ff68250" which created a child
changeset of Kim's:

changeset:   12639:3bc68ff68250
user:        kbarrett
date:        Wed Feb 15 22:19:13 2017 -0500
summary:     8166188: G1 Needs pre barrier on dereference of weak JNI 
handles

The backout changeset:

changeset:   12644:ee34d6aabf5f
parent:      12639:3bc68ff68250
user:        dcubed
date:        Thu Feb 16 10:41:19 2017 -0800
summary:     8175086: [BACKOUT] fix for JDK-8166188

and then I used "hg merge" to merge with current tip.
This was a "branch" merge with no conflicts.


Sanity checks:

- The parent of Kim's changeset is:

   changeset:   12638:35db0413819a
   user:        roland
   date:        Wed Feb 15 17:26:37 2017 -0800
   summary:     8174164: SafePointNode::_replaced_nodes breaks with 
irreducible loops

- hg diff -r 35db0413819a -r ee34d6aabf5f

   shows no output so the backout is clean.

- $ wc -l files.list
       37 files.list

- $ hg diff -r 35db0413819a -r tip `cat files.list`

   shows no output so the merge with the tip is clean.

Thanks, in advance, for reviews from Jesper and Kim!!

Dan