RFR: 8193567: Conversion of comparison nodes affects local slots in optimistic continuation

[Hannes Wallnöfer]

Please review:

Bug: https://bugs.openjdk.java.net/browse/JDK-8193567
Webrev: http://cr.openjdk.java.net/~hannesw/8193567/webrev.00/

I’ve tried finding a smaller fix like just tagging the child nodes of all comparisons as non-optimistic, but that didn't fix the problem as those nodes could still have optimistic children.

Hannes