[11u] RFR: 8238812: assert(false) failed: bad AD file

[Doerr, Martin]

Hi,

JDK-8238812 is backported to 11.0.12-oracle. I'd like to backport it for parity.
It applies cleanly, but the test needs a small modification: StressIGVN is not available in 11u, so I had to remove it.

Bug:
https://bugs.openjdk.java.net/browse/JDK-8238812

Original change:
https://git.openjdk.java.net/jdk/commit/4b5be40a

11u backport:
http://cr.openjdk.java.net/~mdoerr/8238812_C2_bad_AD_11u/webrev.00/

Please review.

Best regards,
Martin