[11u] RFR: 8248901: Signed immediate support in .../share/assembler.hpp is broken.memory chain

[Doerr, Martin]

Hi,

JDK-8248901 is backported to 11.0.11-oracle. I'd like to backport it for parity.
Change applies cleanly, but precond macro is missing in 11u. I've taken it from JDK-8223140 (http://hg.openjdk.java.net/jdk/jdk/rev/6b77693eda6a).

Bug:
https://bugs.openjdk.java.net/browse/JDK-8248901

Original change:
https://hg.openjdk.java.net/jdk/jdk/rev/ce8fb40c9174

Clean 11u backport with added precond and postcond macros:
http://cr.openjdk.java.net/~mdoerr/8248901_assembler_11u/webrev.00/

Please review.

Best regards,
Martin