[8u] RFR + RFA: 8213419: "C2 may hang in MulLNode::Ideal()/MulINode::Ideal() with gcc 8.2.1" and follow up 8214206

[Roland Westrelin]

I'd like to backport 8213419 and follow up 8214206 to 8u as they can
cause c2 to enter an infinite loop in some corner cases when compiled
with a recent version of gcc.

Neither changes apply cleanly. In particular I dropped the
STATIC_ASSERT() from the globalDefinitions.hpp function. My
understanding is that keeping them requires a backport of 8181449: "Fix
debug.hpp / globalDefinitions.hpp dependency inversion", a big and
complicated change.

Webrevs:

http://cr.openjdk.java.net/~roland/8213419.8u/webrev.00/
http://cr.openjdk.java.net/~roland/8214206.8u/webrev.00/

Initial changes:

https://bugs.openjdk.java.net/browse/JDK-8213419
http://hg.openjdk.java.net/jdk/jdk/rev/1089e8fd8439

https://bugs.openjdk.java.net/browse/JDK-8214206
http://hg.openjdk.java.net/jdk/jdk/rev/7d3cde494494

Roland.