[8u] RFR 8160748: Inconsistent types for ideal_reg

[Kevin Walls]

Hi,

I'd like to get a review of this backport from 10 to 8u:

8160748: Inconsistent types for ideal_reg
JBS: https://bugs.openjdk.java.net/browse/JDK-8160748

Backporting this fixes a compile time error when testing a later compiler on Windows (e.g. VS2017).

10 changeset: http://hg.openjdk.java.net/jdk10/jdk10/hotspot/rev/d0f9cd0ff128

10 review thread:
http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2016-July/023705.html

This largely imports.  Various copyright dates don't import, also these files don't exist in the jdk8u-dev repo:
src/cpu/aarch64/vm/aarch64.ad
src/cpu/arm/vm/arm.ad
src/cpu/s390/vm/s390.ad

Also:
src/share/vm/opto/reg_split.cpp:
get_spillcopy_wide is different (assert) so didn't patch automatically

src/share/vm/opto/coalesce.cpp:
In 8u we don't have the same calls to m->ideal_reg() which use the result in an assert message, so they don't apply.

Proposed 8u change: http://cr.openjdk.java.net/~kevinw/8160748/webrev.00/

Many thanks
Kevin