RFR: Backport of JDK-8209686: cleanup arguments to PhaseIdealLoop() constructor

[Roman Kennke]

Hi Aleksey,

>> The original patch applies cleanly on jdk11u-dev, except for some very
>> minor changes that I needed to make in loopnode.hpp because surrounding
>> comments/code did not match.
> 
> The changes are not in the code, though, right? I cannot spot any. I presume you just needed to
> reapply some hunks by hand?

Yes. I did hg transplant to transplant the original change and then
re-applied the changes. It didn't apply due to surrounding changes like
here:

     _dom_lca_tags(arena()), // Thread::resource_area
     _verify_me(NULL),
     _verify_only(true) {
-    build_and_optimize(false, false);
+    build_and_optimize(LoopOptsVerify);
   }


     _verify_me(NULL),
     _verify_only(true),
     _dom_lca_tags(arena()) { // Thread::resource_area
-    build_and_optimize(false, false);
+    build_and_optimize(LoopOptsVerify);
   }

I.e. the changed constructor args order.

>> Bug:
>> https://bugs.openjdk.java.net/browse/JDK-8209686
>> Webrev:
>> http://cr.openjdk.java.net/~rkennke/JDK-8209686-jdk11u/webrev.00/
>> Testing: tier1, tier2
> 
> The backport looks good.

Thanks for reviewing!
Roman