RFR: 8253049: Enhance itable_stub for AArch64 and x86_64 [v2]

[kuaiwei]

> Now itable_stub will go through instanceKlass's itable twice to look up a method entry. resolved klass is used for type
> checking and method holder klass is used to find method entry. In many cases , we observed resolved klass is as same as
> holder klass. So we can improve itable stub based on it. If they are same klass, stub uses a fast loop to check only
> one klass. If not, a slow loop is used to checking both klasses.  Even entering in slow loop, new implementation can be
> better than old one in some cases. Because new stub just need go through itable once and reduce memory operations.
> bug: https://bugs.openjdk.java.net/browse/JDK-8253049

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  8253049: Enhance itable_stub for AArch64 and x86_64

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/128/files
  - new: https://git.openjdk.java.net/jdk/pull/128/files/b2f12ccc..6d79d5ed

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=128&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=128&range=00-01

  Stats: 126 lines in 1 file changed: 126 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/128.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/128/head:pull/128

PR: https://git.openjdk.java.net/jdk/pull/128