RFR: 8252311: AArch64: save two words in itable lookup stub

[Boris Ulasevich]

The change was reviewed on hotspot-compiler-dev, but I missed the time to complete
the commit to the mercural repo. Can I get it approved once again?

Issue: [JDK-8252311](https://bugs.openjdk.java.net/browse/JDK-8252311)

Description:
The interface method lookup stub becomes hot when interface calls
are performed frequently. The stub assembly code can be made
shorter (132->124 bytes) by using a pre-increment instruction variant.

Review by Andrew Dinn && Andrew Haley:
http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2020-September/039818.html
http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2020-September/039833.html

For the reference, benchmark scores with higher iteration number:
Neoverse                              Cnt   Score     Error  ->    Score   Error   Units
InvokeInterface.bench                  25  6163.804 ±  5.116 -> 6303.035 ± 5.450  ops/ms
InvokeInterface.bench:L1-icache-loads   5   305.408 ±  1.895 ->  272.891 ± 0.750    #/op
InvokeInterface.bench:iTLB-loads        5   221.755 ±  0.990 ->  207.635 ± 0.566    #/op
InvokeInterface.bench:instructions      5  1035.468 ±  2.701 ->  953.466 ± 1.667    #/op

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Commit messages:
 - 8252311: AArch64: save two words in itable lookup stub

Changes: https://git.openjdk.java.net/jdk/pull/189/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=189&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8252311
  Stats: 24 lines in 1 file changed: 5 ins; 10 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/189.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/189/head:pull/189

PR: https://git.openjdk.java.net/jdk/pull/189