RFR: [11u] 8217368: AArch64: C2 recursive stack locking optimisation not triggered

[Andrew Dinn]

Could I please have a review for this backport to jdk11u-dev.

  webrev: http://cr.openjdk.java.net/~adinn/8217368-jdk11u/webrev.00/

  upstream patch: http://hg.openjdk.java.net/jdk/jdk/rev/cb43e14dc68b

The original patch does not apply cleanly for two reasons:

1) The upstream change was applied on top of changes included from

  JDK-8210381: Obsolete EmitSync

which has not been backported (for good reason -- it affects generic and
arch-specific code). Where appropriate the modified patch interleaves
the upstream changes into branches protected by tests of EmitSync that
are still present in jdk11u but no longer present upstream.

2) The upstream change includes a modification to LockUnlock.java in the
micro test suite extending that test so it exercises this patch. This
part of the change set has been omitted because the micro test suite has
not been backported to jdk11u (again for good reason).

Testing:
tier1 tests succeed as before

regards,


Andrew Dinn
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