RFR: 8205694: AArch64: Add test to validate volatile load, store and CAS code generation

[Andrew Dinn]

Reviews are welcome for the following webrev

  webrev: http://cr.openjdk.java.net/~adinn/8205694/webrev.00/
  JIRA: https://bugs.openjdk.java.net/browse/JDK-8205694

The patch:
----------

This AArch64-only patch adds tests to ensure that volatile load, store
and CAS operations are either:

  translated to correctly replace memory barriers with combinations of
acquiring loads and releasing

  left untransformed with all necessary memory barriers in place

The test requires a debug, aarch64 vm and is disabled if graal is being
used (debug is necessary because it relies on -XX:+PrintOptoAssembly to
provide evidence of what is in the compiler output).

The main driver test program creates subordinate JVMs to execute
subordinate programs which perform:

   normal and unsafe volatile loads,
   normal and unsafe volatile stores
   unsafe volatile CASes

in each of 5 GC configurations:

  G1
  CMS+CondCardMark
  CMS-CondCardMark
  Parallel
  Serial

Arguments -XXCompileCommand,compileonly and XX:+PrintOptoAssembly are
used to generate Assembly listings and the driver test program parses
these to ensure the correct sequences of instructions are generated
(including omitted memory barriers which are flagged in the output).

A few changes were made to the aarch64.ad file to ensure that the
PrintOptoAssembly output accurately represented the generated code.
These were necessary to ensure that the test could be sure that the
generated code sequences really were what was intended.

Also, some of the comments in aarch64.ad describing the code
transformation were updated following feedback from Zhongwei Yao that
arrived too late to get checked in with the fix for JDK-8204331.

Testing:
--------

The test itself passes when run on an AArch64 debug vm. It is ignored
when run on an AArch64 product vm.

No other testing is needed. Nothing significant in the aarch64.ad file
has been modified (only comments of format sequences which have been
exercised running the new test).

regards,


Andrew Dinn
-----------
Senior Principal Software Engineer
Red Hat UK Ltd
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