RFR: 8257423: [PPC64] Support -XX:-UseInlineCaches

[Martin Doerr]

The JVM currently runs into Unimplemented() when using -XX:-UseInlineCaches in C2 code (postalloc_expand_java_dynamic_call_sched).
I'd like to enable the existing code in postalloc_expand_java_dynamic_call_sched and fix MachCallDynamicJavaNode::ret_addr_offset() and MacroAssembler::instr_size_for_decode_klass_not_null().
I suggest to use scratch emit to determine the size, because there are too many cases and emitting it once is fast.

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Commit messages:
 - 8257423: [PPC64] Support -XX:-UseInlineCaches

Changes: https://git.openjdk.java.net/jdk/pull/1521/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1521&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8257423
  Stats: 31 lines in 2 files changed: 15 ins; 7 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1521.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1521/head:pull/1521

PR: https://git.openjdk.java.net/jdk/pull/1521