[master] RFR: 8303769: [Lilliput] Fix interpreter asymmetric fast-locking

[Roman Kennke]

Currently we get the asymmetric locking check in the interpreters wrong:

ldr(header_reg, Address(rthread, JavaThread::lock_stack_current_offset()));
cmpoop(header_reg, obj_reg);
br(Assembler::NE, slow_case);

The intention is to load the top of the lock-stack, and compare it to the unlocked object, and, if not equal, branch to the slow-path to handle it. However, what it really does is, it loads the *address* of the top of lock-stack, and compares that to the unlocked object. This can never succeed, and therefore we always call the slow-path. Additionally, the address is not the address of the topmost object, it is the address of the next free slot. What we really want to load is the element at -1 oop from that address. This is not incorrect, but it's unnecessarily slow.'

I've already pushed that fix to the upstream fast-locking PR https://github.com/openjdk/jdk/pull/10907

Testing:
 - [x] tier1 (x86_64, x86_32, aarch64)
 - [ ] tier2 (x86_64, x86_32, aarch64)

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Commit messages:
 - 8303769: [Lilliput] Fix interpreter asymmetric fast-locking

Changes: https://git.openjdk.org/lilliput/pull/76/files
 Webrev: https://webrevs.openjdk.org/?repo=lilliput&pr=76&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8303769
  Stats: 3 lines in 2 files changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/lilliput/pull/76.diff
  Fetch: git fetch https://git.openjdk.org/lilliput pull/76/head:pull/76

PR: https://git.openjdk.org/lilliput/pull/76