RFR: 8358568: C2 compilation hits "must have a monitor" assert with -XX:-GenerateSynchronizationCode [v4]

[hanguanqiang]

> This PR fixes JDK-8358568, a JVM crash triggered when running with -XX:-GenerateSynchronizationCode
> 
> Problem：
> When synchronization code generation is disabled by -XX:-GenerateSynchronizationCode, the compiler’s do_monitor_exit() method still tries to access monitor objects without checking if any monitors exist.This causes an assertion failure and JVM crash.
> 
> Root Cause：
> Parse::do_monitor_exit() calls shared_unlock() using monitor info unconditionally,but with GenerateSynchronizationCode disabled, no monitor info is available, leading to invalid access.
> 
> Fix
> Add a check in do_monitor_exit() to skip monitor unlocking if GenerateSynchronizationCode is false, avoiding invalid monitor access and preventing the crash.

hanguanqiang has updated the pull request incrementally with one additional commit since the last revision:

  Delete .gitpod.yml

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Changes:
  - all: https://git.openjdk.org/jdk/pull/26108/files
  - new: https://git.openjdk.org/jdk/pull/26108/files/d01533e1..1d6e8f5c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26108&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26108&range=02-03

  Stats: 10 lines in 1 file changed: 0 ins; 10 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/26108.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26108/head:pull/26108

PR: https://git.openjdk.org/jdk/pull/26108