RFR: 8373114: Redundant MethodCounters in the preimage generated by training run

[Ashutosh Mehra]

Details are mentioned in the bug report and this mail thread https://mail.openjdk.org/pipermail/leyden-dev/2025-December/002843.html
After this patch the number of MethodCounters in the preimage are much less than before this patch. Also the number of MethodCounters in the preimage is the same as in the final AOTCache (these numbers are obtained using -Xlog:aot=trace).

Before this patch for the training run:

[18.610s][debug  ][aot         ]                         ro_cnt   ro_bytes     % |   rw_cnt   rw_bytes     % |  all_cnt  all_bytes     %
[18.610s][debug  ][aot         ] MethodCounters      :        0          0   0.0 |    22471    1438144   6.2 |    22471    1438144   2.6

Before this patch for the assembly phase:

[6.680s][debug][aot         ]                         ro_cnt   ro_bytes     % |   rw_cnt   rw_bytes     % |  all_cnt  all_bytes     %
[6.680s][debug][aot         ] MethodCounters      :        0          0   0.0 |     8588     549632   2.5 |     8588     549632   1.0


After this patch for the training run:

[49.371s][debug  ][aot         ]                         ro_cnt   ro_bytes     % |   rw_cnt   rw_bytes     % |  all_cnt  all_bytes     %
[49.371s][debug  ][aot         ] MethodTrainingData  :        0          0   0.0 |     4658     521696   2.1 |     4658     521696   0.9


After this patch for the assembly phase:

[12.580s][debug][aot         ]                         ro_cnt   ro_bytes     % |   rw_cnt   rw_bytes     % |  all_cnt  all_bytes     %
[12.580s][debug][aot         ] MethodTrainingData  :        0          0   0.0 |     4658     521696   2.1 |     4658     521696   0.9

-------------

Commit messages:
 - 8373114: Redundant MethodCounters in the preimage generated by training run

Changes: https://git.openjdk.org/jdk/pull/28670/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28670&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8373114
  Stats: 7 lines in 1 file changed: 0 ins; 6 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/28670.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28670/head:pull/28670

PR: https://git.openjdk.org/jdk/pull/28670