RFR: 8329096: G1: Change the type of G1BlockOffsetTable::_offset_base to uint8_t*

[Guoxiong Li]

Hi all,

This patch changes the type of `G1BlockOffsetTable::_offset_base` to `uint8_t*`, just like `SerialBlockOffsetSharedArray::_offset_base` and `ObjectStartArray::_offset_base`. The tests `make test-tier1_gc` passed locally.

Thanks for taking the time to review.

Best Regards,
-- Guoxiong

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Commit messages:
 - JDK-8329096

Changes: https://git.openjdk.org/jdk/pull/18502/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18502&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8329096
  Stats: 50 lines in 3 files changed: 0 ins; 1 del; 49 mod
  Patch: https://git.openjdk.org/jdk/pull/18502.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18502/head:pull/18502

PR: https://git.openjdk.org/jdk/pull/18502