RFR: 8287555: Tighten G1 G1BlockOffsetTable::block_start() code [v6]

[Thomas Schatzl]

> Hi all,
> 
>   can I have reviews for this change that specializes `G1BlockOffsetTablePart::block_size` with a variant used for card aligned addresses including some cleanup of comments? This saves some unnecessary lookup of the block size of the object found as for refinement the start address is always aligned.
> 
> Testing: tier1, gha
> 
> Thanks,
>   Thomas

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

  Improve merge, remove unneeded declarations

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9059/files
  - new: https://git.openjdk.org/jdk/pull/9059/files/4666123e..ecda6c96

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9059&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9059&range=04-05

  Stats: 9 lines in 1 file changed: 3 ins; 6 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/9059.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9059/head:pull/9059

PR: https://git.openjdk.org/jdk/pull/9059