RFR: 8304144: G1: Remove unnecessary is_survivor check in G1ClearCardTableTask

[Thomas Schatzl]

On Tue, 14 Mar 2023 15:02:57 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Simple removing redundant check.
> 
> Test: tier1-6

Actually, after some re-reading of code this check is an optimization that should be kept.

The checks make sure to leave the `young` marks on the card table that were written when allocating a PLAB in survivor region (see `G1Allocator::survivor_attempt_allocation`).

I would request to either add a comment here or do not add survivor regions to the `_all_dirty_regions` somewhere else.

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

Changes requested by tschatzl (Reviewer).

PR: https://git.openjdk.org/jdk/pull/13023