RFR: Remove vestigial command line options and removed unused code

[Roman Kennke]

On Mon, 11 Oct 2021 18:40:00 GMT, William Kemper <wkemper at openjdk.org> wrote:

> * Removed ShenandoahUseSimpleCardScanning and ShenandoahPromoteTenuredRegions command line options
> * Removed preprocessor directives FAST_REMEMBERED_SET_SCANNING and CROSSING_OFFSETS_NO_LONGER_NEEDED

Looks good to me, with one very minor nit (and really your choice).

src/hotspot/share/gc/shenandoah/shenandoahScanRemembered.hpp line 541:

> 539:   ShenandoahCardCluster(RememberedSet *rs) {
> 540:     _rs = rs;
> 541:     // HEY!  We don't really need object_starts entries for every card entry.  We only need these for

Consider changing 'HEY!' to 'TODO' or something. IDEs tend to highlight the latter (mine does).

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Marked as reviewed by rkennke (Lead).

PR: https://git.openjdk.java.net/shenandoah/pull/85