RFR: 8296155: Simplify CDS heap region address calculation

[Coleen Phillimore]

On Tue, 1 Nov 2022 21:43:17 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Rewrite and simplify the convoluted logic used to calculate the runtime location of a CDS heap region. Now it's as simple as:
>> 
>> 
>> FileMapRegion::dumptime_base() + ArchiveHeapLoader::runtime_delta();
>> 
>> 
>> See `FileMapInfo::heap_region_runtime_start_address` for an example.
>> 
>> Also removed dead code:
>> 
>> - `FileMapInfo::is_in_shared_region`
>> - `MetaspaceShared::is_in_shared_region`
>> - `FileMapInfo::stop_sharing_and_unmap`
>
> src/hotspot/share/cds/filemap.cpp line 1558:
> 
>> 1556:   _is_bitmap_region = (region_index == MetaspaceShared::bm);
>> 1557: 
>> 1558:   if (_is_heap_region) {
> 
> Explain please.  Only heap region has a non-null dumptime base?

ie add a comment here too.

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

PR: https://git.openjdk.org/jdk/pull/10923