RFR: 8213415: BitMap::word_index_round_up overflow problems

[Thomas Schatzl]

Hi Kim,

On 27.11.19 01:39, Kim Barrett wrote:
>> On Jun 11, 2019, at 12:42 PM, Kim Barrett <kim.barrett at oracle.com> wrote:
>>
>>> On Jun 10, 2019, at 9:14 PM, Kim Barrett <kim.barrett at oracle.com> wrote:
>>> new webrevs:
>>> full: http://cr.openjdk.java.net/~kbarrett/8213415/open.01/
>>> incr: http://cr.openjdk.java.net/~kbarrett/8213415/open.01.inc/
>>
>> Stefan and I have been talking about this offline.  We have some ideas for further changes in
>> a slightly different direction, so no point in anyone else reviewing the open.01 changes right now
>> (or maybe ever).
> 
> Finally returning to this.  Stefan Karlsson and Thomas Shatzl had some
> offline feedback on earlier versions that led to some rethinking and
> rework.  This included an attempt to be a little more consistent with
> nomenclature.  There are still some lingering naming issues, which
> might be worth fixing some other time.
> 
> The basic approach hasn't changed though.  From the original RFR:
> 
> Constructing a BitMap now ensures the size is such that rounding it up
> to a word boundary won't overflow.  This is the new max_size_in_bits()
> value. This lets us add some asserts and otherwise tidy things up in
> some places by making use of that information.
> 
> This engendered some changes to ParallelGC's ParMarkBitMap.  It no
> longer uses the obsolete BitMap::word_align_up, instead having its own
> internal helper for aligning range ends that knows about invariants in
> ParMarkBitMap.
> 
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8213415
> 
> New webrev:
> http://cr.openjdk.java.net/~kbarrett/8213415/open.03/
> 

   lgtm.

Thanks,
   Thomas