RFR: 8225779: Remove unused CollectedHeap::cell_header_size()

[David Holmes]

Thanks for clarifying.

Cheers,
David

On 14/06/2019 4:56 pm, Per Liden wrote:
> Hi,
> 
> On 6/14/19 8:45 AM, David Holmes wrote:
>> Hi Per,
>>
>> On 14/06/2019 4:29 pm, Per Liden wrote:
>>> CollectedHeap::cell_header_size() is no longer used and can be removed. 
>>
>> It seems no longer used simply because you are removing the uses. :)
> 
> Sorry, I should have been more clear. There are no longer any GC that 
> overrides cell_header_size(). Shenandoah used to do that, but doesn't 
> anymore.
> 
>>
>>> This patch is a hg backout of [1] where it was introduced, plus the 
>>> two followup bug fixes [2] & [3].
>>
>> Can you explain why you are rolling back:
>>
>> "8213199: GC abstraction for Assembler::needs_explicit_null_check()"
>>
>> ? Does Shenandoah no longer need it so we can just return to the 
>> simpler code that existed before?
> 
> Exactly. Back when this was introduced, there were discussions about 
> making "cell" and "cell header" first class concepts in the GC 
> infrastructure. However, this never went further than the introduction 
> of cell_header_size(). Since Shenandoah doesn't need this anymore, we 
> can revert back to the old code and not have to think/talk about cells 
> anymore.
> 
>>
>>> This is a clean backout, with the exception of light editing needed 
>>> in two places, because:
>>>
>>> 1) The function Universe::narrow_oop_base() has since been renamed to 
>>> CompressedOops::base().
>>> 2) The include guard CPU_ARM_VM_MACROASSEMBLER_ARM_HPP has since been 
>>> renamed to CPU_ARM_MACROASSEMBLER_ARM_HPP.
>>
>> The backout itself looks good.
> 
> Thanks for reviewing, David!
> 
> cheers,
> Per
> 
>>
>> Thanks,
>> David
>> ----
>>
>>> Testing: Tier1-3 on all Oracle platforms
>>>
>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8225779
>>> Webrev: http://cr.openjdk.java.net/~pliden/8225779/webrev.0
>>>
>>> /Per
>>>
>>> [1] http://hg.openjdk.java.net/jdk/jdk/rev/4ad404da0088
>>> [2] http://hg.openjdk.java.net/jdk/jdk/rev/f642ede2eb07
>>> [3] http://hg.openjdk.java.net/jdk/jdk/rev/18bd95c0e463