RFR: 8178352: BitMap::get_next_zero_offset may give wrong result on Mac

[Kim Barrett]

> On Apr 10, 2017, at 12:48 PM, Stefan Karlsson <stefan.karlsson at oracle.com> wrote:
> 
> On 10/04/17 18:33, Kim Barrett wrote:
>>> On Apr 10, 2017, at 12:18 PM, Kim Barrett <kim.barrett at oracle.com>
>>>  wrote:
>>> 
>>>> You did a couple of stylistic changes that now make the code inconsistent:
>>>> 
>>>> […]
>>>> I think these changes should be kept out of this patch.
>>>> 
>>> Post-decrement in for loops still makes me twitch, even though it doesn’t matter
>>> in this code base.  But okay.
>>> 
>> Updated webrev:
>> 
>> http://cr.openjdk.java.net/~kbarrett/8178352/hotspot.01/
>> 
>> 
>> 
> To be consistent with the other code it in that file (res & 1) == 0 should be !(res & 1).

That would be contrary to hotspot style guide; I think that should take precedence.

> Maybe create a small, trivial cleanup RFE to change the following in the BitMap files:
> * !(res & 1) => (res & 1) == 0
> * res = res >> 1 => res >>= 1

I can do something like that, but would prefer it as a followup.

There are other similar syntactic / style guide cleanups, such as consistent use of
helpers like bit_in_word, word_index, and bit_index.

Having unit tests make these kinds of changes easier.