RFR: 8303621: BitMap::iterate should support lambdas and other function objects [v4]

[Stefan Karlsson]

On Tue, 7 Mar 2023 09:57:48 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Please review this enhancement of BitMap::iterate to support lambdas and other
>> function objects as the operation being applied to the set bit indices. Some
>> for-loops using BitMap::get_next_one_offset have been changed to use
>> BitMap::iterate with a lambda.
>> 
>> (One reason for changing the for-loops is that I'm considering a change to the
>> get_next_one_offset API, and reducing the number of direct uses will simplify
>> that.)
>> 
>> For convenience, the function can either return void (always iterate over the
>> whole range) or bool (stop iteration if returns false).  Iteration using
>> closure objects invoked via a do_bit member function are now implemented by
>> being wrapped in a lambda, so get the same convenience.  (Though, of course,
>> if the closure is derived from BitMapClosure then do_bit returns bool.)
>> 
>> The unit tests are written as "early" tests, not requiring an initialized VM.
>> They also avoid any C heap allocation (even though C heap allocation has very
>> early support). This is done to minimize the requirements for running the
>> tests, since BitMap is used in a lot of places. This attempts to run these
>> tests before uses. (Yes, I know about JDK-8257226; maybe that will be fixed
>> someday.) (Some existing BitMap gtests should be modified to do similarly; see
>> JDK-8303636.)
>> 
>> Testing:
>> mach5 tier1-7
>
> Kim Barrett has updated the pull request incrementally with one additional commit since the last revision:
> 
>   convert to bool rather than calling RT::operator!

Thanks. That's a bit easier to read, for me at least.

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Marked as reviewed by stefank (Reviewer).

PR: https://git.openjdk.org/jdk/pull/12876