[lworld] RFR: Prototype inline cursors for List

[Brian Goetz]

These don't look so good!  I suspect that the Iterator is performing so 
well because it's getting good EA, but not sure why cursors aren't doing 
better?  Guess we'll have to dig into the generated code....

On 3/26/2020 1:14 PM, Roger Riggs wrote:
> Implementation of Cursors and jmh tests comparing
> typical List traversal via direct index, iterator,
> inline cursor, and an iterator implemented on top of cursor.
>
> Sample results:
>
>                                     (size)  Mode  Cnt       Score       Error  Units
> XArrayListCursorTest.getViaArray            100000  avgt    5  507793.484  7086.038  ns/op
> XArrayListCursorTest.getViaCursorForLoop    100000  avgt    5  656461.958  52488.547  ns/op
> XArrayListCursorTest.getViaCursorWhileLoop  100000  avgt    5  641963.323  32219.409  ns/op
> XArrayListCursorTest.getViaIterator         100000  avgt    5  558863.817  23539.256  ns/op
> XArrayListCursorTest.getViaIteratorCurs     100000  avgt    5  733161.466  33721.881  ns/op
>
> -------------
>
> Commit messages:
>   - Prototype inline cursors for List
>
> Changes: https://git.openjdk.java.net/valhalla/pull/5/files
>   Webrev: https://webrevs.openjdk.java.net/valhalla/5/webrev.00
>    Stats: 2139 lines in 3 files changed: 2139 ins; 0 del; 0 mod
>    Patch: https://git.openjdk.java.net/valhalla/pull/5.diff
>    Fetch: git fetch https://git.openjdk.java.net/valhalla pull/5/head:pull/5
>
> PR: https://git.openjdk.java.net/valhalla/pull/5