RFR: 8176894 Provide specialized implementation for default methods putIfAbsent, computeIfAbsent, computeIfPresent, compute, merge in TreeMap

Tagir Valeev amaembo at gmail.com
Mon Jul 15 10:58:00 UTC 2019


Please review the following patch:

Also please review the associated CSR:

The patch was originally submitted by Sergey Kuksenko in March 2017 and
reviewed by some people:
The latest patch submitted by Sergey is here:

I asked Sergey why it was abandoned. Seems there were no particular reason
and Sergey asked if I could pick up this work. I will be happy to finish it.

Here's the list of differences between the latest Sergey patch and my patch:
- A bug is fixed in putIfAbsent implementation. TreeMap.java, lines 576 and
596:  `|| oldValue == null` condition added (the null value should be
overwritten no matter what)
- A testcase is added to cover this problem (InPlaceOpsCollisions.java,
also checks HashMap and LinkedHashMap). Not sure if it's the best place for
such test though. Probably a separate file would be better?
- TreeMap.merge() implementation is added.
- TreeMap is added to the FunctionalCMEs.java test (btw this file copyright
says that it's a subject to Classpath exception which is probably wrong?)
- Simple microbenchmark is added: TreeMapUpdate.java

My quick benchmarking shows that optimized version is indeed faster for the
most of the tests and no regression is observed for put() method. Here's
raw results of jdk13-ea+26 and jdk13-ea+26+patch if anybody is interested.

With best regards,
Tagir Valeev.

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