RFR: 8256883: C2: Add a RegMask iterator [v4]

Claes Redestad redestad at openjdk.java.net
Tue Nov 24 00:14:11 UTC 2020


> By implementing a simple RegMaskIterator we can speed this up and possibly make the code a bit clearer by doing so.
> 
> As a data point, this reduce the `C2Compiler::initialize` overhead from 8.82M instructions to 8.58M instructions, from the improvement in `PhaseChaitin::post_allocate_copy_removal` (~16k insns/compilation). The gain varies with type of compilation, so on the naive tests in `SimpleRepeatCompilation` it's in the noise (~2k insns/compilation on `trivialMath, for example).

Claes Redestad has updated the pull request incrementally with one additional commit since the last revision:

  Remove extra commentary in ZGC aarch code (requested by Per Liden)

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1397/files
  - new: https://git.openjdk.java.net/jdk/pull/1397/files/b928fcc1..f259dd3b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1397&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1397&range=02-03

  Stats: 4 lines in 1 file changed: 1 ins; 3 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1397.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1397/head:pull/1397

PR: https://git.openjdk.java.net/jdk/pull/1397


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