RFR: 8339168: Optimize ClassFile Util slotSize [v4]

[Shaojin Wen]

> A small optimization to improve the performance of jdk.internal.classfile.impl.Util#slotSize/isDoubleSlot

Shaojin Wen has updated the pull request incrementally with one additional commit since the last revision:

  add benchmark

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20747/files
  - new: https://git.openjdk.org/jdk/pull/20747/files/83900373..105ffc01

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20747&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20747&range=02-03

  Stats: 66 lines in 1 file changed: 66 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/20747.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20747/head:pull/20747

PR: https://git.openjdk.org/jdk/pull/20747