RFR: 8261553: Efficient mask generation using BMI2 BZHI instruction [v3]

[Jatin Bhateja]

> BMI2 BHZI instruction can be used to optimize the instruction sequence
> used for mask generation at various place in array copy stubs and partial in-lining for small copy operations.

Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:

  8261553 : Aligning main copy loop to prevent any penalty due to LSD and DSB misses.

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2522/files
  - new: https://git.openjdk.java.net/jdk/pull/2522/files/84c9c2da..7012eed0

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2522&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2522&range=01-02

  Stats: 8 lines in 1 file changed: 4 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2522.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2522/head:pull/2522

PR: https://git.openjdk.java.net/jdk/pull/2522