[vectorIntrinsics] RFR: 8284459: Add x86 back-end implementation for LEADING and TRAILING ZEROS COUNT operations [v3]

[Jatin Bhateja]

> Summary of changes:
> - Patch extends SLP vectorizer to auto-vectorize Integer.numberOfLeadingZeros() and Long.numberOfLeadingZeros() APIs.
> - Adds optimized target feature specific X86 backend implementation for LEADING_ZEROS_COUNT operation for all integral types. 
> 
> Kindly review and share your feedback.
> 
> Best Regards,
> Jatin

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

  8284459: Adding auto-vectorizer and x86 backend support for TRAILING_ZERO_COUNT, also some code re-organization.

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Changes:
  - all: https://git.openjdk.java.net/panama-vector/pull/189/files
  - new: https://git.openjdk.java.net/panama-vector/pull/189/files/20d0d67a..cc42fb7c

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=189&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=189&range=01-02

  Stats: 267 lines in 8 files changed: 196 ins; 26 del; 45 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/189.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/189/head:pull/189

PR: https://git.openjdk.java.net/panama-vector/pull/189