RFR: 8277426: Optimize mask reduction operations on x86

[Mai Đặng Quân Anh]

Hi,

This patch improves the performance of mask reduction operations on AVX by matching the pattern `VectorMaskReduction (VectorStoreMask mask)` to eliminate the extra `VectorStoreMaskNode`. I have also done some refactoring to unify the logic of `toLong` with the other reduction operations.

The patch has been discussed partially in [panama-vector repository](https://github.com/openjdk/panama-vector/pull/158).

Passed all tests except the one being fixed by [JDK-8277324](https://bugs.openjdk.java.net/browse/JDK-8277324).

Thank you very much.

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Commit messages:
 - reduce some dependencies with spare register
 - improve mask reduction logic on AVX

Changes: https://git.openjdk.java.net/jdk/pull/6447/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6447&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8277426
  Stats: 214 lines in 5 files changed: 139 ins; 17 del; 58 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6447.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6447/head:pull/6447

PR: https://git.openjdk.java.net/jdk/pull/6447