RFR: 8287028: AArch64: [vectorapi] Backend implementation of VectorMask.fromLong with SVE2

[Eric Liu]

This patch implements AArch64 codegen for VectorLongToMask using the
SVE2 BitPerm feature. With this patch, the final code (generated on an
SVE vector reg size of 512-bit QEMU emulator) is shown as below:

        mov     z17.b, #0
        mov     v17.d[0], x13
        sunpklo z17.h, z17.b
        sunpklo z17.s, z17.h
        sunpklo z17.d, z17.s
        mov     z16.b, #1
        bdep    z17.d, z17.d, z16.d
        cmpne   p0.b, p7/z, z17.b, #0

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

Commit messages:
 - AArch64: [vectorapi] Backend implementation of VectorMask.fromLong with SVE2

Changes: https://git.openjdk.java.net/jdk/pull/8789/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8789&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8287028
  Stats: 134 lines in 8 files changed: 102 ins; 0 del; 32 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8789.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8789/head:pull/8789

PR: https://git.openjdk.java.net/jdk/pull/8789