RFR: 8279282: [vectorapi] Matcher::supports_vector_comparison_unsigned is not needed on x86 [v3]

[Quan Anh Mai]

> Hi,
> 
> Currently, unsigned comparison on AVX is implemented by zero extending elements and comparing the results. This leads to unnecessary complexity. This patch changes the implementation to use the identity existing in `Integer/Long.compareUnsigned`, that is `compareUnsigned(x, y) == compare(x ^ min_value, y ^ min_value)`.
> 
> Thank you very much.

Quan Anh Mai has updated the pull request incrementally with one additional commit since the last revision:

  use movddup for 128-bit vectors

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6966/files
  - new: https://git.openjdk.java.net/jdk/pull/6966/files/a0444928..59d1fa35

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6966&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6966&range=01-02

  Stats: 30 lines in 5 files changed: 27 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6966.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6966/head:pull/6966

PR: https://git.openjdk.java.net/jdk/pull/6966