RFR: 8255210: [Vector API] jdk/incubator/vector/Int256VectorTests.java crashes on AVX512 machines

[Jie Fu]

Hi all,

Please review the fix of an AVX512 crash for Vector API.
The reason is that reductionI in x86.ad didn't use legVec for code generation, which is required by Assembler::vphaddd.

Testing:
 - test/jdk/jdk/incubator/vector all passed on both AVX256 and AVX512 machines

Thanks.
Best regards,
Jie

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Commit messages:
 - 8255210: [Vector API] jdk/incubator/vector/Int256VectorTests.java crashes on AVX512 machines

Changes: https://git.openjdk.java.net/jdk/pull/791/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=791&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255210
  Stats: 22 lines in 1 file changed: 0 ins; 20 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/791.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/791/head:pull/791

PR: https://git.openjdk.java.net/jdk/pull/791