[vectorIntrinsics] RFR: Improve mask reduction operations on AVX [v2]

[Mai Đặng Quân Anh]

On Wed, 3 Nov 2021 07:55:57 GMT, Mai Đặng Quân Anh <duke at openjdk.java.net> wrote:

>> Hi,
>> This patch improves the logic of vector mask reduction operations on AVX, especially int, float, long, double, by using vmovmskpd and vmovmskps instructions. I also do a little refactoring to reduce duplication in toLong. The patch temporarily disables these operations on Neon, though.
>> Thank you very much.
>
> Mai Đặng Quân Anh has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - fix last true
>  - further improvement

It seems that `Long128Vector` disappoints C2 due to the fact that C2 doesn't know how to box a vector mask of length 2, which in turn is due to `StoreVectorNode` currently don't accept vectors of size 2. I will submit a fix for this later.

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PR: https://git.openjdk.java.net/panama-vector/pull/158