RFR: 8256318: AArch64: Add support for floating-point absolute difference [v4]

[Dong Bo]

On Tue, 17 Nov 2020 08:38:36 GMT, Ningsheng Jian <njian at openjdk.org> wrote:

>> For integer absolute (vector), the accepted arrangements are `T8B, T16B, T4H, T8H, T2S, T4S, T2D`.
>> ARM compiler armasm user guide reference: https://developer.arm.com/documentation/dui0801/h/A64-SIMD-Vector-Instructions/ABS--vector-?lang=en
>> I think the original code `n->as_Vector()->length() == 4 ||` is not right for basic type Byte. So I delete it, I am sorry if I miss something.
>
> We load 4B with loadV4 but handle 4B types with T8B instructions. And current min_vector_size for byte type is 4, so it's possible for vectorizer to generate 4B vector nodes.

Oh, I see. Thanks a lot for clarifying this, I should have taken a deep look.
Really sorry for producing a BUG here, I will fix it.

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PR: https://git.openjdk.java.net/jdk/pull/1215