RFR: 8259948: Aarch64: Add cast nodes for Aarch64 Neon backend [v4]

[Wu Yan]

On Fri, 3 Sep 2021 03:16:23 GMT, Ningsheng Jian <njian at openjdk.org> wrote:

>> Wang Huang has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   fix codes
>
> src/hotspot/cpu/aarch64/aarch64.ad line 2452:
> 
>> 2450:         return false;
>> 2451:       }
>> 2452:       break;
> 
> Why do you remove others but keep this (4Sto4B not implemented)?

Because @theRealELiu suggest us not to have VectorCast with bit_size less than 64 bits support.
In addition, we will add rules for the 4B vector, which will appear in actual situations. I'll refine the code in next commit.

> src/hotspot/cpu/aarch64/aarch64_neon.ad line 274:
> 
>> 272: %}
>> 273: 
>> 274: instruct vcvt4Bto4I(vecX dst, vecD src)
> 
> 4BtoX should be supported as the min_vector_size() for byte type is 4.

OK, I'll add rules for 4B.

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PR: https://git.openjdk.java.net/jdk/pull/4839