RFR: 8297753: AArch64: Add optimized rules for vector compare with zero on NEON [v6]

[Chang Peng]

On Mon, 20 Feb 2023 10:21:50 GMT, Chang Peng <duke at openjdk.org> wrote:

>> We can use the compare-with-zero instructions like cmgt(zero)[1] immediately to avoid the extra scalar2vector operations.
>> 
>> The following instruction sequence
>> 
>> movi  v16.4s, #0x0
>> cmgt  v16.4s, v17.4s, v16.4s
>> 
>> can be optimized to:
>> 
>> cmgt v16.4s, v17.4s, #0x0
>> 
>> This patch does the following:
>> 1. Add NEON floating-point compare-with-zero instructions.
>> 2. Add optimized match rules to generate the compare-with-zero instructions.
>> 
>> [1]: https://developer.arm.com/documentation/ddi0602/2022-06/SIMD-FP-Instructions/CMGT--zero---Compare-signed-Greater-than-zero--vector--
>
> Chang Peng has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Remove some switch-case stmts in c2_MacroAssembler_aarch64.cpp and avoid
>    unsigned comparison.
>  - Revert "Remove switch-case stmts in c2_MacroAssembler_aarch64.cpp"
>    
>    This reverts commit d899238d0cb98fdf375b3011670495c3bfe8bbaf.

@theRealAph Could you please help to review this patch? Thanks.

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

PR: https://git.openjdk.org/jdk/pull/11822