RFR: 8288397: AArch64: Fix register issues in SVE backend match rules

[Xiaohong Gong]

On Fri, 17 Jun 2022 12:32:56 GMT, Nick Gasson <ngasson at openjdk.org> wrote:

>> There are register usage issues in the sve backend match rules, which made the two added jtreg tests fail.
>> 
>> The predicated vector "`not`" rules didn't use the same register for "`src`" and "`dst`", which is necessary to make sure the inactive lanes in "`dst`" save the same elements as "`src`". This patch fixes the rules by using the same register for "`dst`" and "`src`".
>> 
>> And the input idx register in "`gatherL/scatterL`" rules was overwritten by the first unpack instruction. The same issue also existed in the partial and predicated gatherL/scatterL rules. This patch fixes them by saving the unpack results into a temp register and use it as the index for gather/scatter.
>
> Seems fine.

Thanks for the review @nick-arm !

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PR: https://git.openjdk.org/jdk19/pull/17