RFR: 8255287: aarch64: fix SVE patterns for vector shift count

[Andrew Dinn]

On Fri, 23 Oct 2020 09:35:11 GMT, Fei Yang <fyang at openjdk.org> wrote:

> SVE patterns for vector shift count cannot be matched due to bad matching rules.
> Also code gen is not correct in certain cases for vlslS_imm and vlsrS_imm.
> Please refer to JDK-8255287 for details.
> Patch passed tier1 tests using QEMU system emulator which supports SVE.

These changes look ok.

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Marked as reviewed by adinn (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/827