RFR: 8289743: AArch64: Clean up patching logic [v13]

[Dean Long]

On Mon, 18 Jul 2022 13:36:46 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> The current logic for patching is a mess of if-then-elses. By rearranging the logic and using a switch we can make it both easier to understand and faster.
>
> Andrew Haley has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8289743: AArch64: Clean up patching logic

>    offset = offset << (64-21) >> (64-21);

My guess is that ADRP is being used for a target address that is too far away.  The added line above fixes up the high bits so that the assert in spatch() won't fire, hiding the problem:

> 239      guarantee (chk == -1 || chk == 0, "Field too big for insn");

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PR: https://git.openjdk.org/jdk/pull/9398