RFR: 8294087: RISC-V: RVC: Fix a potential alignment issue and add more alignment assertions for the patchable calls/nops [v8]

[Fei Yang]

On Thu, 22 Sep 2022 06:41:47 GMT, Xiaolin Zheng <xlinzheng at openjdk.org> wrote:

>> With RVC turning on, we must carefully keep all runtime-patchable instructions aligned. Code is running at full speed, when patching unaligned instructions spanning cache lines, concurrency issues may occur. This patch fixes a potential alignment issue of the patchable nop after MachUEPNode, with adding some strong alignment assertions as well. (In fact, currently the `nop` in the Verified Entry Point is fortunately aligned to 4 under RVC even without this patch, so this patch doesn't change program behaviors.)
>> 
>> Tested hotspot tier1 and tier2 together with other patches on QEMU.
>
> Xiaolin Zheng has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Some code style modifications

Marked as reviewed by fyang (Reviewer).

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PR: https://git.openjdk.org/jdk/pull/10370