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

[Xiaolin Zheng]

On Wed, 21 Sep 2022 03:54:03 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.

This pull request has now been integrated.

Changeset: a216960d
Author:    Xiaolin Zheng <xlinzheng at openjdk.org>
Committer: Fei Yang <fyang at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/a216960d71bdf111a9c232a0228cc43256a01b29
Stats:     30 lines in 9 files changed: 25 ins; 0 del; 5 mod

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

Reviewed-by: shade, fjiang, fyang

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