RFR: 8300197: Freeze/thaw an interpreter frame using a single copy_to_chunk() call

[Patricio Chilano Mateo]

On Fri, 14 Apr 2023 13:45:12 GMT, Fredrik Bredberg <duke at openjdk.org> wrote:

> On certain architectures (like AARCH64) padding may be inserted between the locals and the rest of the stack frame in order to keep the frame pointer 16-byte-aligned.
> 
> This padding is currently not freezed, instead freezing of a single interpreter stack frame is done using two separate copy_to_chunk() calls (see recurse_freeze_interpreted_frame). Likewise, thawing is done using two separate copy_from_chunk() calls.
> 
> This poses a bit of a problem when trying to relativize stack addresses in interpreter frames ([JDK-8289296](https://bugs.openjdk.org/browse/JDK-8289296)). Since relative offsets may need to be changed during freezing and thawing.
> 
> By both freezing and thawing the padding we remove the need to change any relative offsets in runtime.
> 
> Tested tier1-tier8 on supported platforms, found no new issues. PowerPC and RISC-V was sanity tested using Qemu.

Looks good to me.

src/hotspot/share/runtime/continuationFreezeThaw.cpp line 2152:

> 2150: 
> 2151:   assert((stack_frame_bottom >= stack_frame_top + fsize) &&
> 2152:          (stack_frame_bottom <= stack_frame_top + fsize + 1), ""); // internal alignment on aarch64

Since we didn't add any new padding shouldn't this assert now be stack_frame_bottom == stack_frame_top + fsize?

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PR Review: https://git.openjdk.org/jdk/pull/13477#pullrequestreview-1388783799
PR Review Comment: https://git.openjdk.org/jdk/pull/13477#discussion_r1169164544