RFR: 8356700: Declare incompressible scope in fill_words / zero_memory assembler routines [v2]

[Fei Yang]

On Mon, 12 May 2025 03:25:31 GMT, Anjian-Wen <duke at openjdk.org> wrote:

>> The correctness of the logic depends on the fixed instruction size of the store instructions
>> emitted by the loop in MacroAssembler::fill_words and MacroAssembler::zero_memory assembler
>> routines. These store instructions won't be compressed into 16-bit format due to negative
>> offset immediate. But it will be safer to make it explict by declaring an incompressible scope
>> when emitting these store instructions. This also renames IncompressibleRegion to IncompressibleScope.
>> 
>> Tier1 tested on linux-riscv64 platforms.
>
> Anjian-Wen has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:
> 
>  - Merge branch 'openjdk:master' into declare_incompressible
>  - RISCV: Declare incompressible scope in fill_words / zero_memory assembler routines

Looks reasonable. Thanks!

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Marked as reviewed by fyang (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/25172#pullrequestreview-2831742596