RFR: 8356159: RISC-V: Add Zabha [v12]
Robbin Ehn
rehn at openjdk.org
Tue Jun 3 11:52:43 UTC 2025
> Hi, please consider.
>
> This adds the byte and halfword atomic memory operations (Zabha) - https://github.com/riscv/riscv-zabha.
> All amo-instructions, except load-reserve and store-conditional, can also be performed on natural aligned half-words and bytes. (i.e. the extension do not add lr.h/b or sc.h/b) This includes amocas if zacas extension is present.
>
> The majority of this patch is to support amocas.h/b. We are now starting to really feel the pain of all these extensions, as CAS:ing 16/8-bits can now be done in three different ways:
> - lr.w/sc.w 'narrow' CAS (no extension)
> - amocas.w 'narrow' CAS (Zacas)
> - amocas.h/b (Zacas + Zabha)
>
> There is no hwprobe support yet.
>
> Ran t1-3 with Zacas+Zabha and t1 without Zabha in qemu.
>
> Thanks, Robbin
Robbin Ehn 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 21 additional commits since the last revision:
- Merge branch 'master' into 8356159
- Set ins cost to 2xVOLA for cmpxchg
- Merge branch 'master' into 8356159
- Merge branch 'master' into 8356159
- ins cost fixes, print fixes
- Merge branch 'master' into 8356159
- Reg limits fixed
- Merge branch 'master' into 8356159
- Fixed reg selection
- More indention
- ... and 11 more: https://git.openjdk.org/jdk/compare/2fdd35a2...cc3b8ff7
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/25252/files
- new: https://git.openjdk.org/jdk/pull/25252/files/b496c299..cc3b8ff7
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=25252&range=11
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=25252&range=10-11
Stats: 27302 lines in 350 files changed: 7274 ins; 12599 del; 7429 mod
Patch: https://git.openjdk.org/jdk/pull/25252.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/25252/head:pull/25252
PR: https://git.openjdk.org/jdk/pull/25252
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