RVC by default?

[yangfei at iscas.ac.cn]

Hi Xiaolin,




    I am interested in your new proposal for supporting the RVC extension. 

    Can you provide a simple description of how it works and maybe the new interfaces? 

    I guess developers will need to be aware of this when working on this port. 




Thanks,

Fei




-----Original Messages-----
From:"Xiaolin Zheng" <yunyao.zxl at alibaba-inc.com>
Sent Time:2022-09-08 20:09:59 (Thursday)
To: riscv-port-dev <riscv-port-dev-retn at openjdk.org>, "Aleksey Shipilev" <shade at redhat.com>, "riscv-port-dev at openjdk.org" <riscv-port-dev at openjdk.org>, "Vladimir Kempik" <vladimir.kempik at gmail.com>
Cc:
Subject: Re: RVC by default?


Hi Aleksey and Vladimir,


The current RVC support is okay but not complete: it only covers ~10% of total instructions emitted (mostly C2 code, including some part of Stub code), and we might want to transform instructions into the compressed counterparts as much as possible, so maybe the design will change from a whitelist mode (the class CompressibleRegion) to a black list mode. There is one implementation at my local branch https://github.com/zhengxiaolinX/jdk/commits/REBASE-rvc-beautify (might not be stable yet, I have not gotten enough time to give it a sufficient test on jtregs and specjbb2015/other benchmarks yet). There are plans reserved to commit them (which cover ~20% of instructions under some tests) after reviewing, but this is currently WIP and waiting loom port to merge first.
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