RISC-V International
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benchmark tests are also carried out regularly. So it should be good enough to run most Java programs.
Aleksey Shipilev is building nightlies here [4]. And they have provided build instructions for reference [5].
A JEP has been submitted in order to bring it upstream in JDK mainline [46], but that process will surely take some time.
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[3] https://github.com/openjdk/riscv-port/tree/riscv-port
[4] https://builds.shipilev.net/openjdk-jdk-riscv
[5] http://cr.openjdk.java.net/~fyang/openjdk-riscv-port/BuildRISCVJDK.md
[6] https://openjdk.java.net/jeps/8276797
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