[riscv-port-jdk17u:riscv-port] RFR: 8276799: Implementation of JEP 422: Linux/RISC-V Port

[Fei Yang]

On Tue, 7 Feb 2023 11:20:37 GMT, Yadong Wang <yadongwang at openjdk.org> wrote:

> This PR backports the implementation of RISC-V port into jdk17u. 
> 
> It based on the initial implementation of JEP-422 with some modifications for jdk17u:
> 1.	The initial patch
>     8276799: Implementation of JEP 422: Linux/RISC-V Port
> 2.	 remove features that do not belong to jdk17u
>     revert 8277417: C1 LIR instruction for load-klass
>     revert 8278387: Implement UseHeavyMonitors consistently
>     revert 8227369: pd_disjoint_words_atomic() needs to be atomic
>     revert 8258192: Obsolete the CriticalNatives flag
>     revert 8281632: riscv: Improve interpreter stack banging
>     revert 8283364: Intrinsify countPositives
> 3.	add features that belongs to jdk17u
>     enable the biased locking
> 4.	 Wrap modifications to shared code under RISCV and revert changes to other platforms
> isolate modification to other platforms
> 5.	Patches for making compilation pass
> 8282306: os::is_first_C_frame(frame*) crashes on invalid link access
> 8282477: vmassert(_last_Java_pc == NULL, "already walkable"); fails with async profiler

> > I think that deserves another seperate backporting PR after this one? I see the robot is trying to link each backporting PR with the original issue. So it might not be a good idea to put serveral seperate fixes together into one backporting PR.
> 
> Last time I was backporting JEP ( [openjdk/jdk11u-dev#715](https://github.com/openjdk/jdk11u-dev/pull/715) ) it was ok. Just order scara-bot few commands /issue 8282306 , /issue 8282477.

Hmm, I think that might be a good way when we are doing the final upstreaming. For now, I still prefer to keep a simple/clean relationship between a backporting PR and the corresponding issue unless there is a special reason for this staging repo.
@yadongw : Please link these two issues (8282306 & 8282477) with this backporting PR.

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PR: https://git.openjdk.org/riscv-port-jdk17u/pull/1