RFR: 8343415: RISC-V: Increase maximum size of C2EntryBarrierStub by four [v2]

[Robbin Ehn]

On Fri, 1 Nov 2024 02:43:06 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> Hi, please consider this small change.
>> 
>> There is one jump to continuation (after nmethod entry barriers) in C2EntryBarrierStub [1].
>> The current max_size setting assumes the distance is within 1MB, which means a simple `jal` instruction [2].
>> So I just count one for this jump in [JDK-8343121](https://bugs.openjdk.org/browse/JDK-8343121). This doesn't seem to break for various tests. But I don't think there is a good reason for that assumption to stand. Instead, we should remove this constraint assuming a `auipc+jalr` pair for this jump.
>> 
>> [1] https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/riscv/c2_CodeStubs_riscv.cpp#L66
>> [2] https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/riscv/macroAssembler_riscv.cpp#L965
>> 
>> Testing on linux-riscv64:
>> - [x] tier1 (fastdebug build)
>
> Fei Yang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Comment typo

Thanks!

-------------

Marked as reviewed by rehn (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/21818#pullrequestreview-2412682449