RFR: 8343415: RISC-V: Increase maximum size of C2EntryBarrierStub by one

[Feilong Jiang]

On Fri, 1 Nov 2024 02:13:16 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)

Looks reasonable, thanks.

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Marked as reviewed by fjiang (Committer).

PR Review: https://git.openjdk.org/jdk/pull/21818#pullrequestreview-2409366643