RFR: 8366984: Remove delay slot support [v3]

[Dean Long]

On Tue, 9 Sep 2025 16:59:31 GMT, Daniel Jeliński <djelinski at openjdk.org> wrote:

>> SPARC was the only supported architecture that uses a delay slot. The SPARC port was removed in JDK 15, and the code is effectively dead. Let's remove it.
>> 
>> The changes are no-op on all architectures that do not use delay slots. I still tested tier 1-5 on mach5, no related failures.
>
> Daniel Jeliński has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 14 commits:
> 
>  - Merge remote-tracking branch 'origin/master' into delay-slot
>  - Revert scope_desc change, breaks macos-aarch64
>  - Remove remaining comments
>  - Update copyright
>  - Remove commented out code
>  - Remove unused variables
>  - Comment out unused _unconditional_delay_slot
>  - Remove bundle flags
>  - Remove delay slot support from ADL
>  - Clean up delay slot remnants from arm32 code
>  - ... and 4 more: https://git.openjdk.org/jdk/compare/cc6d34b2...fb68b5a8

Marked as reviewed by dlong (Reviewer).

src/hotspot/share/runtime/sharedRuntime.cpp line 3505:

> 3503:         nm = cb->as_nmethod();
> 3504:         method = nm->method();
> 3505:         for (ScopeDesc *sd = nm->scope_desc_near(fr.pc()); sd != nullptr; sd = sd->sender()) {

It's tempting to try to change this to scope_desc_at(), but also slightly risky if SPARC isn't the only reason it was needed.  Should we investigate this in a separate RFE?

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PR Review: https://git.openjdk.org/jdk/pull/27119#pullrequestreview-3203943528
PR Review Comment: https://git.openjdk.org/jdk/pull/27119#discussion_r2335213805