RFR: 8366984: Remove delay slot support

[Emanuel Peter]

On Fri, 5 Sep 2025 14:24:50 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.

Looks reasonable, thanks for doing the cleanup! I have 2 minor questions though.
(please also run additional stress testing, see slack)

src/hotspot/cpu/arm/arm.ad line 3383:

> 3381:     BR     : R;
> 3382: %}
> 3383: 

Where was this used? Or is it an unrelated cleanup?

src/hotspot/share/adlc/adlparse.cpp line 1394:

> 1392:           parse_err(SYNERR, "Using obsolete token, branch_has_delay_slot");
> 1393:           break;
> 1394:         }

I'm curious: why do you add that special warning? It would fail later anyway, right? Are we expecting anyone to parse things produced by different versions?

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Marked as reviewed by epeter (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/27119#pullrequestreview-3200246647
PR Review Comment: https://git.openjdk.org/jdk/pull/27119#discussion_r2332626258
PR Review Comment: https://git.openjdk.org/jdk/pull/27119#discussion_r2332620923