RFR: 8365166: ARM32: missing os::fetch_bcp_from_context implementation

[Aleksey Shipilev]

On Fri, 8 Aug 2025 14:27:20 GMT, Boris Ulasevich <bulasevich at openjdk.org> wrote:

> Since [JDK-8352251](https://bugs.openjdk.org/browse/JDK-8352251) (JEP 518: JFR Cooperative Sampling), jfrSampleRequest calls os::fetch_bcp_from_context(). On ARM32 port it is still Unimplemented(). It should read the corresponding field from uc_mcontext and return the BCP value.

Looks good, with minor nit.

src/hotspot/os_cpu/linux_arm/os_linux_arm.cpp line 216:

> 214:   assert(os::Posix::ucontext_is_interpreter(uc), "invariant");
> 215: #if (FP_REG_NUM == 11)
> 216:   assert(Rbcp == R7,  "expected FP=R11, Rbcp=R7");

Suggestion:

  assert(Rbcp == R7, "expected FP=R11, Rbcp=R7");

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Marked as reviewed by shade (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/26699#pullrequestreview-3112746558
PR Review Comment: https://git.openjdk.org/jdk/pull/26699#discussion_r2271168432