RFR: 8355698: JDK not supporting sleef could cause exception at runtime after JDK-8353786

[Vladimir Ivanov]

On Mon, 28 Apr 2025 10:34:49 GMT, Hamlin Li <mli at openjdk.org> wrote:

> Hi,
> Can you help to review this patch?
> 
> Before [JDK-8353786](https://bugs.openjdk.org/browse/JDK-8353786), when a released jdk not supportting sleef (for any reason, e.g. low gcc version, intrinsic not supported, rvv not supported, and so on) runs on machine support vector operation (e.g. on riscv, it supports rvv), it can not call into sleef, but will not fail either, it falls back to java scalar version implementation.
> But after [JDK-8353786](https://bugs.openjdk.org/browse/JDK-8353786), it will cause an exception thrown at runtime.
> 
> This change the behaviour of existing jdk, and it should not throw exception anyway.
> 
> @iwanowww @RealFYang 
> 
> Thanks!

The assumption is if vector math library is present, it provides full set of stubs. 

Do we really want to complicate things even more by supporting arbitrary subsets of vector math stubs?

IMO a better way to fix the problem is to avoid building/bundling SLEEF when any stubs are missing.

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PR Review: https://git.openjdk.org/jdk/pull/24914#pullrequestreview-2801649899