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

[Hamlin Li]

On Thu, 1 May 2025 18:27:24 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

> I want to understand the issue with missing entries in vector math native libraries first before making a decision how to proceed.
> 
> > I don't think it's a build issue, the jdk vendor can choose to support it or not, it's just the way passing the information ( whether it's supported or not) are different.
> 
> Sorry, I don't get it. How does it affect the contents of the native library? JDK vendors do have an option to bundle the library or drop it from their distribution. But when SLEEF-based and SVML math libraries are built by JDK there's no distinction between entries being included in the library. If a vendor modifies make files or native library code, it's up to them to adjust JDK accordingly. Upstream JDK doesn't have to take such scenarios into account.

Sorry for confusing you. No, what I mean is vendors can choose their build environment (e.g. with/without support of compiler, I discuss this a bit below), and different environment will lead to whether sleef is supported or not (i.e. whether there are entries in the libsleef.so).

> 
> I looked through SVML and SLEEF-based vector math code and noticed there are some capability check [1] [2] [3] guarding library code. It means that if some library entry is missing, then the whole library is empty. Can you confirm it's the case you see?
> 
> [1] https://github.com/openjdk/jdk/blob/master/src/jdk.incubator.vector/linux/native/libjsvml/globals_vectorApiSupport_linux.S.inc#L35 [2] https://github.com/openjdk/jdk/blob/master/src/jdk.incubator.vector/windows/native/libjsvml/globals_vectorApiSupport_windows.S.inc#L28 [3] https://github.com/openjdk/jdk/blob/master/src/jdk.incubator.vector/unix/native/libsleef/lib/vector_math_rvv.c#L36

In riscv sleef case, yes, it checks native compiler version and a flat, this is required because only these versions (or higher) support vector intrinsics which are used in sleef header files. ( I think arm is the same case, but in a bit simpler way only with a flag).

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PR Comment: https://git.openjdk.org/jdk/pull/24914#issuecomment-2846731509