RFR: 8312425: [vectorapi] AArch64: Optimize vector math operations with SLEEF [v9]

[Ludovic Henry]

On Mon, 15 Jul 2024 17:00:13 GMT, Andrew Haley <aph at openjdk.org> wrote:

> > > I can't tell what problem we're trying to solve by not simply checking in the source code, in its preferred form, to the OpenJDK tree. Thhis has practical advantages to do with traceability and security, and in-principle reasons to do with basic Open Source practice too. On the other side, there are no disadvantages.
> > 
> > 
> > Do you suggest to copy the whole sleef source repo into jdk?
> 
> I think so, along with scripting that generates the preprocessed file we use. It might be the case that there are some sleef files not used at all they could be omitted, but I'm not sure it would be useful, and from a traceability point of view it's probably best to grab it all, unless it's really huge

Given the Sleef build system currently uses cmake, we would have two choices to build the header files as part of the OpenJDK build system:
1. take a dependency on cmake in order to build the Sleef headers
2. write a custom build system for Sleef to integrate into OpenJDK

Neither approach sound good to me as a mandatory option.

However, if we are to allow the person building OpenJDK to _optionally_ generate the headers from a Sleef source checkout (provided by the user with a `--with-sleef-src=/path/to/sleef`), we can then more easily take the assumption that the user has installed the necessary dependencies. That would also be in line with how binutils is being built and integrated.

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PR Comment: https://git.openjdk.org/jdk/pull/18605#issuecomment-2229040615