RFR: 8312425: [vectorapi] AArch64: Optimize vector math operations with SLEEF [v5]

[Magnus Ihse Bursie]

On Tue, 5 Dec 2023 07:21:32 GMT, Xiaohong Gong <xgong at openjdk.org> wrote:

>> also, ideally, you will add the corresponding specific overrides like in ffi:
>> 
>>   AC_ARG_WITH(libffi-include, [AS_HELP_STRING([--with-libffi-include],
>>       [specify directory for the libffi include files])])
>>   AC_ARG_WITH(libffi-lib, [AS_HELP_STRING([--with-libffi-lib],
>>       [specify directory for the libffi library])])
>
> Thanks for the suggestion @magicus !
> 
> The check in current `lib-sleef.m4` is very common:
> 
> -  If user has specified libsleef root by '--with-libsleef', we assume it is the manually built sleef lib. So only `lib/` and `include/` is checked. And the flags are set based on that path.
> - If user has not specified the libsleef root, and no `SYSROOT` is set, we try `PKG_CHECK` (like what you suggested)
> - Otherwise, check `sleef.h`   
>    - We assume the sleef module is installed under one of the valid system paths if the header can be found. So just linking with `-lsleef` will success.
> 
> It's an issue in current flow like what @theRealAph met. I will add the options like `--with-libsleef-lib` and `--with-libsleef-include` like ffi. Regarding to extending the check for`--with-libsleef`, I think we can just make it simple like what it is now. Or, we have to check all the potential valid lib paths like `lib/`, `lib64/`, or maybe `lib/aarch64-linux-gnu`. The same to the `include` part.  @theRealAph @magicus , WDYT?

I'm fine with adding just --with-libsleef-lib and --with-libsleef-include to specify them directly. This makes it at least possible to use, if not overly convenient, for people using a system like Andrew's. If it annoys someone too much, we can extend it later.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16234#discussion_r1415576201