RFR: 8312425: [vectorapi] AArch64: Optimize vector math operations with SLEEF [v3]

[Xiaohong Gong]

On Tue, 21 Nov 2023 14:12:13 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

>> This is just used to print the result of `AC_MSG_CEHCKING[if ARM SVE feature is supported]` in configure.
>
> Ah, now I se what you are trying to do here. First of all, in the detection part, only set `SVE_FEATURE_SUPPORT`. Then you can handle the `SVE_CFLAGS` addition elsewhere/later. 
> 
> Secondly, you should not mix these `SVE_CFLAGS` with the spleef C flags. Keeping them separate will allow for LIBSLEEF_CFLAGS to be named just that.
> 
> Thirdly, I do not like at all how you just come crashing in setting `-march` like that. The `-march` flag is handled by `FLAGS_SETUP_ABI_PROFILE`. 
> 
> Actually, now that I think of it, this is just completely wrong! You are checking on features on the build machine, to determine what target machine code to generate, with no way to override. 
> 
> You need to break out the -march handling separately. It should be moved to FLAGS_SETUP_ABI_PROFILE. I'm guessing you will need to make something like a `aarch64-sve` profile, and possibly try to auto-select it based on the result of the sve test program above. But changing `OPENJDK_TARGET_ABI_PROFILE` can have further consequences; I do not know the full extent on the top of my head.

Thanks for the advice! I will take a consideration for it.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16234#discussion_r1402843737