RFR: 8364184: [REDO] AArch64: [VectorAPI] sve vector math operations are not supported after JDK-8353217

[Fei Gao]

On Mon, 11 Aug 2025 09:08:39 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

>> This patch fixes a typo introduced in JDK-8353217, which incorrectly disabled SVE vector math symbols. As a result, some vector math test cases such as `jdk/incubator/vector/Double256VectorTests.java` threw
>> exceptions on 256-bit `sve` machines with errors like:
>> `java.lang.InternalError: not supported: ACOS Species[double, 4, S_256_BIT] acosdx_u10sve.`
>> 
>> `test/jdk/jdk/incubator/vector` passed on 256-bit `sve` and `neon` machine.
>
> make/autoconf/flags-cflags.m4 line 943:
> 
>> 941:   # libvectormath. Apple Silicon does not support SVE; use macOS as a proxy for
>> 942:   # that check.
>> 943:   if test "x$OPENJDK_TARGET_CPU" = "xaarch64" && test "x$OPENJDK_TARGET_CPU" = "xlinux"; then
> 
> This is really disturbing! Has really no-one noticed until now that SVE support broke with 8353217?
> 
> Also, this PR fixes two unrelated errors -- a bug introduced in JDK-8353217, and a compiler error. I think it would be better for everybody's sanity, and future backport efforts, if you split it into two.

@magicus thanks for reviewing this. That sounds reasonable. 

I’ve prepared a new version of the code that resolves the `gcc `error without introducing any compatibility issues. My plan is to first fix the `gcc` issue, and then follow up with a separate patch to address the bug introduced in [JDK-8353217](https://bugs.openjdk.org/browse/JDK-8353217). Thanks.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26577#discussion_r2269137672