RFR: 8364128: Improve gathering of cpu feature names using stringStream [v5]

[Yudi Zheng]

On Thu, 14 Aug 2025 14:10:37 GMT, Ashutosh Mehra <asmehra at openjdk.org> wrote:

>> src/hotspot/cpu/aarch64/vm_version_aarch64.hpp line 148:
>> 
>>> 146: 
>>> 147:   enum Feature_Flag {
>>> 148: #define DECLARE_CPU_FEATURE_FLAG(id, name, bit) CPU_##id = bit,
>> 
>> It would be greatly appreciated if you could give the Graal devs a heads-up when changing CPU feature flags. JVMCI sees different CPU features with this change, and eventually leads to SIGILL by generating instruction not supported by the underlying CPU.
>
> @mur47x111 sorry for breaking JVMCI with this. I was not aware of such a dependency at all and I touched this code for the first time. For future work, how do I check if my change in hotspot has the potential to break JVMCI? And what is the best forum to inform about such changes?

I will add a JVMCI test to assert this. You can inform us via `/label add graal`

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PR Review Comment: https://git.openjdk.org/jdk/pull/26515#discussion_r2278563087