RFR: 8352218: RISC-V: Zvfh requires RVV [v2]

[Hamlin Li]

On Thu, 20 Mar 2025 15:36:21 GMT, Robbin Ehn <rehn at openjdk.org> wrote:

>> src/hotspot/cpu/riscv/vm_version_riscv.hpp line 92:
>> 
>>> 90:   void update_flag() {                     \
>>> 91:       assert(enabled(), "Must be.");       \
>>> 92:       if (FLAG_IS_DEFAULT(flag)) {         \
>> 
>> As this patch introduces a way to automatically disable a flag based on its dependant flag, this could introduce potential issue if the expected order is not guarantee when writing the code. It's better to have an assert there, this could be acheive by just using the existing `_value`, e.g. 
>> `assert(dep.value() != -1);`
>> Or maybe it's better to introduce a new field like `initialized`?
>
> You can check that in compile time with:
> `STATIC_ASSERT(offsetof(VM_Version, ext_ZvXX) > offsetof(VM_Version, ext_V));`

That's also fine.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24094#discussion_r2005980982