RFR: 8366024: Remove unnecessary InstanceKlass::cast()

[Ioi Lam]

On Wed, 27 Aug 2025 09:17:31 GMT, Andrew Dinn <adinn at openjdk.org> wrote:

> I found two more occurrences of casting super() to InstanceKlass:
> 
> ```
> src/hotspot/share/jfr/leakprofiler/chains/edgeUtils.cpp:79
> 
>     ik = (const InstanceKlass*)ik->super();
> ```

I fixed this one with `java_super()`. Similar to the case in deoptimization.cpp, the cost is dominated by the JavaFieldStream so a virtual call should be fine here.

> ```src/hotspot/share/prims/jni.cpp:209
> 
> intptr_t jfieldIDWorkaround::encode_klass_hash(Klass* k, int offset) {
>  if (offset <= small_offset_mask) {
>     Klass* field_klass = k;
>     Klass* super_klass = field_klass->super();
>     // With compressed oops the most super class with nonstatic fields would
>     // be the owner of fields embedded in the header.
>     while (InstanceKlass::cast(super_klass)->has_nonstatic_fields() &&
>            InstanceKlass::cast(super_klass)->contains_field_offset(offset)) {
>       field_klass = super_klass;   // super contains the field also
>       super_klass = field_klass->super();
>     }
> ```

Here we have the same logic as in the (removed) `superklass()` function, without any explanation why the cast is safe. The code seems to assume that the incoming `k` parameter cannot be a type such as `[Ljava/lang/String;`. I am not familiar with this code, so I will leave it as is.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/26908#issuecomment-3229259517