RFR: 8373633: C2: Use interface receiver type to improve CHA decisions [v2]

[Quan Anh Mai]

On Thu, 29 Jan 2026 11:37:55 GMT, Quan Anh Mai <qamai at openjdk.org> wrote:

>> Vladimir Ivanov has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:
>> 
>>  - addtional case
>>  - Merge branch 'master' into cha.intf.recv
>>  - Use receiver type to improve CHA decisions
>
> src/hotspot/share/opto/type.cpp line 4593:
> 
>> 4591: // For an interface instance reports one of most specific superinterfaces with a unique implementor.
>> 4592: ciInstanceKlass* TypeInstPtr::has_unique_implementor(ciInstanceKlass* context_intf) const {
>> 4593:   if (is_interface() && context_intf->is_interface()) {
> 
> I feel like you are making it unnecessarily complicated. `_interface` is the set of interfaces this `TypeInstPtr` must satisfy. As a result, a check like this would be sufficient (not real code):
> 
>     for (ciInstanceKlass* intf : _interfaces) {
>       ciInstanceKlass* candidate = intf->unique_implementor();
>       if (candidate != nullptr) {
>         return candidate;
>       }
>     }

Even better, since these `_interfaces` are trusted, we don't need to emit a runtime check for the type.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28811#discussion_r2741224374