Would an atomic mutable subclass cache (not sure what it's used for, downcasting?) be unnecessary in a language built around static rather than dynamic dispatch

Would an atomic mutable subclass cache (not sure what it's used for, downcasting?) be unnecessary in a language built around static rather than dynamic dispatch by default, like C/C++/Rust and perhaps Go? Or would it still speed up dynamically dispatched code, but is less practical or worthwhile so it isn't used in practice? (Though Rust's Arc also suffers from atomic contention similar to this blog post, when used across dozens of threads: https://pkolaczk.github.io/server-slower-than-a-laptop/ https://pkolaczk.github.io/server-slower-than-a-laptop/) Also it's somewhat ironic that the JVM source code (https://github.com/openjdk/jdk8u/blob/jdk8u352-b07/hotspot/src/cpu/x86/vm/macroAssembler_x86.cpp#L5093 https://github.com/openjdk/jdk8u/blob/jdk8u352-b07/hotspot/s...) says "This code is rarely used, so simplicity is a virtue here" at the site of a bottleneck.