Missed optimization opportunity: collapsing jump table

While working on a bytecode interpreter, we used the following Rust code that can be found in the attached godbolt link. It does not seem to recognize that the jump table is essentially just an identity and can be completely removed unless we remove one or two more lines from the bottom.

https://godbolt.org/z/bbdbbd595

Start with the Rust reproducer and generated output in the linked Godbolt example. Inspect the optimization behavior around the jump table and compare it with the reduced version that removes the remaining lines. Done means identifying the missed optimization and either producing a focused compiler fix with a regression test or documenting why the jump table cannot be eliminated.

Written by the indexing model from the issue text.