Compilers are usually at a disadvantage compared to human programmers, as they're under pressure to produce code as quickly as possible; seconds if possible, minutes at worst. A human may spend many hours or days writing, profiling, testing, etc. This biases the kinds of algorithms that compilers use (especially JITs, since they have even stricter requirements).

It would be nice to have a compiler/optimiser/analyser/profiler/tester/fuzzer/etc. designed to run for long periods, running all sorts of improvement-finding algorithms, building up a knowledge base about the code on disk (which can be updated incrementally when the code changes), and providing reports and messages to the user.

When we're about to embark on a deep dive, for optimisation/debugging/etc. we can fire up this assistant and have it running for the entire time we're devoting to the problem. It can even keep running overnight if we spend several days on the issue.