Compilers also usually give you the same output for the same input. And fwiw I do spend quite a lot of time reading compiler output to check that it's not doing something stupid or unexpected (usually as part of optimization work).

Also this sort of 'technological whataboutism' really isn't helpful, compilers are entirely different from LLMs. I agree that it doesn't make much sense to read or review LLM output in detail, but I also don't plan to use LLM output for anything important or mission critical. That would be irresponsible.

In addition, when we usually say that triggering undefined behavior on C can start a game of Tetris or format your hard disk we're usually joking (or at least exaggerating), i.e. the most common failure conditions of compilers are really limited in scope, and very likely caught by whatever testing mechanism you use for the software.

No such limits for LLMs where losing all your files is about par for the course for everyone who uses them regularly.

JIT compilers certainly do not give the same machine code for the same input.

The actual machine code depends on several parameters, and it is very hard to replicate them, hence why many devs get benchmarks with JITs wrong.

Additionally, compiler optimisation passes with machine learning is starting to be a thing, yet another way how the machine code differs for the same input across compiler executions.