For safe Rust, sure, there are limitations: you can't turn off bounds checks, for instance. But all Rust is partially unsafe Rust, because the standard library uses unsafe code ⃰. So it's a fuzzy distinction.
⃰ ⃰You wouldn't want it any other way. Implementing low-level functionality as unsafe code allows us to write code, not compiler-code-that-generates-code.
In pseudocode
Goto = Start;
While(Goto!=End) {
Match(Goto) {
...
}
}
* In C++, using goto: https://godbolt.org/z/YqCMbU
* In Rust, with relooped CFG: https://godbolt.org/z/IIXtKo
The compiler was obviously not able to unroll the relooped code into the original CFG.
A specific example: in principle, the compiler could see the exact target of every continue in the Rust code, so the continue on line 34 could go directly to line 27 (or, better, as in C++ the basic blocks could just be laid out adjacently), but the compiler does not actually do this and there are a bunch of unnecessary tests on the path between those two lines.
This doesn't work in general, and is ... impossible to maintain, but it's not an unreasonable approach for generated code.