> What people usually complain about is rustc being slow overall, not the LLVM passes.
The LLVM phases are usually the dominating factor in Rust compile times (the other big single contender is the linking phase). However, when the Rust developers point this out, they are also careful to mention that this may be due to the rustc frontend generating suboptimal IR as input to LLVM; we can both acknowledge that LLVM is often the bottleneck for Rust compilation while also not framing it as a failure on LLVM's part (though at the same time it is uncontroversial to state that LLVM does err on the side of superior codegen versus minimal compilation time, hence the niche that alternative compilers like Cranelift seek to fill).
This is true to some degree — Rust does more work than most programming languages, and that work will always take some time — but the Cranelift backend is also measurably faster than the LLVM one.
Source? LLVM is fast for what it does.
What people usually complain about is rustc being slow overall, not the LLVM passes.