`cargo-clif build` slower than `cargo build`!

[frederikhors]

I'm trying compile times on a medium size project and SURPRISE!

• Windows 11, cargo 1.98.0 (797e8a9bc 2026-08-05):

cargo build: 1m 22s

• Windows 11, cargo 1.100.0-nightly (e8cb624d5 2026-08-22) (cargo-clif @ 2bc05d4):

cargo-clif build: 1m 34s

cargo-clif build is slower than cargo build!

Of course I cargo clean before each command.

Instead the incremental build is different:

cargo build: 27s

cargo-clif build: 18s

Any idea?

[bjorn3]

Can you also check the LLVM backend on nightly to make sure this is not a perf regression of the rustc frontend?

[frederikhors]

Are you asking me to try cargo build on nightly without clif?

[frederikhors]

I have more manual bench:

Windows 11, cargo 1.98.0 (797e8a9bc 2026-08-05)

• cold cargo build 1m 22s

• incremental cargo build 27s

Windows 11, cargo 1.100.0-nightly (e8cb624d5 2026-08-22) (cargo-clif @ 2bc05d4)

• cold cargo-clif build 1m 34s

• incremental cargo-clif build 18s

Windows 11, cargo 1.100.0-nightly (e8cb624d5 2026-08-22)

• cold cargo +nightly build 1m 38s

• incremental cargo +nightly build 19s

---

Ubuntu 26.04, cargo 1.98.0 (797e8a9bc 2026-08-05)

• cold cargo build 54s

• incremental cargo build 10s

Ubuntu 26.04, cargo 1.100.0-nightly (e8cb624d5 2026-08-22) (cargo-clif @ 2bc05d4)

• cold cargo-clif build 1m 1s

• incremental cargo-clif build 10s

Ubuntu 26.04, cargo 1.100.0-nightly (e8cb624d5 2026-08-22)

• cold cargo +nightly build 1m 2s

• incremental cargo +nightly build 10s

For incremental builds cargo-clif is useless today. I'm positively shocked!

[frederikhors]

I have new data with mold:

Ubuntu 26.04, cargo 1.98.0 (797e8a9bc 2026-08-05), mold 2.42.0

• cold cargo build 55s

• incremental cargo build 10s

Ubuntu 26.04, cargo 1.100.0-nightly (e8cb624d5 2026-08-22) (cargo-clif @ 2bc05d4), mold 2.42.0

• cold cargo-clif build 1m 5s

• incremental cargo-clif build 13s

Ubuntu 26.04, cargo 1.100.0-nightly (e8cb624d5 2026-08-22), mold 2.42.0

• cold cargo +nightly build 1m 3s

• incremental cargo +nightly build 10s