Building https://github.com/Nemo157/ripfs-rs with rustc 1.22.0-nightly (692b94ae2 2017-10-09) on a i5-6200U (2 cores, 4 threads) with SSD gives me:
RUSTFLAGS='-C codegen-units=1' cargo +nightly build
355.88s user 9.81s system 230% cpu 2:38.52 total
RUSTFLAGS='-C codegen-units=16' cargo +nightly build
383.83s user 10.60s system 267% cpu 2:27.20 total
RUSTFLAGS='-C codegen-units=1' cargo +nightly build --release
674.13s user 7.93s system 218% cpu 5:12.00 total
550.32s user 5.23s system 238% cpu 3:52.69 total
RUSTFLAGS='-C codegen-units=16 -Z thinlto' cargo +nightly build --release
1081.38s user 9.98s system 314% cpu 5:47.26 total
906.41s user 7.11s system 347% cpu 4:22.85 total
(the second timings for the release builds were performed a few hours after the first set of timings)
so, slightly slower on the release build, but performing much more work during that time. (No benchmarks for any of this code unfortunately).