Binary size impact of enabling -Zshare-generics for opt-level=z #142164
Description
opt-level=z and opt-level=s implicitly enable -Zshare-generics. While this can have positive binary size impacts, it can also have negative binary size impacts because it reduces LLVMs ability to inline functions.
I have done some analysis on a bunch of projects, comparing the output from size for different opt levels.
Script
#!/usr/bin/env bash
set -euxo pipefail
bins=$(cargo metadata --format-version 1 | jq '.packages.[].targets.[] | select(.crate_types == ["bin"]) | select(.src_path | contains("index.crates.io") | not) | .name' -r)
echo checking "$bins"
projdir=$(basename "$(realpath .)")
truncate -s 0 results.csv
build() {
type="$1"
rustflags="$2"
wrapper=$(mktemp)
{
echo '#!/usr/bin/env bash'
echo 'r=$1'
echo "shift"
echo exec '$r' '"$@"' "$rustflags"
} > "$wrapper"
chmod +x "$wrapper"
echo "meow"
cat "$wrapper"
cargo clean
bins=$(RUSTC_WRAPPER="$wrapper" cargo build --release --message-format=json-render-diagnostics | jq 'select(.reason == "compiler-artifact") | select(.executable != null) | .executable' -r)
IFS=$'\n'
for bin in $bins; do
echo "$bin"
s=$(size "$bin" | python3 -c 'import sys;x=sys.stdin.read();print(x.split("\n")[1].split()[0])')
echo "$projdir,$(basename "$bin"),$type,$s" >> results.csv
done
rm "$wrapper"
}
build "2" "-Copt-level=2"
build "3" "-Copt-level=3"
build "s" "-Copt-level=s"
build "s-no-share" "-Copt-level=s -Zshare-generics=false"
build "z" "-Copt-level=z"
build "z-no-share" "-Copt-level=z -Zshare-generics=false"I got the following results:
Results CSV
project,binary,opt-level,text size
rustc-perf,bootstrap-rustc,2,401390
rustc-perf,bootstrap-rustc,3,401518
rustc-perf,bootstrap-rustc,s,401454
rustc-perf,bootstrap-rustc,s-no-share,400286
rustc-perf,bootstrap-rustc,z,402450
rustc-perf,bootstrap-rustc,z-no-share,401562
nextest,build-seed-archive,2,928761
nextest,build-seed-archive,3,928241
nextest,build-seed-archive,s,906783
nextest,build-seed-archive,s-no-share,877006
nextest,build-seed-archive,z,939734
nextest,build-seed-archive,z-no-share,896072
cargo,cargo,2,26769308
cargo,cargo,3,27035766
cargo,cargo,s,23441682
cargo,cargo,s-no-share,22941899
cargo,cargo,z,23003221
cargo,cargo,z-no-share,21949429
nextest,cargo-nextest,2,15327059
nextest,cargo-nextest,3,15331428
nextest,cargo-nextest,s,13378951
nextest,cargo-nextest,s-no-share,13151176
nextest,cargo-nextest,z,13347017
nextest,cargo-nextest,z-no-share,12840776
nextest,cargo-nextest-dup,2,15327071
nextest,cargo-nextest-dup,3,15331440
nextest,cargo-nextest-dup,s,13378951
nextest,cargo-nextest-dup,s-no-share,13151176
nextest,cargo-nextest-dup,z,13347017
nextest,cargo-nextest-dup,z-no-share,12840776
cluelessh,cluelessh,2,3639610
cluelessh,cluelessh,3,3637618
cluelessh,cluelessh,s,3230404
cluelessh,cluelessh,s-no-share,3137054
cluelessh,cluelessh,z,3298182
cluelessh,cluelessh,z-no-share,3160263
cluelessh,cluelessh-agentctl,2,3081768
cluelessh,cluelessh-agentctl,3,3090680
cluelessh,cluelessh-agentctl,s,2752168
cluelessh,cluelessh-agentctl,s-no-share,2668998
cluelessh,cluelessh-agentctl,z,2812587
cluelessh,cluelessh-agentctl,z-no-share,2692805
cluelessh,cluelessh-dos,2,3363901
cluelessh,cluelessh-dos,3,3374685
cluelessh,cluelessh-dos,s,3006511
cluelessh,cluelessh-dos,s-no-share,2909317
cluelessh,cluelessh-dos,z,3069389
cluelessh,cluelessh-dos,z-no-share,2936446
cluelessh,cluelessh-faked,2,3307574
cluelessh,cluelessh-faked,3,3300062
cluelessh,cluelessh-faked,s,2953214
cluelessh,cluelessh-faked,s-no-share,2889345
cluelessh,cluelessh-faked,z,3030640
cluelessh,cluelessh-faked,z-no-share,2939401
cluelessh,cluelessh-key,2,1138744
cluelessh,cluelessh-key,3,1156436
cluelessh,cluelessh-key,s,1031633
cluelessh,cluelessh-key,s-no-share,1003059
cluelessh,cluelessh-key,z,1028888
cluelessh,cluelessh-key,z-no-share,985054
cluelessh,cluelesshd,2,4675529
cluelessh,cluelesshd,3,4666229
cluelessh,cluelesshd,s,4138714
cluelessh,cluelesshd,s-no-share,3995755
cluelessh,cluelesshd,z,4208701
cluelessh,cluelesshd,z-no-share,4024121
cluelessh,cluelesshd-sftp-server,2,2481705
cluelessh,cluelesshd-sftp-server,3,2489701
cluelessh,cluelesshd-sftp-server,s,2244369
cluelessh,cluelesshd-sftp-server,s-no-share,2193279
cluelessh,cluelesshd-sftp-server,z,2304838
cluelessh,cluelesshd-sftp-server,z-no-share,2229436
rustc-perf,collector,2,11333776
rustc-perf,collector,3,11340184
rustc-perf,collector,s,10138920
rustc-perf,collector,s-no-share,9960872
rustc-perf,collector,z,10061628
rustc-perf,collector,z-no-share,9756252
rustc-perf,fetch-latest,2,3041314
rustc-perf,fetch-latest,3,3070746
rustc-perf,fetch-latest,s,2775574
rustc-perf,fetch-latest,s-no-share,2720170
rustc-perf,fetch-latest,z,2766783
rustc-perf,fetch-latest,z-no-share,2687495
hello-world,hello-world,2,344751
hello-world,hello-world,3,344751
hello-world,hello-world,s,344719
hello-world,hello-world,s-no-share,344719
hello-world,hello-world,z,344767
hello-world,hello-world,z-no-share,344767
rustc-perf,import-sqlite,2,7313831
rustc-perf,import-sqlite,3,7395099
rustc-perf,import-sqlite,s,6774471
rustc-perf,import-sqlite,s-no-share,6693379
rustc-perf,import-sqlite,z,6778407
rustc-perf,import-sqlite,z-no-share,6649119
nextest,internal-test,2,339532
nextest,internal-test,3,339532
nextest,internal-test,s,339500
nextest,internal-test,s-no-share,339500
nextest,internal-test,z,339540
nextest,internal-test,z-no-share,339540
Neotron-Pico-BIOS,neotron-pico-bios,2,69320
Neotron-Pico-BIOS,neotron-pico-bios,3,73996
Neotron-Pico-BIOS,neotron-pico-bios,s,52860
Neotron-Pico-BIOS,neotron-pico-bios,s-no-share,52840
Neotron-Pico-BIOS,neotron-pico-bios,z,51192
Neotron-Pico-BIOS,neotron-pico-bios,z-no-share,50960
nextest,passthrough,2,411770
nextest,passthrough,3,411294
nextest,passthrough,s,411125
nextest,passthrough,s-no-share,409746
nextest,passthrough,z,411123
nextest,passthrough,z-no-share,410024
rustc-perf,postgres-to-sqlite,2,7461386
rustc-perf,postgres-to-sqlite,3,7532230
rustc-perf,postgres-to-sqlite,s,6841686
rustc-perf,postgres-to-sqlite,s-no-share,6751134
rustc-perf,postgres-to-sqlite,z,6813466
rustc-perf,postgres-to-sqlite,z-no-share,6664510
ripgrep,rg,2,4378977
ripgrep,rg,3,4435131
ripgrep,rg,s,4013053
ripgrep,rg,s-no-share,3962587
ripgrep,rg,z,3993959
ripgrep,rg,z-no-share,3913056
rust-analyzer,rust-analyzer,2,36815675
rust-analyzer,rust-analyzer,3,36845571
rust-analyzer,rust-analyzer,s,29047888
rust-analyzer,rust-analyzer,s-no-share,30842033
rust-analyzer,rust-analyzer,z,27646232
rust-analyzer,rust-analyzer,z-no-share,28589921
rust-analyzer,rust-analyzer-proc-macro-srv,2,350694
rust-analyzer,rust-analyzer-proc-macro-srv,3,350690
rust-analyzer,rust-analyzer-proc-macro-srv,s,350690
rust-analyzer,rust-analyzer-proc-macro-srv,s-no-share,350550
rust-analyzer,rust-analyzer-proc-macro-srv,z,350610
rust-analyzer,rust-analyzer-proc-macro-srv,z-no-share,350490
rustc-perf,rustc-fake,2,455290
rustc-perf,rustc-fake,3,456474
rustc-perf,rustc-fake,s,452790
rustc-perf,rustc-fake,s-no-share,452150
rustc-perf,rustc-fake,z,453770
rustc-perf,rustc-fake,z-no-share,451770
nextest,rustc-shim,2,398876
nextest,rustc-shim,3,398928
nextest,rustc-shim,s,397635
nextest,rustc-shim,s-no-share,397828
nextest,rustc-shim,z,397343
nextest,rustc-shim,z-no-share,397944
rusty-clock,rusty-clock,2,49052
rusty-clock,rusty-clock,3,51764
rusty-clock,rusty-clock,s,37468
rusty-clock,rusty-clock,s-no-share,37664
rusty-clock,rusty-clock,z,35320
rusty-clock,rusty-clock,z-no-share,35476
rustc-perf,site,2,15569433
rustc-perf,site,3,15585737
rustc-perf,site,s,13880257
rustc-perf,site,s-no-share,13747097
rustc-perf,site,z,13614909
rustc-perf,site,z-no-share,13353497
rustc-perf,sqlite-to-postgres,2,7937442
rustc-perf,sqlite-to-postgres,3,8016754
rustc-perf,sqlite-to-postgres,s,7192830
rustc-perf,sqlite-to-postgres,s-no-share,7104766
rustc-perf,sqlite-to-postgres,z,7154074
rustc-perf,sqlite-to-postgres,z-no-share,6998258
rust-analyzer,xtask,2,1685422
rust-analyzer,xtask,3,1671190
rust-analyzer,xtask,s,1535085
rust-analyzer,xtask,s-no-share,1502505
rust-analyzer,xtask,z,1527938
rust-analyzer,xtask,z-no-share,1479014
Results Table
| project | binary | opt-level | text size |
|---|---|---|---|
| rustc-perf | bootstrap-rustc | 2 | 401390 |
| rustc-perf | bootstrap-rustc | 3 | 401518 |
| rustc-perf | bootstrap-rustc | s | 401454 |
| rustc-perf | bootstrap-rustc | s-no-share | 400286 |
| rustc-perf | bootstrap-rustc | z | 402450 |
| rustc-perf | bootstrap-rustc | z-no-share | 401562 |
| nextest | build-seed-archive | 2 | 928761 |
| nextest | build-seed-archive | 3 | 928241 |
| nextest | build-seed-archive | s | 906783 |
| nextest | build-seed-archive | s-no-share | 877006 |
| nextest | build-seed-archive | z | 939734 |
| nextest | build-seed-archive | z-no-share | 896072 |
| cargo | cargo | 2 | 26769308 |
| cargo | cargo | 3 | 27035766 |
| cargo | cargo | s | 23441682 |
| cargo | cargo | s-no-share | 22941899 |
| cargo | cargo | z | 23003221 |
| cargo | cargo | z-no-share | 21949429 |
| nextest | cargo-nextest | 2 | 15327059 |
| nextest | cargo-nextest | 3 | 15331428 |
| nextest | cargo-nextest | s | 13378951 |
| nextest | cargo-nextest | s-no-share | 13151176 |
| nextest | cargo-nextest | z | 13347017 |
| nextest | cargo-nextest | z-no-share | 12840776 |
| nextest | cargo-nextest-dup | 2 | 15327071 |
| nextest | cargo-nextest-dup | 3 | 15331440 |
| nextest | cargo-nextest-dup | s | 13378951 |
| nextest | cargo-nextest-dup | s-no-share | 13151176 |
| nextest | cargo-nextest-dup | z | 13347017 |
| nextest | cargo-nextest-dup | z-no-share | 12840776 |
| cluelessh | cluelessh | 2 | 3639610 |
| cluelessh | cluelessh | 3 | 3637618 |
| cluelessh | cluelessh | s | 3230404 |
| cluelessh | cluelessh | s-no-share | 3137054 |
| cluelessh | cluelessh | z | 3298182 |
| cluelessh | cluelessh | z-no-share | 3160263 |
| cluelessh | cluelessh-agentctl | 2 | 3081768 |
| cluelessh | cluelessh-agentctl | 3 | 3090680 |
| cluelessh | cluelessh-agentctl | s | 2752168 |
| cluelessh | cluelessh-agentctl | s-no-share | 2668998 |
| cluelessh | cluelessh-agentctl | z | 2812587 |
| cluelessh | cluelessh-agentctl | z-no-share | 2692805 |
| cluelessh | cluelessh-dos | 2 | 3363901 |
| cluelessh | cluelessh-dos | 3 | 3374685 |
| cluelessh | cluelessh-dos | s | 3006511 |
| cluelessh | cluelessh-dos | s-no-share | 2909317 |
| cluelessh | cluelessh-dos | z | 3069389 |
| cluelessh | cluelessh-dos | z-no-share | 2936446 |
| cluelessh | cluelessh-faked | 2 | 3307574 |
| cluelessh | cluelessh-faked | 3 | 3300062 |
| cluelessh | cluelessh-faked | s | 2953214 |
| cluelessh | cluelessh-faked | s-no-share | 2889345 |
| cluelessh | cluelessh-faked | z | 3030640 |
| cluelessh | cluelessh-faked | z-no-share | 2939401 |
| cluelessh | cluelessh-key | 2 | 1138744 |
| cluelessh | cluelessh-key | 3 | 1156436 |
| cluelessh | cluelessh-key | s | 1031633 |
| cluelessh | cluelessh-key | s-no-share | 1003059 |
| cluelessh | cluelessh-key | z | 1028888 |
| cluelessh | cluelessh-key | z-no-share | 985054 |
| cluelessh | cluelesshd | 2 | 4675529 |
| cluelessh | cluelesshd | 3 | 4666229 |
| cluelessh | cluelesshd | s | 4138714 |
| cluelessh | cluelesshd | s-no-share | 3995755 |
| cluelessh | cluelesshd | z | 4208701 |
| cluelessh | cluelesshd | z-no-share | 4024121 |
| cluelessh | cluelesshd-sftp-server | 2 | 2481705 |
| cluelessh | cluelesshd-sftp-server | 3 | 2489701 |
| cluelessh | cluelesshd-sftp-server | s | 2244369 |
| cluelessh | cluelesshd-sftp-server | s-no-share | 2193279 |
| cluelessh | cluelesshd-sftp-server | z | 2304838 |
| cluelessh | cluelesshd-sftp-server | z-no-share | 2229436 |
| rustc-perf | collector | 2 | 11333776 |
| rustc-perf | collector | 3 | 11340184 |
| rustc-perf | collector | s | 10138920 |
| rustc-perf | collector | s-no-share | 9960872 |
| rustc-perf | collector | z | 10061628 |
| rustc-perf | collector | z-no-share | 9756252 |
| rustc-perf | fetch-latest | 2 | 3041314 |
| rustc-perf | fetch-latest | 3 | 3070746 |
| rustc-perf | fetch-latest | s | 2775574 |
| rustc-perf | fetch-latest | s-no-share | 2720170 |
| rustc-perf | fetch-latest | z | 2766783 |
| rustc-perf | fetch-latest | z-no-share | 2687495 |
| hello-world | hello-world | 2 | 344751 |
| hello-world | hello-world | 3 | 344751 |
| hello-world | hello-world | s | 344719 |
| hello-world | hello-world | s-no-share | 344719 |
| hello-world | hello-world | z | 344767 |
| hello-world | hello-world | z-no-share | 344767 |
| rustc-perf | import-sqlite | 2 | 7313831 |
| rustc-perf | import-sqlite | 3 | 7395099 |
| rustc-perf | import-sqlite | s | 6774471 |
| rustc-perf | import-sqlite | s-no-share | 6693379 |
| rustc-perf | import-sqlite | z | 6778407 |
| rustc-perf | import-sqlite | z-no-share | 6649119 |
| nextest | internal-test | 2 | 339532 |
| nextest | internal-test | 3 | 339532 |
| nextest | internal-test | s | 339500 |
| nextest | internal-test | s-no-share | 339500 |
| nextest | internal-test | z | 339540 |
| nextest | internal-test | z-no-share | 339540 |
| Neotron-Pico-BIOS | neotron-pico-bios | 2 | 69320 |
| Neotron-Pico-BIOS | neotron-pico-bios | 3 | 73996 |
| Neotron-Pico-BIOS | neotron-pico-bios | s | 52860 |
| Neotron-Pico-BIOS | neotron-pico-bios | s-no-share | 52840 |
| Neotron-Pico-BIOS | neotron-pico-bios | z | 51192 |
| Neotron-Pico-BIOS | neotron-pico-bios | z-no-share | 50960 |
| nextest | passthrough | 2 | 411770 |
| nextest | passthrough | 3 | 411294 |
| nextest | passthrough | s | 411125 |
| nextest | passthrough | s-no-share | 409746 |
| nextest | passthrough | z | 411123 |
| nextest | passthrough | z-no-share | 410024 |
| rustc-perf | postgres-to-sqlite | 2 | 7461386 |
| rustc-perf | postgres-to-sqlite | 3 | 7532230 |
| rustc-perf | postgres-to-sqlite | s | 6841686 |
| rustc-perf | postgres-to-sqlite | s-no-share | 6751134 |
| rustc-perf | postgres-to-sqlite | z | 6813466 |
| rustc-perf | postgres-to-sqlite | z-no-share | 6664510 |
| ripgrep | rg | 2 | 4378977 |
| ripgrep | rg | 3 | 4435131 |
| ripgrep | rg | s | 4013053 |
| ripgrep | rg | s-no-share | 3962587 |
| ripgrep | rg | z | 3993959 |
| ripgrep | rg | z-no-share | 3913056 |
| rust-analyzer | rust-analyzer | 2 | 36815675 |
| rust-analyzer | rust-analyzer | 3 | 36845571 |
| rust-analyzer | rust-analyzer | s | 29047888 |
| rust-analyzer | rust-analyzer | s-no-share | 30842033 |
| rust-analyzer | rust-analyzer | z | 27646232 |
| rust-analyzer | rust-analyzer | z-no-share | 28589921 |
| rust-analyzer | rust-analyzer-proc-macro-srv | 2 | 350694 |
| rust-analyzer | rust-analyzer-proc-macro-srv | 3 | 350690 |
| rust-analyzer | rust-analyzer-proc-macro-srv | s | 350690 |
| rust-analyzer | rust-analyzer-proc-macro-srv | s-no-share | 350550 |
| rust-analyzer | rust-analyzer-proc-macro-srv | z | 350610 |
| rust-analyzer | rust-analyzer-proc-macro-srv | z-no-share | 350490 |
| rustc-perf | rustc-fake | 2 | 455290 |
| rustc-perf | rustc-fake | 3 | 456474 |
| rustc-perf | rustc-fake | s | 452790 |
| rustc-perf | rustc-fake | s-no-share | 452150 |
| rustc-perf | rustc-fake | z | 453770 |
| rustc-perf | rustc-fake | z-no-share | 451770 |
| nextest | rustc-shim | 2 | 398876 |
| nextest | rustc-shim | 3 | 398928 |
| nextest | rustc-shim | s | 397635 |
| nextest | rustc-shim | s-no-share | 397828 |
| nextest | rustc-shim | z | 397343 |
| nextest | rustc-shim | z-no-share | 397944 |
| rusty-clock | rusty-clock | 2 | 49052 |
| rusty-clock | rusty-clock | 3 | 51764 |
| rusty-clock | rusty-clock | s | 37468 |
| rusty-clock | rusty-clock | s-no-share | 37664 |
| rusty-clock | rusty-clock | z | 35320 |
| rusty-clock | rusty-clock | z-no-share | 35476 |
| rustc-perf | site | 2 | 15569433 |
| rustc-perf | site | 3 | 15585737 |
| rustc-perf | site | s | 13880257 |
| rustc-perf | site | s-no-share | 13747097 |
| rustc-perf | site | z | 13614909 |
| rustc-perf | site | z-no-share | 13353497 |
| rustc-perf | sqlite-to-postgres | 2 | 7937442 |
| rustc-perf | sqlite-to-postgres | 3 | 8016754 |
| rustc-perf | sqlite-to-postgres | s | 7192830 |
| rustc-perf | sqlite-to-postgres | s-no-share | 7104766 |
| rustc-perf | sqlite-to-postgres | z | 7154074 |
| rustc-perf | sqlite-to-postgres | z-no-share | 6998258 |
| rust-analyzer | xtask | 2 | 1685422 |
| rust-analyzer | xtask | 3 | 1671190 |
| rust-analyzer | xtask | s | 1535085 |
| rust-analyzer | xtask | s-no-share | 1502505 |
| rust-analyzer | xtask | z | 1527938 |
| rust-analyzer | xtask | z-no-share | 1479014 |
It looks like -Zshare-generics is sometimes an improvement and sometimes a regression. It is not immediately clear to me whether enabling it as currently is the right tradeoff of whether it would make more sense to disable it by default.