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spirv-builder: force a single CGU (codegen-unit). #1035

Merged
merged 2 commits into from
Apr 17, 2023
Merged

spirv-builder: force a single CGU (codegen-unit). #1035

merged 2 commits into from
Apr 17, 2023

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eddyb
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@eddyb eddyb commented Apr 15, 2023

The main reason rustc has a concept of "codegen units" is to allow running LLVM optimizations in parallel.
We have no such parallelism right now, so all CGUs do for us is cause wasteful duplication of work.
(this came up in other work where it caused a massive explosion of debuginfo)

I ran this to get the data in the table below (both before and after the change):

rm -rf target/spirv-builder/
cargo run -p example-runner-wgpu --release --no-default-features --features use-installed-tools -- -s Mouse
dust -csbrn10 target/spirv-builder/spirv-unknown-vulkan1.1
Before this PR (many CGUs)After this PR (1 CGU)
128M └─┬ spirv-unknown-vulkan1.1
128M   └─┬ release
117M     ├─┬ deps
 44M     │ ├── libcore-f3590347654738e9.rlib
 38M     │ ├── libcore-f3590347654738e9.rmeta
6.2M     │ ├── libglam-07642c7dac08746c.rlib
5.9M     │ └── libglam-07642c7dac08746c.rmeta
 10M     └─┬ incremental
7.9M       └─┬ spirv_std-3rzoyk5mydowb
7.9M         └─┬ s-gk2fjiu00l-scpc61-tw2x301r7v8h
5.5M           └── dep-graph.bin

123M └─┬ spirv-unknown-vulkan1.1
123M   └─┬ release
112M     ├─┬ deps
 43M     │ ├── libcore-b338bddeac41658a.rlib
 38M     │ ├── libcore-b338bddeac41658a.rmeta
6.2M     │ ├── libglam-3dba180d0288b28f.rlib
5.9M     │ └── libglam-3dba180d0288b28f.rmeta
 10M     └─┬ incremental
7.8M       └─┬ spirv_std-3dftucm2yp1ij
7.8M         └─┬ s-gk2fozx3vf-108z0x5-3fc8kftdgx7kt
5.5M           └── dep-graph.bin

@eddyb eddyb marked this pull request as ready for review April 15, 2023 16:03
@eddyb eddyb requested a review from oisyn as a code owner April 15, 2023 16:03
@eddyb eddyb enabled auto-merge (rebase) April 15, 2023 17:28
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@eddyb eddyb merged commit b560a21 into EmbarkStudios:main Apr 17, 2023
@eddyb eddyb deleted the sole-cgu branch April 17, 2023 11:24
@eddyb eddyb mentioned this pull request Apr 21, 2023
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@oisyn oisyn oisyn approved these changes

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@eddyb @LegNeato @oisyn