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Handle LTO with an rlib/cdylib crate type #8254

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merged 1 commit into from
May 18, 2020

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alexcrichton
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In the case that LTO is happening but we're also generating a
cdylib/rlib simultatneously that means that the final artifact will use
the rlib but the cdylib still needs to be produced. To get this to work
the cdylib's dependency tree needs to be compiled with embedded bitcode.
The cdylib itself will be linked with the linker because we can't LTO an
rlib+cdylib compilation, but the final executable will need to load
bitcode from all its deps.

This is meant to address rust-lang/rust#72268

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@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 18, 2020
bar = { path = 'bar' }
registry-shared = "*"

[profile.release]

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The release here isn't necessary. You could use profile.dev and omit the --release further down

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Ah that's ok, these are just internal tests.

// to fully embed bitcode rather than simply generating just bitcode.
match lto_for_deps {
Lto::None => (Lto::None, Lto::None),
_ if unit.target.is_cdylib() => (Lto::EmbedBitcode, Lto::EmbedBitcode),
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Should this also check for staticlib? I did a quick test, and trying to link a .a file generated with -Clinker-plugin-lto causes the linker to seg fault.

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Whoops yes indeed! I've tweaked this a bit to handle both in one go.

In the case that LTO is happening but we're also generating a
cdylib/rlib simultatneously that means that the final artifact will use
the rlib but the cdylib still needs to be produced. To get this to work
the cdylib's dependency tree needs to be compiled with embedded bitcode.
The cdylib itself will be linked with the linker because we can't LTO an
rlib+cdylib compilation, but the final executable will need to load
bitcode from all its deps.

This is meant to address rust-lang/rust#72268
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ehuss commented May 18, 2020

👍
@bors r+

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bors commented May 18, 2020

📌 Commit b45fd8f has been approved by ehuss

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels May 18, 2020
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bors commented May 18, 2020

⌛ Testing commit b45fd8f with merge 500b2bd...

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bors commented May 18, 2020

☀️ Test successful - checks-azure
Approved by: ehuss
Pushing 500b2bd to master...

@bors bors merged commit 500b2bd into rust-lang:master May 18, 2020
bors added a commit to rust-lang-ci/rust that referenced this pull request May 20, 2020
Update cargo

9 commits in cb06cb2696df2567ce06d1a39b1b40612a29f853..500b2bd01c958f5a33b6aa3f080bea015877b83c
2020-05-08 21:57:44 +0000 to 2020-05-18 17:12:54 +0000
- Handle LTO with an rlib/cdylib crate type (rust-lang/cargo#8254)
- Gracefully handle errors during a build. (rust-lang/cargo#8247)
- Update `im-rc` to 15.0.0 (rust-lang/cargo#8255)
- Fix `cargo update` with unused patch. (rust-lang/cargo#8243)
- Rephrased error message for disallowed sections in virtual workspace (rust-lang/cargo#8200)
- Ignore broken console output in some situations. (rust-lang/cargo#8236)
- Expand error message to explain that a string was found (rust-lang/cargo#8235)
- Add context to some fs errors. (rust-lang/cargo#8232)
- Move SipHasher to an isolated module. (rust-lang/cargo#8233)
@alexcrichton alexcrichton deleted the fix-lto-more branch July 29, 2020 17:48
@ehuss ehuss added this to the 1.45.0 milestone Feb 6, 2022
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5 participants