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LTO may hang forever #58674

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kpcyrd opened this issue Feb 23, 2019 · 4 comments
Closed

LTO may hang forever #58674

kpcyrd opened this issue Feb 23, 2019 · 4 comments
Labels
C-bug Category: This is a bug. I-hang Issue: The compiler never terminates, due to infinite loops, deadlock, livelock, etc. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@kpcyrd
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kpcyrd commented Feb 23, 2019 •
edited

After quite a bit of troubleshooting it seems cargo build --release broke for one of my projects due to the size of the codebase.

kpcyrd/sn0int#77

According to the debug log this is related to lto:

 INFO 2019-02-23T14:19:15Z: rustc_codegen_llvm::back::lto: 1470 symbols to preserve in this crate
 INFO 2019-02-23T14:19:15Z: rustc_codegen_llvm::back::lto: going for that thin, thin LTO
 INFO 2019-02-23T14:19:15Z: rustc_codegen_llvm::back::lto: local module: 0 - sn0int.15aj1zuq-cgu.5
 INFO 2019-02-23T14:19:15Z: rustc_codegen_llvm::back::lto: local module: 1 - sn0int.15aj1zuq-cgu.0
 INFO 2019-02-23T14:19:16Z: rustc_codegen_llvm::back::lto: local module: 2 - sn0int.15aj1zuq-cgu.15
 INFO 2019-02-23T14:19:16Z: rustc_codegen_llvm::back::lto: local module: 3 - sn0int.15aj1zuq-cgu.10
 INFO 2019-02-23T14:19:16Z: rustc_codegen_llvm::back::lto: local module: 4 - sn0int.15aj1zuq-cgu.3
 INFO 2019-02-23T14:19:16Z: rustc_codegen_llvm::back::lto: local module: 5 - sn0int.15aj1zuq-cgu.6
 INFO 2019-02-23T14:19:17Z: rustc_codegen_llvm::back::lto: local module: 6 - sn0int.15aj1zuq-cgu.1
 INFO 2019-02-23T14:19:17Z: rustc_codegen_llvm::back::lto: local module: 7 - sn0int.15aj1zuq-cgu.12
 INFO 2019-02-23T14:19:17Z: rustc_codegen_llvm::back::lto: local module: 8 - sn0int.15aj1zuq-cgu.14
 INFO 2019-02-23T14:19:17Z: rustc_codegen_llvm::back::lto: local module: 9 - sn0int.15aj1zuq-cgu.4
 INFO 2019-02-23T14:19:18Z: rustc_codegen_llvm::back::lto: local module: 10 - sn0int.15aj1zuq-cgu.2
 INFO 2019-02-23T14:19:18Z: rustc_codegen_llvm::back::lto: local module: 11 - sn0int.15aj1zuq-cgu.7
 INFO 2019-02-23T14:19:18Z: rustc_codegen_llvm::back::lto: local module: 12 - sn0int.15aj1zuq-cgu.9
 INFO 2019-02-23T14:19:18Z: rustc_codegen_llvm::back::lto: local module: 13 - sn0int.15aj1zuq-cgu.13
 INFO 2019-02-23T14:19:18Z: rustc_codegen_llvm::back::lto: local module: 14 - sn0int.15aj1zuq-cgu.11
 INFO 2019-02-23T14:19:18Z: rustc_codegen_llvm::back::lto: local module: 15 - sn0int.15aj1zuq-cgu.8
 INFO 2019-02-23T14:19:19Z: rustc_codegen_llvm::back::lto: thin LTO data created
 INFO 2019-02-23T14:19:19Z: rustc_codegen_llvm::back::lto: thin LTO import map loaded
 INFO 2019-02-23T14:19:19Z: rustc_codegen_llvm::back::lto: checking which modules can be-reused and which have to be re-optimized.
 INFO 2019-02-23T14:19:19Z: rustc_codegen_llvm::back::lto:  - sn0int.15aj1zuq-cgu.5: re-compiled
 INFO 2019-02-23T14:19:19Z: rustc_codegen_llvm::back::lto:  - sn0int.15aj1zuq-cgu.0: re-compiled
 INFO 2019-02-23T14:19:19Z: rustc_codegen_llvm::back::lto:  - sn0int.15aj1zuq-cgu.15: re-compiled
 INFO 2019-02-23T14:19:19Z: rustc_codegen_llvm::back::lto:  - sn0int.15aj1zuq-cgu.10: re-compiled
 INFO 2019-02-23T14:19:19Z: rustc_codegen_llvm::back::lto:  - sn0int.15aj1zuq-cgu.3: re-compiled
 INFO 2019-02-23T14:19:19Z: rustc_codegen_llvm::back::lto:  - sn0int.15aj1zuq-cgu.6: re-compiled
 INFO 2019-02-23T14:19:19Z: rustc_codegen_llvm::back::lto:  - sn0int.15aj1zuq-cgu.1: re-compiled
 INFO 2019-02-23T14:19:19Z: rustc_codegen_llvm::back::lto:  - sn0int.15aj1zuq-cgu.12: re-compiled
 INFO 2019-02-23T14:19:19Z: rustc_codegen_llvm::back::lto:  - sn0int.15aj1zuq-cgu.14: re-compiled
 INFO 2019-02-23T14:19:19Z: rustc_codegen_llvm::back::lto:  - sn0int.15aj1zuq-cgu.4: re-compiled
 INFO 2019-02-23T14:19:19Z: rustc_codegen_llvm::back::lto:  - sn0int.15aj1zuq-cgu.2: re-compiled
 INFO 2019-02-23T14:19:19Z: rustc_codegen_llvm::back::lto:  - sn0int.15aj1zuq-cgu.7: re-compiled
 INFO 2019-02-23T14:19:19Z: rustc_codegen_llvm::back::lto:  - sn0int.15aj1zuq-cgu.9: re-compiled
 INFO 2019-02-23T14:19:19Z: rustc_codegen_llvm::back::lto:  - sn0int.15aj1zuq-cgu.13: re-compiled
 INFO 2019-02-23T14:19:19Z: rustc_codegen_llvm::back::lto:  - sn0int.15aj1zuq-cgu.11: re-compiled
 INFO 2019-02-23T14:19:19Z: rustc_codegen_llvm::back::lto:  - sn0int.15aj1zuq-cgu.8: re-compiled
 INFO 2019-02-23T14:19:20Z: rustc_codegen_llvm::back::lto: running thin lto passes over sn0int.15aj1zuq-cgu.3
 INFO 2019-02-23T14:19:20Z: rustc_codegen_llvm::back::lto: running thin lto passes over sn0int.15aj1zuq-cgu.2
 INFO 2019-02-23T14:19:20Z: rustc_codegen_llvm::back::lto: running thin lto passes over sn0int.15aj1zuq-cgu.0
 INFO 2019-02-23T14:19:20Z: rustc_codegen_llvm::back::lto: running thin lto passes over sn0int.15aj1zuq-cgu.1
 INFO 2019-02-23T14:19:42Z: rustc_codegen_llvm::back::lto: running thin lto passes over sn0int.15aj1zuq-cgu.6
 INFO 2019-02-23T14:19:48Z: rustc_codegen_llvm::back::lto: running thin lto passes over sn0int.15aj1zuq-cgu.5
 INFO 2019-02-23T14:20:02Z: rustc_codegen_llvm::back::lto: running thin lto passes over sn0int.15aj1zuq-cgu.4
 INFO 2019-02-23T14:20:03Z: rustc_codegen_llvm::back::lto: running thin lto passes over sn0int.15aj1zuq-cgu.8
 INFO 2019-02-23T14:20:09Z: rustc_codegen_llvm::back::lto: running thin lto passes over sn0int.15aj1zuq-cgu.10
 INFO 2019-02-23T14:20:18Z: rustc_codegen_llvm::back::lto: running thin lto passes over sn0int.15aj1zuq-cgu.14
 INFO 2019-02-23T14:20:19Z: rustc_codegen_llvm::back::lto: running thin lto passes over sn0int.15aj1zuq-cgu.15
 INFO 2019-02-23T14:20:28Z: rustc_codegen_llvm::back::lto: running thin lto passes over sn0int.15aj1zuq-cgu.9
 INFO 2019-02-23T14:20:32Z: rustc_codegen_llvm::back::lto: running thin lto passes over sn0int.15aj1zuq-cgu.13
 INFO 2019-02-23T14:20:34Z: rustc_codegen_llvm::back::lto: running thin lto passes over sn0int.15aj1zuq-cgu.11
 INFO 2019-02-23T14:20:38Z: rustc_codegen_llvm::back::lto: running thin lto passes over sn0int.15aj1zuq-cgu.12
 INFO 2019-02-23T14:20:43Z: rustc_codegen_llvm::back::lto: running thin lto passes over sn0int.15aj1zuq-cgu.7

It seems I could confirm this because this command works:

RUSTFLAGS="-C lto=no" cargo build --release

This issue has been reproduced with:

  • rustc 1.32.0 (9fda7c2 2019-01-16)
  • rustc 1.34.0-nightly (e1c6d00 2019-02-22)

I couldn't find a way to make this the default though, adding this to my Cargo.toml didn't work:

[profile.release]
lto = false

Steps to reproduce

git clone https://github.com/kpcyrd/sn0int.git
cd sn0int
git checkout 17f4682
cargo build --release
@jonas-schievink jonas-schievink added T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. C-bug Category: This is a bug. I-hang Issue: The compiler never terminates, due to infinite loops, deadlock, livelock, etc. labels Feb 23, 2019
@meithecatte
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I'd suggest specifying a specific commit with git checkout in the reproducer.

@kpcyrd
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kpcyrd commented Feb 24, 2019

Good point:

Last working commit: 4ce8f00
First broken commit: 17f4682

@kpcyrd
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kpcyrd commented Apr 24, 2019

It seems this has been resolved at some point, 1.34.0 works correctly again. I've asked the original reporter to re-test and I'd close this issue if he reports a success.

@kpcyrd
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kpcyrd commented Apr 25, 2019

It seems this has been resolved.

@kpcyrd kpcyrd closed this as completed Apr 25, 2019
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C-bug Category: This is a bug. I-hang Issue: The compiler never terminates, due to infinite loops, deadlock, livelock, etc. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
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