Fix EII function aliases eliminated by LTO by AsakuraMizu · Pull Request #153648 · rust-lang/rust

AsakuraMizu · 2026-03-10T08:29:17Z

Add EII function aliases to llvm.compiler.used so that LLVM's LTO passes do not eliminate them.

Tracking issue: #125418

rustbot · 2026-03-10T08:29:22Z

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Kivooeo · 2026-03-10T08:39:50Z

r? jdonszelmann

bjorn3 · 2026-03-10T15:12:38Z

I'm not sure if this is the right fix. They might need to be added to exported_symbols_for_lto instead. Otherwise they can still be made private by LTO, which would break dylibs. And I don't know if for_each_exported_symbols_include_dep already contains them to (for proper exporting during linking)

jdonszelmann · 2026-03-11T10:06:13Z

hm, I wonder what the difference is between aliases and these shims. These shims pretty much act like aliases, and their symbol is the same as the EII declatation's. We already handle those symbols specially in a few places (look for the aliases field on CodegenAttrs). In fact, I personally thought we already kept them alive enough. I guess functions are optimized differently which makes some sense. In any case, I expect the problem to fundamentally also affect aliases of statics, something we don't test much at the moment, so the solution should apply to all aliases, not just these shims.

compiler/rustc_codegen_ssa/src/back/symbol_export.rs

AsakuraMizu · 2026-03-11T12:43:05Z

I'm not sure if this is the right fix. They might need to be added to exported_symbols_for_lto instead. Otherwise they can still be made private by LTO, which would break dylibs. And I don't know if for_each_exported_symbols_include_dep already contains them to (for proper exporting during linking)

Thank you for your comment. My previous attempt was more of a hack than a fix. So I redesigned a better solution based on your suggestion. This should fix both my issue and #151271 now.

In any case, I expect the problem to fundamentally also affect aliases of statics, something we don't test much at the moment, so the solution should apply to all aliases, not just these shims.

The new attempt will apply to any foreign_item_symbol_aliases now.

compiler/rustc_codegen_ssa/src/back/symbol_export.rs

jdonszelmann · 2026-03-30T15:21:10Z

been having a bit of a backlog. This was mostly bjorn, but I agree with the discussions had and I think the current state of the PR seems correct to me.

@bors r=me,bjorn3

rust-bors · 2026-03-30T15:21:15Z

📌 Commit d81cc68 has been approved by me,bjorn3

It is now in the queue for this repository.

⚠️ The following reviewer(s) could not be found: me

JonathanBrouwer · 2026-03-30T16:29:03Z

@bors r=jdonszelmann,bjorn3

rust-bors · 2026-03-30T16:29:07Z

📌 Commit d81cc68 has been approved by jdonszelmann,bjorn3

It is now in the queue for this repository.

…donszelmann,bjorn3 Fix EII function aliases eliminated by LTO Add EII function aliases to `llvm.compiler.used` so that LLVM's LTO passes do not eliminate them. Fixes rust-lang#153645 Tracking issue: rust-lang#125418

Rollup of 7 pull requests Successful merges: - #142659 (compiler-builtins: Clean up features) - #153574 (Avoid ICE when param-env normalization leaves unresolved inference variables) - #153648 (Fix EII function aliases eliminated by LTO) - #153790 (Fix regression when dealing with generics/values with unresolved inference) - #153893 (Lex lifetimes as identifiers, recover from emoji and emit appropriate error) - #153980 (refactor: move doc(rust_logo) check to parser) - #154551 (Skip suggestions pointing to macro def for assert_eq)

…donszelmann,bjorn3 Fix EII function aliases eliminated by LTO Add EII function aliases to `llvm.compiler.used` so that LLVM's LTO passes do not eliminate them. Fixes rust-lang#153645 Tracking issue: rust-lang#125418

Rollup of 9 pull requests Successful merges: - #154582 (miri subtree update) - #142659 (compiler-builtins: Clean up features) - #153574 (Avoid ICE when param-env normalization leaves unresolved inference variables) - #153648 (Fix EII function aliases eliminated by LTO) - #153790 (Fix regression when dealing with generics/values with unresolved inference) - #154551 (Skip suggestions pointing to macro def for assert_eq) - #154574 (delete several `ui/consts` tests) - #154577 (Update `mir-opt` 64-bit panic-abort tests for `Alignment` rename) - #154579 (remove debug requirement from hooks)

Rollup merge of #153648 - AsakuraMizu:fix-eii-lto-alias, r=jdonszelmann,bjorn3 Fix EII function aliases eliminated by LTO Add EII function aliases to `llvm.compiler.used` so that LLVM's LTO passes do not eliminate them. Fixes #153645 Tracking issue: #125418

Rollup of 9 pull requests Successful merges: - rust-lang/rust#154582 (miri subtree update) - rust-lang/rust#142659 (compiler-builtins: Clean up features) - rust-lang/rust#153574 (Avoid ICE when param-env normalization leaves unresolved inference variables) - rust-lang/rust#153648 (Fix EII function aliases eliminated by LTO) - rust-lang/rust#153790 (Fix regression when dealing with generics/values with unresolved inference) - rust-lang/rust#154551 (Skip suggestions pointing to macro def for assert_eq) - rust-lang/rust#154574 (delete several `ui/consts` tests) - rust-lang/rust#154577 (Update `mir-opt` 64-bit panic-abort tests for `Alignment` rename) - rust-lang/rust#154579 (remove debug requirement from hooks)

Rollup of 9 pull requests Successful merges: - rust-lang#154582 (miri subtree update) - rust-lang#142659 (compiler-builtins: Clean up features) - rust-lang#153574 (Avoid ICE when param-env normalization leaves unresolved inference variables) - rust-lang#153648 (Fix EII function aliases eliminated by LTO) - rust-lang#153790 (Fix regression when dealing with generics/values with unresolved inference) - rust-lang#154551 (Skip suggestions pointing to macro def for assert_eq) - rust-lang#154574 (delete several `ui/consts` tests) - rust-lang#154577 (Update `mir-opt` 64-bit panic-abort tests for `Alignment` rename) - rust-lang#154579 (remove debug requirement from hooks)

Rollup of 9 pull requests Successful merges: - rust-lang/rust#154582 (miri subtree update) - rust-lang/rust#142659 (compiler-builtins: Clean up features) - rust-lang/rust#153574 (Avoid ICE when param-env normalization leaves unresolved inference variables) - rust-lang/rust#153648 (Fix EII function aliases eliminated by LTO) - rust-lang/rust#153790 (Fix regression when dealing with generics/values with unresolved inference) - rust-lang/rust#154551 (Skip suggestions pointing to macro def for assert_eq) - rust-lang/rust#154574 (delete several `ui/consts` tests) - rust-lang/rust#154577 (Update `mir-opt` 64-bit panic-abort tests for `Alignment` rename) - rust-lang/rust#154579 (remove debug requirement from hooks)

rustbot assigned TaKO8Ki Mar 10, 2026

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AsakuraMizu force-pushed the fix-eii-lto-alias branch from d721f86 to 1aef424 Compare March 10, 2026 08:29

rustbot assigned jdonszelmann and unassigned TaKO8Ki Mar 10, 2026

AsakuraMizu mentioned this pull request Mar 10, 2026

Proposal: remove linkme arceos-org/axcpu#21

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AsakuraMizu force-pushed the fix-eii-lto-alias branch from 1aef424 to a80c922 Compare March 11, 2026 12:33

bjorn3 reviewed Mar 11, 2026

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compiler/rustc_codegen_ssa/src/back/symbol_export.rs Outdated Show resolved Hide resolved

fix: add EII function aliases to exported symbols

d81cc68

AsakuraMizu force-pushed the fix-eii-lto-alias branch from a80c922 to d81cc68 Compare March 11, 2026 12:42

bjorn3 reviewed Mar 12, 2026

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compiler/rustc_codegen_ssa/src/back/symbol_export.rs Show resolved Hide resolved

ZuseZ4 mentioned this pull request Mar 14, 2026

Enable autodiff with thin-lto #153687

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rust-bors bot 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 Mar 30, 2026

tgross35 mentioned this pull request Mar 30, 2026

Rollup of 7 pull requests #154611

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JonathanBrouwer mentioned this pull request Mar 31, 2026

Rollup of 21 pull requests #154629

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tgross35 mentioned this pull request Mar 31, 2026

Rollup of 9 pull requests #154633

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rust-bors bot merged commit 4b23782 into rust-lang:main Mar 31, 2026
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rustbot added this to the 1.96.0 milestone Mar 31, 2026

AsakuraMizu deleted the fix-eii-lto-alias branch March 31, 2026 16:05

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Fix EII function aliases eliminated by LTO#153648

Fix EII function aliases eliminated by LTO#153648
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AsakuraMizu:fix-eii-lto-alias

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