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[opt-dist] Profile-guided optimization of LLVM regressed on Windows hosts

A-PGOArea: Profile-guided optimizations (PGO)Area: Profile-guided optimizations (PGO)

C-bugCategory: This is a bug.Category: This is a bug.

I-prioritizeIssue: Indicates that prioritization has been requested for this issue.Issue: Indicates that prioritization has been requested for this issue.

needs-triageThis issue may need triage. Remove it if it has been sufficiently triaged.This issue may need triage. Remove it if it has been sufficiently triaged.

O-windowsOperating system: WindowsOperating system: Windows

O-windows-msvcToolchain: MSVC, Operating system: WindowsToolchain: MSVC, Operating system: Windows

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

Status: Open.

#144318 In rust-lang/rust;

· ognevny opened on Jul 22, 2025

3 comments

new non-determinism in linker maps introduced recently

A-reproducibilityArea: Reproducible / deterministic buildsArea: Reproducible / deterministic builds

C-bugCategory: This is a bug.Category: This is a bug.

I-prioritizeIssue: Indicates that prioritization has been requested for this issue.Issue: Indicates that prioritization has been requested for this issue.

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#142989 In rust-lang/rust;

· steven807 opened on Jun 24, 2025

14 comments

Possible regression for ui/match/issue-114691.rs

A-LLVMArea: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.

C-bugCategory: This is a bug.Category: This is a bug.

I-prioritizeIssue: Indicates that prioritization has been requested for this issue.Issue: Indicates that prioritization has been requested for this issue.

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

S-needs-reproStatus: This issue has no reproduction and needs a reproduction to make progress.Status: This issue has no reproduction and needs a reproduction to make progress.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#141340 In rust-lang/rust;

· lewis1revill opened on May 21, 2025

4 comments

lemmy_db_views_modlog_combined has a weird performance regression

C-bugCategory: This is a bug.Category: This is a bug.

E-needs-mcveCall for participation: This issue has a repro, but needs a Minimal Complete and Verifiable ExampleCall for participation: This issue has a repro, but needs a Minimal Complete and Verifiable Example

I-compiletimeIssue: Problems and improvements with respect to compile times.Issue: Problems and improvements with respect to compile times.

P-highHigh priorityHigh priority

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#141006 In rust-lang/rust;

· lcnr opened on May 14, 2025

9 comments



A case of compound x86_64 performance regression caused by LLVM 20 and #124810

A-LLVMArea: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.

C-optimizationCategory: An issue highlighting optimization opportunities or PRs implementing suchCategory: An issue highlighting optimization opportunities or PRs implementing such

P-highHigh priorityHigh priority

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

T-libsRelevant to the library team, which will review and decide on the PR/issue.Relevant to the library team, which will review and decide on the PR/issue.

Status: Open.

#139730 In rust-lang/rust;

· MoSal opened on Apr 13, 2025

3 comments

compiler_builtins string.h functions are not available when using std targets with #![no_std]

A-linkageArea: linking into static, shared libraries and binariesArea: linking into static, shared libraries and binaries

C-bugCategory: This is a bug.Category: This is a bug.

E-needs-investigationCall for partcipation: This issues needs some investigation to determine current statusCall for partcipation: This issues needs some investigation to determine current status

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

Status: Open.

#137833 In rust-lang/rust;

· byeongkeunahn opened on Mar 1, 2025

15 comments

Iterator performance regression 1.81 -> 1.82

C-bugCategory: This is a bug.Category: This is a bug.

P-mediumMedium priorityMedium priority

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#137727 In rust-lang/rust;

· Sunshine40 opened on Feb 27, 2025

4 comments

Performance regression in 1.84 for inline-able function in closure

A-LLVMArea: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.

C-bugCategory: This is a bug.Category: This is a bug.

C-optimizationCategory: An issue highlighting optimization opportunities or PRs implementing suchCategory: An issue highlighting optimization opportunities or PRs implementing such

P-mediumMedium priorityMedium priority

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#137273 In rust-lang/rust;

· findepi opened on Feb 19, 2025

8 comments

regression: crate compilation regression on reporting errors with Rust 1.68-nightly (62bf38fa6 2025-01-10)

C-bugCategory: This is a bug.Category: This is a bug.

E-needs-bisectionCall for participation: This issue needs bisection: https://github.com/rust-lang/cargo-bisect-rustcCall for participation: This issue needs bisection: https://github.com/rust-lang/cargo-bisect-rustc

E-needs-mcveCall for participation: This issue has a repro, but needs a Minimal Complete and Verifiable ExampleCall for participation: This issue has a repro, but needs a Minimal Complete and Verifiable Example

I-compiletimeIssue: Problems and improvements with respect to compile times.Issue: Problems and improvements with respect to compile times.

P-lowLow priorityLow priority

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

T-typesRelevant to the types team, which will review and decide on the PR/issue.Relevant to the types team, which will review and decide on the PR/issue.

Status: Open.

#136516 In rust-lang/rust;

· erickt opened on Feb 3, 2025

6 comments

rust-lld: error: undefined symbol: __gxx_personality_v0

A-linkageArea: linking into static, shared libraries and binariesArea: linking into static, shared libraries and binaries

A-linkersArea: linkers... you gotta love linkersArea: linkers... you gotta love linkers

A-lldArea: Linkage issues specific to rust-lldArea: Linkage issues specific to rust-lld

C-bugCategory: This is a bug.Category: This is a bug.

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

requires-nightlyThis issue requires a nightly compiler in some way.This issue requires a nightly compiler in some way.

S-has-mcveStatus: A Minimal Complete and Verifiable Example has been found for this issueStatus: A Minimal Complete and Verifiable Example has been found for this issue

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#135257 In rust-lang/rust;

· hasenbanck opened on Jan 8, 2025

3 comments

Performance regression on toy problem, but not for opt-level=1.

A-LLVMArea: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.

C-optimizationCategory: An issue highlighting optimization opportunities or PRs implementing suchCategory: An issue highlighting optimization opportunities or PRs implementing such

I-slowIssue: Problems and improvements with respect to performance of generated code.Issue: Problems and improvements with respect to performance of generated code.

P-lowLow priorityLow priority

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#135241 In rust-lang/rust;

· TheThirdOne opened on Jan 8, 2025

3 comments

Regression: source code location is bad in nightly (doctests)

A-doctestsArea: Documentation tests, run by rustdocArea: Documentation tests, run by rustdoc

C-bugCategory: This is a bug.Category: This is a bug.

E-needs-mcveCall for participation: This issue has a repro, but needs a Minimal Complete and Verifiable ExampleCall for participation: This issue has a repro, but needs a Minimal Complete and Verifiable Example

regression-from-stable-to-stablePerformance or correctness regression from one stable version to another.Performance or correctness regression from one stable version to another.

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

T-rustdocRelevant to the rustdoc team, which will review and decide on the PR/issue.Relevant to the rustdoc team, which will review and decide on the PR/issue.

Status: Open.

#134532 In rust-lang/rust;

· xmppftw opened on Dec 19, 2024

8 comments

dash: x.py install removes rustc and cargo, without installing them

C-bugCategory: This is a bug.Category: This is a bug.

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

T-bootstrapRelevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap)Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap)

Status: Open.

#133614 In rust-lang/rust;

· dilyanpalauzov opened on Nov 29, 2024

8 comments

Code size regression iterating an array (opt-level=z) after 1.82.0

A-LLVMArea: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.

C-bugCategory: This is a bug.Category: This is a bug.

I-heavyIssue: Problems and improvements with respect to binary size of generated code.Issue: Problems and improvements with respect to binary size of generated code.

P-lowLow priorityLow priority

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#132890 In rust-lang/rust;

· dcci opened on Nov 11, 2024

1 comment

Code size regression (opt-level=z) after 1.82.0

A-LLVMArea: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.

C-bugCategory: This is a bug.Category: This is a bug.

P-lowLow priorityLow priority

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#132888 In rust-lang/rust;

· dcci opened on Nov 11, 2024

1 comment

Code size regression (opt-level=z) after 1.73.0 (~40%)

C-bugCategory: This is a bug.Category: This is a bug.

I-heavyIssue: Problems and improvements with respect to binary size of generated code.Issue: Problems and improvements with respect to binary size of generated code.

P-lowLow priorityLow priority

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#132887 In rust-lang/rust;

· dcci opened on Nov 11, 2024

1 comment

Regression in performance (poor codegen) between 1.81 and 1.82

A-LLVMArea: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.

C-bugCategory: This is a bug.Category: This is a bug.

I-slowIssue: Problems and improvements with respect to performance of generated code.Issue: Problems and improvements with respect to performance of generated code.

P-mediumMedium priorityMedium priority

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#132636 In rust-lang/rust;

· tobz opened on Nov 5, 2024

10 comments



Fails to link verbatim libary in 1.82 on macOS

A-linkageArea: linking into static, shared libraries and binariesArea: linking into static, shared libraries and binaries

C-bugCategory: This is a bug.Category: This is a bug.

O-macosOperating system: macOSOperating system: macOS

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#132264 In rust-lang/rust;

· anatawa12 opened on Oct 28, 2024

2

5 comments

Invalid metadata for arm64e due to Xcode 15+ on ARM64e macOS

C-bugCategory: This is a bug.Category: This is a bug.

O-ArmTarget: 32-bit Arm processors (armv6, armv7, thumb...), including 64-bit Arm in AArch32 stateTarget: 32-bit Arm processors (armv6, armv7, thumb...), including 64-bit Arm in AArch32 state

O-macosOperating system: macOSOperating system: macOS

P-highHigh priorityHigh priority

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

T-bootstrapRelevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap)Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap)

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#130834 In rust-lang/rust;

· arttet opened on Sep 25, 2024

4 comments

Slow code generated for _mm256_mulhi_epi16

A-LLVMArea: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.

C-optimizationCategory: An issue highlighting optimization opportunities or PRs implementing suchCategory: An issue highlighting optimization opportunities or PRs implementing such

E-needs-testCall for participation: An issue has been fixed and does not reproduce, but no test has been added.Call for participation: An issue has been fixed and does not reproduce, but no test has been added.

I-slowIssue: Problems and improvements with respect to performance of generated code.Issue: Problems and improvements with respect to performance of generated code.

P-mediumMedium priorityMedium priority

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

Status: Open.

#130782 In rust-lang/rust;

· turalcar opened on Sep 24, 2024

6 comments

Inefficient codegen in builder pattern with existed copyable base value

A-LLVMArea: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.

C-bugCategory: This is a bug.Category: This is a bug.

P-mediumMedium priorityMedium priority

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#130592 In rust-lang/rust;

· CrazyboyQCD opened on Sep 20, 2024

3 comments

Significantly worse codegen for SIMD shuffles after Rust 1.73.0

A-LLVMArea: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.

C-optimizationCategory: An issue highlighting optimization opportunities or PRs implementing suchCategory: An issue highlighting optimization opportunities or PRs implementing such

I-slowIssue: Problems and improvements with respect to performance of generated code.Issue: Problems and improvements with respect to performance of generated code.

llvm-fixed-upstreamIssue expected to be fixed by the next major LLVM upgrade, or backported fixesIssue expected to be fixed by the next major LLVM upgrade, or backported fixes

P-mediumMedium priorityMedium priority

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

Status: Open.

#129132 In rust-lang/rust;

· TDecking opened on Aug 15, 2024

3 comments

suboptimal llvm-ir due to missing noalias annotations after mir inlining

A-mir-opt-inliningArea: MIR inliningArea: MIR inlining

C-bugCategory: This is a bug.Category: This is a bug.

P-mediumMedium priorityMedium priority

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

Status: Open.

#129128 In rust-lang/rust;

· sarah-quinones opened on Aug 15, 2024

2 comments

100% CPU usage when running doc tests

A-doctestsArea: Documentation tests, run by rustdocArea: Documentation tests, run by rustdoc

C-bugCategory: This is a bug.Category: This is a bug.

I-compiletimeIssue: Problems and improvements with respect to compile times.Issue: Problems and improvements with respect to compile times.

perf-regressionPerformance regression.Performance regression.

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

S-needs-reproStatus: This issue has no reproduction and needs a reproduction to make progress.Status: This issue has no reproduction and needs a reproduction to make progress.

T-rustdocRelevant to the rustdoc team, which will review and decide on the PR/issue.Relevant to the rustdoc team, which will review and decide on the PR/issue.

Status: Open.

#128538 In rust-lang/rust;

· tingerrr opened on Aug 2, 2024

17 comments

Rust 1.81-nightly slower than Rust 1.79 ?

A-mir-opt-inliningArea: MIR inliningArea: MIR inlining

C-bugCategory: This is a bug.Category: This is a bug.

I-slowIssue: Problems and improvements with respect to performance of generated code.Issue: Problems and improvements with respect to performance of generated code.

O-AArch64Armv8-A or later processors in AArch64 modeArmv8-A or later processors in AArch64 mode

O-macosOperating system: macOSOperating system: macOS

P-mediumMedium priorityMedium priority

regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

S-has-mcveStatus: A Minimal Complete and Verifiable Example has been found for this issueStatus: A Minimal Complete and Verifiable Example has been found for this issue

Status: Open.

#126937 In rust-lang/rust;

· GuillaumePressiat opened on Jun 25, 2024

46 comments