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Missed optimization: multiple instances of a small struct don't reuse the stack allocation

A-codegenArea: Code generationArea: Code generation

A-MIRArea: Mid-level IR (MIR) - https://blog.rust-lang.org/2016/04/19/MIR.htmlArea: Mid-level IR (MIR) - https://blog.rust-lang.org/2016/04/19/MIR.html

A-mir-optArea: MIR optimizationsArea: MIR optimizations

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

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-opsemRelevant to the opsem teamRelevant to the opsem team

Status: Open.

#141649 In rust-lang/rust;

· ohadravid opened on May 27, 2025

ICE: mir opts crash rustc with -Zmir-preserve-ub in compiler/rustc_mir_transform/src/simplify_comparison_integral.rs

A-mir-optArea: MIR optimizationsArea: MIR optimizations

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

I-ICEIssue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️

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.

#141454 In rust-lang/rust;

· matthiaskrgr opened on May 23, 2025

GVN misunderstands aliasing, can create overlapping assignments (again)

A-mir-optArea: MIR optimizationsArea: MIR optimizations

A-mir-opt-GVNArea: MIR opt Global Value Numbering (GVN)Area: MIR opt Global Value Numbering (GVN)

A-rustlantisA miscompilation found by RustlantisA miscompilation found by Rustlantis

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

I-miscompileIssue: Correct Rust code lowers to incorrect machine codeIssue: Correct Rust code lowers to incorrect machine code

I-unsoundIssue: A soundness hole (worst kind of bug), see: https://en.wikipedia.org/wiki/SoundnessIssue: A soundness hole (worst kind of bug), see: https://en.wikipedia.org/wiki/Soundness

P-mediumMedium priorityMedium priority

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.

#141313 In rust-lang/rust;

· saethlin opened on May 20, 2025

CopyProp doesn't always respect Tree Borrows

A-mir-optArea: MIR optimizationsArea: MIR optimizations

A-rustlantisA miscompilation found by RustlantisA miscompilation found by Rustlantis

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

I-miscompileIssue: Correct Rust code lowers to incorrect machine codeIssue: Correct Rust code lowers to incorrect machine code

I-unsoundIssue: A soundness hole (worst kind of bug), see: https://en.wikipedia.org/wiki/SoundnessIssue: A soundness hole (worst kind of bug), see: https://en.wikipedia.org/wiki/Soundness

P-mediumMedium priorityMedium priority

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.

#141122 In rust-lang/rust;

· saethlin opened on May 17, 2025

ReferencePropagation tries to reuse moved-from Operands

A-mir-optArea: MIR optimizationsArea: MIR optimizations

A-rustlantisA miscompilation found by RustlantisA miscompilation found by Rustlantis

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

I-miscompileIssue: Correct Rust code lowers to incorrect machine codeIssue: Correct Rust code lowers to incorrect machine code

I-unsoundIssue: A soundness hole (worst kind of bug), see: https://en.wikipedia.org/wiki/SoundnessIssue: A soundness hole (worst kind of bug), see: https://en.wikipedia.org/wiki/Soundness

P-mediumMedium priorityMedium priority

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.

#141101 In rust-lang/rust;

· saethlin opened on May 16, 2025

[mir-opt] SRoA away the tuple in <code>match (a, b)</code>

A-mir-optArea: MIR optimizationsArea: MIR optimizations

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

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.

Enhancement

#139739 In rust-lang/rust;

· scottmcm opened on Apr 13, 2025

Ensure we can optimize out does-nothing <code>drop</code>s like <code>array::IntoIter&lt;NotNeedsDrop, N&gt;</code>

A-mir-optArea: MIR optimizationsArea: MIR optimizations

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

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.

#139422 In rust-lang/rust;

· scottmcm opened on Apr 5, 2025

Promoted constants lead to poor MIR from comparisons

A-MIRArea: Mid-level IR (MIR) - https://blog.rust-lang.org/2016/04/19/MIR.htmlArea: Mid-level IR (MIR) - https://blog.rust-lang.org/2016/04/19/MIR.html

A-mir-optArea: MIR optimizationsArea: MIR optimizations

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

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.

WG-mir-optWorking group: MIR optimizationsWorking group: MIR optimizations

Status: Open.

#139093 In rust-lang/rust;

· scottmcm opened on Mar 29, 2025

Simple <code>Option</code> use, like in <code>checked_sub</code>, should optimize out fully in MIR

A-mir-optArea: MIR optimizationsArea: MIR optimizations

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

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.

Enhancement

#138544 In rust-lang/rust;

· scottmcm opened on Mar 15, 2025

ICE：called <code>Result::unwrap()</code> on an <code>Err</code> value: ReferencesError(ErrorGuaranteed(()))

A-mir-optArea: MIR optimizationsArea: MIR optimizations

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

I-ICEIssue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️

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.

#138225 In rust-lang/rust;

· sososopy opened on Mar 8, 2025

CopyProp miscompilation when src is moved more than once

A-mir-optArea: MIR optimizationsArea: MIR optimizations

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

I-miscompileIssue: Correct Rust code lowers to incorrect machine codeIssue: Correct Rust code lowers to incorrect machine code

I-unsoundIssue: A soundness hole (worst kind of bug), see: https://en.wikipedia.org/wiki/SoundnessIssue: A soundness hole (worst kind of bug), see: https://en.wikipedia.org/wiki/Soundness

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

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.

#137936 In rust-lang/rust;

· tmiasko opened on Mar 3, 2025

ICE: <code>Failed to normalize Alias(Projection</code>

A-mir-optArea: MIR optimizationsArea: MIR optimizations

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

I-ICEIssue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️

S-bug-has-testStatus: This bug is tracked inside the repo by a `known-bug` test.Status: This bug is tracked inside the repo by a `known-bug` test.

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.

#137468 In rust-lang/rust;

· matthiaskrgr opened on Feb 23, 2025