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bounds check may not be properly elminated with (Bound<usize>, Bound<usize>) indexer but elminated with some cases

A-codegenArea: Code generationArea: Code generation

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.

Status: Open.

#157909 In rust-lang/rust;

· anatawa12 opened on Jun 15, 2026

step_by() on new ranges is less optimized than the old ranges.

A-iteratorsArea: IteratorsArea: Iterators

A-specializationArea: Trait impl specializationArea: Trait impl specialization

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

F-new_range`#![feature(new_range)]``#![feature(new_range)]`

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

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.

#157754 In rust-lang/rust;

· theemathas opened on Jun 11, 2026

codegen: Unnecessary memcpy when returning a mutated mut self

A-codegenArea: Code generationArea: Code generation

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

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

Status: Open.

#157685 In rust-lang/rust;

· Filiprogrammer opened on Jun 9, 2026

Stack slots are not being reused due to missing LLVM IR lifetime annotations.

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

I-prioritizeIssue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}Issue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}

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

Status: Open.

#157676 In rust-lang/rust;

· VinceQu opened on Jun 9, 2026

missed optimization when writing a value with inner padding.

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

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.

Status: Open.

#157373 In rust-lang/rust;

· Morgane55440 opened on Jun 3, 2026

Incrementing &mut Option<u32> generates verbose instructions 1.94.0 -> 1.95.0

A-codegenArea: Code generationArea: Code generation

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-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

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

O-x86_32Target: x86 processors, 32 bit (like i686-*) (also known as IA-32, i386, i586, i686)Target: x86 processors, 32 bit (like i686-*) (also known as IA-32, i386, i586, i686)

O-x86_64Target: x86-64 processors (like x86_64-*) (also known as amd64 and x64)Target: x86-64 processors (like x86_64-*) (also known as amd64 and x64)

P-lowLow priorityLow priority

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

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.

#157337 In rust-lang/rust;

· JL-Money opened on Jun 2, 2026

Codegen struggles to infer information about a value computed before branching on related info

A-codegenArea: Code generationArea: Code generation

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.

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.

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.

#155809 In rust-lang/rust;

· Apersoma opened on Apr 26, 2026

Allow inlining of array::map()

A-codegenArea: Code generationArea: Code generation

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-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

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.

#155667 In rust-lang/rust;

· nazar-pc opened on Apr 23, 2026

Missed optimization: destructor of variable needlessly called before unreachable_unchecked

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

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.

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.

#154294 In rust-lang/rust;

· ClaytonKnittel opened on Mar 24, 2026

Stdout and StdoutLock make unnecessary repeated syscalls via is_console on Windows

A-ioArea: `std::io`, `std::fs`, `std::net` and `std::path`Area: `std::io`, `std::fs`, `std::net` and `std::path`

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

O-windowsOperating system: WindowsOperating system: Windows

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.

#154071 In rust-lang/rust;

· Pr0methean opened on Mar 19, 2026

Worse optimization with fn() -> ! than fn() or fn() -> () with -Crelocation-model=static

A-codegenArea: Code generationArea: Code generation

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

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.

Status: Open.

#153976 In rust-lang/rust;

· eebop opened on Mar 17, 2026

Optimizations to be performed on BTreeMap::merge

A-collectionsArea: `std::collections`Area: `std::collections`

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

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.

#153040 In rust-lang/rust;

· asder8215 opened on Feb 24, 2026