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Possibly missed optimizations with strided slice access autovectorization

A-autovectorizationArea: Autovectorization, which can impact perf or code sizeArea: Autovectorization, which can impact perf or code size

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.

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.

#144005 In rust-lang/rust;

· okaneco opened on Jul 16, 2025

iter::zip changes vectorization behaviour even if value is unused

A-autovectorizationArea: Autovectorization, which can impact perf or code sizeArea: Autovectorization, which can impact perf or code size

A-iteratorsArea: IteratorsArea: Iterators

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.

#143016 In rust-lang/rust;

· BloodStainedCrow opened on Jun 25, 2025

<code>Slice::contains</code> produces worse output than <code>.iter().any</code>

A-autovectorizationArea: Autovectorization, which can impact perf or code sizeArea: Autovectorization, which can impact perf or code size

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-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.

#142954 In rust-lang/rust;

· coastalwhite opened on Jun 24, 2025

Byte count has poor codegen with autovectorization

A-autovectorizationArea: Autovectorization, which can impact perf or code sizeArea: Autovectorization, which can impact perf or code size

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

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.

#136500 In rust-lang/rust;

· danielhuang opened on Feb 3, 2025

More instructions generated for <code>Ord::clamp</code> than manual <code>max(X).min(Y)</code> for saturating truncating cast from <code>i32</code> to <code>u8</code>

A-autovectorizationArea: Autovectorization, which can impact perf or code sizeArea: Autovectorization, which can impact perf or code size

A-codegenArea: Code generationArea: Code generation

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

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.

#125738 In rust-lang/rust;

· okaneco opened on May 29, 2024

Autovectorization fails if a field follows an array

A-autovectorizationArea: Autovectorization, which can impact perf or code sizeArea: Autovectorization, which can impact perf or code size

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

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.

#121276 In rust-lang/rust;

· EsotericPyramid opened on Feb 18, 2024

for loop in closure is not unrolled and not vectorlized correctly

A-autovectorizationArea: Autovectorization, which can impact perf or code sizeArea: Autovectorization, which can impact perf or code size

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.

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.

Status: Open.

#120189 In rust-lang/rust;

· shuangsilab opened on Jan 21, 2024

Rustc fails to perform autovectorization for a loop when targeting aarch64-apple-darwin

A-autovectorizationArea: Autovectorization, which can impact perf or code sizeArea: Autovectorization, which can impact perf or code size

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.

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

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.

#117345 In rust-lang/rust;

· Pzixel opened on Oct 29, 2023

Missed autovectorization for slice.iter.fold, works for slice.iter.copied.fold

A-autovectorizationArea: Autovectorization, which can impact perf or code sizeArea: Autovectorization, which can impact perf or code size

A-codegenArea: Code generationArea: Code generation

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

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.

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.

#113789 In rust-lang/rust;

· jhorstmann opened on Jul 17, 2023

Initialization of stack-based arrays does not get automatically vectorized.

A-autovectorizationArea: Autovectorization, which can impact perf or code sizeArea: Autovectorization, which can impact perf or code size

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.

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.

#112459 In rust-lang/rust;

· TDecking opened on Jun 9, 2023

SIMD path never taken in simple vectorized loop

A-autovectorizationArea: Autovectorization, which can impact perf or code sizeArea: Autovectorization, which can impact perf or code size

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.

A-SIMDArea: SIMD (Single Instruction Multiple Data)Area: SIMD (Single Instruction Multiple Data)

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.

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.

#108187 In rust-lang/rust;

· linkmauve opened on Feb 17, 2023

rustc can not inline simple for-loop when arm neon is enabled

A-autovectorizationArea: Autovectorization, which can impact perf or code sizeArea: Autovectorization, which can impact perf or code size

A-codegenArea: Code generationArea: Code generation

A-SIMDArea: SIMD (Single Instruction Multiple Data)Area: SIMD (Single Instruction Multiple Data)

A-target-featureArea: Enabling/disabling target features like AVX, Neon, etc.Area: Enabling/disabling target features like AVX, Neon, etc.

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

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.

#102220 In rust-lang/rust;

· Nugine opened on Sep 24, 2022