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Missed optimization: <code>matches!</code> results in worse codgen than a logical or

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

Status: Open.

#141497 In rust-lang/rust;

· ohadravid opened on May 24, 2025

Bounds check not elided for index that should be known to be in-bounds

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

Status: Open.

#139759 In rust-lang/rust;

· okaneco opened on Apr 13, 2025

Removing trailing zeros of a NonZero

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

Status: Open.

#138497 In rust-lang/rust;

· leonardo-m opened on Mar 14, 2025

LLVM assertion failure on Wasm exceptions

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-crashIssue: The compiler crashes (SIGSEGV, SIGABRT, etc). Use I-ICE instead when the compiler panics.Issue: The compiler crashes (SIGSEGV, SIGABRT, etc). Use I-ICE instead when the compiler panics.

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

O-emscriptenTarget: 50% off wasm32-unknown-musl. the savings come out of stdio.h, but hey, you get SDL!Target: 50% off wasm32-unknown-musl. the savings come out of stdio.h, but hey, you get SDL!

O-wasiOperating system: Wasi, Webassembly System InterfaceOperating system: Wasi, Webassembly System Interface

O-wasmTarget: WASM (WebAssembly), http://webassembly.org/Target: WASM (WebAssembly), http://webassembly.org/

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.

#135665 In rust-lang/rust;

· purplesyringa opened on Jan 18, 2025

<code>slice::Iter</code> + <code>max</code> on array: Regression since Rust 1.65 (LLVM 15)

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.

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-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.

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.

#129583 In rust-lang/rust;

· seritools opened on Aug 25, 2024

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

<code>-C target_cpu=cortex-a72</code> (and <code>-target-cpu=native</code> on Raspberry Pi) wrongly enables crypto features that are optional on Cortex-A72

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

A-targetsArea: Concerning the implications of different compiler targetsArea: Concerning the implications of different compiler targets

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

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

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

P-highHigh priorityHigh 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.

#125033 In rust-lang/rust;

· briansmith opened on May 12, 2024

Noop loop is only optimized away when the range is half-open

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-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.

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

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.

#123845 In rust-lang/rust;

· krtab opened on Apr 12, 2024

Match on two-variant enum optimizes poorly

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

Status: Open.

#122734 In rust-lang/rust;

· clubby789 opened on Mar 19, 2024

Unreachable overflow checks not optimized out of compiler-builtins i128 conversions

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-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.

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

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.

#116832 In rust-lang/rust;

· saethlin opened on Oct 17, 2023

Excessive overflow checks that can be proven unnecessary

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.

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

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.

#114386 In rust-lang/rust;

· ProgramCrafter opened on Aug 2, 2023

AddressSanitizer detects a stack-use-after-scope in Chain::new when optimizations are enabled

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-sanitizersArea: Sanitizers for correctness and code qualityArea: Sanitizers for correctness and code quality

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

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

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.

#98454 In rust-lang/rust;

· saethlin opened on Jun 24, 2022