llvm/llvm-project

Trivial memset optimization not applied to loops under -Oz (LoopIdiomRecognize)

Open

#50,308 opened on Jul 2, 2021

View on GitHub
 (31 comments) (0 reactions) (0 assignees)C++ (10,782 forks)batch import
bugzillagood first issuellvm:codesizellvm:optimizationsmissed-optimization

Repository metrics

Stars
 (26,378 stars)
PR merge metrics
 (Avg merge 1d 2h) (1,000 merged PRs in 30d)

Description
Bugzilla Link 50964
Version 12.0
OS All
CC @fhahn,@TH3CHARLie

Extended Description

Issue description: https://llvm.discourse.group/t/loops-not-optimized-under-oz-that-should-have-been/3734/1

Contributor guide

Research direction
Study the LoopIdiomRecognize pass and the Oz optimization level to determine why memset recognition is skipped. Review the discourse thread for additional context.
Tech stack
cpp
Domain
compilersbackend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
C++LLVMcompiler optimizations
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20