llvm/llvm-project

[ARM][AArch64] Remove CLS special handling and use generic ISD::CTLS node

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#174337 opened on Jan 4, 2026

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backend:AArch64backend:ARMgood first issue

Description

Once #173417 has landed, the arm/aarch64 intrinsics (int_arm_mve_vcls/int_arm_neon_vcls/int_aarch64_cls/int_aarch64_cls64 etc.) can be expanded to ISD::CTLS in DAG/GISel and the remaining patterns/setOperationAction calls converted to use ISD::CTLS

Contributor guide

Tech stack
cpp
Domain
backend
Issue type
refactor
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
5
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 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.
clear
Prerequisites
PR #173417LLVM ARM/AArch64 backendDAG/GlobalISel knowledge
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
15
Research direction
First, verify that PR #173417 has landed and understand how it implements ISD::CTLS. Then, in the LLVM source tree, locate all patterns and setOperationAction calls related to the intrinsics int arm mve vcls, int arm neon vcls, int aarch64 cls, and int aarch64 cls64 in lib/Target/ARM and lib/Target/AArch64. Convert these to use ISD::CTLS directly, removing the special handling. Ensure the changes are consistent across both DAG and GlobalISel code paths. Refer to the issue comments for any additional guidance from maintainers.