llvm/llvm-project

[CodeGen] llc silently ignores -{start|stop}-{after|before} options

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#138,831 opened on May 7, 2025

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good first issuellvm:codegen

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Description

Particularly, llc -mtriple=amdgcn-- -start-after=dead-mi-elimination,4 should be running remaining passes in the pipeline after the last instance of dead-mi-elimination, but instead this runs no passes.

Contributor guide

Research direction
Investigate how the llc tool processes the start after option and identify why it stops the pass pipeline prematurely. Look at the pass manager integration in llc.cpp and the PassBuilder handling.
Tech stack
ccpp
Domain
backendcli
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
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
C++
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70