llvm/llvm-project

[DAG] computeKnownFPClass - add ISD::MAXNUM/MINNUM handling + test coverage

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#189694 opened on Mar 31, 2026

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good first issuellvm:SelectionDAG

Description

ISD::FMAXIMUM/ISD::FMINIMUM + ISD::FMAXIMUMNUM/ISD::FMINIMUMNUM handling can be added as well

This will need to be based off the implementation in computeKnownFPClass in ValueTracking.cpp - DenormalMode access might take some additional patches / test coverage

This should be tested with IR tests and not unit tests

Contributor guide

Tech stack
cpp
Domain
backend
Issue type
feature
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.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
blocked
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
LLVM codegen experienceSelectionDAGC++
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
10
Research direction
Examine the existing computeKnownFPClass implementation in llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (or ValueTracking.cpp as mentioned). Understand how FMAXIMUM/FMINIMUM are handled and replicate the logic for MAXNUM/MINNUM. Check for any pending patches related to DenormalMode access that may be needed. Write IR tests for the new handling, ensuring coverage for different floating point scenarios.