llvm/llvm-project

[DAG] computeKnownFPClass - add ISD::SINT_TO_FP/UINT_TO_FP handling

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#189479 opened on Mar 30, 2026

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good first issuellvm:SelectionDAG

Description

This will need to be based off the implementation in computeKnownFPClass in ValueTracking.cpp.

Hopefully once https://github.com/llvm/llvm-project/pull/189476 lands the ISD::SINT_TO_FP/UINT_TO_FP handling can be removed from DAG.isKnownNeverNaN and the generic fallback to computeKnownFPClass can be used instead.

Must include DemandedElts handling and IR test coverage.

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.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
C++LLVM internalsCompiler backendFloating point handling
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
15
Research direction
Study the implementation of computeKnownFPClass in llvm/lib/Analysis/ValueTracking.cpp. Wait for PR #189476 to land, then examine how ISD::SINT TO FP/UINT TO FP handling can be removed from DAG.isKnownNeverNaN and replaced with the generic fallback. Implement DemandedElts handling and add IR test coverage in relevant test files.