llvm/llvm-project

[libc][math] Add missing isnan variants for float16, bfloat16, and float128

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#195,400 创建于 2026年5月2日

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good first issuelibc

描述

The current implementations of isnan are limited to float, double, and long double. We should add support for the remaining types (float16, bfloat16, and float128).

Additionally, the existing implementations currently rely on __builtin_isnan. I think refactoring them to use fputil would be better, especially since issignaling already uses fputil.

贡献者指南

技术栈
cpp
领域
api
议题类型
feature
难度面向新贡献者的预计实现难度，1 表示很小改动，5 表示专家级工作。
4
预计时间有经验贡献者完成调查、实现、测试并准备 pull request 的粗略时间范围。
3-5 days
活动状态议题当前的可参与程度：新鲜、活跃、陈旧、阻塞或等待维护者输入。
active
清晰度议题是否清楚说明期望改动、验收标准和下一步。
clear
前置要求
Familiarity with floating point types (float16, bfloat16, float128)Understanding of C/C++ math function implementationKnowledge of LLVM libc structureExperience with compiler built ins like builtin isnan
新手友好度1-100 的估计分数，表示该议题对首次贡献者的友好程度。
35
研究方向
Examine existing isnan implementations for float, double, and long double to understand the pattern. Look at the issignaling implementation to see how it uses fputil. Determine which files need modification (likely in libc/src/math/) for the new types. Check the comments in this issue for any discussion about specific files or approaches. The refactoring to fputil may require understanding of the fputil library.