llvm/llvm-project

[InstCombiner] foldIntrinsicIsFPClass - incorrect submasking of FPClassTest masks

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#189,949 创建于 2026年4月1日

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 (15 评论) (0 反应) (1 负责人)C++ (26,378 star) (10,782 fork)batch import
floating-pointgood first issuellvm:instcombine

描述

As mentioned here when creating the DAG equivalent: https://github.com/llvm/llvm-project/pull/189944#discussion_r3021637130

We shouldn't be looking for equality, we should be testing that they are a subset of the known classes:

https://github.com/llvm/llvm-project/blob/03b5539dd58584e6821e11123d5c8546147a6f41/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp#L1180-L1184

贡献者指南

技术栈
cpp
领域
backendperformance
议题类型
bug
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。
over 1 week
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。
blocked
清晰度议题是否清楚说明期望改动、验收标准和下一步。
mostly clear
前置要求
C++LLVM IRInstCombine passFP class test masks
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。
15
研究方向
Investigate the InstCombineCalls.cpp file at lines 1180-1184 where the equality check is used for FP class test masks. The correct behavior should be testing that the masks are a subset of known classes, not equality. Review the linked PR discussion for context. Implement the fix and add corresponding test cases in the appropriate test file.
[InstCombiner] foldIntrinsicIsFPClass - incorrect submasking of FPClassTest masks · llvm/llvm-project#189949 | Good First Issue