llvm/llvm-project

[InstCombiner] foldIntrinsicIsFPClass - incorrect submasking of FPClassTest masks

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#189,949 建立於 2026年4月1日

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 (15 留言) (0 反應) (1 負責人)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

貢獻者指南

技術棧
cpp
領域
backendperformance
議題類型
bug
難度面向新貢獻者的預計實作難度，1 表示很小改動，5 表示專家級工作。
4
預計時間有經驗貢獻者完成調查、實作、測試並準備 pull request 的粗略時間範圍。
over 1 week
活動狀態議題目前的可參與程度：新鮮、活躍、陳舊、阻塞或等待維護者輸入。
blocked
清晰度議題是否清楚說明預期改動、驗收標準和下一步。
mostly clear
前置要求
C++LLVM IRInstCombine passFP class test masks
新手友善度1-100 的估計分數，表示該議題對首次貢獻者的友善程度。
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.