| Issue |
97427
|
| Summary |
SimplifyDemandedBits should handle fneg/fabs/fcopysign
|
| Labels |
good first issue,
floating-point,
llvm:SelectionDAG
|
| Assignees |
|
| Reporter |
arsenm
|
fneg, fabs and fcopysign are defined as bit operations, and should be subject to bitwise simplification. Fneg is xor with a signbit mask, fabs is and with a sign mask, and fcopysign is and signbit mask, and inverted signbit mask, and or.
This would allow deleting [more specific optimizations in visitFCOPYSIGN](https://github.com/llvm/llvm-project/blob/5ee53d417f41e8f452255ded1ff6a522afe17f08/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp#L17552)
This was brought up in https://github.com/llvm/llvm-project/pull/97180#discussion_r1660844076_
Attaching starter patch to point where this needs to go:
[0001-TODO-Support-FABS-FCOPYSIGN-FNEG-in-SimplifyDemanded.patch](https://github.com/user-attachments/files/16070829/0001-TODO-Support-FABS-FCOPYSIGN-FNEG-in-SimplifyDemanded.patch)
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