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Summary: In D61918 i was looking at dropping it in DAGCombiner `visitShiftByConstant()`, but as @craig.topper pointed out, it was copied from here. That check claims that the transform is illegal otherwise. That isn't true: 1. For `ISD::ADD`, we only process `ISD::SHL` outer shift => sign bit does not matter https://rise4fun.com/Alive/K4A 2. For `ISD::AND`, there is no restriction on constants: https://rise4fun.com/Alive/Wy3 3. For `ISD::OR`, there is no restriction on constants: https://rise4fun.com/Alive/GOH 3. For `ISD::XOR`, there is no restriction on constants: https://rise4fun.com/Alive/ml6 So, why is it there then? As far as i can tell, it dates all the way back to original check-in rL7793. I think we should just drop it. Reviewers: spatel, craig.topper, efriedma, majnemer Reviewed By: spatel Subscribers: llvm-commits, craig.topper Tags: #llvm Differential Revision: https://reviews.llvm.org/D61938 llvm-svn: 361043
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This directory and its subdirectories contain source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and runtime environments.