search for: ismuladdwithconstprofit

Thanks. I have checked the hook DAGCombiner::isMulAddWithConstProfitable And I think the above condition is too aggressive. // If the add only has one use, this would be OK to do. if (AddNode.getNode()->hasOneUse()) return true; Shall we make it to if (AddNode.getNode()->hasOneUse() && TargetLowering.isCheaperCommuteAddMul(......)) r...

Yes - this has been in InstCombine for a long time: https://github.com/llvm/llvm-project/blob/master/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp#L268 We could say that the canonicalization should be reversed, but that probably uncovers more missing optimizations. The code size concern is legitimate. For example on x86, gcc asm is 2 bytes smaller on this example: