[PATCH] D148341: [DAGCombiner] Fold add (mul x, C), x to mul x, C+1

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


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Comment at: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:3061
 
+  // add (mul x, C), x -> mul x, C+1
+  if (N0.getOpcode() == ISD::MUL && N0.getOperand(0) == N1 &&
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goldstein.w.n wrote:
> Does the equivilent ever come up for sub?
I don't think so. You'd need something like `gep(x, sub(0, mul(x, C)))` for that, and that would be canonicalized to `gep(x, mul(x, -C))` rather than becoming `sub(x, mul(x, C))` in the backend.


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  https://reviews.llvm.org/D148341/new/

https://reviews.llvm.org/D148341