[llvm] [RISCV] Support 3-argument associative add for transformAddShlImm (PR #86883)

[Craig Topper via llvm-commits]

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@@ -12777,6 +12769,46 @@ static SDValue transformAddShlImm(SDNode *N, SelectionDAG &DAG,
   return DAG.getNode(ISD::SHL, DL, VT, NA1, DAG.getConstant(Bits, DL, VT));
 }
 
+// Generalized form of above which looks through one level of add
+// reassociation for oppurtunities.
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topperc wrote:

opportunities*

https://github.com/llvm/llvm-project/pull/86883