Group commutative ops with constants

[Pangoraw]

module {
  func.func @main(%arg0: tensor<3xi64>) -> tensor<3xi64> {
    %c = stablehlo.constant dense<1> : tensor<3xi64>
    %0 = stablehlo.add %arg0, %c : tensor<3xi64>
    %1 = stablehlo.add %0, %c : tensor<3xi64>
    %2 = stablehlo.add %1, %c : tensor<3xi64>
    return %2 : tensor<3xi64>
  }
}

could be transformed to:

module {
  func.func @main(%arg0: tensor<3xi64>) -> tensor<3xi64> {
    %c = stablehlo.constant dense<3> : tensor<3xi64>
    %0 = stablehlo.add %arg0, %c : tensor<3xi64>
    return %0 : tensor<3xi64>
  }
}

with (%x + %cst0) + %cst1 -> %x + (%cst0 + %cst1)

Not sure if we can apply this for floats though.

[wsmoses]

Yeah here we can do add of (add x, c1), c2 -> add x (c1+c2)