Init canonicalize infrastructure

[rikhuijzer]

Allow canonicalization (mlir-opt tmp.mlir --canonicalize) from

module {
  func.func @test_addi(%arg0 : i64) -> i64 {
    %0 = arith.constant 1 : i64
    %1 = arith.constant 2 : i64
    %2 = arith.addi %0, %1 : i64
    %3 = arith.addi %arg0, %2 : i64
    return %3 : i64
  }
}

to

module {
  func.func @test_addi(%arg0 : i64) -> i64 {
    %0 = arith.constant 1 : i64
    %1 = arith.constant 2 : i64
    %2 = arith.constant 3 : i64
    %3 = arith.addi %arg0, %2 : i64
    return %3 : i64
  }
}

So, it applied const prop to %2.

Next step

The next step is to do dead code elimination in order to transform the code to

module {
  func.func @test_addi(%arg0: i64) -> i64 {
    %c3_i64 = arith.constant 3 : i64
    %0 = arith.addi %arg0, %c3_i64 : i64
    return %0 : i64
  }
}