missing simplifications

[redianthus]

Hi @filipeom,

I'm seeing this kind of expressions:

owi: [ERROR] Assert failure: (bool.ne
                              (i32.add
                               (i32.add
                                (i32.add (i32.sub symbol_0 6)
                                 (i32.add (i32.sub symbol_0 7)
                                  (i32.sub symbol_0 6)))
                                (i32.add
                                 (i32.add (i32.sub symbol_0 7)
                                  (i32.sub symbol_0 6))
                                 (i32.add (i32.sub symbol_0 6)
                                  (i32.add (i32.sub symbol_0 7)
                                   (i32.sub symbol_0 6)))))
                               (i32.add
                                (i32.add
                                 (i32.add (i32.sub symbol_0 7)
                                  (i32.sub symbol_0 6))
                                 (i32.add (i32.sub symbol_0 6)
                                  (i32.add (i32.sub symbol_0 7)
                                   (i32.sub symbol_0 6))))
                                (i32.add
                                 (i32.add (i32.sub symbol_0 6)
                                  (i32.add (i32.sub symbol_0 7)
                                   (i32.sub symbol_0 6)))
                                 (i32.add
                                  (i32.add (i32.sub symbol_0 7)
                                   (i32.sub symbol_0 6))
                                  (i32.add (i32.sub symbol_0 6)
                                   (i32.add (i32.sub symbol_0 7)
                                    (i32.sub symbol_0 6))))))) 13)

The only symbol here is symbol_0 so I'm almost sure this could be simplified much more.

For instance:

(i32.add (i32.sub symbol_0 7) (i32.sub symbol_0 6))

Is basically: (x - 7) + (x - 6)

And it should be simplified at least into:

(x + (x - 13))

And then, we could probably simplify much more. WDYT? I'm not sure how annoying it would be to add this kind of simplifications...