"Panu-Kristian Poiksalo" <panu.poiksalo@xxxxxxx> writes: > Sorry to bother you with an idiotic question, but I might have > misunderstood something rather profoundly. > > See GCC internals chapter 16.14 "Canonicalization of Instructions". > In item #4 of the list of canonicalizations, it is stated: > "(plus (mult (neg A) B) C) is canonicalized as (minus A (mult B C))." > > Now, that looks a bit strange. Does that mean that > ((-a) * b) + c) is-equal-to (a - (b * c)) > > because it doesn't seem that way if I substitute a=3, b=5, c=7 I get > ((-3) * 5) + 7) = (-15 + 7) = -8 and > (3 - (5 * 7)) = (3 - (35)) = -32. You're right, the docs are wrong. It should say that (plus (mult (neg B) C) A) is canonicalized as (minus A (mult B C)). I'll fix it. Thanks. Ian
