On 08/17/2017 09:43 AM, Alexander Monakov wrote: > On Thu, 17 Aug 2017, Wilco Dijkstra wrote: > >> This patch simplifies pow (C, x) into exp (x * C1) if C > 0, C1 = log (C). > > Note this changes the outcome for C == +Inf, x == 0 (pow is specified to > return 1.0 in that case, but x * C1 == NaN). There's another existing > transform with the same issue, 'pow(expN(x), y) -> expN(x*y)', so this is > not a new problem. That may be part of the reason why they're guarded with -ffast-math. In addition to the changes in accuracy. I haven't followed those transformations on the GCC side to know with any certainty.
jeff
