[Bug middle-end/71614] ppc __gcc_qmul is mis-optimized not to be commutative

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71614

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Two things, try -fno-strict-aliasing first.
Since your main violates C aliasing rules.
Second thing to try is -ffp-contract=off as I am suspecting:
  v = a*d;
  w = b*c;
  tau += v + w;     /* Add in other second-order terms.  */
  u = t + tau;

is using an fmadd here.