User`s guide

6 Optimizing Performance
6-6
If you compile this with the -O none option, you get
...
mlfAssign(
&y,
mclMtimes(
mlfDoubleMatrix(2, 2, _array0_, (double *)NULL),
mlfDoubleMatrix(2, 2, _array1_, (double *)NULL)));
...
Compiling with -O none -O fold_non_scalar_mxarrays:on gives
...
mlfAssign(&y, _mxarray0_);
...