PowerPC64/PowerPC64le supports the builtin function __builtin_setrnd to set the floating point rounding mode. This function will use the least significant two bits of integer argument to set the floating point rounding mode.

double __builtin_setrnd(int mode);

The effective values for mode are:

0 - round to nearest 1 - round to zero 2 - round to +infinity 3 - round to -infinity

Note that the mode argument will modulo 4, so if the int argument is greater than 3, it will only use the least significant two bits of the mode. Namely, __builtin_setrnd(102)) is equal to __builtin_setrnd(2).