In standard C library, both rint and nearbyint returns rounding result in current rounding mode. But nearbyint never raises inexact exception. On PowerPC, x(v|s)r(d|s)pic may modify FPSCR XX, raising inexact exception. So we can't select constrained fnearbyint into xvrdpic.
One exception here is xsrqpi, which will not raise inexact exception, so fnearbyint f128 is okay here.