// operations can be combined. This functions assumes the two opcodes can
// be merged, and returns an encoded rotate+mask value of the combined RLDICL.
func mergePPC64RLDICLandSRDconst(encoded, s int64) int64 {
	mb := s
	r := 64 - s
	// A larger mb is a smaller mask.
	if (encoded>>8)&0xFF < mb {
		encoded = (encoded &^ 0xFF00) | mb<<8
	}
	// The rotate is expected to be 0.