data_Chacha64.txt

//for vX.Y  of P

// low-order bit of Rd (7) is 0 to ensure even-numbered Rd
I	CHACHA	 CHACHA	    101--00----------000----01110111	chacha	Zchacha

S	CHACHA	"fun_chacha(input(SRC1), input(SRC2), input(SRC3), input(INSTRUCTION)(28 downto 27))"

P	"""
	def fun_chacha(rs1: Bits, rs2: Bits, rs3: Bits, num: Bits) : Bits = {
	    val rotv = (num).mux(
			B"2'b00" -> U(16),
			B"2'b01" -> U(12),
			B"2'b10" -> U( 8),
			B"2'b11" -> U( 7)
			)
		val a = rs3
		val b = rs1
		val d = rs2
		val sum = (a.asUInt + b.asUInt).asBits.resize(32)
		val xor = sum ^ d
		val rot = xor.rotateLeft(rotv)
		rot ## sum // return value
	}
"""