2.4h J-Type

J-Type Instruction

The J-type (jump) format is designed for the jal operation, since it only requires a destination and a label. It follows the format:

31	30-20	19-15	14-12	11-7	6-0
imm[20]	imm[10:1]	imm[11]	imm[19:12]	rd	opcode

where the instruction’s label is stored as a 21-bit immediate offset multiple of 4 whose 0th bit is constant and is not stored since it is known. This layout resembles U-type’s imm[19:12] and I-type’s imm[10:1]. Finally, imm[20] holds the integer’s sign and is most efficiently accessed at the beginning of the instruction.