RISC-V Quick Reference

opcodes #

• R: 0110011
• I: 0010011
• S: 0100011
• B: 1100011

registers #

Registers

Example instruction

j vs jr vs jal vs jalr #

j label is a pseudoinstruction for jal x0, label

ret = jr ra = jalr x0, ra, 0

jal ra, label calls function within $2^{18}$ instructions of PC

• is a J instruction
• saves PC + 4 in register ra
• Sets PC to PC + offset

jalr rd, rs, immediate:

• is an I instruction
• saves PC + 4 in register rd
• sets PC to rs + immediate (doesn’t use PC itself in calculation)
• Absolute use: lui x1, <hi20bits> then jalr ra, x1, <lo12bits>
• Relative use: auipc x1, <hi20bits> then jalr x0, x1, <lo12bits>

Psuedoinstructions #

Memory allocation #