Applicability of this chapter to configurations:
This chapter is applicable to all CV32A6 configurations.
Configuration |
Implementation |
|---|---|
CV32A60AX |
Implemented extension |
CV32A60X |
Implemented extension |
Note: CV64A6 implements RV64I that includes additional instructions.
RV32I Base Integer Instruction Set
This section describes the RV32I base integer instruction set.
Integer Register-Immediate Instructions
ADDI: Add Immediate
Format: addi rd, rs1, imm[11:0]
Description: add sign-extended 12-bit immediate to register rs1, and store the result in register rd.
Pseudocode: x[rd] = x[rs1] + sext(imm[11:0])
Invalid values: NONE
Exception raised: NONE
ANDI: AND Immediate
Format: andi rd, rs1, imm[11:0]
Description: perform bitwise AND on register rs1 and the sign-extended 12-bit immediate and place the result in rd.
Pseudocode: x[rd] = x[rs1] & sext(imm[11:0])
Invalid values: NONE
Exception raised: NONE
ORI: OR Immediate
Format: ori rd, rs1, imm[11:0]
Description: perform bitwise OR on register rs1 and the sign-extended 12-bit immediate and place the result in rd.
Pseudocode: x[rd] = x[rs1] | sext(imm[11:0])
Invalid values: NONE
Exception raised: NONE
XORI: XOR Immediate
Format: xori rd, rs1, imm[11:0]
Description: perform bitwise XOR on register rs1 and the sign-extended 12-bit immediate and place the result in rd.
Pseudocode: x[rd] = x[rs1] ^ sext(imm[11:0])
Invalid values: NONE
Exception raised: NONE
SLTI: Set Less Then Immediate
Format: slti rd, rs1, imm[11:0]
Description: set register rd to 1 if register rs1 is less than the sign extended immediate when both are treated as signed numbers, else 0 is written to rd.
Pseudocode: if (x[rs1] < sext(imm[11:0]) x[rd] = 1 else x[rd] = 0
Invalid values: NONE
Exception raised: NONE
SLTIU: Set Less Then Immediate Unsigned
Format: sltiu rd, rs1, imm[11:0]
Description: set register rd to 1 if register rs1 is less than the sign extended immediate when both are treated as unsigned numbers, else 0 is written to rd.
Pseudocode: if (x[rs1] <u sext(imm[11:0]) x[rd] = 1 else x[rd] = 0
Invalid values: NONE
Exception raised: NONE
SLLI: Shift Left Logic Immediate
Format: slli rd, rs1, imm[4:0]
Description: logical left shift (zeros are shifted into the lower bits).
Pseudocode: x[rd] = x[rs1] << imm[4:0]
Invalid values: NONE
Exception raised: NONE
SRLI: Shift Right Logic Immediate
Format: srli rd, rs1, imm[4:0]
Description: logical right shift (zeros are shifted into the upper bits).
Pseudocode: x[rd] = x[rs1] >> imm[4:0]
Invalid values: NONE
Exception raised: NONE
SRAI: Shift Right Arithmetic Immediate
Format: srai rd, rs1, imm[4:0]
Description: arithmetic right shift (the original sign bit is copied into the vacated upper bits).
Pseudocode: x[rd] = x[rs1] >>s imm[4:0]
Invalid values: NONE
Exception raised: NONE
LUI: Load Upper Immediate
Format: lui rd, imm[19:0]
Description: place the immediate value in the top 20 bits of the destination register rd, filling in the lowest 12 bits with zeros.
Pseudocode: x[rd] = sext(imm[31:12] << 12)
Invalid values: NONE
Exception raised: NONE
AUIPC: Add Upper Immediate to PC
Format: auipc rd, imm[19:0]
Description: form a 32-bit offset from the 20-bit immediate, filling in the lowest 12 bits with zeros, adds this offset to the pc, then place the result in register rd.
Pseudocode: x[rd] = pc + sext(immediate[31:12] << 12)
Invalid values: NONE
Exception raised: NONE
Integer Register-Register Instructions
ADD: Addition
Format: add rd, rs1, rs2
Description: add rs2 to register rs1, and store the result in register rd.
Pseudocode: x[rd] = x[rs1] + x[rs2]
Invalid values: NONE
Exception raised: NONE
SUB: Subtraction
Format: sub rd, rs1, rs2
Description: subtract rs2 from register rs1, and store the result in register rd.
Pseudocode: x[rd] = x[rs1] - x[rs2]
Invalid values: NONE
Exception raised: NONE
AND: AND logical operator
Format: and rd, rs1, rs2
Description: perform bitwise AND on register rs1 and rs2 and place the result in rd.
Pseudocode: x[rd] = x[rs1] & x[rs2]
Invalid values: NONE
Exception raised: NONE
OR: OR logical operator
Format: or rd, rs1, rs2
Description: perform bitwise OR on register rs1 and rs2 and place the result in rd.
Pseudocode: x[rd] = x[rs1] | x[rs2]
Invalid values: NONE
Exception raised: NONE
XOR: XOR logical operator
Format: xor rd, rs1, rs2
Description: perform bitwise XOR on register rs1 and rs2 and place the result in rd.
Pseudocode: x[rd] = x[rs1] ^ x[rs2]
Invalid values: NONE
Exception raised: NONE
SLT: Set Less Then
Format: slt rd, rs1, rs2
Description: set register rd to 1 if register rs1 is less than rs2 when both are treated as signed numbers, else 0 is written to rd.
Pseudocode: if (x[rs1] < x[rs2]) x[rd] = 1 else x[rd] = 0
Invalid values: NONE
Exception raised: NONE
SLTU: Set Less Then Unsigned
Format: sltu rd, rs1, rs2
Description: set register rd to 1 if register rs1 is less than rs2 when both are treated as unsigned numbers, else 0 is written to rd.
Pseudocode: if (x[rs1] <u x[rs2]) x[rd] = 1 else x[rd] = 0
Invalid values: NONE
Exception raised: NONE
SLL: Shift Left Logic
Format: sll rd, rs1, rs2
Description: logical left shift (zeros are shifted into the lower bits).
Pseudocode: x[rd] = x[rs1] << x[rs2]
Invalid values: NONE
Exception raised: NONE
SRL: Shift Right Logic
Format: srl rd, rs1, rs2
Description: logical right shift (zeros are shifted into the upper bits).
Pseudocode: x[rd] = x[rs1] >> x[rs2]
Invalid values: NONE
Exception raised: NONE
SRA: Shift Right Arithmetic
Format: sra rd, rs1, rs2
Description: arithmetic right shift (the original sign bit is copied into the vacated upper bits).
Pseudocode: x[rd] = x[rs1] >>s x[rs2]
Invalid values: NONE
Exception raised: NONE
Control Transfer Instructions
Unconditional Jumps
JAL: Jump and Link
Format: jal rd, imm[20:1]
Description: offset is sign-extended and added to the pc to form the jump target address (pc is calculated using signed arithmetic), then setting the least-significant bit of the result to zero, and store the address of instruction following the jump (pc+4) into register rd.
Pseudocode: x[rd] = pc+4; pc += sext(imm[20:1])
Invalid values: NONE
Exception raised: jumps to an unaligned address (4-byte or 2-byte boundary) will usually raise an exception.
JALR: Jump and Link Register
Format: jalr rd, rs1, imm[11:0]
Description: target address is obtained by adding the 12-bit signed immediate to the register rs1 (pc is calculated using signed arithmetic), then setting the least-significant bit of the result to zero, and store the address of instruction following the jump (pc+4) into register rd.
Pseudocode: t = pc+4; pc = (x[rs1]+sext(imm[11:0]))&∼1 ; x[rd] = t
Invalid values: NONE
Exception raised: jumps to an unaligned address (4-byte or 2-byte boundary) will usually raise an exception.
Conditional Branches
BEQ: Branch Equal
Format: beq rs1, rs2, imm[12:1]
Description: takes the branch (pc is calculated using signed arithmetic) if registers rs1 and rs2 are equal.
Pseudocode: if (x[rs1] == x[rs2]) pc += sext({imm[12:1], 1’b0}) else pc += 4
Invalid values: NONE
Exception raised: no instruction fetch misaligned exception is generated for a conditional branch that is not taken. An Instruction address misaligned exception is raised if the target address is not aligned on 4-byte or 2-byte boundary, because the core supports compressed instructions.
BNE: Branch Not Equal
Format: bne rs1, rs2, imm[12:1]
Description: takes the branch (pc is calculated using signed arithmetic) if registers rs1 and rs2 are not equal.
Pseudocode: if (x[rs1] != x[rs2]) pc += sext({imm[12:1], 1’b0}) else pc += 4
Invalid values: NONE
Exception raised: no instruction fetch misaligned exception is generated for a conditional branch that is not taken. An Instruction address misaligned exception is raised if the target address is not aligned on 4-byte or 2-byte boundary, because the core supports compressed instructions.
BLT: Branch Less Than
Format: blt rs1, rs2, imm[12:1]
Description: takes the branch (pc is calculated using signed arithmetic) if registers rs1 less than rs2 (using signed comparison).
Pseudocode: if (x[rs1] < x[rs2]) pc += sext({imm[12:1], 1’b0}) else pc += 4
Invalid values: NONE
Exception raised: no instruction fetch misaligned exception is generated for a conditional branch that is not taken. An Instruction address misaligned exception is raised if the target address is not aligned on 4-byte or 2-byte boundary, because the core supports compressed instructions.
BLTU: Branch Less Than Unsigned
Format: bltu rs1, rs2, imm[12:1]
Description: takes the branch (pc is calculated using signed arithmetic) if registers rs1 less than rs2 (using unsigned comparison).
Pseudocode: if (x[rs1] <u x[rs2]) pc += sext({imm[12:1], 1’b0}) else pc += 4
Invalid values: NONE
Exception raised: no instruction fetch misaligned exception is generated for a conditional branch that is not taken. An Instruction address misaligned exception is raised if the target address is not aligned on 4-byte or 2-byte boundary, because the core supports compressed instructions.
BGE: Branch Greater or Equal
Format: bge rs1, rs2, imm[12:1]
Description: takes the branch (pc is calculated using signed arithmetic) if registers rs1 is greater than or equal rs2 (using signed comparison).
Pseudocode: if (x[rs1] >= x[rs2]) pc += sext({imm[12:1], 1’b0}) else pc += 4
Invalid values: NONE
Exception raised: no instruction fetch misaligned exception is generated for a conditional branch that is not taken. An Instruction address misaligned exception is raised if the target address is not aligned on 4-byte or 2-byte boundary, because the core supports compressed instructions.
BGEU: Branch Greater or Equal Unsigned
Format: bgeu rs1, rs2, imm[12:1]
Description: takes the branch (pc is calculated using signed arithmetic) if registers rs1 is greater than or equal rs2 (using unsigned comparison).
Pseudocode: if (x[rs1] >=u x[rs2]) pc += sext({imm[12:1], 1’b0}) else pc += 4
Invalid values: NONE
Exception raised: no instruction fetch misaligned exception is generated for a conditional branch that is not taken. An Instruction address misaligned exception is raised if the target address is not aligned on 4-byte or 2-byte boundary, because the core supports compressed instructions.
Load and Store Instructions
LB: Load Byte
Format: lb rd, imm(rs1)
Description: loads a 8-bit value from memory, then sign-extends to 32-bit before storing in rd (rd is calculated using signed arithmetic), the effective address is obtained by adding register rs1 to the sign-extended 12-bit offset.
Pseudocode: x[rd] = sext(M[x[rs1] + sext(imm[11:0])][7:0])
Invalid values: NONE
Exception raised: loads with a destination of x0 must still raise any exceptions and action any other side effects even though the load value is discarded.
LH: Load Halfword
Format: lh rd, imm(rs1)
Description: loads a 16-bit value from memory, then sign-extends to 32-bit before storing in rd (rd is calculated using signed arithmetic), the effective address is obtained by adding register rs1 to the sign-extended 12-bit offset.
Pseudocode: x[rd] = sext(M[x[rs1] + sext(imm[11:0])][15:0])
Invalid values: NONE
Exception raised: loads with a destination of x0 must still raise any exceptions and action any other side effects even though the load value is discarded, also an exception is raised if the memory address isn’t aligned (2-byte boundary).
LW: Load Word
Format: lw rd, imm(rs1)
Description: loads a 32-bit value from memory, then storing in rd (rd is calculated using signed arithmetic). The effective address is obtained by adding register rs1 to the sign-extended 12-bit offset.
Pseudocode: x[rd] = sext(M[x[rs1] + sext(imm[11:0])][31:0])
Invalid values: NONE
Exception raised: loads with a destination of x0 must still raise any exceptions and action any other side effects even though the load value is discarded, also an exception is raised if the memory address isn’t aligned (4-byte boundary).
LBU: Load Byte Unsigned
Format: lbu rd, imm(rs1)
Description: loads a 8-bit value from memory, then zero-extends to 32-bit before storing in rd (rd is calculated using unsigned arithmetic), the effective address is obtained by adding register rs1 to the sign-extended 12-bit offset.
Pseudocode: x[rd] = zext(M[x[rs1] + sext(imm[11:0])][7:0])
Invalid values: NONE
Exception raised: loads with a destination of x0 must still raise any exceptions and action any other side effects even though the load value is discarded.
LHU: Load Halfword Unsigned
Format: lhu rd, imm(rs1)
Description: loads a 16-bit value from memory, then zero-extends to 32-bit before storing in rd (rd is calculated using unsigned arithmetic), the effective address is obtained by adding register rs1 to the sign-extended 12-bit offset.
Pseudocode: x[rd] = zext(M[x[rs1] + sext(imm[11:0])][15:0])
Invalid values: NONE
Exception raised: loads with a destination of x0 must still raise any exceptions and action any other side effects even though the load value is discarded, also an exception is raised if the memory address isn’t aligned (2-byte boundary).
SB: Store Byte
Format: sb rs2, imm(rs1)
Description: stores a 8-bit value from the low bits of register rs2 to memory, the effective address is obtained by adding register rs1 to the sign-extended 12-bit offset.
Pseudocode: M[x[rs1] + sext(imm[11:0])][7:0] = x[rs2][7:0]
Invalid values: NONE
Exception raised: NONE
SH: Store Halfword
Format: sh rs2, imm(rs1)
Description: stores a 16-bit value from the low bits of register rs2 to memory, the effective address is obtained by adding register rs1 to the sign-extended 12-bit offset.
Pseudocode: M[x[rs1] + sext(imm[11:0])][15:0] = x[rs2][15:0]
Invalid values: NONE
Exception raised: an exception is raised if the memory address isn’t aligned (2-byte boundary).
SW: Store Word
Format: sw rs2, imm(rs1)
Description: stores a 32-bit value from register rs2 to memory, the effective address is obtained by adding register rs1 to the sign-extended 12-bit offset.
Pseudocode: M[x[rs1] + sext(imm[11:0])][31:0] = x[rs2][31:0]
Invalid values: NONE
Exception raised: an exception is raised if the memory address isn’t aligned (4-byte boundary).
Memory Ordering
FENCE: Fence Instruction
Format: fence pre, succ
Description: order device I/O and memory accesses as viewed by other RISC-V harts and external devices or coprocessors. Any combination of device input (I), device output (O), memory reads (R), and memory writes (W) may be ordered with respect to any combination of the same. Informally, no other RISC-V hart or external device can observe any operation in the successor set following a FENCE before any operation in the predecessor set preceding the FENCE, as the core support 1 hart, the fence instruction has no effect so we can considerate it as a nop instruction.
Pseudocode: No operation (nop)
Invalid values: NONE
Exception raised: NONE
Environment Call and Breakpoints
ECALL: Environment Call
Format: ecall
Description: make a request to the supporting execution environment, which is usually an operating system. The ABI for the system will define how parameters for the environment request are passed, but usually these will be in defined locations in the integer register file.
Pseudocode: RaiseException(EnvironmentCall)
Invalid values: NONE
Exception raised: Raise an Environment Call exception.
EBREAK:Environment Break
Format: ebreak
Description: cause control to be transferred back to a debugging environment.
Pseudocode: RaiseException(Breakpoint)
Invalid values: NONE
Exception raised: Raise a Breakpoint exception.