AMOADD.D

Atomic Add Doubleword

AMOADD.D rd, rs2, (rs1)

Atomically adds a value to a 64-bit doubleword in memory.

Encoding

Binary Layout

00000

31:27

aq

26

rl

25

rs2

24:20

rs1

19:15

011

14:12

rd

11:7

0101111

6:0

 

Format R-Type (Atomic)

Opcode 0x0000302F

Extension A

Operands

• rd
  Dest (Old Value)
• rs2
  Value to Add
• rs1
  Address

Example

AMOADD.D x10, x11, (x12)

// 64-bit atomic add.

Related

Across architectures

Atomic Fetch and Add : how x86, ARM, RISC-V, and PowerISA each do this.

More in A

Reference

View in RISC-V Unprivileged ISA Specification ↗ RISC-V ISA Manual

Description

AMOADD.D atomically loads a doubleword from the address in rs1 into rd, adds rs2, and stores the result back (RV64 only).

Operation

temp = M[R[rs1]]; M[R[rs1]] = temp + R[rs2]; R[rd] = temp;