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RISC-V assembly language

Assembly languages for the RISC-V computer architecture From Wikipedia, the free encyclopedia

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RISC-V assembly language is a low-level programming language that is used to produce object code for the RISC-V class of processors. Assembly languages are closely tied to the architecture's machine code instructions, allowing for precise control over hardware.

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Assemblers include GNU Assembler and LLVM.

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Keywords

Reserved keywords of RISC-V assembly language.

  • add
  • addi
  • and
  • andi
  • beq
  • bge
  • bgeu
  • blt
  • bltu
  • bne
  • lb
  • lbu
  • lh
  • lhu
  • lw
  • or
  • ori
  • sb
  • sh
  • sll
  • slli
  • slt
  • slti
  • sltiu
  • sltu
  • sra
  • srai
  • srl
  • srli
  • sub
  • sw
  • xor
  • xori

Mnemonics and opcodes

Each instruction in the RISC-V assembly language is represented by a mnemonic which often combines with one or more operands to translate into one or more bytes known as an opcode.

Registers

RISC-V processors feature a set of registers that serve as storage for binary data and addresses during program execution. These registers are categorized into integer registers and floating-point registers.

Instruction types

RISC-V instructions use variable-length encoding.

Extensions:

  • atomic instructions
  • single-precision floating-point
  • double-precision floating-point
  • bit manipulation
  • cryptography
  • hypervisor
  • supervisor
  • packed-SIMD instructions
  • vector

Floating-point instructions

RISC-V assembly language includes instructions for a floating-point unit (FPU).

SIMD instructions

These largely perform the same operation in parallel on many values.

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Program flow

The RISC-V assembly has conditional branch instructions based on comparison: beq (equal), bne (not equal), blt (less than, signed), bltu (less than, unsigned), bge (greater than or equal, signed), and bgeu (greater than or equal, unsigned).

Examples

.section .text
.globl _start
_start:
	    lui  a1,      %hi(msg)       # load msg(hi)
	    addi a1, a1,  %lo(msg)       # load msg(lo)
	    jalr ra, puts
2:	    j    2b

.section .rodata
msg:
	    .string "Hello World\n"

See also

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