RISC-V assembly language
 | |
| Filename extension |
.s |
|---|---|
| Developed by | RISC-V Foundation |
| Type of format | Assembly language |
| Open format? | Yes |
| Free format? | Yes |
| Website | riscv |
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.
Assemblers include GNU Assembler and LLVM.
Keywords
[edit]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
[edit]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
[edit]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
[edit]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
[edit]RISC-V assembly language includes instructions for a floating-point unit (FPU).
SIMD instructions
[edit]These largely perform the same operation in parallel on many values.
Program flow
[edit]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
[edit].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"
