RISC-VでHELLO WORLD

hello.S

# hello
#
# $ riscv64-unknown-elf-gcc -march=rv32i -mabi=ilp32 -Wl,-Ttext=0x00 -nostdlib -o hello.elf hello.S
# $ riscv64-unknown-elf-objcopy -O binary hello.elf hello.rom
# $ ruby rv32sim.rb hello.rom

  .text
  .globl _start
  .type _start, @function
_start:
  // 1024を18ビットシフトさせて gp へ 0x10000000 をセットする
  addi gp, zero, 1024
  slli gp, gp, 18

  addi t0, zero, 'H'
  sw t0, 0(gp)
  addi t0, zero, 'E'
  sw t0, 0(gp)
  addi t0, zero, 'L'
  sw t0, 0(gp)
  addi t0, zero, 'L'
  sw t0, 0(gp)
  addi t0, zero, 'O'
  sw t0, 0(gp)
  addi t0, zero, ' '
  sw t0, 0(gp)
  addi t0, zero, 'W'
  sw t0, 0(gp)
  addi t0, zero, 'O'
  sw t0, 0(gp)
  addi t0, zero, 'R'
  sw t0, 0(gp)
  addi t0, zero, 'L'
  sw t0, 0(gp)
  addi t0, zero, 'D'
  sw t0, 0(gp)
  addi t0, zero, '!'
  sw t0, 0(gp)
  addi t0, zero, '!'
  sw t0, 0(gp)
  addi t0, zero, '\n'
  sw t0, 0(gp)
  nop
  nop
  nop
  nop
  nop