path: root/subx/examples/ex3.subx

## add the first 10 numbers, and return the result in the exit code
#
# To run (from the subx directory):
#   $ subx translate examples/ex3.subx -o examples/ex3
#   $ subx run examples/ex3
# Expected result:
#   $ echo $?
#   55

== code
# instruction                     effective address                                                   operand     displacement    immediate
# op          subop               mod             rm32          base        index         scale       r32
# 1-3 bytes   3 bits              2 bits          3 bits        3 bits      3 bits        2 bits      2 bits      0/1/2/4 bytes   0/1/2/4 bytes
  # result: EBX = 0
  bb/copy                         .               .             .           .             .           .           .               0/imm32           # copy to EBX
  # counter: ECX = 1
  b9/copy                         .               .             .           .             .           .           .               1/imm32           # copy to ECX

$loop:
  # while (counter <= 10)
  81          7/subop/compare     3/mod/direct    1/rm32/ECX    .           .             .           .           .               0xa/imm32         # compare ECX
  7f/jump-if-greater  $exit/disp8
  # result += counter
  01/add                          3/mod/direct    3/rm32/EBX    .           .             .           1/r32/ECX   .               .                 # add ECX to EBX
  # ++counter
  41/inc-ECX
  # loop
  eb/jump  $loop/disp8

$exit:
  # exit(EBX)
  b8/copy                         .               .             .           .             .           .           .               1/imm32           # copy to EAX
  cd/syscall  0x80/imm8

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