path: root/subx/051test.subx

# Rudimentary test harness

== code
#   instruction                     effective address                                                   register    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

# main:  (manual test if this is the last file loaded)
    # check-ints-equal(34, 34)
    # . . push args
    68/push  "error in check-ints-equal"/imm32
    68/push  34/imm32
    68/push  34/imm32
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
    # syscall(exit, 0)
    bb/copy-to-EBX  0/imm32
    b8/copy-to-EAX  1/imm32/exit
    cd/syscall  0x80/imm8

# print msg to stderr if a != b, otherwise print "."
check-ints-equal:  # (a : int, b : int, msg : (address array byte)) -> <void>
    # . prolog
    55/push-EBP
    89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
    # . save registers
    50/push-EAX
    51/push-ECX
    53/push-EBX
    # load first 2 args into EAX and EBX
    8b/copy                         1/mod/*+disp8   5/rm32/EBP    .           .             .           0/r32/EAX   8/disp8         .                 # copy *(EBP+8) to EAX
    8b/copy                         1/mod/*+disp8   5/rm32/EBP    .           .             .           3/r32/EBX   0xc/disp8       .                 # copy *(EBP+12) to EBX
    # if (EAX == EBX) success
    39/compare                      3/mod/direct    0/rm32/EAX    .           .             .           3/r32/EBX   .               .                 # compare EAX and EBX
    75/jump-if-unequal  $check-ints-equal:else/disp8
    # . _write(2/stderr, '.')
    # . . push args
    68/push  "."/imm32
    68/push  2/imm32/stderr
    # . . call
    e8/call  _write/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # . return
    eb/jump  $check-ints-equal:end/disp8
    # otherwise print error message
$check-ints-equal:else:
    # . _write(2/stderr, msg)
    # . . push args
    8b/copy                         1/mod/*+disp8   5/rm32/EBP    .           .             .           1/r32/ECX   0x10/disp8      .                 # copy *(EBP+16) to ECX
    51/push-ECX
    68/push  2/imm32/stderr
    # . . call
    e8/call  _write/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # . _write(2/stderr, Newline)
    # . . push args
    68/push  Newline/imm32
    68/push  2/imm32/stderr
    # . . call
    e8/call  _write/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # increment Num-test-failures
    ff          0/subop/increment   0/mod/indirect  5/rm32/.disp32            .             .           .           Num-test-failures/disp32          # increment *Num-test-failures
$check-ints-equal:end:
    # . restore registers
    5b/pop-to-EBX
    59/pop-to-ECX
    58/pop-to-EAX
    # . epilog
    89/copy                         3/mod/direct    4/rm32/ESP    .           .             .           5/r32/EBP   .               .                 # copy EBP to ESP
    5d/pop-to-EBP
    c3/return

== data

# length-prefixed string containing just a single newline
# convenient to have when printing messages and so on
Newline:
    # size
    01 00 00 00
    # data
    0a/newline

# every test failure increments this counter
Num-test-failures:
    00 00 00 00

# . . vim:nowrap:textwidth=0