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# Read .subx source and desugar programming constructs like %reg, and fcall()

== 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

Entry:  # run tests if necessary, convert stdin if not
    # initialize heap
    # . Heap = new-segment(64KB)
    # . . push args
    68/push  Heap/imm32
    68/push  0x10000/imm32/64KB
    # . . call
    e8/call  new-segment/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP

    # . prolog
    89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
    # - if argc > 1 and argv[1] == "test", then return run_tests()
    # . argc > 1
    81          7/subop/compare     1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0/disp8         1/imm32           # compare *EBP
    7e/jump-if-lesser-or-equal  $run-main/disp8
    # . argv[1] == "test"
    # . . push args
    68/push  "test"/imm32
    ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           8/disp8         .                 # push *(EBP+8)
    # . . call
    e8/call  kernel-string-equal?/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # . check result
    3d/compare-EAX-and  1/imm32
    75/jump-if-not-equal  $run-main/disp8
    # . run-tests()
    e8/call  run-tests/disp32
    8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           3/r32/EBX   Num-test-failures/disp32          # copy *Num-test-failures to EBX
    eb/jump  $main:end/disp8
$run-main:
    # - otherwise convert stdin
    # var ed/EAX : exit-descriptor
    81          5/subop/subtract    3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # subtract from ESP
    89/copy                         3/mod/direct    0/rm32/EAX    .           .             .           4/r32/ESP   .               .                 # copy ESP to EAX
    # configure ed to really exit()
    # . ed->target = 0
    c7          0/subop/copy        0/mod/direct    0/rm32/EAX    .           .             .           .           .               0/imm32           # copy to *EAX
    # return convert(Stdin, 1/stdout, 2/stderr, ed)
    # . . push args
    50/push-EAX/ed
    68/push  Stderr/imm32
    68/push  Stdout/imm32
    68/push  Stdin/imm32
    # . . call
    e8/call  convert/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0x10/imm32        # add to ESP
    # . syscall(exit, 0)
    bb/copy-to-EBX  0/imm32
$main:end:
    b8/copy-to-EAX  1/imm32/exit
    cd/syscall  0x80/imm8

convert:  # in : (address buffered-file), out : (address buffered-file) -> <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
    52/push-EDX
    53/push-EBX
    # var line/ECX : (address stream byte) = stream(512)
    81          5/subop/subtract    3/mod/direct    4/rm32/ESP    .           .             .           .           .               0x200/imm32       # subtract from ESP
    68/push  0x200/imm32/length
    68/push  0/imm32/read
    68/push  0/imm32/write
    89/copy                         3/mod/direct    1/rm32/ECX    .           .             .           4/r32/ESP   .               .                 # copy ESP to ECX
    # var word-slice/EDX = {0, 0}
    68/push  0/imm32/end
    68/push  0/imm32/start
    89/copy                         3/mod/direct    2/rm32/EDX    .           .             .           4/r32/ESP   .               .                 # copy ESP to EDX
    # var in-code?/EBX = false
    31/xor                          3/mod/direct    3/rm32/EBX    .           .             .           3/r32/EBX   .               .                 # clear EBX
$convert:loop:
    # clear-stream(line)
    # . . push args
    51/push-ECX
    # . . call
    e8/call  clear-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
    # read-line-buffered(in, line)
    # . . push args
    51/push-ECX
    ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           8/disp8         .                 # push *(EBP+8)
    # . . call
    e8/call  read-line-buffered/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # next-word(line, word-slice)
    # . . push args
    52/push-EDX
    51/push-ECX
    # . . call
    e8/call  next-word/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
$convert:check0:
    # if (line->write == 0) break
    81          7/subop/compare     0/mod/indirect  1/rm32/ECX    .           .             .           .           .               0/imm32           # compare *ECX
    0f 84/jump-if-equal  $convert:break/disp32
$convert:check1:
    # if (slice-empty?(word-slice)) write-stream-data(out, line)
    # . EAX = slice-empty?(word-slice)
    # . . push args
    52/push-EDX
    # . . call
    e8/call  slice-empty?/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
    # . if (EAX != 0) write-stream-data(out, line)
    3d/compare-EAX-and  0/imm32
    0f 85/jump-if-not-equal  $convert:pass-through/disp32
$convert:check2:
    # if (!slice-starts-with?(word-slice, "%") goto pass-through
    # . EAX = slice-starts-with?(word-slice, "%")
    # . . push args
    68/push  "%"/imm32
    52/push-EDX
    # . . call
    e8/call  slice-starts-with?/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    3d/compare-EAX-and  1/imm32
    75/jump-if-not-equal  $convert:pass-through/disp8
    # else: write(desugar-register(word/EDX))
    # . EAX = desugar-register(word/EDX)
    52/push-EDX
    e8/call  desugar-register/disp32
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
    # . write(register-string/EAX)
    50/push-EAX
    68/push 1/imm32
    e8/call  write/disp32
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # loop
    e9/jump  $convert:loop/disp32
$convert:pass-through:
    # write-stream-data(out, line)
    # . . push args
    51/push-ECX
    ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0xc/disp8       .                 # push *(EBP+12)
    # . . call
    e8/call  write-stream-data/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # . loop
    e9/jump  $convert:loop/disp32
$convert:break:
    # flush(out)
    # . . push args
    ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0xc/disp8       .                 # push *(EBP+12)
    # . . call
    e8/call  flush/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
$convert:end:
    # . reclaim locals
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0x214/imm32       # add to ESP
    # . restore registers
    5b/pop-to-EBX
    5a/pop-to-EDX
    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

desugar-register: # word : (address slice) -> register : (address byte array)
    # ECX holds return value
    # . prolog
    55/push-EBP
    89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
    # . save registers
    51/push-ECX
    # if slice-equal?(word, "%eax") return "0"
    # . EAX = slice-equal?(word, "%eax")
    68/push  "%eax"/imm32
    ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           8/disp8         .                 # push *(EBP+8)
    # . . call
    e8/call  slice-equal?/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # . return "0"
    b9/copy-to-ECX  "0"/imm32
    3d/compare-EAX-and  1/imm32
    0f 84/jump-if-equal  $desugar-register:end/disp32
    # if slice-equal?(word, "%ecx") return "1"
    # . EAX = slice-equal?(word, "%ecx")
    68/push  "%ecx"/imm32
    ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           8/disp8         .                 # push *(EBP+8)
    # . . call
    e8/call  slice-equal?/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # . return "1"
    b9/copy-to-ECX  "1"/imm32
    3d/compare-EAX-and  1/imm32
    0f 84/jump-if-equal  $desugar-register:end/disp32
    # if slice-equal?(word, "%edx") return "2"
    # . EAX = slice-equal?(word, "%edx")
    68/push  "%edx"/imm32
    ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           8/disp8         .                 # push *(EBP+8)
    # . . call
    e8/call  slice-equal?/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # . return "2"
    b9/copy-to-ECX  "2"/imm32
    3d/compare-EAX-and  1/imm32
    0f 84/jump-if-equal  $desugar-register:end/disp32
    # if slice-equal?(word, "%ebx") return "3"
    # . EAX = slice-equal?(word, "%ebx")
    68/push  "%ebx"/imm32
    ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           8/disp8         .                 # push *(EBP+8)
    # . . call
    e8/call  slice-equal?/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # . return "3"
    b9/copy-to-ECX  "3"/imm32
    3d/compare-EAX-and  1/imm32
    74/jump-if-equal  $desugar-register:end/disp8
    # if slice-equal?(word, "%esp") return "4"
    # . EAX = slice-equal?(word, "%esp")
    68/push  "%esp"/imm32
    ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           8/disp8         .                 # push *(EBP+8)
    # . . call
    e8/call  slice-equal?/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # . return "4"
    b9/copy-to-ECX  "4"/imm32
    3d/compare-EAX-and  1/imm32
    74/jump-if-equal  $desugar-register:end/disp8
    # if slice-equal?(word, "%ebp") return "5"
    # . EAX = slice-equal?(word, "%ebp")
    68/push  "%ebp"/imm32
    ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           8/disp8         .                 # push *(EBP+8)
    # . . call
    e8/call  slice-equal?/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # . return "5"
    b9/copy-to-ECX  "5"/imm32
    3d/compare-EAX-and  1/imm32
    74/jump-if-equal  $desugar-register:end/disp8
    # if slice-equal?(word, "%esi") return "6"
    # . EAX = slice-equal?(word, "%esi")
    68/push  "%esi"/imm32
    ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           8/disp8         .                 # push *(EBP+8)
    # . . call
    e8/call  slice-equal?/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # . return "6"
    b9/copy-to-ECX  "6"/imm32
    3d/compare-EAX-and  1/imm32
    74/jump-if-equal  $desugar-register:end/disp8
    # if slice-equal?(word, "%edi") return "7"
    # . EAX = slice-equal?(word, "%edi")
    68/push  "%edi"/imm32
    ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           8/disp8         .                 # push *(EBP+8)
    # . . call
    e8/call  slice-equal?/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # . return "7"
    b9/copy-to-ECX  "7"/imm32
    3d/compare-EAX-and  1/imm32
    74/jump-if-equal  $desugar-register:end/disp8
    # else, fail
    eb/jump  $desugar-register:abort/disp8
$desugar-register:end:
    # put return value in EAX
    89/copy                         3/mod/direct    0/rm32/EAX    .           .             .           1/r32/ECX   .               .                 # copy ECX to EAX
    # . restore registers
    59/pop-to-ECX
    # . epilog
    89/copy                         3/mod/direct    4/rm32/ESP    .           .             .           5/r32/EBP   .               .                 # copy EBP to ESP
    5d/pop-to-EBP
    c3/return
$desugar-register:abort:
    # . _write(2/stderr, error)
    # . . push args
    68/push  "unknown symbol to desugar\n"/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
    52/push-EDX
    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
    # . syscall(exit, 1)
    bb/copy-to-EBX  1/imm32
    b8/copy-to-EAX  1/imm32/exit
    cd/syscall  0x80/imm8

test-desugar-register:
    # . prolog
    55/push-EBP
    89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
$test-desugar-register-1:
    b8/copy-to-EAX  "%eax"/imm32
    8b/copy                         0/mod/indirect  0/rm32/EAX    .           .             .           1/r32/ECX   .               .                 # copy *EAX to ECX
    8d/copy-address                 1/mod/*+disp8   4/rm32/sib    0/base/EAX  1/index/ECX   .           1/r32/ECX   4/disp8         .                 # copy EAX+ECX+4 to ECX
    05/add-to-EAX  4/imm32
    # var slice/ECX = {EAX, ECX}
    51/push-ECX
    50/push-EAX
    89/copy                         3/mod/direct    1/rm32/ECX    .           .             .           4/r32/ESP   .               .                 # copy ESP to ECX
    # result/EAX = desugar-register(str/ECX)
    51/push-ECX
    e8/call  desugar-register/disp32
    # . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32         # add to ESP
    # string-equal?(expected, result/EAX)
    50/push-EAX
    68/push  "0"/imm32
    e8/call  string-equal?/disp32
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32         # add to ESP
    # check-ints-equal(EAX, 1, msg)
    # . . push args
    68/push  "F - test-desugar-register 1"/imm32
    68/push  1/imm32/true
    50/push-EAX
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
$test-desugar-register-2:
    b8/copy-to-EAX  "%edi"/imm32
    8b/copy                         0/mod/indirect  0/rm32/EAX    .           .             .           1/r32/ECX   .               .                 # copy *EAX to ECX
    8d/copy-address                 1/mod/*+disp8   4/rm32/sib    0/base/EAX  1/index/ECX   .           1/r32/ECX   4/disp8         .                 # copy EAX+ECX+4 to ECX
    05/add-to-EAX  4/imm32
    # var slice/ECX = {EAX, ECX}
    51/push-ECX
    50/push-EAX
    89/copy                         3/mod/direct    1/rm32/ECX    .           .             .           4/r32/ESP   .               .                 # copy ESP to ECX
    # result/EAX = desugar-register(str/ECX)
    51/push-ECX
    e8/call  desugar-register/disp32
    # . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32         # add to ESP
    # string-equal?(expected, result/EAX)
    50/push-EAX
    68/push  "7"/imm32
    e8/call  string-equal?/disp32
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32         # add to ESP
    # check-ints-equal(EAX, 1, msg)
    # . . push args
    68/push  "F - test-desugar-register 1"/imm32
    68/push  1/imm32/true
    50/push-EAX
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
    # . epilog
    89/copy                         3/mod/direct    4/rm32/ESP    .           .             .           5/r32/EBP   .               .                 # copy EBP to ESP
    5d/pop-to-EBP
    c3/return