1 # Port of https://github.com/akkartik/crenshaw/blob/master/tutor2.1.pas
  2 # which corresponds to the section "single digits" in https://compilers.iecc.com/crenshaw/tutor2.txt
  3 # except that we support hex numbers of multiple digits.
  4 #
  5 # To run:
  6 #   $ ./subx translate init.linux 0*.subx apps/crenshaw2-1b.subx -o apps/crenshaw2-1b
  7 #   $ echo '1a'  |./subx run apps/crenshaw2-1b
  8 # Expected output:
  9 #   # syscall(exit, 1a)
 10 #   bb/copy-to-ebx  3/imm32
 11 #   b8/copy-to-eax  1/imm32/exit
 12 #   cd/syscall  0x80/imm8
 13 #
 14 # To run the generated output:
 15 #   $ echo '1a'  |./subx run apps/crenshaw2-1b > z1.subx
 16 #   $ ./subx translate init.linux z1.subx -o z1
 17 #   $ ./subx run z1
 18 #   $ echo $?
 19 #   26  # 0x1a in decimal
 20 #
 21 # Stdin must contain just a single hex digit. Other input will print an error:
 22 #   $ echo 'xyz'  |./subx run apps/crenshaw2-1b
 23 #   Error: integer expected
 24 #
 25 # Names in this file sometimes follow Crenshaw's original rather than my usual
 26 # naming conventions.
 27 
 28 == code
 29 #   instruction                     effective address                                                   register    displacement    immediate
 30 # . op          subop               mod             rm32          base        index         scale       r32
 31 # . 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
 32 
 33 Entry:  # run tests if necessary, call 'compile' if not
 34     # . prologue
 35     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
 36 
 37     # initialize heap
 38     # . Heap = new-segment(Heap-size)
 39     # . . push args
 40     68/push  Heap/imm32
 41     ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Heap-size/disp32                  # push *Heap-size
 42     # . . call
 43     e8/call  new-segment/disp32
 44     # . . discard args
 45     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
 46 
 47     # - if argc > 1 and argv[1] == "test", then return run_tests()
 48     # if (argc <= 1) goto run-main
 49     81          7/subop/compare     1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0/disp8         1/imm32           # compare *ebp
 50     7e/jump-if-<=  $run-main/disp8
 51     # if (!kernel-string-equal?(argv[1], "test")) goto run-main
 52     # . eax = kernel-string-equal?(argv[1], "test")
 53     # . . push args
 54     68/push  "test"/imm32
 55     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
 56     # . . call
 57     e8/call  kernel-string-equal?/disp32
 58     # . . discard args
 59     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
 60     # . if (eax == false) goto run-main
 61     3d/compare-eax-and  0/imm32/false
 62     74/jump-if-=  $run-main/disp8
 63     # run-tests()
 64     e8/call  run-tests/disp32
 65     # syscall(exit, *Num-test-failures)
 66     8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           3/r32/ebx   Num-test-failures/disp32          # copy *Num-test-failures to ebx
 67     eb/jump  $main:end/disp8
 68 $run-main:
 69     # - otherwise read a program from stdin and emit its translation to stdout
 70     # var ed/eax : exit-descriptor
 71     81          5/subop/subtract    3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # subtract from esp
 72     89/copy                         3/mod/direct    0/rm32/eax    .           .             .           4/r32/esp   .               .                 # copy esp to eax
 73     # configure ed to really exit()
 74     # . ed->target = 0
 75     c7          0/subop/copy        0/mod/direct    0/rm32/eax    .           .             .           .           .               0/imm32           # copy to *eax
 76     # compile(Stdin, 1/stdout, 2/stderr, ed)
 77     # . . push args
 78     50/push-eax/ed
 79     68/push  2/imm32/stderr
 80     68/push  1/imm32/stdout
 81     68/push  Stdin/imm32
 82     # . . call
 83     e8/call  compile/disp32
 84     # . . discard args
 85     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0x10/imm32        # add to esp
 86     # syscall(exit, 0)
 87     bb/copy-to-ebx  0/imm32
 88 $main:end:
 89     b8/copy-to-eax  1/imm32/exit
 90     cd/syscall  0x80/imm8
 91 
 92 # the main entry point
 93 compile:  # in : (addr buffered-file), out : fd or (addr stream byte), err : fd or (addr stream byte), ed : (addr exit-descriptor)
 94     # . prologue
 95     55/push-ebp
 96     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
 97     # . save registers
 98     50/push-eax
 99     51/push-ecx
100     # prime the pump
101     # . Look = get-char(in)
102     # . . push args
103     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8      .                    # push *(ebp+8)
104     # . . call
105     e8/call  get-char/disp32
106     # . . discard args
107     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
108     # var num/ecx : (stream byte 7)
109     # Numbers can be 32 bits or 8 hex bytes long. One of them will be in 'Look', so we need space for 7 bytes.
110     # Sizing the stream just right buys us overflow-handling for free inside 'get-num'.
111     # Add 12 bytes for 'read', 'write' and 'length' fields, for a total of 19 bytes, or 0x13 in hex.
112     # The stack pointer is no longer aligned, so dump_stack() can be misleading past this point.
113     81          5/subop/subtract    3/mod/direct    4/rm32/esp    .           .             .           .           .               0x13/imm32        # subtract from esp
114     89/copy                         3/mod/direct    1/rm32/ecx    .           .             .           4/r32/esp   .               .                 # copy esp to ecx
115     # initialize the stream
116     # . num->length = 7
117     c7          0/subop/copy        1/mod/*+disp8   1/rm32/ecx    .           .             .           .           8/disp8         7/imm32           # copy to *(ecx+8)
118     # . clear-stream(num)
119     # . . push args
120     51/push-ecx
121     # . . call
122     e8/call  clear-stream/disp32
123     # . . discard args
124     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .          (lineNum);
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<a href='https://github.com/akkartik/mu/blob/master/apps/ex4.subx'>https://github.com/akkartik/mu/blob/master/apps/ex4.subx</a>
<pre id='vimCodeElement'>
<span id="L1" class="LineNr"> 1 </span><span class="subxComment"># Read a character from stdin, save it to a global, write it to stdout.</span>
<span id="L2" class="LineNr"> 2 </span><span class="subxComment">#</span>
<span id="L3" class="LineNr"> 3 </span><span class="subxComment"># To run:</span>
<span id="L4" class="LineNr"> 4 </span><span class="subxComment">#   $ ./bootstrap translate init.linux apps/ex4.subx -o apps/ex4</span>
<span id="L5" class="LineNr"> 5 </span><span class="subxComment">#   $ ./bootstrap run apps/ex4</span>
<span id="L6" class="LineNr"> 6 </span>
<span id="L7" class="LineNr"> 7 </span>== data
<span id="L8" class="LineNr"> 8 </span>
<span id="L9" class="LineNr"> 9 </span><span class="subxComment"># the global variable we save to</span>
<span id="L10" class="LineNr">10 </span><span class="SpecialChar">X</span>:
<span id="L11" class="LineNr">11 </span>    0/imm32  <span class="subxComment"># space for read() to write to</span>
<span id="L12" class="LineNr">12 </span>
<span id="L13" class="LineNr">13 </span>== code
<span id="L14" class="LineNr">14 </span>
<span id="L15" class="LineNr">15 </span><span class="SpecialChar">Entry</span>:
<span id="L16" class="LineNr">16 </span><span class="subxComment"># read(stdin, X, 1)</span>
<span id="L17" class="LineNr">17 </span><span class="subxS1Comment"># . fd = 0 (stdin)</span>
<span id="L18" class="LineNr">18 </span>bb/copy-to-ebx  0/imm32
<span id="L19" class="LineNr">19 </span><span class="subxS1Comment"># . data = X (location to write result to)</span>
<span id="L20" class="LineNr">20 </span>b9/copy-to-ecx  <span class="SpecialChar"><a href='ex4.subx.html#L10'>X</a></span>/imm32
<span id="L21" class="LineNr">21 </span><span class="subxS1Comment"># . size = 1 character</span>
<span id="L22" class="LineNr">22 </span>ba/copy-to-edx  1/imm32
<span id="L23" class="LineNr">23 </span><span class="subxS1Comment"># . syscall</span>
<span id="L24" class="LineNr">24 </span>e8/call  syscall_read/disp32
<span id="L25" class="LineNr">25 </span>
<span id="L26" class="LineNr">26 </span><span class="subxComment"># write(stdout, X, 1)</span>
<span id="L27" class="LineNr">27 </span><span class="subxS1Comment"># . fd = 1 (stdout)</span>
<span id="L28" class="LineNr">28 </span>bb/copy-to-ebx  1/imm32
<span id="L29" class="LineNr">29 </span><span class="subxS1Comment"># . initialize X (location to read from)</span>
<span id="L30" class="LineNr">30 </span>b9/copy-to-ecx  <span class="SpecialChar"><a href='ex4.subx.html#L10'>X</a></span>/imm32
<span id="L31" class="LineNr">31 </span><span class="subxS1Comment"># . size = 1 character</span>
<span id="L32" class="LineNr">32 </span>ba/copy-to-edx  1/imm32
<span id="L33" class="LineNr">33 </span><span class="subxS1Comment"># . syscall</span>
<span id="L34" class="LineNr">34 </span>e8/call  syscall_write/disp32
<span id="L35" class="LineNr">35 </span>
<span id="L36" class="LineNr">36 </span><span class="subxComment"># exit(ebx)</span>
<span id="L37" class="LineNr">37 </span>e8/call  syscall_exit/disp32
<span id="L38" class="LineNr">38 </span>
<span id="L39" class="LineNr">39 </span><span class="subxS2Comment"># . . vim&#0058;nowrap:textwidth=0</span>
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