## port of https://github.com/akkartik/crenshaw/blob/master/tutor2.1.pas
# corresponds to the section "single digits" in https://compilers.iecc.com/crenshaw/tutor2.txt
#
# To run:
#   $ subx translate apps/crenshaw2.1.subx crenshaw 2.1
#   $ echo '3'  |subx run apps/crenshaw2.1  |xxd -
# Expected output:
#   TODO
#
# The output is the code a function would need to include, returning the
# result in EAX.
#
# Major note: byte strings are not null-terminated. Instead they're prefixed
# with a 32-bit length.

== 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

# main:
  # abort("Integer")
    # push args
  68/push  "Integer"/imm32
    # call
  e8/call  abort/disp32
    # discard arg
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add 4 to ESP
  # exit(0)
  bb/copy                         .               .             .           .             .           .           .               0/imm32           # copy 0 to EBX
  b8/copy                         .               .             .           .             .           .           .               1/imm32/exit      # copy 1 to EAX
  cd/syscall  0x80/imm8

## compiler helpers

# print error message and exit
# really maps to the 'Expected' function in Crenshaw
abort:  # s : (address array byte) -> <void>
  # error(s)
    # push args
  ff          6/subop/push        1/mod/*+disp8   4/rm32/sib    4/base/ESP  4/index/none  .           .           4/disp8         .                 # push *(ESP+4)
    # call
  e8/call  error/disp32
    # discard arg
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add 4 to ESP
  # exit(1)
  bb/copy                         .               .             .           .             .           .           .               1/imm32           # copy 1 to EBX
  b8/copy                         .               .             .           .             .           .           .               1/imm32/exit      # copy 1 to EAX
  cd/syscall  0x80/imm8

# print out "Error: #{s} expected\n" to stderr
error:  # s : (address array byte) -> <void>
  # write_stderr("Error: ")
    # push args
  68/push  "Error: "/imm32
    # call
  e8/call  write_stderr/disp32
    # discard arg
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add 4 to ESP
  # write_stderr(s)
    # push args
  ff          6/subop/push        1/mod/*+disp8   4/rm32/sib    4/base/ESP  4/index/none  .           .           4/disp8         .                 # push *(ESP+4)
    # call
  e8/call  write_stderr/disp32
    # discard arg
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add 4 to ESP
  # write_stderr(" expected")
    # push args
  68/push  " expected"/imm32
    # call
  e8/call  write_stderr/disp32
    # discard arg
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add 4 to ESP
  # write_stderr("\n")
    # push args
  68/push  Newline/imm32
    # call
  e8/call  write_stderr/disp32
    # discard arg
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add 4 to ESP
  # end
  c3/return

## helpers

# print msg to stderr if a != b, otherwise print "."
check_ints_equal:  # (a : int, b : int, msg : (address array byte)) -> boolean
  # load args into EAX, EBX and ECX
  8b/copy                         1/mod/*+disp8   4/rm32/sib    4/base/ESP  4/index/none  .           0/r32/EAX   0xc/disp8       .                 # copy *(ESP+12) to EAX
  8b/copy                         1/mod/*+disp8   4/rm32/sib    4/base/ESP  4/index/none  .           3/r32/EBX   0x8/disp8       .                 # copy *(ESP+8) to EBX
  # if EAX == b/EBX
  39/compare                      3/mod/direct    0/rm32/EAX    .           .             .           3/r32/EBX   .               .                 # compare EAX and EBX
  75/jump-if-unequal  $check_ints_equal:else/disp8
    # print('.')
      # push args
  68/push  "."/imm32
      # call
  e8/call  write_stderr/disp32
      # discard arg
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add 4 to ESP
    # return
  c3/return
  # else:
$check_ints_equal:else:
  # copy msg into ECX
  8b/copy                         1/mod/*+disp8   4/rm32/sib    4/base/ESP  4/index/none  .           1/r32/ECX   4/disp8         .                 # copy *(ESP+4) to ECX
    # print(ECX)
      # push args
  51/push-ECX
      # call
  e8/call  write_stderr/disp32
      # discard arg
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add 4 to ESP
    # print newline
      # push args
  68/push  Newline/imm32
      # call
  e8/call  write_stderr/disp32
      # discard arg
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add 4 to ESP
  # end
  c3/return

# compare a null-terminated ascii string with a more idiomatic length-prefixed byte array
# reason for the name: the only place we should have null-terminated ascii strings is from commandline args
argv_equal:  # s : null-terminated ascii string, benchmark : length-prefixed ascii string -> EAX : boolean
# {{{
  # pseudocode:
  #   initialize n = b.length
  #   initialize s1 = s
  #   initialize s2 = b.data
  #   i = 0
  #   for (i = 0; i < n; ++n)
  #     c1 = *s1
  #     c2 = *s2
  #     if c1 == 0
  #       return false
  #     if c1 != c2
  #       return false
  #   return *s1 == 0
  # initialize s into EDI
  8b/copy                         1/mod/*+disp8   4/rm32/sib    4/base/ESP  4/index/none  .           7/r32/EDI   8/disp8         .                 # copy *(ESP+8) to EDI
  # initialize benchmark length n into EDX
  8b/copy                         1/mod/*+disp8   4/rm32/sib    4/base/ESP  4/index/none  .           2/r32/EDX   4/disp8         .                 # copy *(ESP+4) to EDX
  8b/copy                         0/mod/indirect  2/rm32/EDX    .           .             .           2/r32/EDX   .               .                 # copy *EDX to EDX
  # initialize benchmark data into ESI
  8b/copy                         1/mod/*+disp8   4/rm32/sib    4/base/ESP  4/index/none  .           6/r32/ESI   4/disp8         .                 # copy *(ESP+4) to ESI
  81          0/subop/add         3/mod/direct    6/rm32/ESI    .           .             .           .           .               4/imm32           # add 4 to ESI
  # initialize loop counter i into ECX
  b9/copy                         .               .             .           .             .           .           .               0/imm32/exit      # copy 1 to ECX
  # while (i/ECX < n/EDX)
$argv_loop:
  39/compare                      3/mod/direct    1/rm32/ECX    .           .             .           2/r32/EDX   .               .                 # compare ECX with EDX
  74/jump-if-equal  $argv_break/disp8
    # c1/EAX, c2/EBX = *s, *benchmark
  b8/copy  0/imm32  # clear EAX
  8a/copy                         0/mod/indirect  7/rm32/EDI    .           .             .           0/r32/EAX   .               .                 # copy byte at *EDI to lower byte of EAX
  bb/copy  0/imm32  # clear EBX
  8a/copy                         0/mod/indirect  6/rm32/ESI    .           .             .           3/r32/EBX   .               .                 # copy byte at *ESI to lower byte of EBX
    # if (c1 == 0) return false
  3d/compare                      .               .             .           .             .           .           .               0/imm32           # compare EAX with 0
  74/jump-if-equal  $argv_fail/disp8
    # if (c1 != c2) return false
  39/compare                      3/mod/direct    0/rm32/EAX    .           .             .           3/r32/EBX   .               .                 # compare EAX with EBX
  75/jump-if-not-equal  $argv_fail/disp8
    # ++s1, ++s2, ++i
  41/inc-ECX
  46/inc-ESI
  47/inc-EDI
  # end while
  eb/jump  $argv_loop/disp8
$argv_break:
  # if (*s/EDI == 0) return true
  b8/copy  0/imm32  # clear EAX
  8a/copy                         0/mod/indirect  7/rm32/EDI    .           .             .           0/r32/EAX   .               .                 # copy byte at *EDI to lower byte of EAX
  81          7/subop/compare     3/mod/direct    0/rm32/EAX    .           .             .           .           .               0/imm32           # compare EAX with 0
  75/jump-if-not-equal  $argv_fail/disp8
  b8/copy                         .               .             .           .             .           .           .               1/imm32           # copy 1 to EAX
  c3/return
  # return false
$argv_fail:
  b8/copy                         .               .             .           .             .           .           .               0/imm32           # copy 0 to EAX
  c3/return
# }}}
# tests for argv_equal {{{
test_compare_null_argv_with_empty_array:
  # EAX = argv_equal(Null_argv, "")
    # push args
  68/push  Null_argv/imm32
  68/push  ""/imm32
    # call
  e8/call  argv_equal/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add 8 to ESP
  # call check_ints_equal(EAX, 1)
  50/push-EAX
  68/push  1/imm32/true
  68/push  "F - test_compare_null_argv_with_empty_array"/imm32
    # call
  e8/call  check_ints_equal/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add 12 to ESP
  c3/return

test_compare_null_argv_with_non_empty_array:
  # EAX = argv_equal(Null_argv, "Abc")
    # push args
  68/push  Null_argv/imm32
  68/push  "Abc"/imm32
    # call
  e8/call  argv_equal/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add 8 to ESP
  # call check_ints_equal(EAX, 0)
  50/push-EAX
  68/push  0/imm32/false
  68/push  "F - test_compare_null_argv_with_non_empty_array"/imm32
    # call
  e8/call  check_ints_equal/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add 12 to ESP
  c3/return

test_compare_argv_with_equal_array:
  # EAX = argv_equal(Abc_argv, "Abc")
    # push args
  68/push  Abc_argv/imm32
  68/push  "Abc"/imm32
    # call
  e8/call  argv_equal/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add 8 to ESP
  # call check_ints_equal(EAX, 1)
  50/push-EAX
  68/push  1/imm32/true
  68/push  "F - test_compare_argv_with_equal_array"/imm32
    # call
  e8/call  check_ints_equal/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add 12 to ESP
  c3/return

test_compare_argv_with_inequal_array:
  # EAX = argv_equal(Abc_argv, "Adc")
    # push args
  68/push  Abc_argv/imm32
  68/push  "Adc"/imm32
    # call
  e8/call  argv_equal/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add 8 to ESP
  # call check_ints_equal(EAX, 0)
  50/push-EAX
  68/push  0/imm32/false
  68/push  "F - test_compare_argv_with_equal_array"/imm32
    # call
  e8/call  check_ints_equal/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add 12 to ESP
  c3/return

test_compare_argv_with_empty_array:
  # EAX = argv_equal(Abc_argv, "")
    # push args
  68/push  Abc_argv/imm32
  68/push  ""/imm32
    # call
  e8/call  argv_equal/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add 8 to ESP
  # call check_ints_equal(EAX, 0)
  50/push-EAX
  68/push  0/imm32/false
  68/push  "F - test_compare_argv_with_equal_array"/imm32
    # call
  e8/call  check_ints_equal/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add 12 to ESP
  c3/return

test_compare_argv_with_shorter_array:
  # EAX = argv_equal(Abc_argv, "Ab")
    # push args
  68/push  Abc_argv/imm32
  68/push  "Ab"/imm32
    # call
  e8/call  argv_equal/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add 8 to ESP
  # call check_ints_equal(EAX, 0)
  50/push-EAX
  68/push  0/imm32/false
  68/push  "F - test_compare_argv_with_shorter_array"/imm32
    # call
  e8/call  check_ints_equal/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add 12 to ESP
  c3/return

test_compare_argv_with_longer_array:
  # EAX = argv_equal(Abc_argv, "Abcd")
    # push args
  68/push  Abc_argv/imm32
  68/push  "Abcd"/imm32
    # call
  e8/call  argv_equal/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add 8 to ESP
  # call check_ints_equal(EAX, 0)
  50/push-EAX
  68/push  0/imm32/false
  68/push  "F - test_compare_argv_with_longer_array"/imm32
    # call
  e8/call  check_ints_equal/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add 12 to ESP
  c3/return
# }}}

write_stderr:  # s : (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
  52/push-EDX
  53/push-EBX
  # write(2/stderr, (data) s+4, (size) *s)
    # fd = 2 (stderr)
  bb/copy                         .               .             .           .             .           .           .               2/imm32           # copy 2 to EBX
    # x = s+4
  8b/copy                         1/mod/*+disp8   4/rm32/SIB    5/base/EBP  4/index/none  .           1/r32/ECX   8/disp8         .                 # copy *(EBP+8) to ECX
  81          0/subop/add         3/mod/direct    1/rm32/ECX    .           .             .           .           .               4/imm32           # add 4 to ECX
    # size = *s
  8b/copy                         1/mod/*+disp8   4/rm32/SIB    5/base/EBP  4/index/none  .           2/r32/EDX   8/disp8         .                 # copy *(EBP+8) to EDX
  8b/copy                         0/mod/indirect  2/rm32/EDX    .           .             .           2/r32/EDX   .               .                 # copy *EDX to EDX
    # call write()
  b8/copy                         .               .             .           .             .           .           .               4/imm32/write     # copy 1 to EAX
  cd/syscall  0x80/imm8
  # restore registers
  5b/pop-EBX
  5a/pop-EDX
  59/pop-ECX
  58/pop-EAX
  # end
  89/copy                         3/mod/direct    4/rm32/ESP    .           .             .           5/r32/EBP   .               .                 # copy EBP to ESP
  5d/pop-to-EBP
  c3/return

write_stdout:  # s : (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
  52/push-EDX
  53/push-EBX
  # write(1/stdout, (data) s+4, (size) *s)
    # fd = 1 (stdout)
  bb/copy                         .               .             .           .             .           .           .               1/imm32           # copy 1 to EBX
    # x = s+4
  8b/copy                         1/mod/*+disp8   4/rm32/SIB    4/base/ESP  4/index/none  .           1/r32/ECX   8/disp8         .                 # copy *(ESP+8) to ECX
  81          0/subop/add         3/mod/direct    1/rm32/ECX    .           .             .           .           .               4/imm32           # add 4 to ECX
    # size = *s
  8b/copy                         1/mod/*+disp8   4/rm32/SIB    4/base/ESP  4/index/none  .           2/r32/EDX   8/disp8         .                 # copy *(ESP+8) to EDX
  8b/copy                         0/mod/indirect  2/rm32/EDX    .           .             .           2/r32/EDX   .               .                 # copy *EDX to EDX
    # call write()
  b8/copy                         .               .             .           .             .           .           .               4/imm32/write     # copy 1 to EAX
  cd/syscall  0x80/imm8
  # restore registers
  5b/pop-EBX
  5a/pop-EDX
  59/pop-ECX
  58/pop-EAX
  # end
  89/copy                         3/mod/direct    4/rm32/ESP    .           .             .           5/r32/EBP   .               .                 # copy EBP to ESP
  5d/pop-to-EBP
  c3/return

== data
Newline:
  # size
  01 00 00 00
  # data
  0a/newline

# for argv_equal tests
Null_argv:
  00/null
Abc_argv:
  41/A 62/b 63/c 00/null

# vim:ft=subx:nowrap:so=0