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## 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 (from the subx directory):
# $ ./subx translate *.subx apps/crenshaw2-1.subx -o crenshaw2-1
# $ echo '3' |./subx run apps/crenshaw2-1
# Expected output (not working yet):
# # syscall(exit, 3)
# bb/copy-to-EBX 3/imm32
# b8/copy-to-EAX 1/imm32/exit
# cd/syscall 0x80/imm8
#
# To run the generated output:
# $ echo '3' |./subx run apps/crenshaw2-1 > z1.subx
# $ ./subx translate z1.subx -o z1
# $ ./subx run z1
# $ echo $?
# 3
#
# Stdin must contain just a single hex number. Other input will print an error:
# $ echo 'xyz' |./subx run apps/crenshaw2-1
# Error: integer expected
== 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:
# allocate space for an exit-descriptor
# var ed/EAX : (address exit-descriptor)
81 5/subop/subtract 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # subtract from ESP
8d/copy-address 0/mod/indirect 4/rm32/sib 4/base/ESP 4/index/none . 0/r32/EAX . . # copy ESP to EAX
# clear ed->target (so we really exit)
c7/copy 0/mod/direct 0/rm32/EAX . . . . . 0/imm32 # copy to *EAX
# expected(ed, 2/stderr, "integer")
# push args
68/push "integer"/imm32
68/push 2/imm32/stderr
50/push-EAX
# call
e8/call expected/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
## helpers
expected: # ed : (address exit-descriptor), f : fd or (address stream), s : (address array byte)
# prolog
55/push-EBP
89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP
# write(f, "Error: ")
# push args
68/push "Error: "/imm32
ff 6/subop/push 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . . 0xc/disp8 . # push *(EBP+12)
# call
e8/call write/disp32
# discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# write(f, s)
# push args
ff 6/subop/push 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . . 0x10/disp8 . # push *(EBP+16)
ff 6/subop/push 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . . 0xc/disp8 . # push *(EBP+12)
# call
e8/call write/disp32
# discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# write(f, " expected")
# push args
68/push " expected"/imm32
ff 6/subop/push 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . . 0xc/disp8 . # push *(EBP+12)
# call
e8/call write/disp32
# discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# write(f, Newline)
# push args
68/push Newline/imm32
ff 6/subop/push 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . . 0xc/disp8 . # push *(EBP+12)
# call
e8/call write/disp32
# discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# stop(ed, 1)
# push args
68/push 1/imm32
ff 6/subop/push 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . . 8/disp8 . # push *(EBP+8)
# call
e8/call stop/disp32
## should never get past this point
# epilog
89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP
5d/pop-to-EBP
c3/return
# vim:nowrap:textwidth=0
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