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| -rwxr-xr-x | subx/examples/ex9 | bin | 0 -> 129 bytes | |||
| -rw-r--r-- | subx/examples/ex9.subx | 49 |
2 files changed, 49 insertions, 0 deletions
diff --git a/subx/examples/ex9 b/subx/examples/ex9 new file mode 100755 index 00000000..874efe52 --- /dev/null +++ b/subx/examples/ex9 Binary files differdiff --git a/subx/examples/ex9.subx b/subx/examples/ex9.subx new file mode 100644 index 00000000..aa519dc1 --- /dev/null +++ b/subx/examples/ex9.subx @@ -0,0 +1,49 @@ +## Example showing arg order on the stack. +# Show difference between ascii codes of first letter of first arg and first +# letter of second arg. +# +# To run: +# $ subx translate ex9.subx ex9 +# $ subx run ex9 z x +# Expected result: +# $ echo $? +# 2 +# +# At the start of a SubX program: +# argc: *ESP +# argv[0]: *(ESP+4) +# argv[1]: *(ESP+8) +# ... +# Locals start from ESP-4 downwards. + +== 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 + # s1 = argv[1] (EAX) + 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none 0/r32/EAX 8/disp8 . # copy *(ESP+8) to EAX + # s2 = argv[2] (EBX) + 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none 3/r32/EBX 0xc/disp8 . # copy *(ESP+12) to EBX + # call string_equal(s1, s2) + # push args + 50/push . . . . . . . . # push EAX + 53/push . . . . . . . . # push EBX + # call + e8/call ascii_difference/disp32 + # discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add 8 to ESP + # exit(EAX) + 89/copy 3/mod/direct 3/rm32/EBX . . . 0/r32/EAX . . # copy EAX to EBX + b8/copy . . . . . . . 1/imm32/exit # copy 1 to EAX + cd/syscall . . . . . . . 0x80/imm8 # int 80h + +ascii_difference: # (s1, s2) : null-terminated ascii strings + # a = first letter of s1 (ECX) + 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none 0/r32/EAX 8/disp8 # copy *(ESP+8) to EAX + 8b/copy 0/mod/indirect 0/rm32/EAX . . . 0/r32/EAX . . # copy *EAX to EAX + # b = first letter of s2 (EDX) + 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none 1/r32/ECX 4/disp8 # copy *(ESP+4) to ECX + 8b/copy 0/mod/indirect 1/rm32/ECX . . . 1/r32/ECX . . # copy *ECX to ECX + # a-b + 29/subtract 3/mod/direct 0/rm32/EAX . . . 1/r32/ECX . . # subtract ECX from EAX + c3/return |