path: root/linux/ex3.subx

# Add the first 10 numbers, and return the result in the exit code.
#
# To run:
#   $ bootstrap/bootstrap translate apps/ex3.subx -o apps/ex3
#   $ bootstrap/bootstrap run ex3
# Expected result:
#   $ echo $?
#   55

== 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:
    # result: ebx = 0
    bb/copy-to-ebx  0/imm32
    # counter: ecx = 1
    b9/copy-to-ecx  1/imm32

$loop:
    # if (counter > 10) break
    81          7/subop/compare     3/mod/direct    1/rm32/ecx    .           .             .           .           .               0xa/imm32         # compare ecx
    7f/jump-if->  $exit/disp8
    # result += counter
    01/add                          3/mod/direct    3/rm32/ebx    .           .             .           1/r32/ecx   .               .                 # add ecx to ebx
    # ++counter
    41/increment-ecx
    # loop
    eb/jump  $loop/disp8

$exit:
    # exit(ebx)
    e8/call  syscall_exit/disp32

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