diff options
Diffstat (limited to 'linux/factorial.subx')
| -rw-r--r-- | linux/factorial.subx | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/linux/factorial.subx b/linux/factorial.subx new file mode 100644 index 00000000..b4f8888b --- /dev/null +++ b/linux/factorial.subx @@ -0,0 +1,153 @@ +## compute the factorial of 5, and print the result +# +# To run: +# $ ./bootstrap translate init.linux [01]*.subx apps/factorial.subx -o apps/factorial +# $ ./bootstrap run apps/factorial +# Expected result: +# $ echo $? +# 120 +# +# You can also run the automated test suite: +# $ ./bootstrap run apps/factorial test +# Expected output: +# ........ +# Every '.' indicates a passing test. Failing tests get a 'F'. + +== 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 + +factorial: # n: int -> _/eax: int + # . prologue + 55/push-ebp + 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp + 51/push-ecx + # if (n <= 1) return 1 + b8/copy-to-eax 1/imm32 + 81 7/subop/compare 1/mod/*+disp8 5/rm32/ebp . . . . 8/disp8 1/imm32 # compare *(ebp+8) + 7e/jump-if-<= $factorial:end/disp8 + # var ecx: int = n-1 + 8b/copy 1/mod/*+disp8 5/rm32/ebp . . 1/r32/ecx 8/disp8 . # copy *(ebp+8) to ecx + 49/decrement-ecx + # var eax: int = factorial(n-1) + # . . push args + 51/push-ecx + # . . call + e8/call factorial/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp + # return n * factorial(n-1) + f7 4/subop/multiply 1/mod/*+disp8 5/rm32/ebp . . 8/disp8 . # multiply *(ebp+8) into eax + # TODO: check for overflow +$factorial:end: + # restore registers + 59/pop-to-ecx + # . epilogue + 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp + 5d/pop-to-ebp + c3/return + +test-factorial: + # factorial(5) + # . . push args + 68/push 5/imm32 + # . . call + e8/call factorial/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp + # check-ints-equal(eax, 120, msg) + # . . push args + 68/push "F - test-factorial"/imm32 + 68/push 0x78/imm32/expected-120 + 50/push-eax + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp + # end + c3/return + +Entry: # run tests if necessary, compute `factorial(5)` if not + # . prologue + 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp + + # initialize heap (needed by tests elsewhere) + # . Heap = new-segment(Heap-size) + # . . push args + 68/push Heap/imm32 + ff 6/subop/push 0/mod/indirect 5/rm32/.disp32 . . . Heap-size/disp32 # push *Heap-size + # . . call + e8/call new-segment/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp + + # if (argc <= 1) return factorial(5) +$run-main: + 81 7/subop/compare 1/mod/*+disp8 5/rm32/ebp . . . . 0/disp8 1/imm32 # compare *ebp + 7f/jump-if-> $main:run-tests/disp8 + # eax = factorial(5) + # . . push args + 68/push 5/imm32 + # . . call + e8/call factorial/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp + # var buffer/ecx: (stream byte 10) # number of decimal digits a 32-bit number can have + 81 5/subop/subtract 3/mod/direct 4/rm32/esp . . . . . 0xa/imm32 # subtract from esp + 68/push 0xa/imm32/decimal-digits-in-32bit-number + 68/push 0/imm32/read + 68/push 0/imm32/write + 89/copy 3/mod/direct 1/rm32/ecx . . . 4/r32/esp . . # copy esp to ecx + # write-int32-decimal(buffer, eax) + # . . push args + 50/push-eax + 51/push-ecx + # . . call + e8/call write-int32-decimal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp + # write-stream(stderr, buffer) + # . . push args + 51/push-ecx + 68/push 2/imm32/stderr + # . . call + e8/call write-stream/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp + # write(stderr, Newline) + # . . push args + 68/push Newline/imm32 + 68/push 2/imm32/stderr + # . . call + e8/call write/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp + # + 89/copy 3/mod/direct 3/rm32/ebx . . . 0/r32/eax . . # copy eax to ebx + eb/jump $main:end/disp8 +$main:run-tests: + # otherwise if first arg is "test", then return run_tests() + # if (!kernel-string-equal?(argv[1], "test")) goto do-nothing + # . eax = kernel-string-equal?(argv[1], "test") + # . . push args + 68/push "test"/imm32 + ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 8/disp8 . # push *(ebp+8) + # . . call + e8/call kernel-string-equal?/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp + # . if (eax == false) goto do-nothing + 3d/compare-eax-and 0/imm32/false + 74/jump-if-= $main:do-nothing/disp8 + # run-tests() + e8/call run-tests/disp32 + # exit(*Num-test-failures) + 8b/copy 0/mod/indirect 5/rm32/.disp32 . . 3/r32/ebx Num-test-failures/disp32 # copy *Num-test-failures to ebx + eb/jump $main:end/disp8 +$main:do-nothing: + bb/copy-to-ebx 0/imm32 +$main:end: + e8/call syscall_exit/disp32 + +# . . vim:nowrap:textwidth=0 |