## compute the factorial of 5, and return the result in the exit code
#
# Uses syntax sugar for:
# rm32 operands
#
# To run:
# $ ./translate_subx init.linux 0*.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
Entry: # run tests if necessary, compute `factorial(5)` if not
# . prologue
89/<- %ebp 4/r32/esp
# initialize heap
# . Heap = new-segment(Heap-size)
# . . push args
68/push Heap/imm32
ff 6/subop/push *Heap-size
# . . call
e8/call new-segment/disp32
# . . discard args
81 0/subop/add %esp 8/imm32
# - if argc > 1 and argv[1] == "test", then return run_tests()
# if (argc <= 1) goto run-main
81 7/subop/compare *ebp 1/imm32
7e/jump-if-<= $run-main/disp8
# if (!kernel-string-equal?(argv[1], "test")) goto run-main
# . eax = kernel-string-equal?(argv[1], "test")
# . . push args
68/push "test"/imm32
ff 6/subop/push *(ebp+8)
# . . call
e8/call kernel-string-equal?/disp32
# . . discard args
81 0/subop/add %esp 8/imm32
# . if (eax == false) goto run-main
3d/compare-eax-and 0/imm32/false
74/jump-if-= $run-main/disp8
# run-tests()
e8/call run-tests/disp32
# syscall(exit, *Num-test-failures)
8b/-> *Num-test-failures 3/r32/ebx
eb/jump $main:end/disp8
$run-main:
# - otherwise return factorial(5)
# eax = factorial(5)
# . . push args
68/push 5/imm32
# . . call
e8/call factorial/disp32
# . . discard args
81 0/subop/add %esp 4/imm32
# syscall(exit, eax)
89/<- %ebx 0/r32/eax
$main:end:
b8/copy-to-eax 1/imm32/exit
cd/syscall 0x80/imm8
factorial: # n: int -> int/eax
# . prologue
55/push-ebp
89/<- %ebp 4/r32/esp
53/push-ebx
# if (n <= 1) return 1
b8/copy-to-eax 1/imm32
81 7/subop/compare *(ebp+8) 1/imm32
7e/jump-if-<= $factorial:end/disp8
# var ebx: int = n-1
8b/-> *(ebp+8) 3/r32/ebx
4b/decrement-ebx
# var eax: int = factorial(n-1)
# . . push args
53/push-ebx
# . . call
e8/call factorial/disp32
# . . discard args
81 0/subop/add %esp 4/imm32
# return n * factorial(n-1)
f7 4/subop/multiply-into-eax *(ebp+8)
# TODO: check for overflow
$factorial:end:
# . epilogue
5b/pop-to-ebx
89/<- %esp 5/r32/ebp
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 %esp 4/imm32
# 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 %esp 0xc/imm32
# end
c3/return