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Diffstat (limited to 'assembler/gcd-x86_64-linux.s')
| -rw-r--r-- | assembler/gcd-x86_64-linux.s | 126 |
1 files changed, 0 insertions, 126 deletions
diff --git a/assembler/gcd-x86_64-linux.s b/assembler/gcd-x86_64-linux.s deleted file mode 100644 index ad92477..0000000 --- a/assembler/gcd-x86_64-linux.s +++ /dev/null @@ -1,126 +0,0 @@ -# This program is for Linux on Intel x86_64 arch (64 bits). -# Written for GNU Assembler (as) with AT&T syntax - -# To make an executable binary: -# gcc -nostdlib gcd-x86_64-linux.s -o gcd-x86_64-linux -# or -# as gcd-x86_64-linux.s -o gcd-x86_64-linux.o && \ -# ld gcd-x86_64-linux.o -o gcd-x86_64-linux - - -.data - -# Buffer for output: -buffer: - .space 64 # enough for 64 bits integer -buf_end: - .byte 10 # new line - - -.text -.globl _start - - -# GCD of two numbers. -# input: rax, rbx - two numbers -# output: rax - GCD -# uses: rax, rbx, rdx -gcd2: - and %rbx, %rbx # is %rbx == 0 ? - jz gcd2_exit # %rbx == 0, go to exit and return %rax (GCD) - xor %rdx, %rdx # set %rdx = 0 */ - div %rbx # divide: %rdx:%rax / %rbx, actually: %rax / %rbx - mov %rbx, %rax # drop quotient in %rax and keep prrvious %rbx in %rax - mov %rdx, %rbx # put remainder in %rbx - jmp gcd2 -gcd2_exit: - ret - - - -# Print an unsigned integer in rax. -# input: rax - unsigned integer to print -# uses: rax, rbx, rcx, rdx, rdi, buffer -print: - mov $10, %rcx # set %rcx = 10 (radix) - mov $buf_end, %rsi - -next_digit: - xor %rdx, %rdx # set %rdx = 0 - div %rcx # divide: %rdx:%rax / %rcx, actually: %rax / %rcx - # %rdx is a remainder (0-9), it fits into %dl - add $48, %dl # get ASCII code: 0 => 48 = '0', 1 => 49 = '1' - dec %rsi # put remainders going from the end of the buffer - mov %dl, (%rsi) - # now rax is a quotient - and %rax, %rax # is quotient == 0 ? - jnz next_digit # quotient is not 0, go on - - # printing the number: - mov $1, %rax # syscall `write' - mov $1, %rdi # write to stdout - mov $buf_end, %rdx - sub %rsi, %rdx # rdx is a number of characters to write (buf_end - rsi) - inc %rdx # + new line - syscall # do syscall (print the number at rsi) - - ret - - -# Convert string into unsigned integer -# input: rsi - pointer to string -# output: rbx - unsigned integer -# uses: rax, rbx, rcx, rdi, direction flag -str2uint: - xor %rcx, %rcx # it will be the string length - dec %rcx # rcx = -1 != 0 for repne - xor %rax, %rax # search for 0 (%rax = %al = 0) - mov %rsi, %rdi - cld # Search forward (std - backward) - repne scasb # search for 0 (in %al), incrementing rdi, decrementing rcx - not %rcx # invert rcx to have the string length - dec %rcx # minus ending zero - - xor %rbx, %rbx -str2uint_loop: - lodsb # going forward from rsi - # HINT: assert '0' <= al <= '9' - lea (%rbx, %rbx, 4), %rbx # rbx = 4*rbx + rbx = 5*rbx ;-) - lea -48(%rax, %rbx, 2), %rbx # rbx = 2*rbx + %rax - 48 - # rbx is multiplied by 10 each iteration, - # rax-48 will be multiplied at the next iteration ;-) - loop str2uint_loop - ret - - - -# Entry point for the program -_start: - - # Access command line, see: - # http://www.cin.ufpe.br/~if817/arquivos/asmtut/index.html - # Example: ./gcd-x86_64-linux 11 22 33 - pop %rcx # Get the number of command-line options (4) - pop %rsi # Get the pointer to the program name (./gcd-x86_64-linux), - dec %rcx # minus program name - jz exit # no arguments are given - exiting - - xor %rax, %rax -gcd_loop: - pop %rsi # get next command line argument - mov %rcx, %r8 # save argument counter - mov %rax, %r9 # save current GCD - call str2uint # convert string at rsi to integer at rbx - mov %r9, %rax # restore current GCD - call gcd2 # gcd of rax and rbx (returned by str2uint) - # now rax is a GCD - mov %r8, %rcx # restore argument counter - loop gcd_loop - - call print # print rax with GCD - -exit: - mov $60, %rax # exit syscall - xor %rdi, %rdi # exit code = 0 - syscall - |