adding x86_64 assembly code

Author: Gathros

contents/euclidean_algorithm/code/x64/euclidean_example.s

@@ -0,0 +1,92 @@
+.intel_syntax noprefix
+
+.section .rodata
+  fmt:  .string "%d\n"
+
+.section .text
+  .global main
+  .extern printf
+
+euclid_mod:
+  # Abs of the first argument
+  mov    rax, rdi
+  sar    rax, 31
+  xor    rdi, rax
+  sub    rdi, rax
+
+  # Abs of the second argument
+  mov    rax, rsi
+  sar    rax, 31
+  xor    rsi, rax
+  sub    rsi, rax
+
+  # While loop
+  jmp    mod_check
+mod_loop:
+  xor    rdx, rdx
+  mov    rax, rdi
+  div    rsi
+  mov    rdi, rsi
+  mov    rsi, rdx
+mod_check:
+  cmp    rsi, 0
+  jne    mod_loop
+
+  mov    rax, rdi
+  ret
+
+euclid_sub:
+  # Abs of the first argument
+  mov    rax, rdi
+  sar    rax, 31
+  xor    rdi, rax
+  sub    rdi, rax
+
+  # Abs of the second argument
+  mov    rax, rsi
+  sar    rax, 31
+  xor    rsi, rax
+  sub    rsi, rax
+
+  # While loop
+  jmp    check
+loop:
+  cmp    rdi, rsi
+  jle    if_true
+
+  sub    rdi, rsi
+  jmp    check
+if_true:
+  sub    rsi, rdi
+check:
+  cmp    rsi, rdi
+  jne    loop
+
+  mov    rax, rdi
+  ret
+
+main:
+  # Calling euclid_mod
+  mov    rdi, 4288
+  mov    rsi, 5184
+  call   euclid_mod
+
+  # Printing euclid_mod output
+  mov    rdi, OFFSET fmt
+  mov    rsi, rax
+  xor    rax, rax
+  call   printf
+
+  # Calling euclid_sub
+  mov    rdi, 1536
+  mov    rsi, 9856
+  call   euclid_sub
+
+  # Printing euclid_sub output
+  mov    rdi, OFFSET fmt
+  mov    rsi, rax
+  xor    rax, rax
+  call   printf
+
+  xor    rax, rax
+  ret