Merge pull request #367 from Gathros/euclid_asm

Adding Euclidean Algorithms in X86-64 Assembly

Author: Gathros

contents/euclidean_algorithm/code/asm-x64/euclidean_example.s

@@ -0,0 +1,74 @@
+.intel_syntax noprefix
+
+.section .rodata
+  fmt:  .string "%d\n"
+
+.section .text
+  .global main
+  .extern printf
+
+# rdi - a
+# rsi - b
+# RET rax - gcd of a and b
+euclid_mod:
+  mov    rax, rdi           # Get abs of a
+  sar    rax, 31
+  xor    rdi, rax
+  sub    rdi, rax
+  mov    rax, rsi           # Get abs of b
+  sar    rax, 31
+  xor    rsi, rax
+  sub    rsi, rax
+  jmp    mod_check
+mod_loop:
+  xor    rdx, rdx           # Take the mod of a and b
+  mov    rax, rdi
+  div    rsi
+  mov    rdi, rsi           # Set b to the mod of a and b
+  mov    rsi, rdx           # Set a to b
+mod_check:
+  cmp    rsi, 0             # Check if b is non-zero
+  jne    mod_loop
+  mov    rax, rdi           # Return the result
+  ret
+
+euclid_sub:
+  mov    rax, rdi           # Get abs of a
+  sar    rax, 31
+  xor    rdi, rax
+  sub    rdi, rax
+  mov    rax, rsi           # Get abs of b
+  sar    rax, 31
+  xor    rsi, rax
+  sub    rsi, rax
+  jmp    check
+loop:
+  cmp    rdi, rsi           # Find which is bigger
+  jle    if_true
+  sub    rdi, rsi           # If a is bigger then a -= b
+  jmp    check
+if_true:
+  sub    rsi, rdi           # Else b -= a
+check:
+  cmp    rsi, rdi           # Check if a and b are not equal
+  jne    loop
+  mov    rax, rdi           # Return results
+  ret
+
+main:
+  mov    rdi, 4288          # Call euclid_mod
+  mov    rsi, 5184
+  call   euclid_mod
+  mov    rdi, OFFSET fmt    # Print output
+  mov    rsi, rax
+  xor    rax, rax
+  call   printf
+  mov    rdi, 1536          # Call euclid_sub
+  mov    rsi, 9856
+  call   euclid_sub
+  mov    rdi, OFFSET fmt    # Print output
+  mov    rsi, rax
+  xor    rax, rax
+  call   printf
+  xor    rax, rax           # Return 0
+  ret

contents/euclidean_algorithm/euclidean_algorithm.md

@@ -39,6 +39,8 @@ The algorithm is a simple way to find the *greatest common divisor* (GCD) of two
 [import:12-25, lang="julia"](code/julia/euclidean.jl)
 {% sample lang="nim" %}
 [import:13-24, lang="nim"](code/nim/euclid_algorithm.nim)
+{% sample lang="asm-x64" %}
+[import:43-78, lang="asm-x64"](code/asm-x64/euclidean_example.s)
 {% sample lang="f90" %}
 [import:1-19, lang="fortran"](code/fortran/euclidean.f90)
 {% sample lang="php" %}
@@ -106,6 +108,8 @@ Modern implementations, though, often use the modulus operator (%) like so
 [import:1-10, lang="julia"](code/julia/euclidean.jl)
 {% sample lang="nim" %}
 [import:1-11, lang="nim"](code/nim/euclid_algorithm.nim)
+{% sample lang="asm-x64" %}
+[import:8-41, lang="asm-x64"](code/asm-x64/euclidean_example.s)
 {% sample lang="f90" %}
 [import:21-34, lang="fortran"](code/fortran/euclidean.f90)
 {% sample lang="php" %}
@@ -178,6 +182,8 @@ The Euclidean Algorithm is truly fundamental to many other algorithms throughout
 [import, lang="julia"](code/julia/euclidean.jl)
 {% sample lang="nim" %}
 [import, lang="nim" %](code/nim/euclid_algorithm.nim)
+{% sample lang="asm-x64" %}
+[import, lang="asm-x64"](code/asm-x64/euclidean_example.s)
 {% sample lang="f90" %}
 [import, lang="fortran"](code/fortran/euclidean.f90)
 {% sample lang="php" %}