Added description. x86 solutions for some problemsHEADmaster

1 files changed, 45 insertions, 0 deletions

diff --git a/03-Largest-Prime-Factor/asm/lpf.asm b/03-Largest-Prime-Factor/asm/lpf.asm
new file mode 100644
index 0000000..3e67ed3
--- /dev/null
+++ b/03-Largest-Prime-Factor/asm/lpf.asm
@@ -0,0 +1,45 @@
+; What is the largest prime factor of the number 600851475143 ?
+extern printf
+SECTION .data
+flag:   db  "%d",10,0           ; "%d\n\0"
+
+SECTION .text
+    global main    
+
+main:
+        push rbp                ; set up stack
+        mov rbp, rsp
+
+
+        mov rcx, 2              ; smallest prime factor: 2
+        mov rax, 0x8BE589EAC7   ; target = 600851475143
+
+.loop   xor rdx, rdx            ; clear rdx (remainder)
+        push rax
+        div rcx                 ; divide rdx:rax/rcx
+        cmp rdx, 0              ; compare only remainder
+        jnz .next               ; if r = 0 , its a factor
+                                ; we already divided the number so
+                                ; we just need to save the value in rax
+                                ; as the new number to factorize
+        add rsp, 8              ; delete the old
+        push rax
+        mov rcx, 1              ; reset the counter (normally would start at 2,
+                                ; but we increment anyway
+.next   pop rax                 ; refresh value 
+        inc rcx                 ; factor ++
+        cmp rax, rcx            ; while rax > rcx  number > factor
+                                ; i.e. not a prime factor
+        jg .loop
+        
+        mov rdi, flag           ; arg 1 (format)
+        mov rsi, rcx            ; arg 2 (value)
+        mov rax, 0		; no xmm registers
+        call printf wrt ..plt
+
+        mov rsp, rbp            ; reset to the top of the stack
+        pop rbp
+
+        mov rax, 0
+        ret
+