Added description. x86 solutions for some problemsHEADmaster

1 files changed, 44 insertions, 0 deletions

diff --git a/05-Smallest-Multiple/asm/smallmult.asm b/05-Smallest-Multiple/asm/smallmult.asm
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+++ b/05-Smallest-Multiple/asm/smallmult.asm
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+; 2520 is the smallest number that can be divided by each of the numbers 
+; from 1 to 10 without any remainder.
+; What is the smallest positive number that is evenly divisible by all 
+; of the numbers from 1 to 20?
+
+extern printf
+SECTION .data
+flag:   db  "%d",10,0           ; "%d\n\0"
+
+SECTION .text
+    global main    
+    global is_divisible
+
+main:
+        push rbp                ; set up stack
+        mov rbp, rsp
+
+        mov rax, 2520           ; value to start at (given)
+        mov rcx, 20             ; divisor (counting down)
+.loop   add rax, rcx
+        push rcx
+.isdiv  xor rdx, rdx            ; clear rdx for div
+        push rax                ; save rax before dividing
+        div rcx                 ; rdx:rax/rcx = rax remainder rdx
+        pop rax                 ; reload rax to be divided again
+        cmp rdx, 0              ; the number was divisible, keep going
+        loopz .isdiv            ; loop exits if rdx is non zero OR rcx is 0
+        cmp rcx, 0              ; if rcx = 0, it means it looped 20 to 1 w/o
+        jz .print               ; any remainders, that's our number!
+        ; if you get here, number couldn't be evenly divided by all numbers
+        pop rcx
+        jmp .loop
+
+
+
+.print: mov rdi, flag           ; arg 1 (format)
+        mov rsi, rax            ; arg 2 (value)
+        mov rax, 0		; no xmm registers
+        call printf wrt ..plt
+        pop rbp
+
+        mov rax, 0
+        ret
+