"collatz problem func"

.gitignore

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+-test
+test
+main

collatz.S

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+        # bedir t karaabalı
+        # 2025
+        # collatz problem
+
+.text
+# void collatz_len_and_peek(uint64_t x, uint64_t *steps, uint64_t *peek)
+.global collatz_len_and_peek
+collatz_len_and_peek:
+    # Collatz problem implementation
+    # x -> rdi, steps -> rsi, peak -> rdx
+
+    movq $0, (%rsi) # *steps=0
+    movq %rdi, (%rdx) # *peak = x
+    movq %rdi, %r8 # r8(n) (caller-saved) = x
+    
+.loop:
+    cmpq $1, %r8 # while (n != 1)
+    je .done
+    testq $1, %r8 # 1 and n
+    jz .even
+    # odd case
+    leaq (%r8, %r8, 2), %r8 # n *= 3 -> lea base + index * scale
+    addq $1,%r8 # n += 1
+    jmp .next_step
+.even:
+    shrq $1, %r8 # n /= 2
+.next_step:
+    cmpq (%rdx), %r8 # if (n > *peek) n - *peek
+    jle .next
+    movq %r8, (%rdx) # *peek = n
+.next:
+    addq $1, (%rsi) # (*steps)++
+    jmp .loop
+.done:
+    ret

main.c

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+#include <stdint.h>
+#include <stdio.h>
+
+void collatz_len_and_peek(uint64_t x, uint64_t *steps, uint64_t *peek);
+
+int main() {
+    uint64_t steps, peak;
+    collatz_len_and_peek(13, &steps, &peak);
+    printf("steps=%lu, peak=%lu\n", steps, peak);
+    return 0;
+}