Improve day21p2

Should now properly handle all inputs

day21p2/main.c

@@ -177,10 +177,15 @@ int main(int argc, char *argv[])
     while (regs[ip] >= 0 && regs[ip] < instructions_len) {
         struct instr *instr = &instructions[regs[ip]];
 
-        // Day 21 part 2 optimizations...
-        if (regs[ip] == 17) {
-            regs[5] >>= 8;
-            regs[ip] = 8;
+        // Day 21 part 2 optimization...
+        if (instr->i == INSTR_GTIR && instr->a == 0x100) {
+            reg_t *reg = &regs[instr->b];
+            if (0x100 <= *reg) {
+                *reg >>= 8;
+                regs[ip] = 8;
+            } else {
+                regs[ip] = 28;
+            }
             continue;
         }