Use custom distance function

src/instruction.cpp

@@ -74,14 +74,29 @@ bool operator==(const instruction& i, instruction_ref ref)
     return std::addressof(i) == std::addressof(*ref);
 }
 
+static void debug_name(std::ostream& os, const instruction& ins);
+
 bool instruction::valid(instruction_ref start, bool check_order) const
 {
+    // Need this lambda because std::distance has undefined behavior when comparing iterators of
+    // from different ranges
+    auto ins_dist = [](instruction_ref s, instruction_ref e) {
+        int dist = 0;
+        while((*s) != (*e))
+        {
+            ++s;
+            ++dist;
+        }
+        return dist;
+    };
+
     return valid() && std::all_of(arguments.begin(), arguments.end(), [&](instruction_ref i) {
                auto self = std::find(i->outputs().begin(), i->outputs().end(), *this);
                bool ret  = self != i->outputs().end();
                if(check_order)
                {
-                   ret = ret and (std::distance(start, i) < std::distance(start, *self));
+                   // arguments for this instruction before this instruction
+                   ret = ret and (ins_dist(start, i) < ins_dist(start, *self));
                }
                return ret;
            });