C++ dynamic_cast runtime overhead

dynamic_cast.cpp

/**
 * CXXFLAGS := -std=c++17 -O3 -pedantic -Wall -Wextra ${CXXFLAGS}
 * LDLIBS := -lstdc++ ${LDLIBS}
 *
 * Example stderr on AMD Ryzen 7 5800X, with gcc 10.2.1, Linux 4.4.0-19041-Microsoft (WSL, W10 Pro 22H2):
 *
 * static avg:  64121 ns
 * dynamic avg: 75674 ns
 */
 
#include <chrono>
#include <iostream>
#include <random>
#include <vector>

class Base {
	static constexpr int foo = 12;

public:
	virtual void exclaim() const {
		std::cout << foo << "\n";
	}

	virtual bool is_sub1() const { return false; }
	virtual bool is_sub2() const { return false; }
};

class Sub1 : public Base {
	static constexpr int bar = 16384;

public:
	void yell() const {
		std::cout << bar << "!!!\n";
	}

	bool is_sub1() const override { return true; }
};

class Sub2 : public Base {
	static constexpr int baz = 65536;

public:
	void scream() const {
		std::cout << baz << "!!!!!!\n";
	}

	bool is_sub2() const override { return true; }
};

int main() {
	using namespace std::chrono;

	std::vector<Base*> objects;

	srand(time(NULL));

	uint64_t total_static = 0;
	uint64_t total_dynamic = 0;
	constexpr int runs = 256;

	for (auto i = 0; i < runs; i++) {
		objects.clear();

		for (auto i = 0; i < 1024; i++) {
			Base* obj;
			if (rand() % 2) obj = new Sub1();
			else obj = new Sub2();
			objects.push_back(obj);
		}

		time_point start_st = high_resolution_clock::now();
		for (const auto obj: objects) {
			if (obj->is_sub1()) static_cast<Sub1*>(obj)->yell();
			if (obj->is_sub2()) static_cast<Sub2*>(obj)->scream();
		}
		time_point end_st = high_resolution_clock::now();
		total_static += duration_cast<nanoseconds>(end_st - start_st).count();

		time_point start_dyn = high_resolution_clock::now();
		for (const auto obj : objects) {
			const auto sub1 = dynamic_cast<Sub1*>(obj);
			if (sub1) sub1->yell();
			const auto sub2 = dynamic_cast<Sub2*>(obj);
			if (sub2) sub2->scream();
		}
		time_point end_dyn = high_resolution_clock::now();
		total_dynamic += duration_cast<nanoseconds>(end_dyn - start_dyn).count();
	}

	std::cerr << "static avg:  " << total_static / runs << " ns\n";
	std::cerr << "dynamic avg: " << total_dynamic / runs << " ns\n";

	return 0;
}