Put peppercorns in a mortar and crush roughly with a pestle. Or put peppercorns in a large resealable plastic bag, spread out on a hard, flat surface, and crush with the bottom of a heavy frying pan or rolling pin.
Put shrimp, half of the crushed peppercorns, and 1 tsp. salt in a large bowl and toss to coat shrimp evenly. Set aside.
Heat a wok or large (not nonstick) pot over high heat. Add oil, garlic, remaining crushed peppercorns, and remaining 1 tsp. salt and cook, stirring constantly, until fragrant, about 1 minute. Add shrimp and cook, stirring constantly, until pink and cooked through, 3 to 4 minutes. Add cilantro, turn off heat, and toss to combine. Serve immediately.
Note: Nutritional analysis is per serving.