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Py_MEMCPY() has a special case for small blocks on Windows to work around an ancient performance issue in MSVC. Can we safely assume that recent MSVC properly optimize memcpy()? See #28055
/* Py_MEMCPY can be used instead of memcpy in cases where the copied blocks
 * are often very short. While most platforms have highly optimized code for
 * large transfers, the setup costs for memcpy are often quite high. MEMCPY
 * solves this by doing short copies "in line".
 */
#if defined(_MSC_VER)
#define Py_MEMCPY(target, source, length) do { \
 size_t i_, n_ = (length); \
 char *t_ = (void*) (target); \
 const char *s_ = (void*) (source); \
 if (n_ >= 16) \
 memcpy(t_, s_, n_); \
 else \
 for (i_ = 0; i_ < n_; i_++) \
 t_[i_] = s_[i_]; \
 } while (0)
#else
#define Py_MEMCPY memcpy
#endif