Huh? C is fast (compared to Swift) because using it doesn't imply sprinkling lots of sugar (like ARC) into the resulting machine code.
Simpler languages like Fortran can turn into even faster code than a C implementation. UB optimizations aren't that relevant for real-world performance.
Simpler languages like Fortran can turn into even faster code than a C implementation. UB optimizations aren't that relevant for real-world performance.