It seems that the early exit (the return false) in the middle of the loop prohibits the compiler from vectorizing the loop. The compiler can't know if part of t

It seems that the early exit (the return false) in the middle of the loop prohibits the compiler from vectorizing the loop. The compiler can't know if part of the memory is inaccessible and so reading memory not being sure that the loop would run up to this point is illegal. If you introduce a result variable and set it during the loop, the compiler can vectorize the loop. At least icc does, but I didn't play with the compiler settings of the other compilers too much. Also compilers can still exit the loop early and at least MSVC does, because a segfault is UB and can be "optimized away".