c++ - Minimum for loop length for auto vectorization?

Question

I am wondering what should be the minimum for loop length for the auto vectorizer to enable the vectorization. ?

for eg:

       for (int i= 0 ; i< 4 ; i+= 3)
        // Some operations

using Rpass flag, I am getting following remark.

loop control flow is not understood by vectorizer [-Rpass-analysis=loop-vectorize]

can someone help me understand what are the basic requirement for a for loop to get vectorized. ?

Answer 1

等待大神答复