If it's the first time the CPU has seen this code, then the predictor has nothing to go off of, but it will learn "taken" pretty quickly when it sees the `while

If it's the first time the CPU has seen this code, then the predictor has nothing to go off of, but it will learn "taken" pretty quickly when it sees the `while` loop continue to iterate. However, branch predictors also learn based on branch-history context, and sometimes with reasonably long history lengths (see Agner Fog's guide for some numbers), so it's possible that on the second time into this snippet, the predictor might actually get the lengths right for each entry in `stringList`. It really depends on the specific chip. (There have been some research proposals for "branch confidence predictors" that would halt fetch until the conditional branch is resolved in the backend, for efficiency reasons, but I don't think anything like this has actually been built. See e.g. [1].) [1] http://people.engr.ncsu.edu/ericro/publications/conference_MICRO-29_jrs.pdf http://people.engr.ncsu.edu/ericro/publications/conference_M...