Methods and apparatuses associated with vectorization of scalar callee functions are disclosed herein. In various embodiments, compiling a first program may include generating one or more vectorized versions of a scalar callee function of the first program, based at least in part on vectorization annotations of the first program. Additionally, compiling may include generating one or more vectorized function signatures respectively associated with the one or more vectorized versions of the scalar callee function. The one or more vectorized function signatures may enable an appropriate vectorized version of the scalar callee function to be matched and invoked for a generic call from a caller function of a second program to a vectorized version of the scalar callee function.