Enforce vectorization of the source loop by means of SIMD instructions and/or create a SIMD version of the function(s) using a directive:
Target Directive
Source loop #pragma omp simd
Inner function definition or declaration #pragma omp declare simd
If using the Ob or inline-level compiler option to control inline expansion with the 1 argument, use an inline keyword to enable inlining or replace the 1 argument with 2 to enable inlining of any function at compiler discretion.

Target	Directive
Source loop	#pragma omp simd
Inner function definition or declaration	#pragma omp declare simd

Example

#pragma omp declare simd
int f (int x)
{
    return x+1;
}
...

#pragma omp declare simd
int f (int x)
{
    return x+1;
}
#pragma omp simd
for (int k = 0; k < N; k++)
{
    a[k] = f(k);
}