Sun Studio 12 Update 1: Fortran User's Guide

3.4.98 –unroll=n

Enable unrolling of DO loops where possible.

n is a positive integer. The choices are:

Loop unrolling generally improves performance, but will increase the size of the executable file. For more information on this and other compiler optimizations, see the “Performance and Optimization” chapter in the Fortran Programming Guide. See also The UNROLL Directive.