Computing bounds on poly_ints (GNU Compiler Collection (GCC) Internals)

poly_int also provides routines for calculating lower and upper bounds:

‘constant_lower_bound (a)’: Assert that a is nonnegative and return the smallest value it can have.
‘lower_bound (a, b)’: Return a value that is always less than or equal to both a and b. It will be the greatest such value for some indeterminate values but necessarily for all.
‘upper_bound (a, b)’: Return a value that is always greater than or equal to both a and b. It will be the least such value for some indeterminate values but necessarily for all.