Using and Porting GNU Fortran
21.6.3 Transforming Iterative DO
(one that specifies an iteration variable)
is required by the Fortran standards
to be implemented as though an iteration count
is computed before entering the loop body,
and that iteration count used to determine
the number of times the loop body is to be performed
(assuming the loop isn't cut short via
The FFE handles this by allocating a temporary variable
to contain the computed number of iterations.
Since this variable must be in a scope that includes the entire loop,
a GBEL block is created for that loop,
and the variable declared as belonging to the scope of that block.