Although the Vitis HLS GUI lets you
apply directives to specific code objects, the directives are added to the scope that contains
the object. For example, you can apply the
to an interface object in the Vitis HLS GUI, but the
directive is applied to the top-level function (scope). The interface port (object) is
identified in the directive.
You can apply optimization directives to the following objects and scopes:
- When you apply directives to functions, Vitis
HLS applies the directive to all objects within the scope of that function. The effect of
any directive stops at the next level of the function hierarchy, and does not apply to
sub-functions.Tip: Directives that include a recursive option, such as the
PIPELINEdirective, can be applied recursively through the hierarchy.
- Vitis HLS applies the directive to the top-level function, which is the scope that contains the interface.
- Directives apply to all objects within the scope of the loop.
For example, if you apply the
LOOP_MERGEdirective to a loop, Vitis HLS applies the directive to any sub-loops within the loop, but not to the loop itself. The loop to which the directive is applied is not merged with siblings at the same level of hierarchy.
- Directives are applied to the scope that contains the array.