Netlist objects with DONT_TOUCH properties can prevent optimizations from being carried out that improve design performance. The following section of the RQA report shows which objects have the DONT_TOUCH property set on them:
Figure 1. Netlist Objects with DONT_TOUCH Property
The RQA report shows the following objects as well as their cause:
- Hierarchical cells
- Leaf cells
- Nets
Note: DONT_TOUCH properties prevent the tools
from optimizing paths and can be added through the use of other properties automatically
by Vivado. Removing DONT_TOUCH properties should be
done with care. For instance, the DFX flow uses
DONT_TOUCH to prevent cross boundary optimizations between the static and
reconfigurable module, so should not be removed. A DONT_TOUCH property added as a result
of MARK_DEBUG, by contrast, is not critical to the flow, but it
does mean that the signal is not available for hardware probing if optimized.