Netlist Objects With DONT_TOUCH Properties - 2023.2 English

Vivado Design Suite User Guide: Design Analysis and Closure Techniques (UG906)

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2023.2 English

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.