Impact on QoR - 2025.1 English - UG1118

Vivado Design Suite User Guide: Creating and Packaging Custom IP (UG1118)

Document ID
UG1118
Release Date
2025-06-19
Version
2025.1 English

When encrypting IP that contains multiple sub-modules, the best practice is to encrypt at the highest level possible as in cases where multiple modules are independently encrypted there can be an impact on the design QoR as logic optimization between independently encrypted modules can be limited for security reasons.

For QoR that most closely matches the plain-text design, applying encryption to the highest-level module, Case 3 would be preferred. If sub-modules of the design are encrypted independently, Case 1 or Case 2, there could be an impact to the design QoR, as optimizations between the encrypted sub-modules do not occur.

Table 1. QOR Impact Table
# Encrypted Sources w/ Optimization (Impact on QOR)
1 Keep_hierarchy=yes No optimization is allowed
2 Keep_hierarchy=soft Limited optimization is allowed
3 Keep_hierarchy=no Full optimization is allowed
4 DON’T_TOUCH=True No optimization is allowed
5 DON’T_TOUCH=False Full optimization is allowed
6 -flatten_hierarchy=full Limited optimization is allowed among plain text sources only