Physical Optimization Reports - 2023.2 English

Vivado Design Suite User Guide: Implementation (UG904)

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2023.2 English
The Tcl reporting command report_phys_opt provides details of each optimization performed by phys_opt_design at a very fine level of detail. It must be run in the same Vivado session as phys_opt_design while the optimization history resides in memory.

Therefore, if a report is desired, it is recommended to include the report_phys_opt command in Tcl scripts immediately following the last phys_opt_design command.

The reports are available only for post-placement phys_opt_design optimizations. The reports are not cumulative. Each phys_opt run has a different phys_opt report that only accounts for the changes made during that particular run of phys_opt_design.

The following report example shows the first entry of a fanout optimization involving a register named pipeline_en. The following details are shown in the report:

  1. The original driver pipeline_en drives 816 loads and the paths containing this high fanout net fail timing with WNS of -1.057 ns.
  2. The driver pipeline_en was replicated to create one new cell, pipeline_en_replica.
  3. The 816 loads were split between pipeline_en_replica, which takes 386 loads, and the original driver pipeline_en, which takes the remaining 430 loads.
  4. After replication and placement of pipeline_en_replica, the WNS of pipeline_en_replica paths is +0.464 ns, and the WNS of pipeline_en paths is reduced to zero.
  5. The placement of the original driver pipeline_en was changed to improve WNS based on the locations of its reduced set of loads.
Figure 1. Fanout Optimization Report