Stage 3: Last Mile Timing Closure - Stage 3: Last Mile Timing Closure - 2026.1 English - UG906

The last mile timing closure stage takes the best implementation run from either of the previous two stages and attempts to close timing. Although QoR gains in this phase can be small compared to compile time, this step is still important for meeting timing. The stage only runs if the design meets the last mile timing closure entry requirements.

The last mile directive continues from an existing routed checkpoint and focuses on fixing failing paths. Timing closure is achieved in about 20 percent of designs with a WNS below –0.100 ns.

The goal of this stage is to close timing. This goal differs from the default tool flow, which focuses on achieving the best possible WNS and timing-closed WHS. The algorithms in this stage improve timing without significantly changing place and route results.

To achieve this goal, the flow applies the last mile incremental directive and QoR suggestions. The flow applies the following suggestions:

• It reuses suggestions with the APPLIED property from the reference run.
• It applies suggestions with the INCREMENTAL_FRIENDLY property.

After routing completes, phys_opt_design can run to further improve timing.

To enter the last mile timing closure stage from stage 1 or 2, your design must meet the following requirements:

• You must have a fully routed run.
• You must have a WNS greater than –0.250.
• You must have an RQA score of 3 or greater.