Synthesis & Logic Optimization · All levels
Equivalence Hooks: Comparison Matrix
Comparison Matrix for Equivalence Hooks.
Comparison matrix
Patch aggressiveness trades turnaround time against validation burden.
+------------------+----------------+----------------+----------------+
| Approach | Strength | Weakness | Best when |
+------------------+----------------+----------------+----------------+
| Conservative | stable | slower | new design spin |
| Balanced | practical | needs monitoring | normal closure |
| Aggressive | fast | higher risk | schedule crunch |
| Structural | durable | long loop | repeat offender |
+------------------+----------------+----------------+----------------+When to choose each approach
Select strategy by risk budget, not convenience.
Interview traps
Skipping manifest diff
No side-effect regression
Evidence comparison
SYNTHESIS EVIDENCE MATRIX — Equivalence Hooks
+--------------------+------------------------+--------------------------+-------------------------+
| Evidence | Tells you | Does not prove | Next action |
+--------------------+------------------------+--------------------------+-------------------------+
| compile QoR report | metric movement | root-cause class | inspect transform logs |
| SDC diff | constraint drift | library quality | rerun with baseline SDC |
| library map diff | cell view changes | RTL intent quality | lock/validate lib set |
| topo vs logical QoR | physical correlation | final route signoff | PD trial correlation |
| regression matrix | closure stability | architecture optimality | decide merge/rollback |
+--------------------+------------------------+--------------------------+-------------------------+Synthesis deep dive
Incremental and ECO synthesis protect schedule only with strict regression discipline.
Concept diagram
INCREMENTAL ECO LOOP
identify delta -> localized compile -> patch -> regression -> releaseMetric graph
ECO CYCLE TIME
full compile ███████████
incremental █████Reports and artifacts
incremental reuse
ECO patch list
LEC status
regression matrix
Mini case study
Localized compile cut turnaround 40%, but skipped LEC caused rollback.
Debug branches
Reuse ratio is not enough
Patch locality check
Always include equivalence hooks
Senior review question
Ask: what evidence proves this QoR move is real and stable?
Key takeaways
State exact run context (RTL, SDC, libs, switches) with every QoR claim.
Re-run timing, area, and power regressions after each synthesis ECO.
Common pitfalls
Comparing runs with mismatched constraints or library views.
Timing-only fixes that violate power or area budgets.
Skipping equivalence checks after structural changes.
Principal synthesis review addendum
Equivalence hooks align synthesis and ECO transformations with formal checking so aggressive optimization remains provably correct.
Metric: LEC pass rate, unresolved points, debug turnaround