Synthesis & Logic Optimization · All levels

ECO Netlist Patches: Debug Playbook

Debug Playbook for ECO Netlist Patches.

Debug playbook

Debug Playbook for ECO Netlist Patches focuses on patch count, setup/hold recovery, patch-induced side effects. The goal is to connect observed QoR movement to mechanism, ownership, and regression risk.

Synthesis debug finds the first causal drift, not the loudest downstream symptom.

Root-cause tree

diagram

ROOT-CAUSE TREE — ECO Netlist Patches

patch count, setup/hold recovery, patch-induced side effects regressed
        |
   same RTL/constraints tag?
     /              \
   no                yes
   |                  |
input drift      transform side-effect
 /    \             /         \
SDC    libs      mapping      physical estimate
diff   diff      choice       mismatch

Freeze baseline and regressed run manifests.
Verify RTL/SDC/library deltas before transform tuning.
Classify issue: constraints, mapping choice, physical estimate, or ECO side effect.
Pick one minimal reversible change.
Re-run full timing/area/power checks with ownership signoff.

Review memo template

diagram

STAFF SYNTHESIS REVIEW MEMO — Incremental & ECO Synthesis / ECO Netlist Patches

1. Symptom
   - Watched metric: patch count, setup/hold recovery, patch-induced side effects
   - Affected compile run: <tag/build ID>
   - Impacted path/class: <critical group / power lane / area lane>
   - Database tags: <RTL, SDC, libs, switches>

2. Mechanism hypothesis
   - Primary mechanism: ECO patching edits gate-level logic for urgent fixes; patch quality depends on locality, observability, and verification closure.
   - Competing hypothesis: <constraint drift, mapping choice, physical estimate mismatch>
   - Missing evidence: <report diff, dashboard trend, ownership board>

3. Proposed action
   - Minimal reversible change: <constraint patch, compile knob, ECO cell move>
   - Expected movement: <timing / area / power delta>
   - Regression risk: hold, power spike, leakage drift, formal mismatch

4. Signoff
   - Re-run artifact: netlist diff, ECO patch log, post-patch timing report
   - Required owners: synthesis owner, STA owner, formal owner
   - Final decision: merge, rollback, or escalate

Synthesis deep dive

Incremental and ECO synthesis protect schedule only with strict regression discipline.

Concept diagram

diagram

INCREMENTAL ECO LOOP

identify delta -> localized compile -> patch -> regression -> release

Metric graph

diagram

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

ECO patching edits gate-level logic for urgent fixes; patch quality depends on locality, observability, and verification closure.

Metric: patch count, setup/hold recovery, patch-induced side effects

Practice this lesson