Synthesis & Logic Optimization · All levels

Leakage Recovery: Design Space

Design Space for Leakage Recovery.

Design space exploration

For Leakage Recovery, options trade QoR gain, risk, and schedule.

Option A — conservative

Conservative constraints: helps predictability
Risk: slower PPA gains
Validate with: first-silicon safety

Option B — balanced

Balanced QoR tuning: helps stable closure
Risk: requires discipline
Validate with: typical product mode

Option C — aggressive compile

Aggressive compile push: helps fast timing recovery
Risk: power/hold regressions
Validate with: late schedule

Option D — structural change

Structural RTL change: helps long-term fix
Risk: schedule impact
Validate with: recurring bottleneck

diagram

DESIGN SPACE — Leakage Recovery
QoR gain <-> regression risk <-> schedule pressure

Design pitfalls

Single-metric optimization
No rollback path
Weak run comparability

Tradeoff curve

diagram

BEFORE / AFTER QOR — Leakage Recovery

QoR score
  0 |                     --- target zone
 -1 |        ● regression
 -2 |             ● baseline
 -0.5|                  ● after fix
    +----------------------------------> iteration

Validate timing + area + power, not one number.

Synthesis deep dive

PPA closure is a constrained tradeoff problem, not a timing-only exercise.

Concept diagram

diagram

PPA TRIAD

timing target <-> power budget <-> area cap

Metric graph

diagram

PARETO PROGRESSION

early runs      o o
balanced point    o
over-tuned          o (risk)

Reports and artifacts

VT mix
leakage trend
dynamic power trend
PPA Pareto table

Mini case study

LVT-heavy fix recovered setup but violated leakage target; balanced VT strategy closed both.

Debug branches

Timing-only claims need power check
Validate hold on VT swaps
Use Pareto memo

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

Leakage recovery replaces fast cells with higher-VT alternatives while preserving margin on critical paths and corners.

Metric: leakage delta, WNS guardband consumed, swapped-cell count

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