Signoff Regression Hygiene: Inputs & Outputs

Inputs and outputs contract

Inputs & Outputs for Signoff Regression Hygiene focuses on run-to-run WNS drift, database tag consistency, closure memo completeness. The goal is to connect the observable symptom to timing mechanism, ownership, and regression risk.

Treat these as a signed interface contract. Ambiguity here is the single biggest source of wasted integration weeks, because two teams debug against different assumptions.

INPUTS
  - SDC (clocks, IO delays, exceptions)
  - Liberty libraries per corner
  - SPEF/parasitics and RC corner
  - MMMC scenario definition

OUTPUTS
  - WNS/TNS reports per scenario
  - path group summaries
  - constraint audit / waiver log
  - signoff closure memo

Timing path sequence

TIMING PATH — Signoff Regression Hygiene

launch FF --logic stages--> capture FF
     |                           |
  launch clock                capture clock
     |                           |
  required: arrival < capture_edge - setup
  metric: run-to-run WNS drift, database tag consistency, closure memo completeness

Ownership map

OWNERSHIP MAP — Signoff Regression Hygiene

artifact              owner
----------------      -----------------
timing report       STA lead
SDC/constraint      CAD owner
implementation      program management

Every WNS cluster needs a named owner before ECO.

STA deep dive

Debug hygiene separates senior STA leads from report readers.

Concept diagram

DEBUG ORDER

1. same tags?  2. constraints?  3. view?  4. real path?  5. ECO

Metric graph

ROOT CAUSE MIX (typical)

constraint bugs  ████████  35%
view mismatch    ██████    25%
real path        ██████    25%
methodology      ████      15%

Reports and artifacts

• run manifest

• SDC diff

• SPEF tag

• scenario isolation

Mini case study

Mystery regression: SPEF corner tag typo in run script — not a design bug.

Debug branches

• Manifest every run

• War room by path group

Senior review question

Ask: what corner/mode/view proves this topic is closed or failing?

Key takeaways

• State corner, mode, view, and database tag with every slack claim.

• Run setup and hold plus MMMC regression after every ECO.

Common pitfalls

• Comparing STA runs with different SPEF or SDC tags.

• Broad false_path to green-wash violations.

• Setup-only ECO without hold check.

Principal STA review addendum

Signoff quality depends on reproducible runs: same lib, SPEF, SDC, scenarios, and tool versions — tagged and archived.

Metric: run-to-run WNS drift, database tag consistency, closure memo completeness