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ci: guard the shared-datapath invariant + report area across topologies - #1875

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ci: guard the shared-datapath invariant + report area across topologies#1875
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@gHashTag gHashTag commented Aug 7, 2026

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The gate proved bit-exactness and synthesizability but did not guard the core architectural claim — one shared GftSmul + one shared GftSadd regardless of topology. A change that accidentally parallelized the datapath would instantiate N multipliers (area explosion) yet still pass the sim + synth gates.

datapath_check now asserts exactly 1 GftSmul + 1 GftSadd in the emitted RTL for every topology (2-layer, multi-output, deep) — version-independent (text check, no toolchain); verified it catches a 2-multiplier violation. The synth phase now prints a per-topology area report (cells/FF/LUT), framed as a trend to watch across PRs (counts are yosys-version-specific), making the 'depth ~ constant area' claim visible (deep [2,4,3,1] ~ 2-layer (2,4,2)). Version-robust area-regression guard: guard the invariant that prevents blowup, surface raw numbers for review. Refs #1764

The gate proved bit-exactness and synthesizability but did not guard the core
architectural claim -- one shared GftSmul + one shared GftSadd regardless of
topology. A change that accidentally parallelized the datapath would instantiate
N multipliers (area explosion) yet still pass the sim + synth gates. datapath_check
now asserts exactly 1 GftSmul + 1 GftSadd in the emitted RTL for every topology
(2-layer, multi-output, deep) -- version-independent (a text check, no toolchain);
verified it catches a 2-multiplier violation.

The synth phase now prints a per-topology area report (cells/FF/LUT); counts are
yosys-version-specific so it is framed as a trend to watch across PRs, not an
absolute gate. The numbers make the depth ~ constant-area claim visible (deep
[2,4,3,1] ~ 2-layer (2,4,2)). This is the area-regression guard done version-robustly:
guard the invariant that prevents blowup (one multiplier), surface raw numbers for
human review, rather than a fragile absolute baseline (CI yosys != local yosys).

Refs #1764

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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📓 NotebookLM Notebook linked to this PR

This notebook contains session context, decisions, and artifacts for this work.

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PR Dashboard

Generated at: 2026-08-07 14:03:15 UTC

Summary

Status Count
Total Open PRs 13
PRs with Failing Checks 0
PRs with All Checks Green 13
READY 5
FAILING 0
PENDING 0

Seal Status

  • ⚠️ STALE -- sha256(compiler.rs)=4c1aaad5309a != manifest seal=87e5cbd3ad94.
    The committed NMSE numbers were certified against an older compiler.rs.
    Run scripts/reseal-check.sh locally for the two-step reseal command (advisory; not a merge gate).

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gHashTag merged commit ac0f4df into master Aug 7, 2026
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gHashTag deleted the feat/datapath-invariant-area branch August 7, 2026 14:11
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