Does the rewrite-versus-sweep verdict for a 16-bit leading-zero count survive five ABC scripts?

research/chip-logic-script

Re-scores chip-ppa-logic's popcount, leading-zero-count and |a−b| candidates under five ABC scripts with every mapped netlist proved equivalent: the clz16 sweep-versus-rewrite verdict flips with the script (best 0.35× the reference); stylised, generic gates.

6 tests

What it found

A follow-up to chip-ppa-logic: its 34 equivalent candidates for popcount, leading-zero count (clz16) and absolute difference are re-scored under five ABC scripts, and every mapped netlist is proved equivalent to the reference (none of 170 failed). On clz16 the verdict flips with the script: the no-model sweep wins under the default and dc2 scripts (344, 405), while a session-written nibble-combine file wins under three others (216–336 against the sweep’s 344–462); the overall best is 0.35× the reference’s default score. Popcount’s winner holds under all five scripts; absolute difference’s under three. Stylised: three tiny blocks, one Yosys version, hand-written proposer files, generic-gate cells×depth rather than layout.

A figure from its own output

Figure produced by research/chip-logic-script: clz16_scripts — chip-logic-script/experiments/clz16_scripts.svg, written by the project's own experiment code.

Paper, code and results

More in LLM chip design loops

Does fusing the accumulate into the partial-product tree beat multiply-then-add once the ABC script varies?A fused 4×4 multiply-accumulate: no written rewrite beats a*b+c under the default or three of five ABC scripts, but carry-save forms win by up to 9% cells×depth under dch and resyn2 (stylised, generic-gate).
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Produced with AI assistance (Claude). Results are from the code in this repository and are simulated or stylised unless the abstract says otherwise; nothing here implies affiliation with or endorsement by any lab, researcher or company cited. MIT licensed.