Sequential Equivalence Checking of Circuits with Different State Encodings by Pruning Simulation-based Multi-Node Invariants

Verification is an important step for Integrated Circuit (IC) design. In fact, literature has reported that up to 70% of the design effort is spent on checking if the design is functionally correct. One of the core verification tasks is Equivalence Checking (EC), which attempts to check if two structurally different designs are functionally equivalent for all reachable states. Powerful equivalence checking can also provide opportunities for more aggressive logic optimizations, meeting different goals such as smaller area, better performance, etc. The success of Combinational Equivalence Checking (CEC) has laid a foundation to industry-level combinational logic synthesis and optimization. However, Sequential Equivalence Checking (SEC) still faces much challenge, especially for those complex circuits that have different state encodings and few internal signal equivalences. In this thesis, we propose a novel simulation-based multi-node inductive invariant generation and pruning technique to check the equivalence of sequential circuits that have different state encodings and very few equivalent signals between them. By first grouping flip-flops into smaller subsets to make it scalable for large designs, we then propose a constrained logic synthesis technique to prune potential multi-node invariants without inadvertently losing important constraints. Our pruning technique guarantees the same conclusion for different instances (proving SEC or not) compared to previous approaches in which merging of such potential invariants might lose important relations if the merged relation does not turn out to be a true invariant. Experimental results show that the smaller invariant set can be very effective for sequential equivalence checking of such hard SEC instances. Our approach is up to 20x-- faster compared to previous mining-based methods for larger circuits.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Computer Engineering

Department dc:contributor.department

Electrical and Computer Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2015

Author dc:creator

• Yuan, Zeying

Chair dc:contributor.committeechair

• Hsiao, Michael S.

Committee members dc:contributor.committeemember

• Wang, Chao
• Schaumont, Patrick R.

• Sequential Equivalence Checking(SEC)
• Multi-node Inductive Invariants
• Constrained Logic Synthesis

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

vt_gsexam:5720

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/56693