Assertion Checkers – Enablers of Quality Design

1. Assertion Checkers – Enablers of Quality Design Presenter: PCLee – 2011.03.02

2. Abstract This paper outlines the MBAC tool for the generation of assertion checkers in hardware. We begin with a high-level presentation of the automated compilation of assertions into checkers, and proceed to overview the multitude of applications of resource-efficient circuit-level checkers in the field of logic design and verification. A summary of experimental results is also given to show the current state of the MBAC tool, compared to the best known checker generator from IBM.

3. Introduction of assertions • Assertions are high-level statement built on temporal logical that formally specifying correctness properties of a design. • Assertions are usually written in PSL(Property Specification Language) or SVA(System Verilog Assertion). Thus it can used to observe the design if it obey the behavior we want. • Their real benefits are exploited when they can be processed by EDA (Electronic Design Automation) tools. • Assertion language: • Based on temporal logic languages and regular expressions. • Boolean expressions are chained to form a sequence. ( |-> ) • Ex:assert always ({!req; req} |–> {!gnt[∗0:15] ; gnt}); • Assertion checker: • It is a circuit that captures the behavior of a given assertion, and can be included in the design for in-circuit assertion monitoring.

4. What’s the problem? • Problem: • Running a simulation can assist to debugging. But the power ofassertions can not typically be exploited outside the realm ofsoftware-based verification tools. • Proposed method: • Providing the efficient means to automatically generate assertion-checking circuits(HDL) from the assertions. • Once assertions are converted into circuits, assertion checkers can be used in a variety of applications outside the traditional simulation and formal verification techniques.

5. Related work • [3],[6]: FoCs, [5]:HORUS, [4]:previous vision • [7]: Introduction to automata theory, languages and computation • [9]:Assertion-based design Checker generator [3],[4],[5],[6] Classical automata algorithm[7] Assertion-based verification design[9] This paper

6. My related work • [1]:Airwolf-TG: A Test Generator for Assertion-Based Dynamic Verification PSL/SVA THIS PAPER Dynamic Verification[1]

7. Checker Generation Techniques • Three generation tool(PSL only): • IBM’s FoCs Property Checkers Generator • HORUS checker generator - TIMA • MBAC – this paper • Previous version of generator • Using modular approach whereby sub-modules for each property operator(ex: always) are built and interconnected according to the expression being implemented.

8. Checker Generation Techniques(cont.) • Current version of generator(MBAC) • Assertions are transformed into an intermediate representation in automaton form (the graph in the top-right box), for subsequent conversion into RTL (Register Transfer Level). • A critical of automata algorithms for generating hardware checkers is the novel use of partial nondeterminismand the unique minimization algorithm. • Rewrite rules play a key role in MBAC to help handle the large variety of “sugaring” and other more involved temporal operators found in PSL, and SVA to a lesser degree. • Using rewrite rules and specialized automata algorithms, MBAC supports the full synthesizable subset of PSL, and SVA, and produces behaviorally correct checkers in experimental benchmarks with simulators and model checkers.

9. Application of assertion checkers

10. Checkers in verification • Dynamic verification: • Simulation and hardware emulation • When simulators or emulators do not support PSL and SVA, generating assertion checkers and adding them to the source design is an effective way of allowing the continued use of assertions. • Static verification: • When formal proofs of correctness are required. • When formal verification tools such as model checkers do not support PSL and SVA, generating assertion checkers and adding them to the source design also allows the continued use of assertions.

11. Checkers in silicon debug • Some errors sensitive to timing constraints can only be checked in the actual fabricated silicon. • Checkers can be purposely left in the fabricated IC for debugging purposes. • When the prototype silicon is found to operate as desired, checkers can be removed or left in chip for in field chip testing.

12. Checkers in EDA Tools • Synthesis tool: • In order to synthesize assertions, assertion generator can be integrated to synthesis tool. • IP generator tool: • Assertion checkers can also be offered as a class of cores of core generator tool: users simply enter their assertion and the tool can generate the corresponding core (checker).

13. Checkers in EDA Tools(cont.) • The expressive power of assertions going beyond the bounds of verification and debugging. • Any form of monitoring circuit that can be expressed by an assertion, once given to the checker generator, can produce a complex error-free circuit instantly. These circuit-level checkers are in fact more akin to actual design modules rather than verification modules. • Using assertions and a checker generator as a means of logic design poses difficulties when it comes to generating complex output signals; however, the design of many types of analysis circuits can benefit directly from these techniques.

14. Experimental result

15. Conclusion of this paper • Present a variety direction for checker generator. • MBAC is the most effective at compiling assertions into circuit-checkers due to the now automata method and rewrite rules. • This paper enhances the benefit of assertion, and it really enhances the design quality.

16. My conclusion • This method of paper is different from the protocol checker, it can widens my knowledge. • This paper gives the overview of what assertion checker have done. I can look up for more detail about checker generator.