Nicola Bombieri

A mutation model for the SystemC TLM 2.0 communication interfaces

Mutation analysis is a widely-adopted strategy in software testing with two main purposes: measuring the quality of test suites, and identifying redundant code in programs. Similar approaches are applied in hardware verification and testing too, especially at RTL or gate level, where mutants are generally referred as faults, and mutation analysis is performed by means of fault modeling and fault simulation. However, in modern embedded systems there is a close integration between HW and SW parts, and verification strategies should be applied early in the design flow. This requires the definition of new mutation analysis-based strategies that work at system level, where HW and SW functionalities are not partitioned yet. In this context, the paper proposes a mutation model for perturbing transaction level modeling (TLM) SystemC descriptions. In particular, the main constructs provided by the SystemC TLM 2.0 library have been analyzed, and a set of mutants is proposed to perturb the primitives related to the TLM communication interfaces.

Automatic Abstraction of RTL IPs into Equivalent TLM Descriptions

Transaction-level modeling (TLM) is the most promising technique to deal with the increasing complexity of modern embedded systems. However, modeling a complex system completely at transaction level could be inconvenient when IP cores are available on the market, since they are usually modeled at register transfer level (RTL). In this context, modeling and verification methodologies based on transactors allow designers to reuse RTL IPs into TLM-RTL mixed designs, thus guaranteeing a considerable saving of time. Practical advantages of such an approach are evident, but mixed TLM-RTL designs cannot completely provide the well-known effectiveness in terms of simulation speed provided by TLM. This paper presents a methodology to automatically abstract RTL IPs into equivalent TLM descriptions. To do that, the paper first proposes a formal definition of equivalence based on events, showing how such a definition can be applied to prove the correctness of a code manipulation methodology, such as code abstraction. Then, the paper proposes a technique to automatically abstract RTL IPs into TLM descriptions. Finally, the paper shows that the TLM descriptions obtained by applying the proposed technique are correct by construction, relying on the given definition of event-based equivalence. A set of experimental results is reported to confirm the effectiveness of the methodology.

Towards Equivalence Checking Between TLM and RTL Models

The always increasing complexity of digital system is overcome in design flows based on transaction level modeling (TLM) by designing and verifying the system at different abstraction levels. The design implementation starts from a TLM high-level description and, following a top- down approach, it is refined towards a corresponding RTL model. However, the bottom-up approach is also adopted in the design flow when already existing RTL IPs are abstracted to be reused into the TLM system. In this context, proving the equivalence between a model and its refined or abstracted version is still an open problem. In fact, traditional equivalence definitions and formal equivalence checking methodologies presented in the literature cannot be applied due to the very different internal characteristics of the models, including structure organization and timing. Targeting this topic, the paper presents a formal definition of equivalence based on events, and then, it shows how such a definition can be used for proving the equivalence in the RTL vs. TLM context, without requiring timing or structural similarities between the modules to be compared. Finally, the paper presents a practical use of the proposed theory, by proving the correctness of a methodology that automatically abstracts RTL IPs towards TLM implementations.

On the Evaluation of Transactor-based Verification for Reusing TLM Assertions and Testbenches at RTL

Transaction level modeling (TLM) is becoming a usual practice for simplifying system-level design and architecture exploration. It allows the designers to focus on the functionality of the design, while abstracting away implementation details that will be added at lower abstraction levels. However, moving from transaction level to RTL requires redefining TLM test benches and assertions. Such a wasteful and error prone conversion can be avoided by adopting transactor-based verification (TBV). Many recent works adopt this strategy to propose verification methodologies that allow: (1) mixing TLM and RTL components; and (2) reusing TLM assertions and test benches at RTL. Even if practical advantages of such an approach are evident, there are no papers in the literature that evaluate the effectiveness of the TBV compared to a more traditional RTL verification strategy. This paper is intended to fill in the gap. It theoretically compares the quality of the TBV towards the rewriting of assertions and test benches at RTL with respect to both fault coverage and assertion coverage

HIFsuite: tools for HDL code conversion and manipulation

HIFSuite ia a set of tools and application programming interfaces (APIs) that provide support for modeling and verification of HW/SW systems. The core of HIFSuite is the HDL Intermediate Format (HIF) language upon which a set of front-end and back-end tools have been developed to allow the conversion of HDL code into HIF code and vice versa. HIFSuite allows designers to manipulate and integrate heterogeneous components implemented by using different hardware description languages (HDLs). Moreover, HIFSuite includes tools, which rely on HIF APIs, for manipulating HIF descriptions in order to support code abstraction/refinement and postrefinement verification.

Functional qualification of TLM verification

The topic will cover the use of functional qualification for measuring the quality of functional verification of TLM models. Functional qualification is based on the theory of mutation analysis but considers a mutation to have been killed only if a test case fails. A mutation model of TLM behaviors is proposed to qualify a verification environment based on both testcases and assertions. The presentation describes at first the theoretic aspects of this topic and then it focuses on its application to real cases by using actual EDA tools, thus showing advantages and limitations of the application of mutation analysis to TLM.

Integrating RTL IPs into TLM designs through automatic transactor generation

Transaction Level Modeling (TLM) is an emerging design practice for overcoming increasing design complexity. It aims at simplifying the design flow of embedded systems by designing and verifying a system at different abstraction levels. In this context, transactors play a fundamental role since they allow communication between the system components, implemented at different abstraction levels. Reuse of RTL IPs into TLM systems is a meaningful example of key advantage guaranteed by exploiting transactors. Nevertheless, transactors implementation is still manual, tedious and error-prone, and the effort spent to verify their correctness often overcomes the benefits of the TLM-based design flow. In this paper we present a methodology to automatically generate transactors for RTL IPs. We show how the transactor code can be automatically generated by exploiting the testbench of any RTL IP.

Incremental ABV for functional validation of TL-to-RTL design refinement

Transaction-level modeling (TLM) has been proposed as the leading strategy to address the always increasing complexity of digital systems. However, its introduction arouses a new challenge for designers and verification engineers, since there are no mature tools to automatically synthesize an RTL implementation from a transaction-level (TL) design, thus manual refinements are mandatory. In this context, the paper presents an incremental assertion-based verification (ABV) methodology to check the correctness of the TL-to-RTL refinement. The methodology relies on reusing assertions and already checked code, and it is guided by an assertion coverage metrics

System/network design-space exploration based on TLM for networked embedded systems

This article presents a methodology for the design of Networked Embedded Systems (NESs), which extends Transaction Level Modeling (TLM) to perform system/network design-space exploration. As a result, a new design dimension is added to the traditional TLM refinement process to represent network configuration alternatives. Each network configuration can be used to drive both architecture exploration and system validation after each refinement step. A system/network simulation taxonomy is investigated aiming at precisely identifying the role of cosimulation in system/network design-space exploration. Furthermore, a general criterion to map functionalities to system and network models is presented. As a case study, the proposed methodology is applied to the design of a Voice-over-IP client.

Hybrid, Incremental Assertion-Based Verification for TLM Design Flows

Transaction-level modeling is an emerging design practice for overcoming increasing design complexity. This article proposes a methodology for verifying the correctness of RTL refinement from transaction-level modeling. The authors demonstrate the effectiveness of this methodology, guided by an assertion coverage metric on the modules of an industry design.