R Roel Jordans

ASAM: Automatic architecture synthesis and application mapping

This paper focuses on mastering the automatic architecture synthesis and application mapping for heterogeneous massively-parallel MPSoCs based on customizable application-specific instruction-set processors (ASIPs). It presents an overview of the research being currently performed in the scope of the European project ASAM of the ARTEMIS program. The paper briefly presents the results of our analysis of the main challenges to be faced in the design of such heterogeneous MPSoCs. It explains which system, design, and electronic design automation (EDA) concepts seem to be adequate to address the challenges and solve the problems. Finally, it discusses the ASAM design-flow, its main stages and tools and their application to a real-life case study.

ASAM: Automatic Architecture Synthesis and Application Mapping

This paper focuses on mastering the automatic architecture synthesis and application mapping for heterogeneous massively-parallel MPSoCs based on customizable application-specific instruction-set processors (ASIPs). It presents an over-view of the research being currently performed in the scope of the European project ASAM of the ARTEMIS program. The paper briefly presents the results of our analysis of the main problems to be solved and challenges to be faced in the design of such heterogeneous MPSoCs. It explains which system, design, and electronic design automation (EDA) concepts seem to be adequate to resolve the problems and address the challenges. Finally, it introduces and briefly discusses the ASAM design-flow and its main stages.

Exploring processor parallelism: Estimation methods and optimization strategies

Former research on automatic exploration of ASIP architectures mostly focused on either the internal memory hierarchy, or the addition of complex custom operations to RISC based architectures. This paper focuses on VLIW architectures and, more specifically, on automating the selection of an application specific VLIW issue-width. An accurate and efficient issue-width estimation strongly influences all the important processor properties (e.g. processing speed, silicon area, and power consumption). We first compare different methods for estimating the required issue-width, and subsequently introduce a new force-based parallelism measure which is capable of estimating the required issue-width within 3% on average. Moreover, we show that we can quickly estimate the latency-parallelism Pareto-front of an example ECG application with less than 10% error using our issue-width estimations.

Instruction-set architecture exploration strategies for deeply clustered VLIW ASIPs

Instruction-set architecture exploration for clustered VLIW processors is a very complex problem. Most of the existing exploration methods are hand-crafted and time consuming. This paper presents and compares several methods for automating this exploration. We propose and discuss a two-phase method which can quickly explore many different architectures and experimentally demonstrate that this method is capable of automatically achieving a 50% improvement on the energy-delay product cost of an automatically generated architecture for an ECG detection application and a 1% energy-delay product cost improvement compared to a hand-crafted design.

Instruction-set Architecture Exploration of VLIW ASIPs Using a Genetic Algorithm

Genetic algorithms are commonly used for automatically solving complex design problem because exploration using genetic algorithms can consistently deliver good results when the algorithm is given a long enough run-time. However, the exploration time for problems with huge design spaces can be very long, often making exploration using a genetic algorithm practically infeasible. In this work, we present a genetic algorithm for exploring the instruction-set architecture of VLIW ASIPs and demonstrate its effectiveness by comparing it to two heuristic algorithms. We present several optimizations to the genetic algorithm configuration, and demonstrate how caching of intermediate compilation and simulation results can reduce the exploration time by an order of magnitude.

Construction and exploitation of VLIW ASIPs with heterogeneous vector-widths

Numerous applications in important domains, such as communication and multimedia, show a significant data-level parallelism (DLP). A large part of the DLP is usually exploited through application vectorization and implementation of vector operations in processors executing the applications. While the amount of DLP varies between applications of the same domain or even within a single application, processor architectures usually support a single vector width. This may not be optimal and may cause a substantial energy inefficiency. Therefore, an adequate more sophisticated exploitation of DLP is highly relevant. This paper proposes the use of heterogeneous vector widths and a method to explore the heterogeneous vector widths for VLIW ASIPs. In our context, heterogeneity corresponds to the usage of two or more different vector widths in a single ASIP. After a brief explanation of the target ASIP architecture model, the paper describes the vector-width exploration method and explains the associated design automation tools. Subsequently, experimental results are discussed.

An automated flow to map throughput constrained applications to a MPSoC

This paper describes a design flow to map throughput constrained applications on a Multi-processor System-on-Chip (MPSoC). It integrates several state-of-the-art mapping and synthesis tools into an automated tool flow. This flow takes as input a throughput constrained application, modeled with a synchronous dataflow graph, a C-based implementation for each actor in the graph, and a template based architecture description. Using these inputs, the tool flow generates an MPSoC platform tailored to the application requirements and it subsequently maps the application to this platform. The output of the flow is an FPGA programmable bit file. An easily extensible template based architecture is presented, this architecture allows fast and flexible generation of a predictable platform that can be synthesized using the presented tool flow. The effectiveness of the tool flow is demonstrated by mapping an MJPEG-decoder onto our MPSoC platform. This case study shows that our flow is able to provide a tight, conservative bound on the worst-case throughput of the FPGA implementation. The presented tool flow is freely available at http://www.es.ele.tue.nl/mamps.

An Efficient Method for Energy Estimation of Application Specific Instruction-Set Processors

Design space exploration for ASIP instruction-set design is a very complex problem, involving a large set of architectural choices. Existing methods are usually handcrafted and time-consuming. In this paper, we propose and investigate a rapid method to estimate the energy consumption of candidate architectures for VLIW ASIP processors. The proposed method avoids the time-consuming simulation of the candidate prototypes, without any loss of accuracy in the predicted energy consumption. We experimentally show the effect of this fast cost evaluation method when used in an automated instruction-set architecture exploration. In our experiments, we compare three different methods for cost estimation and find that we can accurately predict the energy consumption of proposed architectures while avoiding simulation of the complete system.

Algorithm Parallelism Estimation for Constraining Instruction-Set Synthesis for VLIW Processors

Customization of a (generic) processor to a particular application makes it possible to achieve high performance within a tight energy budget. Most of the published research works on processor customization extend a simple base processor with custom instructions. Only few works have considered a full instruction-set customization for complex highly parallel Very Long Instruction Word (VLIW) architectures. This paper discusses the parallelism estimation for a full instruction-set synthesis for VLIW processors and evaluates four methods to compute the maximum parallelism of a given application. We explain important reasons for computing and using such parallelism bounds, discuss the implementation of several methods, and our experimental research performed to evaluate the efficiency of each method.

High-level software-pipelining in LLVM

Software-pipelining is an important technique for increasing the instruction level parallelism of loops during compilation. Currently, the LLVM compiler infrastructure does not offer this optimization although some target specific implementations do exist. We have implemented a high-level method for software-pipelining within the LLVM framework. By implementing this within LLVMs optimization layer we have taken the first steps towards a target independent software-pipelining method.