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  4. Optimized Memory Access For Dynamically Scheduled High Level Synthesis
 
research report

Optimized Memory Access For Dynamically Scheduled High Level Synthesis

Bhattacharyya, Atri
•
Ienne, Paolo  
2018

Dynamically-scheduled elastic circuits generated by High-Level Synthesis (HLS) tools are inherently out-of-order, following the flow of data rather than the evolution of an instruction pointer. Components of the circuit which access memory need to be connected to a Load-Store Queue (LSQ) that dynamically checks for memory dependencies, performs store ordering and forwarding, and allows unordered access to Random-Access Memory (RAM) whenever possible. While connecting every memory access (load/store) component to an LSQ ensures correctness of program execution, the hardware and power cost makes this solution unattractive. Statically ruling out dependencies allows circuits to access memory via lightweight components that use an arbitrator to handle RAM port sharing. Reducing the number of components using the LSQ allows the compiler to generate smaller queues which results in superlinear savings in hardware and power for the memory subsystem. This work describes additions to the Elastic Compiler (EC) that allow it to analyze algorithms expressed in LLVM-IR, an intermediate code representation, to rule out memory dependencies between load/store instructions and their underlying insights. These analyses leverage pointer analysis as well as array access patterns to narrow down the list of possibly dependent instructions. We also enhance the compiler to leverage our analyses and automatically generate relevant memory-access components for the circuit and to connect them to the relevant arbitrator or LSQ.

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Type
research report
Author(s)
Bhattacharyya, Atri
Ienne, Paolo  
Date Issued

2018

Total of pages

56

Subjects

high level synthesis

•

elastic circuit

•

FPGA

•

synthesis

•

architecture

•

load store queue

•

LSQ

•

Automated synthesis

•

Automated LSQ allocation

•

Optimize circuit

URL

IEEE publication

https://ieeexplore.ieee.org/abstract/document/8335150
Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
LAP  
RelationURL/DOI

IsDerivedFrom

https://infoscience.epfl.ch/record/232862
Available on Infoscience
December 3, 2018
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/151674
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