Skip to content

Overview

About the Project

ARC DSP and the MetaWare tools provide means to address different scenarios through different options.

The required code transformations can be different, depending on the type and quality of reference code and the desired result (optimization targets) and thus require different development effort.

Out-of-the box optimization (OOB) technique targets minimal effort with reasonable performance gain.

Targeting better optimizations requires more code transformations and deeper optimizations:

  • Algorithmic optimizations, including changing the precision of output (if applicable).
  • Data flow and memory-mapping optimizations that minimize memory usage and access.
  • Utilization of FXAPI primitives for fractional operations and mapping of data types to enable usage of fractional DSP instructions by the compiler.
  • Re-writing code patterns, to make them more compiler and platform friendly. In particular:
    • Manual loop transformations (such as loops splitting to enable accumulator usage in MAC instructions)
    • Using 32-bit data types (instead of accumulator data types) where multiple, frequently accessed variables are needed.

In general, 32-bit data types provide the best efficiency cycle-wise and code-size-wise.

embARC Audio codec collection is an OOB (Out-Of-the Box) optimized library of speech and audio codecs for ARCv2DSP. For better optimization, contact Synopsys.

Out-Of-the-Box Optimizations

Out-Of-the Box optimization (OOB optimization) technique usually achieves reasonable performance with minimal or no source code modifications and thus minimal effort. This typically includes following steps:

  • Replacing ETSI/ITU-T standard BASOP headers by MetaWare Development Toolkit provided and excluding from compilation BASOP sources (C files).

  • Tuning the compiler options to find the best performance vs. code-size trade-offs. For global optimization, try -Hmerge or -Hlto:

    • -Hmerge requires compiling all files at once by specifying all C files in command line.

    • -Hlto (enables Link Time Optimization) allows file-by-file compilation and linking. It uses higher-level intermediate representation in object files instead of platform object code, allowing to proceed with global optimizations at the "linking" step.

    Selection of the best options is an iterative step with several sets of options.

Terms and Definitions

  • AGU - Address Generation Unit
  • API - Application Programming Interface
  • ARCv2DSP - Synopsys DesignWare® ARC® Processors Family of 32-bit CPUs
  • ARC EMxD - Family of 32-bit ARC Processor Cores. Single-core, 3-Step Pipeline, ARCv2DSP
  • ARC HS4xD - Family of 32-bit ARC Processor Cores. Multi-core, Dual-Issue, 10-Step Pipeline, ARCv2DSP
  • CCAC - MetaWare Compiler
  • DMA - Direct Memory Access
  • DSP - Digital Signal Processor
  • FXAPI - Fixed-point API
  • LTO - Link-Time Optimization
  • MAC - Multiply-Accumulate
  • MDB - MetaWare Debugger
  • MPY - Multiply Command
  • MWDT - MetaWare Development Toolset
  • nSIM - Instruction Set Simulator
  • OOB - Out-Of-the Box
  • PCM - Pulse Code Modulation
  • TCF - Tool Configuration File. Holds information about ARC processor build configuration and extensions.
  • xCAM - Cycle Accurate Model