Altera Nios II C2H Compiler Manual do Utilizador descarregar pdf (Página 19)

Altera Corporation 9.1 1–13

November 2009 Nios II C2H Compiler User Guide

Introduction to the C2H Compiler

C Code

Appropriate for

Hardware

Acceleration

This section describes guidelines for identifying code that is appropriate

for the C2H Compiler.

Ideal Acceleration Candidates

Sections of C code that consume the most CPU time with the least amount

of code are excellent candidates for acceleration. These tend to have the

following characteristics:

■ They contain a relatively small and simple loop or set of nested

loops.

■ They iterate over a set of data, performing one or more operations on

the data per iteration, and then store the result.

Examples of such iterative tasks include memory copy-and-modify tasks,

checksum calculations, data encryption, decryption, and filtering

operations. In each of these cases, the C code iterates over a set of data

many times, with either one or more memory reads or writes performed

during each iteration.

Example 1–1 demonstrates a routine that performs a checksum

calculation. This code excerpt is from a TCP/IP stack, and it calculates the

checksum over ranges of data in a network protocol stack. Checksum

calculations are typically a time-consuming part of an IP stack, because all

data transmitted and received must be validated, which requires the

processor to loop through all bytes.

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