Altera Nios II C2H Compiler - Manual (Page 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.