Altera Nios II C2H Compiler Instrukcja Użytkownika Pobierz pdf (Strona 41)

Altera Corporation 9.1 3–1

November 2009

3. C-to-Hardware Mapping

Reference

This chapter describes how the Nios

II C-to-Hardware Acceleration

(C2H) Compiler translates ANSI C constructs into functional blocks in a

hardware accelerator. Understanding the C-to-hardware mappings

enables you to write C functions optimized for the C2H Compiler to

achieve higher performance and lower resource utilization.

One-to-One

C-to-Hardware

Mapping

The C2H Compiler translates each element of C syntax to an equivalent

hardware structure using straightforward mapping rules. The mapping

rules provide a one-to-one association between elements of C syntax and

their equivalent hardware structures. By learning the C-to-hardware

mappings, you can control the hardware structure of an accelerator, based

on the structure of the C code.

The C2H Compiler can perform resource-sharing optimizations which

reduce the resource utilization for an accelerator. In these cases, the result

is a better than one-to-one mapping.

Arithmetic and Logical Operators

Every arithmetic and logical operator in the C code translates to a

corresponding hardware block in the accelerator. Consider the function

MAC() shown in Example 3–1.

Example 3–1. Function with Arithmetic and Logical Operators

long long MAC (int* a, int* b, int len)

{

long long result = 0;

while (len > 0)

{

result += *a++ * *b++;

len--;

}

return result;

}

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