Altera Nios II C2H Compiler Bedienungsanleitung PDF herunterladen (Seite 79)

Altera Corporation 9.1 3–39

November 2009 Nios II C2H Compiler User Guide

C-to-Hardware Mapping Reference

Figure 3–18. Early Scheduling of Read Operation with Latency

The C2H Compiler optimizes the dependency graph for this function by

moving the read operation for ptr_in up to state 0. This optimization

allows the calculation of xy and xy_plus_z to occur during the two

cycles of latency required to fetch data for ptr_in.

Stalling

A state machine stalls when data needed for an operation is not available.

A state machine might stall while waiting for one or more of the following

actions to complete:

■ Inner loop

■ Subfunction call

■ Memory transfer

The state machine does not proceed until all reasons for stalling are

resolved.

Inner Loops

Each loop is implemented as a state machine, and an inner loop translates

to a particular state within the state machine for its containing function or

outer loop. In other words, an inner loop translates to a state machine

within a state machine. As the state machine for an inner loop executes,

the outer state machine stalls until the inner loop has completed.

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Altera Nios II C2H Compiler Bedienungsanleitung Seite 79