Altera Nios II C2H Compiler Manuel d'utilisateur télécharger pdf (Page 84)

3–44 9.1 Altera Corporation

Nios II C2H Compiler User Guide November 2009

Scheduling

Figure 3–21 illustrates how the C2H Compiler schedules successive

iterations of the loop shown in Figure 3–20. The C2H Compiler is able to

start a new iteration of the loop immediately after the prior iteration

completes State 0.

This is an example of an ideally-pipelined loop. Although the

C2H Compiler can pipeline many loops ideally, it is sometimes not

possible due to the lack of inherent parallelism in the code, as shown in

“Loop-Carried Dependencies”.

Figure 3–21. Pipelined Loop Iterations

Loop-Carried Dependencies

Loop-carried dependencies are data dependencies that manifest when

pipelining successive iterations of a loop. If the result of one calculation

in an iteration of the loop is used in a later iteration of the loop, then a

loop-carried dependency exists between the two operations.

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Altera Nios II C2H Compiler Manuel d'utilisateur Page 84