Pipeline Directive - 2023.1 English - XD098

ACTION: Back out the prior change before proceeding. Go back to the Config Editor window and hover your mouse to the left of the compile.pipeline_loops command to display and click the More Actions command. Click the Reset to Default command. Alternatively, you can just remove the command from the hls_config.cfg file.

Another possible optimization is to tell the tool that a function or loop should occur before processing another sample. The Pipeline pragma or directive defines an acceptable level of performance, and can eliminate II violations from the reports because the latency would then match your specification. The overall latency of an application could indicate that perhaps II=4 is acceptable for some loops.

This configuration might be an acceptable response to II violations when the loops are not in the critical path of the design, or they represent a small problem relative to some larger problems that must be resolved. In other words, not all violations need to be resolved, and in some cases, not all violations can be resolved. They are simply artifacts of performance.

1. In the Settings Form of the Config File Editor go to the bottom of the categories on the left side and go to Design Directives > Pipeline. This shows the hls.syn.directive.pipeline with the syntax of options and accepted values.

2. Click Add Item under Pipeline. This displays a text entry box

3. Type the following text:

dct_2d II=4

1. Click OK

When using the GUI to edit the hls_config.cfg file you can enter the options in abbreviated form as shown above. The GUI adds the complete directive. When editing the text file you must use the whole command as shown in the text editor: syn.directive.pipeline=dct_2d II=4

1. In the Flow Navigator click the Run command under C Synthesis to rerun with the new directive.

2. Examine the updated reports to see if there is any performance improvement.