Top-Level Dataflow - 2022.2 English

Vitis HLS Messaging (UG1448)

Document ID
UG1448
Release Date
2022-12-16
Version
2022.2 English

Description

Warning: [200-786] Detected dataflow on top in function %s with default interface mode 'ap_ctrl_hs'. Overlapped execution of successive kernel calls will not happen unless interface mode is set to 'ap_ctrl_chain' (or 'ap_ctrl_none' for a purely data-driven design).
This message reports a possible throughput improvement.

Explanation

If the user code has dataflow at the top-level function, and if the user wants to execute the kernel in a pipeline mode, then it is not possible with an ap_ctrl_hs protocol. For more information on the protocol, see Defining Interfaces.

Solution

Multiple kernel executions can be overlapped for performance improvements if the user specifies the below interface pragma.

#pragma HLS INTERFACE mode= ap_ctrl_chain bundle=control