Intel® FPGA SDK for OpenCL™ Pro Edition: Programming Guide

ID 683846
Date 10/04/2021

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7.23.3. Limitations of the Incremental Compilation Feature

The Intel® FPGA SDK for OpenCL™ incremental compilation feature is only available to OpenCL designs targeting the Intel® Arria® 10 FPGAs.

In addition to device support, the incremental compilation has the following limitations:

  • You experience area, Fmax, and power degradations when you enable the incremental compilation feature ( -incremental ) or the fast compilation feature ( -fast-compile ), or both.
  • In congested designs, incremental compilations can experience severe (that is, 25% or more) Fmax reductions compared to the initial setup compilation. If the Fmax reduction is unacceptable, perform a non-incremental fast compilation instead to reduce the amount of Fmax degradation while preserving some of the savings in compilation time.
  • The offline compiler does not detect changes in RTL libraries that you have included by invoking the -l <library_name>.aoclib offline compiler command option. After you modify an RTL library, you must perform a setup compilation again.

    The offline compiler prints a warning message as a reminder to rerun the setup compilation.

  • When compiling an OpenCL kernel containing calls to HLS tasks, incremental compile may trigger recompilation for unaffected kernels. However, this is not a functional bug. It may result in a more conservative incremental compile.