Functional Hardware Emulation (MM & Streaming HLS C/C++ Kernel)

This example demonstrates how a user can run functional model of HLS kernel in HW Emulation.

KEY CONCEPTS: Emulation Functional mode

KEYWORDS: emulationMode=func

This example demonstrates the simulation of HLS C/C++ streaming free running kernel in functional mode. The functional mode in v++ generates the SCTLM code for the HLS kernel. HW Emulation is mainly targeted for HW Kernel Debug with detailed, cycle accurate view of kernel activity and functional model is an advanced use case when user wants to speedup the emulation by compiling desired kernels in functional mode. In this example, there are two stream free running HLS kernels out of which increment_func and its datamovers (mm2s and s2mm) are compiled in functional mode whereas increment_rtl and its corresponding datamovers (mm2s and s2mm) are compiled as default RTL during hardware emulation.

XO generation

During v++ compile flow, while creating hw_emu XO, the user provides a switch describing the intention to do a functional simulation that will generate XO with the SystemC wrapper on C code.

Input from the user

  1. Create a config file config <hw_emu_func.cfg> with following advanced compiler options:

[advanced]
param=compiler.emulationMode=func

  1. In the Makefile, add the following flag in the v++ flow while compiling the kernel. For example, you can add flag as below -

VPP_FLAGS_increment_func += --config hw_emu_func.cfg
increment_func.xo: increment_func.cpp
mkdir -p $(TEMP_DIR)
$(VPP) $(VPP_FLAGS) $(VPP_FLAGS_increment1) -c -k increment_func --temp_dir $(TEMP_DIR)  -I'$(<D)' -o'$@' '$<'

Speedup Analysis: Functional (TLM) vs RTL kernels

Below is the wall-clock time for the kernels to finish the execution in functional and RTL mode. You can see approx 15x speedup having one of the kernel suite compiled in functional mode.

Kernel

Wall-Clock Time (s)

read-incrFunc-write

1.14532

read-incrRtl-write

17.139

Speedup:

14.9643

  • read-incrFunc-write is fully functional suite with kernel logic (increment) and read/write kernels compiled in functional mode.

  • read-incrRtl-write is default RTL suite with kernel logic (increment) and read/write kernels compiled as default RTL.

  • Note: All the kernel logics are same and there is no change in the kernel code. Only mode of compilation differs.

EXCLUDED PLATFORMS:

  • Versal DFX platform

DESIGN FILES

Application code is located in the src directory. Accelerator binary files will be compiled to the xclbin directory. The xclbin directory is required by the Makefile and its contents will be filled during compilation. A listing of all the files in this example is shown below

src/host.cpp
src/increment_func.cpp
src/increment_rtl.cpp
src/mem_read_func.cpp
src/mem_read_rtl.cpp
src/mem_write_func.cpp
src/mem_write_rtl.cpp

Access these files in the github repo by clicking here.

COMMAND LINE ARGUMENTS

Once the environment has been configured, the application can be executed by

./mm_stream_func_mode <krnl_incr XCLBIN>