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CMake build system

Variables

  • USE_CONDA - Whether to rely on conda to supply external binaries (e.g. yosys, vpr).

  • VPR_BASE_ARGS - Base VPR arguments used during pack, place and route. Default arguments.

  • VPR_EXTRA_ARGS - Additional arguments to pass to VPR during pack, place and route.

To set CMake variable, use the -D flag during the configuration process. Example:

mkdir build
cd build
cmake -DUSE_CONDA=FALSE ..
make

Terminology

The CMake system in symbiflow-arch-defs uses the following hierarchy:

  • ARCH - Architecture is the high level grouping of a set of "similar" FPGA types. An example would be the "Lattice iCE40 Series" (ice40) or the "Xilinx Artix 7 Series" (artix7).

  • DEVICE_TYPE - A type of device. This is defined as an ARCH and the arch.xml which defines the units with this device type.

  • DEVICE - A specific instance of a DEVICE_TYPE. A device definition is a DEVICE_TYPE, a PACKAGE list, and IO map definitions for each package if needed. Each DEVICE should correspond with a layout definition within the DEVICE_TYPE.

  • BOARD - A specific DEVICE and PACKAGE instance, along with a PROG_TOOL/PROG_CMD (e.g. commands to program a specified board).

Creating a new FPGA target

If you are familiar with cmake, ADD_FPGA_TARGET is the rough equivalent to the normal ADD_EXECUTABLE target you would use with a C project.

ADD_FPGA_TARGET will create the targets needed to take a design from Verilog to bitstream through the synthesis, place and route, bitstream and potentially even programming. The required arguments are the BOARD and input files see ADD_FPGA_TARGET documentation for further information on other target configuration options.

If you want to target multiple boards, ADD_FPGA_TARGET_BOARDS exists that will call ADD_FPGA_TARGET correctly for each board you request. See ADD_FPGA_TARGET_BOARDS documentation.

Note on ADD_FILE_TARGET and ADD_FPGA_BOARD

All source files in the symbiflow-arch-defs are required to have a file target associated with them. This is done via ADD_FILE_TARGET. By default ADD_FPGA_TARGET and ADD_FPGA_TARGET_BOARDS will both implicitly invoke ADD_FILE_TARGET for you. This handles the common case where input sources are not generated files. However, if you are using generated files, then you will need to add ADD_FILE_TARGET calls for all inputs to ADD_FPGA_TARGET.

For non-generated verilog, ADD_FILE_TARGET should be invoked like:

add_file_target(FILE <current source dir relative path> SCANNER_TYPE verilog)

For generated verilog, ADD_FILE_TARGET should be invoked like:

add_file_target(FILE <current source dir relative path> GENERATED)

Note that the input path must be current source dir relative, not absolute, and not relative to the cmake current binary dir. Also note that CMake cannot take depedendencies during build time, so for generated files you must supply the dependencies for the target. See APPEND_FILE_DEPENDENCY for adding dependencies to other file targets.

It is generally suggested that all source forms within symbiflow-arch-defs are file targets, but it is required for verilog files because of how verilog handles relative include paths. Verilog defines relative paths as relative to the location of the file, not to the location of the compiler. As a result, if you use relative includes to include both a generated and non-generated file, unless the files are moved to a unified source tree, verilog relative includes will not work. ADD_FILE_TARGET solves this by copying non-generated files to the binary directory.