Snitch Cluster System

The Snitch cluster system (hw/system/snitch_cluster) is a fundamental system around a Snitch core. The cluster can be configured using a config file.

The configuration parameters are documented using JSON schema, and documentation is generated for the schema. The configuration options can be found here.

The cluster testbench simulates an infinite memory. The RISC-V ELF file is preloaded using RISC-V's Front-end Server (fesvr).

Getting Started

In hw/system/snicht_cluster:

• Build the software:

  mkdir sw/build
  cd sw/build
  cmake ..
  make
  

• Compile the model for your simulator:

  Verilator

  make bin/snitch_cluster.vlt
  

  Questasim

  make bin/snitch_cluster.vsim
  

  VCS

  make bin/snitch_cluster.vcs
  

• Run a binary on the simulator:

  Verilator

  bin/snitch_cluster.vlt path/to/riscv/binary
  

  Questasim

  # Headless
  bin/snitch_cluster.vsim path/to/riscv/binary
  # GUI
  bin/snitch_cluster.vsim.gui path/to/riscv/binary
  

  VCS

  bin/snitch_cluster.vcs path/to/riscv/binary
  

• Build the traces in .logs/trace_hart_.txt with the help of spike-dasm:

  make traces
  

• Annotate the traces in .logs/trace_hart_.s with the source code related with the retired instructions:

  make annotate
  

• Get an overview of all Makefile targets:

  make help
  

Configure the Cluster

To configure the cluster with a different configuration, either edit the configuration files in the cfg folder or create a new configuration file and pass it to the Makefile:

make bin/snitch_cluster.vlt CFG=cfg/single-core.hjson

The default config is in cfg/cluster.default.hjson. Alternatively, you can also set your CFG environment variable, the Makefile will pick it up and override the standard config.

Using Verilator with LLVM

LLVM+clang can be used to build the Verilator model. Optionally specify a path to the LLVM toolchain in CLANG_PATH and set VLT_USE_LLVM=ON. For the verilated model itself to be complied with LLVM, verilator must be built with LLVM (CC=clang CXX=clang++ ./configure). The VLT environment variable can then be used to point to the verilator binary.

# Optional: Specify which llvm to use
export CLANG_PATH=/path/to/llvm-12.0.1
# Optional: Point to a verilator binary compiled with LLVM
export VLT=/path/to/verilator-llvm/bin/verilator
make VLT_USE_LLVM=ON bin/snitch_cluster.vlt