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Directory Structure

The project is organized as a monolithic repository. Both hardware and software are co-located.

The file tree is visualized as follows:

├── hw
│   ├── chisel
│   │   ├── csr_manager
│   │   └── streamer
│   ├── snax_accelerator_1
│   ├── snax_accelerator_2
│   ├── snitch_stuff
│   └── templates
├── sw
├── target
│   └── snitch_cluster
│       ├── config
│       ├── generated
│       └── sw
│           ├── apps
│           │   ├── snax_system_1
│           │   └── snax_system_2
│           └── snax_lib 
│               ├── snax_system_1
│               └── snax_system_2
└── util
    ├── clustergen
    └── wrappergen

The top-level is structured as follows:

  • docs: Documentation of the generator and software. Contains additional user guides.
  • hw: All hardware IP components. The source files are either specified by SystemVerilog, Chisel, or a template to generate these files.
  • sw: Hardware independent software, libraries, runtimes etc.
  • target: Contains the testbench setup, cluster configuration specific hardware and software, libraries, runtimes etc.
  • util: Utility and helper scripts.

Hardware hw Directory

The hw directory contains various HW IPs which are instantiated in the Snitch Cluster design e.g., they are not stand-alone. Some of the IPs have stand-alone test benches. The top level structure of the hw folder is as follows:

  • <snitch_ip>: IP components for the snitch cluster
  • chisel: SNAX Framework componets written in the Chisel HDL.
  • <snax_ip>: SNAX Accelerators
  • templates: Template files which are used to generate the snax wrappers and Chisel parameters based on the supplied config files.

All IPs inside the hw directory are structured as follows:

  • <ip_name>: each directory contains one IP that is instantiated in the cluster design
  • doc: documentation if existing
  • src: RTL sources
  • test: Standalone testbenches if existing
  • util: Helper scripts to run standalone test benches if existing

The exact structure for chisel differs from this, but is very similar:

  • chisel
  • doc: documentation
  • src/main/scala/snax/<component>: RTL sources
  • src/test/scala/snax/<component>: Standalone testbenches

Target target Directory

This subdirectory contains the supported systems and their simulation environment including testbenches and bootrom.

  • shared: contains the shared fesvr related testbench components.
  • snitch_cluster
    • cfg: containing the configuration files *.hsjon for a specific snax-cluster configuration. This is the only place where system specific parameters are set.
    • generated: contains the generated bootdata.cc and wrapper files for the snax cluster.
    • snax-acc-1
      • csr_wrapper.sv
      • streamer_wrapper.sv
      • top_wrapper.sv
      • ...
    • snax-acc-2
    • src: contains the Banshee configuration for the snitch cluster.
    • sw: contains all shared
    • apps: contains applications for the snitch cluster.
    • runtime: contains the HW specific runtime implementation for the snitch cluster.
      • rtl: RTL-related startup implmentations.
      • banshee: Banshee-related startup SW implmentations.
    • tests: lists of tests that can run on the snitch cluster.
      • snax-cluster-1
      • snax-cluster-2
    • snax-lib: C libraries to run specific kernels on a snax-cluster.
      • snax-cluster-1
      • snax-cluster-2
    • test: contains testharness and bootrom of the snitch cluster

Software sw Directory

This subdirectory contains the various bits and pieces of software for the Snitch ecosystem.

Libraries

  • applications: Contains applications and kernels, mostly NN-related with SW testbenches for performance profiling.
  • cmake: Bits and pieces for integration with the CMake build system.
  • snRuntime: The fundamental, bare-metal runtime for Snitch systems. Exposes a minimal API to manage execution of code across the available cores and clusters, query information about a thread's context, and to coordinate and exchange data with other threads. Hardware configuration dependent implementations of the snRuntime can be found, e.g., under target/snitch_cluster/sw/snRuntime.
  • snBLAS: A minimal reference implementation of the basic linear algebra subprograms that demonstrates the use of Snitch and its extensions.

math

The math sources are taken from the musl library, patched with our own modifications. The bender vendor snippet in Bender.yml was used to copy in the original sources. Patches were generated using the following command (from the root of the repo): 

git format-patch --relative -o sw/deps/patches/musl/ HEAD^1
And can be applied by running (in the root of the repo): 
git apply sw/deps/patches/musl/0001-musl-Patch-to-build-math-library-for-Snitch.patch

The all target in sw/math/Makefile should be run to generate some files.

Tests

  • benchmark: Benchmarking executables that evaluate the performance characteristics of a system.
  • test: Unit tests for various aspects of a system, including the instruction set extensions. These complement the library-specific unit tests that live within the library directories proper.

Third-Party

The deps directory contains third-party tools that we inline into this repository for ease of use.

  • deps/riscv-opcodes: Utilities to manage instruction encodings and generate functions and data structurse for parsing and representation in various languages.
  • deps/printf: A printf / sprintf implementation for embedded systems.