# Documentation

A draft version of the specification is available at
<https://ftp.libre-soc.org/power-spec-draft.pdf>

# Codebase Structure

The SOC is partitioned into four repositories. The subrepositories are
intended as general purpose standalone projects useful outside of LibreSOC. For example,
the IEE754 FPU repository is a general purpose IEEE754 toolkit for the
construction of FSMs and arbitrary length pipelines.

| Git Repo | Online docs   | Description   | Pypi    |
|----------|---------------|---------------|--------
| [SOC](https://git.libre-soc.org/?p=soc.git;a=tree) | [Libre-SOC](https://docs.libre-soc.org/soc/) | Main OpenPOWER Hybrid CPU-GPU | TBD |
| [FPU](https://git.libre-soc.org/?p=ieee754fpu.git;a=tree) | [ieee754fpu](https://docs.libre-soc.org/ieee754fpu/) | Equivalent to hardfloat-3 | [libresoc-ieee754fpu](https://pypi.org/project/libresoc-ieee754fpu) |
| [nmutil](https://git.libre-soc.org/?p=nmutil.git;a=tree) | [nmutil](https://docs.libre-soc.org/nmutil/) | Equivalent to Chisel3.util | [libresoc-nmutil](https://pypi.org/project/libresoc-nmutil) |
| [OpenPOWER ISA](https://git.libre-soc.org/?p=nmutil.git;a=tree) | [OpenPOWER ISA](https://docs.libre-soc.org/openpower-isa/) | Simulator, ISA spec compiler, co-simulation infrastructure |  [libresoc-openpower-isa](https://pypi.org/project/libresoc-openpower-isa/)  |

# Installing the Codebase

Installation is much easier when using the
[install scripts](https://git.libre-soc.org/?p=dev-env-setup.git;a=blob;f=hdl-dev-repos;hb=HEAD).
A separate script also helps install
[dependencies](https://git.libre-soc.org/?p=dev-env-setup.git;a=blob;f=install-hdl-apt-reqs;hb=HEAD)
and a third can be used to set up a
[debootstrap chroot](
https://git.libre-soc.org/?p=dev-env-setup.git;a=blob;f=mk-deb-chroot;hb=HEAD).
The chroot is useful to ensure stability and repeatable builds: no
errors or issues introduced by libraries being wrong versions.
Also relevant is the [gdb gcc build](https://git.libre-soc.org/?p=dev-env-setup.git;a=blob;f=ppc64-gdb-gcc;hb=HEAD).

For a simple set of commands to follow, see [[HDL_workflow/devscripts]]. If
you prefer to do a manual install and explicitly install dependencies
yourself, in order to verify them, see [[HDL_workflow]]

# Tutorials and documentation

* [[SOC Architecture|3d_gpu/architecture]]
* Gtkwave Tutorial [[docs/gtkwave_tutorial]]
* Formal proof notes [[docs/notes_on_formal_proofs]]
* Learning nmigen [[docs/learning_nmigen]]
* Test API [[docs/testapi]]
* Pinmux and JTAG Boundary Scan [[docs/pinmux]]
* pypowersim python-based command-line simulator [[docs/pypowersim]]
* First steps [[docs/firststeps]]
* Adding an instruction [[docs/adding_instr]] - see also below

# SVP64

Currently in Draft form, [[openpower/sv/svp64]] is the basis of the
Supercomputing Cray-style Vectorisation of the Power ISA.

# Checklist for adding an instruction

TODO.  use the commit diffs for these instructions as a guide

* fmvis <https://bugs.libre-soc.org/show_bug.cgi?id=887>
* avgadd etc. <https://bugs.libre-soc.org/show_bug.cgi?id=863>
* int min/max <https://bugs.libre-soc.org/show_bug.cgi?id=234#c1>
* ternlogi <https://bugs.libre-soc.org/show_bug.cgi?id=745> which included
  adding a hardware implementation as well