[Caml-list] [ANN] RISC-V backend for the native-code OCaml compiler

[Nicolas Ojeda Bar]

Dear list,

I am happy two announce an ALPHA release of a new native-code backend
for the OCaml compiler.

It targets the RISC-V instruction set (http://riscv.org) being
developed at UC Berkeley. The lowRISC project at the University of
Cambridge (http://www.lowrisc.org) is developing open-source SoCs
based on this instruction set.

This release is in the form of a cross-compiler. It depends on the
cross-compiling support recently added to 4.02.0+trunk. It outputs
ELF binaries that can be simulated directly on the RISC-V ISA
simulator (spike) or run natively in a suitable virtual machine.

For detailed installation instructions, please visit:
https://github.com/nojb/riscv-ocamlopt.

The new backend is based on the old 3.12 MIPS backend and the
currently shipping arm64 backend. Most compiler tests that can
compile in the RISC-V environment pass successfully (including the
"big" ones such as misc-bk, misc/hamming, misc/boyer, misc/nucleic,
misc/bdd, etc.).

Limitations (some are due to the state of RISC-V software tools, some
are due to limitations of the cross-compiling support in the current
OCaml compiler, some just need work):

- Only 64-bit for now (in particular the host has to be 64-bit as well)
- Unix module is not yet supported
- The current version uses the Newlib C library, which is somewhat
less capable than glibc.
- Shared library support may or may not work (has not been tested)

Planned short term improvements (patches welcome!):

- 32-bit support
- cfi directives (and/or frame pointer inclusion) for easier debugging
- switch to glibc
- soft float support
- Unix support

Development is ongoing.

Suggestions, questions of any kind very welcome!

Thanks very much,

Best wishes,
Nicolas

[Richard W.M. Jones]

(Resurrecting the old thread ...)

Post by Nicolas Ojeda Bar
This release is in the form of a cross-compiler. It depends on the
cross-compiling support recently added to 4.02.0+trunk. It outputs
ELF binaries that can be simulated directly on the RISC-V ISA
simulator (spike) or run natively in a suitable virtual machine.
https://github.com/nojb/riscv-ocamlopt.

Hi Nicolas,

I'm confused here -- where is the upstream source? For example, is
there a fork of the upstream OCaml git repo with your changes on top?

Rich.

[Gabriel Scherer]

The given link is an opam repository that contains a description of the
forked compiler for easy installation via opam. Looking at the description
file for the compiler


https://github.com/nojb/riscv-ocamlopt/blob/master/compilers/4.02.0/4.02.0%2Briscv64-unknown-elf/4.02.0%2Briscv64-unknown-elf.comp

it appears that the upstream source (currently) is a branch of the
github:nojb/ocaml repository:

https://github.com/nojb/ocaml/commits/4.02.0%2Briscv64-unknown-elf

Post by Richard W.M. Jones
(Resurrecting the old thread ...)

Post by Nicolas Ojeda Bar
This release is in the form of a cross-compiler. It depends on the
cross-compiling support recently added to 4.02.0+trunk. It outputs
ELF binaries that can be simulated directly on the RISC-V ISA
simulator (spike) or run natively in a suitable virtual machine.
https://github.com/nojb/riscv-ocamlopt.

Hi Nicolas,
I'm confused here -- where is the upstream source? For example, is
there a fork of the upstream OCaml git repo with your changes on top?
Rich.
--
https://sympa.inria.fr/sympa/arc/caml-list
Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
Bug reports: http://caml.inria.fr/bin/caml-bugs

[Richard W.M. Jones]

Post by Gabriel Scherer
The given link is an opam repository that contains a description of the
forked compiler for easy installation via opam. Looking at the description
file for the compiler
https://github.com/nojb/riscv-ocamlopt/blob/master/compilers/4.02.0/4.02.0%2Briscv64-unknown-elf/4.02.0%2Briscv64-unknown-elf.comp
it appears that the upstream source (currently) is a branch of the
https://github.com/nojb/ocaml/commits/4.02.0%2Briscv64-unknown-elf

Just what I was looking for, thanks.

FWIW we are currently porting Fedora to RISC-V, so of course I
want to have a go at compiling OCaml too.

https://fedoraproject.org/wiki/Architectures/RISC-V

Rich.

[Nicolas Ojeda Bar]

Hi Richard,

- As Gabriel explained the upstream is the branch riscv64-unknown-elf
of the official 4.02 release found at
github.com/nojb/ocaml. It should be trivial to bring it up to date (I
will do it if there is interest).

- I have been following your efforts on the RISC-V mailing list and I
agree that it would be great to have
OCaml running in Fedora userland on RISC-V. The native-code backend I
wrote was only tested with the spike simulator
(I don't remember the details now, but I had to build OCaml with
newlib instead of libc for this).

Do get back to me if you detect any issues with the port - I haven't
updated it in quite some time and some adjustments may be
needed.

Are there any step-by-step instructions on how to run Fedora on RISC-V
at this stage ?

Thanks!

Best wishes,
Nicolas

Post by Richard W.M. Jones

Post by Gabriel Scherer
The given link is an opam repository that contains a description of the
forked compiler for easy installation via opam. Looking at the description
file for the compiler
https://github.com/nojb/riscv-ocamlopt/blob/master/compilers/4.02.0/4.02.0%2Briscv64-unknown-elf/4.02.0%2Briscv64-unknown-elf.comp
it appears that the upstream source (currently) is a branch of the
https://github.com/nojb/ocaml/commits/4.02.0%2Briscv64-unknown-elf

Just what I was looking for, thanks.
FWIW we are currently porting Fedora to RISC-V, so of course I
want to have a go at compiling OCaml too.
https://fedoraproject.org/wiki/Architectures/RISC-V
Rich.
--
Richard Jones