all: port to RISC-V

[tklauser]

This issue serves to track the port to the RISC-V architecture. There is an out-of-tree port at https://github.com/riscv/riscv-go based on Go 1.8 which - according to riscvarchive/riscv-go#19 - is no longer maintained and would need quite some work to be updated to the current Go tip.

Also see https://golang.org/cl/106256#message-2d9a5c5b89ad55b8b7999f794983f993649232c8 and https://groups.google.com/forum/#!searchin/golang-dev/RISC%7Csort:date/golang-dev/VpsyGdi-sQQ/FMu6IB_2CwAJ where @josharian summarized the current state of the existing port.

The GOARCH values riscv and riscv64 were reserved in https://golang.org/cl/106256. These values are already used by gccgo. Additional changes were made to debug/elf (https://golang.org/cl/107339), cmd/cgo (https://golang.org/cl/110066), cmd/dist and cmd/types (https://golang.org/cl/118618) in order be able to generate type definition files in the x/sys/unix package (https://golang.org/cl/133735).

/cc @bradfitz @ianlancetaylor @josharian

[gopherbot]

Change https://golang.org/cl/133735 mentions this issue: unix: add support for linux/riscv64

[davidlt]

/cc myself as Fedora/RISC-V maintainer.

I would be happy to incl. this into the distribution (once it compiles) and do some testing.

[ghost]

Thanks for raising this.

Does anyone know where I can get hardware to test on ?

[ghost]

New house, CPU and fgpa efforts are going on using risc-v.
Quite a turning point and opportunity for golang programmers.

Here is the main news feed on all of it:
https://riscv.org/news/

[junland]

@gedw99 At the moment SiFive is the only company that has produced a RISC-V dev board (HiFive Unleashed). One caveat to this board is the price, which is around $1,000 USD.

[hugelgupf]

cc @GanShun and @rjoleary the three of us were also about to start looking at a port. We got a couple of SiFive boards to try it out on.

[bradfitz]

@hugelgupf, when you're far enough along to want a builder set up, file a bug and copy me and I'd be more than happy to help.

[jasonmoo]

I recently starting using qemu to run a riscv fedora build. Here are the links in case it's useful for devving without a board.

https://github.com/riscv/riscv-qemu
https://fedoraproject.org/wiki/Architectures/RISC-V/Installing#Download_the_latest_disk_image
https://fedoraproject.org/wiki/Architectures/RISC-V/Installing#Boot_under_qemu

Using dnf install gccgo I've been able to build and run go apps in emulation.

[davidlt]

Just reminder that RISC-V is supported in released versions of QEMU and libvirt, which makes it easy to setup multiple VMs with management. See: https://fedoraproject.org/wiki/Architectures/RISC-V/Installing#Boot_with_libvirt

Note, that our libffi does not support Go closures thus some functionality does not work. The patch exist already, but I need to backport it to our libffi version. Should I bump priority on this?

[tklauser]

FWIW, I started rebasing the Go 1.18-based https://github.com/riscv/go-riscv to current Go tip at https://github.com/tklauser/go-riscv. It currently builds on linux/amd64 but cannot generate valid riscv64 binaries yet.

I currently lack the time and resources to really push it forward but maybe someone else working on it might find it useful.

[bradfitz]

Just saw that you can apparently run RISC-V in the cloud via an FPGA AWS instance:

https://www.cnx-software.com/2017/02/22/amazon-ec2-f1-instances-put-xilinx-virtex-ultrascale-fpga-boards-in-the-cloud/

That might be a possible temporary builder strategy.

[jasonmoo]

@bradfitz https://fires.im/ is a risc-v deployment on aws fpgas but the underlying risc-v implementation only runs up to something like 100mhz. Working with a team that's doing some research in that area and it seems to be the norm. So far emulation has been the most performant by far.

[davidlt]

QEMU supports up to 8 cores (MTTCG - multi-threaded TCG), which is great if you can compile in parallel.

Alternatively contact Palmer Dabbelt from SiFive and ask for a free SiFive HiFive Unleashed board (multiple projects have received one for porting efforts).

[gopherbot]

Change https://golang.org/cl/157899 mentions this issue: unix: use Renameat2 to implement Renameat on linux/riscv64

[gopherbot]

Change https://golang.org/cl/157900 mentions this issue: unix: use int8 for RawSockaddrUnix.Path on linux/riscv64

[gopherbot]

Change https://golang.org/cl/157901 mentions this issue: unix: add assembly for riscv64 syscalls

[tklauser]

Issue for setting up a qemu-based RISC-V builder: #30262

[gopherbot]

Change https://golang.org/cl/217301 mentions this issue: [release-branch.go1.14] go/analysis/passes/asmdecl: add support for riscv64

[gopherbot]

Change https://golang.org/cl/217359 mentions this issue: go.mod: update golang.org/x/sys to fix riscv64 build

[gopherbot]

Change https://golang.org/cl/211917 mentions this issue: cmd/internal/obj/riscv: rework instruction generation

[davidlt]

Would it be possible to upload rc1 binaries to the download page?

[bradfitz]

@davidlt, RISC-V is still considered an experimental port in Go 1.14 so we won't be providing downloads.

[aurel32]

@davidlt It is quite easy to bootstrap golang from another architecture (e.g. amd64), see for example:
https://github.com/carlosedp/riscv-bringup/blob/master/build-golang.md

[carlosedp]

I've also built Go 1.14rc1 for riscv64 and made the tarball available on https://github.com/carlosedp/riscv-bringup/releases.

[4a6f656c]

@dmitshur - is there anything preventing this issue from being closed?

[marcopeereboom]

cgo support :)

[tklauser]

cgo support for riscv is tracked in #36641

[gopherbot]

Change https://golang.org/cl/240377 mentions this issue: doc: add riscv64 to ports list

[advancedwebdeveloper]

Anyone having a a desire to support RISC-V for https://go.googlesource.com/gollvm/ ?

[gopherbot]

Change https://golang.org/cl/250997 mentions this issue: doc: add linux/riscv64 valid combination

[tklauser]

Experimental support was added in Go 1.14 and Go 1.15 improved stability and performance. Support for cgo on linux/riscv64 is tracked in #36641.

Thus, I'm considering basic support for RISC-V to be done and am closing this issue. Let's open separate, specific issues for any further development (e.g. gollvm support) and improvements.

Thanks everybody for contributing!

[gopherbot]

Change https://golang.org/cl/257917 mentions this issue: dashboard: add linux-riscv64-jsing builder (reverse)