rustc_codegen_gcc: Progress Report #35

What is rustc_codegen_gcc?

rustc_codegen_gcc is a GCC ahead-of-time codegen for rustc, meaning that it can be loaded by the existing rustc frontend, but benefits from GCC by having more architectures supported and having access to GCC’s optimizations. It is not to be confused with gccrs, which is a GCC frontend for Rust.

GCC patches status

We implemented new patches that are yet to be sent to the mailing list:

We also had our patch to reorganize the CPU feature detection code to remove duplication between gccrs and rustc_codegen_gcc merged:

I hope this is the first of many contributions we’ll have between the two projects and that we can continue to collaborate with and help each other.

We also got reviews of some patches that were sent in the past.

State of rustc_codegen_gcc

Here’s what has been done during the past months:

Apart from that, there was a lot of progress towards having rustup distribution thanks to Kobzol:

Let’s hope that we can get rustup distribution soon in order to make it easier for people to try this project.

I still struggle with the current sync: this time, I’m blocked by a regression in libm. Hopefully, these PRs will be merged soon in order to unblock me:

Next month, I’ll finish this sync, I’ll continue adding support for other non-default ABIs and improve the documentation for new contributors.

Here’s a rough summary of what has been implemented:

Feature Last month completion Completion Delta

Unwinding.

80%

80%

LTO.

80%

80%

More function and variable attributes.

22%

22%

Target features (to detect what is supported in an architecture, like SIMD).

82%

82%

Debug info.

20%

Thin LTO.

5%

5%

Rustup distribution.

0%

30%

+30%

SIMD for other architectures than x86-64.

0%

Support for new architectures in libraries (libc, object, …) and rustc.

0%

Refactor to rustc_codegen_ssa to make it easier for the GCC codegen

0%

Endianness support for non-native 128-bit integers.

Done

SIMD (x86-64).

Done

Basic and aggregate types.

Done

Operations, local and global variables, constants, functions, basic blocks.

Done

Atomics.

Done

Thread-local storage.

Done

Inline assembly.

Done

Many intrinsics.

Done

Metadata.

Done

Setting optimization level.

Done

Packed structures.

Done

Alignment, symbol visibility, attributes.

Done

128-bit integers.

Done

UI tests progress

Here are the results of running the UI tests in the CI:

Category Last Month This Month Delta

Passed

6125

6156

+31

Failed

129

48

-81

How to contribute

rustc_codegen_gcc

If you want to help on the project itself, please do the following:

  1. Run the tests locally.

  2. Choose a test that fails.

  3. Investigate why it fails.

  4. Fix the problem.

Even if you can’t fix the problem, your investigation could help, so if you enjoy staring at assembly code, have fun!

Crates and rustc

If you would like to contribute on adding support for Rust on currently unsupported platforms, you can help by adding the support for those platforms in some crates like libc and object and also in the rust compiler itself.

Test this project

Otherwise, you can test this project on new platforms and also compare the assembly with LLVM to see if some optimization is missing.

To do so, follow these instructions to build the project and run a program via the cargo command of our script.

If you find a bug, please open an issue.

Good first issue

Finally, another good way to help is to look at good first issues. Those are issues that should be easier to start with.

Thanks for your support!

I wanted to personally thank all the people that sponsor this project: your support is very much appreciated.

A special thanks to the following sponsors:

  • Futurewei

  • Shnatsel

  • Rust Foundation

A big thank you to bjorn3 for his help, contributions and reviews. And a big thank you to lqd and GuillaumeGomez for answering my questions about rustc’s internals and to Kobzol and GuillaumeGomez for their contributions. Another big thank you to Commeownist for his contributions.

Also, a big thank you to the rest of my sponsors:

  • kpp

  • 0x7CFE

  • oleid

  • acshi

  • joshtriplett

  • djc

  • sdroege

  • pcn

  • alanfalloon

  • davidlattimore

  • colelawrence

  • zmanian

  • berkus

  • belzael

  • yvt

  • Shoeboxam

  • yerke

  • srijs

  • kkysen

  • riking

  • Lemmih

  • memoryruins

  • senden9

  • robjtede

  • Jonas Platte

  • Sam Harrington

  • Jonas

  • Eugene Bulkin

  • Joseph Garvin

  • MarcoFalke

  • athre0z

  • Sebastian Zivota

  • Oskar Nehlin

  • Nicolas Barbier

  • Daniel

  • Justin Ossevoort

  • kiyoshigawa

  • Daniel Sheehan

  • Marvin Löbel

  • nacaclanga

  • 0x0177b11f

  • L.apz

  • JockeTF

  • davidcornu

  • stuhood

  • Mauve

  • icewind1991

  • nicholasbishop

  • David Vasak

  • Eric Driggers

  • Olaf Leidinger

  • UtherII

  • simonlindholm

  • lemmih

  • Eddddddd

  • rrbutani

  • Mateusz K

  • thk1

  • teh

  • KirilMihaylov

  • Vladislav Sukhmel

  • ximou

  • Kate Kiesel

  • jplatte

  • VasanthakumarV

  • thesamesam

  • sbstp

  • g4titanx

  • teohhanhui

  • Laine Taffin Altman

and a few others who preferred to stay anonymous.

Former sponsors/patreons:

  • igrr

  • embark-studios

  • saethlin

  • Traverse-Research

  • finfet

  • Alovchin91

  • wezm

  • mexus

  • raymanfx

  • ghost

  • gilescope

  • olanod

  • Denis Zaletaev

  • Chai T. Rex

  • Paul Ellenbogen

  • Dakota Brink

  • Botlabs

  • Cass

  • Oliver Marshall

  • pthariensflame

  • tedbyron

  • sstadick

  • Absolucy

  • rafaelcaricio

  • dandxy89

  • luizirber

  • regiontog

  • vincentdephily

  • zebp

  • Hofer-Julian

  • messense

  • fanquake

  • jam1garner

  • evanrichter

  • Nehliin

  • nevi-me

  • TimNN

  • steven-joruk

  • seanpianka

  • spike grobstein

  • Jeff Muizelaar

  • robinmoussu

  • Chris Butler

  • sierrafiveseven

  • icewind

  • Thomas Colliers

  • Tommy Thorn

  • Bálint Horváth

  • Matthew Conolly

  • Lapz

  • Myrik Lord

  • T

  • Emily A. Bellows

  • Chris

  • repi

  • opensrcsec

  • NobodyXu

  • alexkirsz

  • 0xdeafbeef

  • l-const

  • CohenArthur

  • bes