rustc_codegen_gcc: Progress Report #19

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

No progress on this front for this month, but I worked on the following that I’ll need to clean up later and send as patches:

State of rustc_codegen_gcc

Here’s what has been done this month:

That was one big feature that was remaining to be implemented and I finally got it to work. I’ll need to clean up that stuff and fix the issues that make some tests fail, but that’s a big achievement.

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

Feature Last month completion Completion Delta

SIMD (x86-64).

95%

95%

Missing simd_reduce_add_unordered, simd_reduce_mul_unordered, simd_gather and simd_scatter

Unwinding.

0%

80%

+80%

LTO.

0%

Debug info.

0%

Endianness support for non-native 128-bit integers.

0%

Rustup distribution.

0%

SIMD for other architectures than x86-64.

0%

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

0%

More function and variable attributes.

0%

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

0%

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

4796

4821

+25

Failed

43

65

+22

There are more failures since I re-enabled the tests for panics and unwinding.

For the next month, I’ll fix the undefined behavior issues that we have and that cause some tests to fail when compiled in release mode.

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.

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:

  • saethlin

  • embark-studios

  • Traverse-Research

  • Shnatsel

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. Another big thank you to Commeownist for his contributions.

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

  • kpp

  • 0x7CFE

  • repi

  • nevi-me

  • oleid

  • acshi

  • joshtriplett

  • djc

  • TimNN

  • sdroege

  • pcn

  • alanfalloon

  • steven-joruk

  • davidlattimore

  • Nehliin

  • colelawrence

  • zmanian

  • alexkirsz

  • berkus

  • belzael

  • jam1garner

  • yvt

  • Shoeboxam

  • evanrichter

  • yerke

  • bes

  • seanpianka

  • srijs

  • kkysen

  • messense

  • riking

  • Lemmih

  • memoryruins

  • senden9

  • robjtede

  • Jonas Platte

  • zebp

  • spike grobstein

  • Oliver Marshall

  • Sam Harrington

  • Jonas

  • Jeff Muizelaar

  • Eugene Bulkin

  • Chris Butler

  • sierrafiveseven

  • Joseph Garvin

  • MarcoFalke

  • athre0z

  • icewind

  • Tommy Thorn

  • Sebastian Zivota

  • Oskar Nehlin

  • Nicolas Barbier

  • Daniel

  • Thomas Colliers

  • Justin Ossevoort

  • sbstp

  • Chris

  • Bálint Horváth

  • fanquake

  • kiyoshigawa

  • robinmoussu

  • Daniel Sheehan

  • Marvin Löbel

  • nacaclanga

  • Matthew Conolly

  • 0x0177b11f

  • L.apz

  • JockeTF

  • davidcornu

  • stuhood

  • 0xdeafbeef

  • Myrik Lord

  • Mauve

  • icewind1991

  • T

  • nicholasbishop

  • Emily A. Bellows

and a few others who preferred to stay anonymous.

Former sponsors/patreons:

  • igrr

  • finfet

  • Alovchin91

  • wezm

  • mexus

  • raymanfx

  • ghost

  • gilescope

  • Hofer-Julian

  • olanod

  • Denis Zaletaev

  • Chai T. Rex

  • Paul Ellenbogen

  • Dakota Brink

  • Botlabs

  • Cass

  • Oliver Marshall

  • pthariensflame

  • tedbyron

  • sstadick

  • Absolucy

  • rafaelcaricio

  • dandxy89

  • luizirber

  • regiontog

  • vincentdephily