rustc_codegen_gcc: Progress Report #12

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

Again this month, there was a lot of progress! The following patches were posted to the mailing list:

The last patch was already approved and is merged.

I still have a few that I need to prepare and send for review and I’ll send them on the GCC mailing list this month.

State of rustc_codegen_gcc

Here’s what has been done this month:

The work on SIMD is still not completed as I cannot compile stdarch yet, but there’s been good progress. I believe I’m close to getting it to compile as I currently need to debug an RTL issue, so hopefully next month it will compile.

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

Feature Last month completion Completion Delta

target-specific builtins support in libgccjit

Done

support for vector shuffle (equivalent of __builtin_shufflevector) in libgccjit

Done

simd_extract

Done

simd_select, simd_select_bitmask

Done

simd_reduce_min, simd_reduce_max

Done

simd_reduce_and, simd_reduce_or

Done

simd_saturating_add and simd_saturating_sub

implemented for x86

simd_insert

20% implemented

100%

+80%

simd_cast

20% implemented

100%

+80%

simd_bitmask

0%

100%

+100%

LLVM SIMD intrinsics

~70% implemented for x86

~90% implemented for x86

+20%

simd_reduce_add_unordered, simd_reduce_mul_unordered

50%

50%

0

simd_reduce_add_ordered, simd_reduce_mul_ordered

0%

0%

0

simd_reduce_min_nanless, simd_reduce_max_nanless

0%

0%

0

simd_reduce_xor, simd_reduce_all, simd_reduce_any

0%

0%

0

SIMD float intrinsics

0%

0%

0

simd_gather and simd_scatter

0%

0%

0

simd_as

0%

0%

0

UI tests progress

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

Category Last Month This Month Delta

Passed

4598

4697

+99

Failed

64

61

-3

For the next month, I’ll continue working on SIMD support.

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

  • regiontog

  • berkus

  • belzael

  • vincentdephily

  • jam1garner

  • yvt

  • Shoeboxam

  • evanrichter

  • yerke

  • bes

  • seanpianka

  • srijs

  • kkysen

  • messense

  • riking

  • rafaelcaricio

  • Lemmih

  • memoryruins

  • pthariensflame

  • senden9

  • robjtede

  • Jonas Platte

  • zebp

  • spike grobstein

  • Oliver Marshall

  • Sam Harrington

  • Jonas

  • Jeff Muizelaar

  • Eugene Bulkin

  • Absolucy

  • Chris Butler

  • sierrafiveseven

  • Joseph Garvin

  • MarcoFalke

  • icewind

  • Tommy Thorn

  • Sebastian Zivota

  • Oskar Nehlin

  • Nicolas Barbier

  • Daniel

  • Thomas Colliers

  • Justin Ossevoort

  • sbstp

  • Chris

  • Bálint Horváth

  • fanquake

  • sstadick

  • luizirber

  • kiyoshigawa

  • robinmoussu

  • Daniel Sheehan

  • Marvin Löbel

  • nacaclanga

  • Matthew Conolly

and a few others who preferred to stay anonymous.

Former sponsors/patreons:

  • igrr

  • finfet

  • Alovchin91

  • wezm

  • stuhood

  • mexus

  • raymanfx

  • 0xdeafbeef

  • ghost

  • gilescope

  • thesamesam

  • Hofer-Julian

  • olanod

  • Denis Zaletaev

  • Chai T. Rex

  • Paul Ellenbogen

  • Dakota Brink

  • Botlabs

  • Cass

  • Oliver Marshall