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Rustc_codegen_GCC can now bootstrap rustc

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Re: Rustc_codegen_GCC can now bootstrap rustc

#21

Post by jcelerier »

bregma wrote: post #16
meinersbur wrote: post #13

Earlier quoted context omitted.

`mkdir build && cmake ../llvm -GNinja && ninja` better?

You missed the part where you upgrade your RAM to at least 128 GB and up the swap to 512 GB and use gold as your linker because the OOM killer will still raise it's head for ld under those extreme restrictions.

I don't understand why anyone would use ld or gold in 2022. Every distro has shipped lld for years and it links in less than seconds. It's a default to not break compatibility, not because it's good ; makes as much sense to use as ed(1). For reference on a 8C/16T CPU from 2016 an llvm initial build is ~10-12 minutes here.. not instant but not the end of the world either.

Re: Rustc_codegen_GCC can now bootstrap rustc

#22

Post by stjohnswarts »

mahkoh wrote: post #20
mhh__ wrote: post #17

Earlier quoted context omitted.

GCC is still basically better overall but it's basically chaotic. LLVM seems to have better defaults for branch-y compiler code, but GCC has a lot of tricks up its sleeve that LLVM hasn't got. FWIW though I think GCC is really playing with fire when it comes to it's future - the mailing list approach to development deters new contributors, the testing infrastructure is quite arcane, etc. GCC should be an aspirational…

>FWIW though I think GCC is really playing with fire when it comes to it's future - the mailing list approach to development deters new contributors, the testing infrastructure is quite arcane, etc. And LLVM is better? At the start of last year I found and fixed a small bug in LLVM[1]. I submitted the fix via their Phabricator instance and it was approved by project members after a few days. As per the contributor gu…

Did you try again? I'm not discounting your efforts but n=1 is not an optimal way to determine that LLVM change/bugfix process is "broken".

Re: Rustc_codegen_GCC can now bootstrap rustc

#23

Post by xxpor »

jcelerier wrote: post #21
bregma wrote: post #16

Earlier quoted context omitted.

You missed the part where you upgrade your RAM to at least 128 GB and up the swap to 512 GB and use gold as your linker because the OOM killer will still raise it's head for ld under those extreme restrictions.

I don't understand why anyone would use ld or gold in 2022. Every distro has shipped lld for years and it links in less than seconds. It's a default to not break compatibility, not because it's good ; makes as much sense to use as ed(1). For reference on a 8C/16T CPU from 2016 an llvm initial build is ~10-12 minutes here.. not instant but not the end of the world either.

When LLVM doesn't support your platform :(

Granted, that means no Rust support today so probably not relevent to most people reading this thread, but yeah I'm still salty :|

Re: Rustc_codegen_GCC can now bootstrap rustc

#24

Post by xxpor »

OskarS wrote: post #14
da-x wrote: post #11

Earlier quoted context omitted.

Compiling LLVM for what purpose? Hacking on it? Producing an optimized build? Installing a build on a user's machine? You should be more specific. The default clean build works just fine. On my machine I can clone the Git repo, do `mkdir build && cmake ../llvm && make -j64` and end up with working binaries after 5 minutes. The build take 37GB by default here, and the binaries under bin/ are immediately usable work. I…

64 cores, and it takes 5 minutes? That’s… not awesome. Most people do not have 64 (presumably high performance) cores lying around for the purpose of building dependencies.

10 minutes of a c6i.32xlarge costs less than a dollar at on-demand rates in the us-east-2 AWS region. That'll get you 128 vCPUs and 256 gb of memory.

I think people put up with a lot of stuff that there's no reason to any more with on-demand computing.

Re: Rustc_codegen_GCC can now bootstrap rustc

#25

Post by jmorse2 »

mahkoh wrote: post #20
mhh__ wrote: post #17

Earlier quoted context omitted.

GCC is still basically better overall but it's basically chaotic. LLVM seems to have better defaults for branch-y compiler code, but GCC has a lot of tricks up its sleeve that LLVM hasn't got. FWIW though I think GCC is really playing with fire when it comes to it's future - the mailing list approach to development deters new contributors, the testing infrastructure is quite arcane, etc. GCC should be an aspirational…

>FWIW though I think GCC is really playing with fire when it comes to it's future - the mailing list approach to development deters new contributors, the testing infrastructure is quite arcane, etc. And LLVM is better? At the start of last year I found and fixed a small bug in LLVM[1]. I submitted the fix via their Phabricator instance and it was approved by project members after a few days. As per the contributor gu…

(NB: the developers guide says to ping if there's no activity for a week)

Re: Rustc_codegen_GCC can now bootstrap rustc

#26

Post by junon »

hardware2win wrote: post #6
goombacloud wrote: post #3

It's really great to be able to skip compiling LLVM when bootstrapping a whole OS/toolchain from source and only Rust happens to pull LLVM in. Besides the gcc work I'm actually also hoping for the rustc_codegen_cranelift work to land one day!

Compiling llvm is a nightmare

it's two commands for me. What issues do you face?

Re: Rustc_codegen_GCC can now bootstrap rustc

#27

Post by jcelerier »

xxpor wrote: post #23
jcelerier wrote: post #21

Earlier quoted context omitted.

I don't understand why anyone would use ld or gold in 2022. Every distro has shipped lld for years and it links in less than seconds. It's a default to not break compatibility, not because it's good ; makes as much sense to use as ed(1). For reference on a 8C/16T CPU from 2016 an llvm initial build is ~10-12 minutes here.. not instant but not the end of the world either.

When LLVM doesn't support your platform :( Granted, that means no Rust support today so probably not relevent to most people reading this thread, but yeah I'm still salty :|

... which platform is that ?

Re: Rustc_codegen_GCC can now bootstrap rustc

#28

Post by westurner »

xxpor wrote: post #24
OskarS wrote: post #14

Earlier quoted context omitted.

64 cores, and it takes 5 minutes? That’s… not awesome. Most people do not have 64 (presumably high performance) cores lying around for the purpose of building dependencies.

10 minutes of a c6i.32xlarge costs less than a dollar at on-demand rates in the us-east-2 AWS region. That'll get you 128 vCPUs and 256 gb of memory. I think people put up with a lot of stuff that there's no reason to any more with on-demand computing.

Q: "Does my data fit in RAM?" https://news.ycombinator.com/item?id=22309883

A: https://yourdatafitsinram.net

Is there a one-liner to build llvm e.g. with k8s and containers, or just a `git push` to a PR? #GitOps

And another to publish a locally-signed tagged build?

`conda install rust` does install `cargo`.

`conda install -c conda-forge -y mamba; mamba install -y rust libllvm14 lit llvm llvm-tools llvmdev`

conda-forge/llvmdev-feedstock; ninja, cmake, python >= 3 https://github.com/conda-forge/llvmdev-feedstock/blob/main/r...

.scripts/run_docker_build.sh is called by build-locally.py: https://github.com/conda-forge/llvmdev-feedstock/blob/main/....

Re: Rustc_codegen_GCC can now bootstrap rustc

#29

Post by JoshTriplett »

jcelerier wrote: post #21
bregma wrote: post #16

Earlier quoted context omitted.

You missed the part where you upgrade your RAM to at least 128 GB and up the swap to 512 GB and use gold as your linker because the OOM killer will still raise it's head for ld under those extreme restrictions.

I don't understand why anyone would use ld or gold in 2022. Every distro has shipped lld for years and it links in less than seconds. It's a default to not break compatibility, not because it's good ; makes as much sense to use as ed(1). For reference on a 8C/16T CPU from 2016 an llvm initial build is ~10-12 minutes here.. not instant but not the end of the world either.

lld is not 100% compatible with ld; switching to it usually works, but occasionally breaks the build of some software. That's especially true for complex cases involving linker scripts and unusual binary layouts with various sections. (Those cases also tend to be hard to debug.)

Re: Rustc_codegen_GCC can now bootstrap rustc

#30

Post by steveklabnik »

jcelerier wrote: post #21
bregma wrote: post #16

Earlier quoted context omitted.

You missed the part where you upgrade your RAM to at least 128 GB and up the swap to 512 GB and use gold as your linker because the OOM killer will still raise it's head for ld under those extreme restrictions.

I don't understand why anyone would use ld or gold in 2022. Every distro has shipped lld for years and it links in less than seconds. It's a default to not break compatibility, not because it's good ; makes as much sense to use as ed(1). For reference on a 8C/16T CPU from 2016 an llvm initial build is ~10-12 minutes here.. not instant but not the end of the world either.

lld is good, but you answered why in your own comment: it's not always compatible, and so when you need ld, you need ld.
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