Add support for ARMv5TE architecture by atilag · Pull Request #37615 · rust-lang/rust

atilag · 2016-11-06T12:10:23Z

No description provided.

rust-highfive · 2016-11-06T12:10:37Z

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @nrc (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

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japaric · 2016-11-06T13:55:28Z

r? @alexcrichton

japaric · 2016-11-06T13:57:17Z

+
+ options: TargetOptions {
+ features: "+soft-float".to_string(),
+ max_atomic_width: Some(64),


LLVM can't lower atomic stuff to actual ARMv5 instructions because there are no instructions in the instruction set to implement atomics. This is going to require something like rust-lang/compiler-builtins#115
cc @Amanieu

Even with my PR the maximum atomic width would be 32 bits, not 64 bits.

alexcrichton · 2016-11-07T04:42:53Z

cc @rust-lang/tools, thoughts on adding a new target?

alexcrichton · 2016-11-07T04:43:34Z

Thanks for the PR @atilag! Could you also expand a bit on your use case for this target and why you'd like to see it in the compiler itself? (as opposed to using custom target specs)

Amanieu · 2016-11-07T05:01:49Z

Another question is, should we also add support for ARMv4T as a target? This is the minimum architecture that Debian armel requires.

atilag · 2016-11-07T09:29:06Z

Hi guys!
Well, me and me colleagues were trying to build a project around a hardware that, despite of being a little oldish, seems to be still very common in IoT based products. We could use other technologies, like C/C++ of course, but our experience in Rust is being very positive and we would love to keep using it and prove that Rust is a valid option even for these elderly platforms. We don't have special desires to include it as part of the compiler, so maybe using a custom target would work for us, but, is there any strong reason to not include it?
Thanks guys!
Keep up the good work!

japaric · 2016-11-07T13:47:00Z

@alexcrichton

Not the OP but if they are building std programs then having the target in-tree + binary releases of std is the most ergonomic option until we get std-aware Cargo. Or, IOW, compiling std for custom targets is a pain in the neck.

@Amanieu

Do you know for how long does Debian intent to provide ARMv4+ support?

fabricedesre · 2016-11-07T15:11:08Z

Indeed we are building std programs (the OS is Linux), so having an in-tree target helps.

Amanieu · 2016-11-07T18:59:33Z

@japaric I don't think Debian has any intention of dropping armel any time soon. Debian currently supports only two ARM variants: armel (ARMv4t+, soft float) and armhf (ARMv7+, hard float).

atilag · 2016-11-07T19:47:16Z

@japaric @Amanieu @Amanieu so I have updated the max_atomic_width to 32 bits. I guess that we need to merge rust-lang/compiler-builtins#115 before merging this one, right?

japaric · 2016-11-07T19:57:58Z

@atilag #36992 would have to land as well.

Amanieu · 2016-11-07T19:59:56Z

We also need to decide whether we want to support ARMv4T, ARMv5TE, or both.

atilag · 2016-11-08T15:11:13Z

@Amanieu I guess that in case we need to support ARMv4T, this could be done in another PR.
My understanding is that supporting ARMv5TE would only increase the added value of the language, so the question would be whether there's any drawback that outperforms this support. If we don't want to deal with a potential instability because of the atomic support, is there any way to mark this support as "unstable" or "experimental" ?

alexcrichton · 2016-11-08T16:43:48Z

Thanks for the explanation @atilag! I think we should hold off on armv4 here and perhaps add that in a future PR (if at all).

If ARMv5 doesn't have atomic instructions, though, then the current stance of the libs team is to set the max_atomic_width field to Some(0) as we can't actually create any instructions there. The fallbacks in compiler-builtins are intended to be optional for other use cases, if needed. We haven't figured out a great story yet, unfortunately, for pulling in those intrinsics on demand.

…RMv5

alexcrichton · 2016-11-10T21:54:28Z

@bors: r+

Thanks @atilag! cc @rust-lang/tools, a new target, but not necessarily libstd support just yet

bors · 2016-11-10T21:54:30Z

📌 Commit 365ea80 has been approved by alexcrichton

Add support for ARMv5TE architecture

Rollup of 30 pull requests - Successful merges: #37190, #37368, #37481, #37503, #37527, #37535, #37551, #37584, #37600, #37613, #37615, #37659, #37662, #37669, #37682, #37688, #37690, #37692, #37693, #37694, #37695, #37696, #37698, #37699, #37705, #37708, #37709, #37716, #37724, #37727 - Failed merges: #37640, #37689, #37717

Add armv4t-unknown-linux-gnueabi target armv4t was left out of #37615 (armv5te addition) to be included in a [future PR](#37615 (comment)). So this PR adds armv4t target. armv4t target is useful because the [armel](https://wiki.debian.org/ArmEabiPort) port of Debian targets armv4t

Add support for ARMv5TE architecture
8016dc3

rust-highfive assigned nrc Nov 6, 2016

japaric reviewed Nov 6, 2016
View reviewed changes

atilag force-pushed the armv5te-support branch from 6e04c1a to 5d94532Compare November 9, 2016 12:52

Set max_atomic_width to 0 because there's no atomic instructions on A…
365ea80
…RMv5

atilag force-pushed the armv5te-support branch from 5d94532 to 365ea80Compare November 10, 2016 09:54

alexcrichton added the T-tools label Nov 10, 2016

brson added the relnotes Marks issues that should be documented in the release notes of the next release. label Nov 11, 2016

eddyb added a commit to eddyb/rust that referenced this pull request Nov 11, 2016
Rollup merge ofrust-lang#37615- atilag:armv5te-support, r=alexcrichton
df060c4
Add support for ARMv5TE architecture

eddyb mentioned this pull request Nov 11, 2016
Rollup of 29 pull requests #37726
Closed

eddyb added a commit to eddyb/rust that referenced this pull request Nov 12, 2016
Rollup merge ofrust-lang#37615- atilag:armv5te-support, r=alexcrichton
8d2da2b
Add support for ARMv5TE architecture

eddyb mentioned this pull request Nov 12, 2016
Rollup of 30 pull requests #37730
Merged

bors merged commit 365ea80 into rust-lang:masterNov 12, 2016

malbarbo mentioned this pull request Dec 26, 2017
Add armv4t-unknown-linux-gnueabi target #47018
Merged

davidtwco mentioned this pull request Sep 20, 2023
target tier policy compliance #116004
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atilag commented Nov 7, 2016•
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