target: default to the medium code model on LoongArch targets#130266

heiher · 2024-09-12T07:45:38Z

The Rust LoongArch targets have been using the default LLVM code model so far, which is "small" in LLVM-speak and "normal" in LoongArch-speak. As described in the "Code Model" section of LoongArch ELF psABI spec v20231219 1, one can only make function calls as far as ±128MiB with the "normal" code model; this is insufficient for very large software containing Rust components that needs to be linked into the big text section, such as Chromium.

Because:

we do not want to ask users to recompile std if they are to build such software,
objects compiled with larger code models can be linked with those with smaller code models without problems, and
the "medium" code model is comparable to the "small"/"normal" one performance-wise (same data access pattern; each function call becomes 2-insn long and indirect, but this may be relaxed back into the direct 1-insn form in a future LLVM version), but is able to perform function calls within ±128GiB,

it is better to just switch the targets to the "medium" code model, which is also "medium" in LLVM-speak.

Relands 2: #120661

The Rust LoongArch targets have been using the default LLVM code model so far, which is "small" in LLVM-speak and "normal" in LoongArch-speak. As described in the "Code Model" section of LoongArch ELF psABI spec v20231219 [1], one can only make function calls as far as ±128MiB with the "normal" code model; this is insufficient for very large software containing Rust components that needs to be linked into the big text section, such as Chromium. Because: * we do not want to ask users to recompile std if they are to build such software, * objects compiled with larger code models can be linked with those with smaller code models without problems, and * the "medium" code model is comparable to the "small"/"normal" one performance-wise (same data access pattern; each function call becomes 2-insn long and indirect, but this may be relaxed back into the direct 1-insn form in a future LLVM version), but is able to perform function calls within ±128GiB, it is better to just switch the targets to the "medium" code model, which is also "medium" in LLVM-speak. [1]: https://github.com/loongson/la-abi-specs/blob/v2.30/laelf.adoc#code-models Co-authored-by: WANG Rui <wangrui@loongson.cn>

rustbot · 2024-09-12T07:45:46Z

r? @petrochenkov

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rustbot · 2024-09-12T07:45:48Z

These commits modify compiler targets.
(See the Target Tier Policy.)

heiher · 2024-09-12T07:46:59Z

cc @xen0n @xry111

xen0n · 2024-09-12T07:53:05Z

It's better to mention in the PR description the comment suggesting the reland for some more context. It really helps Git archaeology several years later according to my experience...

compiler-errors · 2024-09-13T11:45:39Z

@bors r+ rollup

bors · 2024-09-13T11:45:42Z

📌 Commit 82777a9 has been approved by compiler-errors

It is now in the queue for this repository.

…iaskrgr Rollup of 6 pull requests Successful merges: - rust-lang#129320 (Fix crash when labeling arguments for call_once and friends) - rust-lang#130266 (target: default to the medium code model on LoongArch targets) - rust-lang#130297 (Dataflow cleanups) - rust-lang#130299 (Add set_dcx to ParseSess) - rust-lang#130301 (some fixes for clashing_extern_declarations lint) - rust-lang#130305 (Clippy: consider msrv for const context for const_float_bits_conv) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of rust-lang#130266 - heiher:loong-medium-cmodel, r=compiler-errors target: default to the medium code model on LoongArch targets The Rust LoongArch targets have been using the default LLVM code model so far, which is "small" in LLVM-speak and "normal" in LoongArch-speak. As described in the "Code Model" section of LoongArch ELF psABI spec v20231219 [1], one can only make function calls as far as ±128MiB with the "normal" code model; this is insufficient for very large software containing Rust components that needs to be linked into the big text section, such as Chromium. Because: * we do not want to ask users to recompile std if they are to build such software, * objects compiled with larger code models can be linked with those with smaller code models without problems, and * the "medium" code model is comparable to the "small"/"normal" one performance-wise (same data access pattern; each function call becomes 2-insn long and indirect, but this may be relaxed back into the direct 1-insn form in a future LLVM version), but is able to perform function calls within ±128GiB, it is better to just switch the targets to the "medium" code model, which is also "medium" in LLVM-speak. Relands [2]: rust-lang#120661 [1]: https://github.com/loongson/la-abi-specs/blob/v2.30/laelf.adoc#code-models [2]: rust-lang#121289 (comment)

The context for this is rust-lang#130266: setting the medium code model for the 'loongarch64-linux-ohos' target.

Default to the medium code model on OpenHarmony LoongArch target The context for this is rust-lang#130266: setting the medium code model for the `loongarch64-linux-ohos` target. r? `@jieyouxu`

Default to the medium code model on OpenHarmony LoongArch target The context for this is rust-lang#130266: setting the medium code model for the `loongarch64-linux-ohos` target. r? ``@jieyouxu``

Default to the medium code model on OpenHarmony LoongArch target The context for this is rust-lang#130266: setting the medium code model for the `loongarch64-linux-ohos` target. r? ```@jieyouxu```

Rollup merge of rust-lang#131874 - heiher:loong-ohos-medium, r=jieyouxu Default to the medium code model on OpenHarmony LoongArch target The context for this is rust-lang#130266: setting the medium code model for the `loongarch64-linux-ohos` target. r? ```@jieyouxu```

Since rust-lang#130266 loongarch defaults to medium code model.

…ingjubilee Update default loongarch code model in docs Since rust-lang#130266 loongarch defaults to medium code model.

Rollup merge of rust-lang#137166 - nikic:loongarch-code-model, r=workingjubilee Update default loongarch code model in docs Since rust-lang#130266 loongarch defaults to medium code model.

Update default loongarch code model in docs Since rust-lang/rust#130266 loongarch defaults to medium code model.

rustbot assigned petrochenkov Sep 12, 2024

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Sep 12, 2024

bors removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Sep 13, 2024

compiler-errors self-assigned this Sep 13, 2024

bors added the S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. label Sep 13, 2024

compiler-errors unassigned petrochenkov Sep 13, 2024

matthiaskrgr mentioned this pull request Sep 13, 2024

Rollup of 6 pull requests #130312

Merged

bors merged commit 778f6fb into rust-lang:master Sep 13, 2024

rustbot added this to the 1.83.0 milestone Sep 13, 2024

heiher deleted the loong-medium-cmodel branch September 14, 2024 02:01

xen0n mentioned this pull request Sep 14, 2024

[LoongArch] dead loop after nightly-2024-02-12 #121289

Closed

heiher added a commit to heiher/rust that referenced this pull request Oct 18, 2024

Default to the medium code model on OpenHarmony LoongArch target

275ec06

The context for this is rust-lang#130266: setting the medium code model for the 'loongarch64-linux-ohos' target.

heiher mentioned this pull request Oct 18, 2024

Default to the medium code model on OpenHarmony LoongArch target #131874

Merged

nikic added a commit to nikic/rust that referenced this pull request Feb 17, 2025

Update default loongarch code model in docs

9cbc310

Since rust-lang#130266 loongarch defaults to medium code model.

nikic mentioned this pull request Feb 17, 2025

Update default loongarch code model in docs #137166

Merged

xen0n mentioned this pull request Oct 13, 2025

[ABI] Default to the medium code model across the board loongson-community/discussions#43

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target: default to the medium code model on LoongArch targets#130266