Use rust rather than LLVM target features in the target spec #149173

bjorn3 · 2025-11-21T10:15:48Z

This works better with non-LLVM codegen backends.

rustbot · 2025-11-21T10:15:50Z

Some changes occurred in compiler/rustc_codegen_gcc

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

rustbot · 2025-11-21T10:15:52Z

rustbot has assigned @chenyukang.
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RalfJung · 2025-11-21T10:58:46Z

I haven't looked at the code yet, but I like the general direction!

The doc comment for https://doc.rust-lang.org/nightly/nightly-rustc/rustc_target/spec/struct.TargetOptions.html#structfield.features should also be updated.

chenyukang · 2025-11-22T01:19:21Z

haven't touched this part, so @rustbot reroll

lcnr · 2025-11-24T18:51:01Z

@rustbot reroll

RalfJung · 2025-11-24T18:53:32Z

r? @RalfJung

RalfJung

Another nice step towards pushing LLVM target features out of the core of the compiler. :)

View changes since this review

compiler/rustc_target/src/spec/mod.rs

compiler/rustc_interface/src/util.rs

compiler/rustc_codegen_ssa/src/target_features.rs

compiler/rustc_codegen_llvm/src/llvm_util.rs

RalfJung · 2025-11-25T14:37:27Z

Thanks, LGTM! r=me after squashing the history so we don't have "fix" commits.

This works better with non-LLVM codegen backends.

bjorn3 · 2025-11-25T14:40:13Z

@bors r=RalfJung

bors · 2025-11-25T14:40:22Z

📌 Commit fedbccd has been approved by RalfJung

It is now in the queue for this repository.

…r=RalfJung Use rust rather than LLVM target features in the target spec This works better with non-LLVM codegen backends.

Rollup of 9 pull requests Successful merges: - #147936 (Offload intrinsic) - #148358 (Fix some issues around `rustc_public`) - #148452 (Mangle symbols with a mangled name close to PDB limits with v0 instead of legacy mangling to avoid linker errors) - #148751 (Build gnullvm toolchains on Windows natively) - #148951 (rustc_target: aarch64: Remove deprecated FEAT_TME) - #149173 (Use rust rather than LLVM target features in the target spec) - #149307 (Deny const auto traits) - #149312 (Mark riscv64gc-unknown-linux-musl as tier 2 target) - #149341 (Add `Copy` to some AST enums.) r? `@ghost` `@rustbot` modify labels: rollup

Rollup of 12 pull requests Successful merges: - #147936 (Offload intrinsic) - #148358 (Fix some issues around `rustc_public`) - #148452 (Mangle symbols with a mangled name close to PDB limits with v0 instead of legacy mangling to avoid linker errors) - #148751 (Build gnullvm toolchains on Windows natively) - #148951 (rustc_target: aarch64: Remove deprecated FEAT_TME) - #149149 ([rustdoc] misc search index cleanups) - #149173 (Use rust rather than LLVM target features in the target spec) - #149307 (Deny const auto traits) - #149312 (Mark riscv64gc-unknown-linux-musl as tier 2 target) - #149317 (Handle inline asm in has_ffi_unwind_calls) - #149326 (Remove unused `Clone` derive on `DelayedLint`) - #149341 (Add `Copy` to some AST enums.) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #149173 - bjorn3:target_spec_rust_features, r=RalfJung Use rust rather than LLVM target features in the target spec This works better with non-LLVM codegen backends.

Rollup of 12 pull requests Successful merges: - rust-lang/rust#147936 (Offload intrinsic) - rust-lang/rust#148358 (Fix some issues around `rustc_public`) - rust-lang/rust#148452 (Mangle symbols with a mangled name close to PDB limits with v0 instead of legacy mangling to avoid linker errors) - rust-lang/rust#148751 (Build gnullvm toolchains on Windows natively) - rust-lang/rust#148951 (rustc_target: aarch64: Remove deprecated FEAT_TME) - rust-lang/rust#149149 ([rustdoc] misc search index cleanups) - rust-lang/rust#149173 (Use rust rather than LLVM target features in the target spec) - rust-lang/rust#149307 (Deny const auto traits) - rust-lang/rust#149312 (Mark riscv64gc-unknown-linux-musl as tier 2 target) - rust-lang/rust#149317 (Handle inline asm in has_ffi_unwind_calls) - rust-lang/rust#149326 (Remove unused `Clone` derive on `DelayedLint`) - rust-lang/rust#149341 (Add `Copy` to some AST enums.) r? `@ghost` `@rustbot` modify labels: rollup

…r=RalfJung Use rust rather than LLVM target features in the target spec This works better with non-LLVM codegen backends.

Rollup of 12 pull requests Successful merges: - rust-lang#147936 (Offload intrinsic) - rust-lang#148358 (Fix some issues around `rustc_public`) - rust-lang#148452 (Mangle symbols with a mangled name close to PDB limits with v0 instead of legacy mangling to avoid linker errors) - rust-lang#148751 (Build gnullvm toolchains on Windows natively) - rust-lang#148951 (rustc_target: aarch64: Remove deprecated FEAT_TME) - rust-lang#149149 ([rustdoc] misc search index cleanups) - rust-lang#149173 (Use rust rather than LLVM target features in the target spec) - rust-lang#149307 (Deny const auto traits) - rust-lang#149312 (Mark riscv64gc-unknown-linux-musl as tier 2 target) - rust-lang#149317 (Handle inline asm in has_ffi_unwind_calls) - rust-lang#149326 (Remove unused `Clone` derive on `DelayedLint`) - rust-lang#149341 (Add `Copy` to some AST enums.) r? `@ghost` `@rustbot` modify labels: rollup

Rollup of 12 pull requests Successful merges: - rust-lang/rust#147936 (Offload intrinsic) - rust-lang/rust#148358 (Fix some issues around `rustc_public`) - rust-lang/rust#148452 (Mangle symbols with a mangled name close to PDB limits with v0 instead of legacy mangling to avoid linker errors) - rust-lang/rust#148751 (Build gnullvm toolchains on Windows natively) - rust-lang/rust#148951 (rustc_target: aarch64: Remove deprecated FEAT_TME) - rust-lang/rust#149149 ([rustdoc] misc search index cleanups) - rust-lang/rust#149173 (Use rust rather than LLVM target features in the target spec) - rust-lang/rust#149307 (Deny const auto traits) - rust-lang/rust#149312 (Mark riscv64gc-unknown-linux-musl as tier 2 target) - rust-lang/rust#149317 (Handle inline asm in has_ffi_unwind_calls) - rust-lang/rust#149326 (Remove unused `Clone` derive on `DelayedLint`) - rust-lang/rust#149341 (Add `Copy` to some AST enums.) r? `@ghost` `@rustbot` modify labels: rollup

…-fix, r=Amanieu Fix d32 usage in Arm target specs Fixes rust-lang#149399 - after checking with an LLVM engineer Rust's feature implications do correctly map to LLVM's. The target specs originally had +vfp3,+d16, but were mistakenly fixed to +vfp3,-d32 which disables vfp3 again. Some targets specify +vfp2,-d32, and since vfp2 shouldn't imply d32 the -d32 is unneeded. The list of Arm features is quite old and since Arm is now a target maintainer of many of them we'll go in and update them. We should probably add vfp3d16 and similar as rust has no way to express these right now after d16 was removed. The LLVM features expand like this: ``` vfp4 -> vfp3 + fp16 + vfp4d16 + vfp4sp vfp4d16 -> vfp3d16 + fp16 + fp64 + vfp4d16sp vfp4sp -> vfp3sp + fp16 + d32 + vfp4d16sp vfp4d16sp -> vfp3d16sp + fp16 vfp3 -> vfp2 + vfp3d16 + vfp3sp vfp3d16 -> vfp2 + fp64 + vfp3d16sp vfp3sp -> vfp2 + d32 + vfp3d16sp vfp3d16sp -> vfp2sp vfp2 -> vfp2sp + fp64 vfp2sp -> fpregs ``` `-neon` might be unnecessary too in many of these cases, but some default CPUs that Rust specifies will turn Neon on so that needs a bit more care. I can't see any LLVM cpus that enable D32. Old description: > Fixes rust-lang#149399 - this implication was likely a mistake and isn't enforced by LLVM. This is is a breaking change and any users specifying `vfp2/3/4` via `-Ctarget-features` or the `target_feature` attribute will need to add `d32` in to get the same behaviour. The target features are unstable so this is ok for Rust, and this is necessary as otherwise there's no way to specify a `vfp2-d16` configuration, for example. > > I expect these targets would have been broken by rust-lang#149173 as `-d32` would have disabled any `+vfpX` feature before it. With the removal of the implication the `-d32` went back to being unnecessary, but I've removed it anyway. > > As `@RalfJung` pointed out, thumbv7a-nuttx-eabihf looks to have been relying on this implication so I've added `+d32` to it's target spec.

…-fix, r=Amanieu Fix d32 usage in Arm target specs Fixes rust-lang#149399 - after checking with an LLVM engineer Rust's feature implications do correctly map to LLVM's. The target specs originally had +vfp3,+d16, but were mistakenly fixed to +vfp3,-d32 which disables vfp3 again. Some targets specify +vfp2,-d32, and since vfp2 shouldn't imply d32 the -d32 is unneeded. The list of Arm features is quite old and since Arm is now a target maintainer of many of them we'll go in and update them. We should probably add vfp3d16 and similar as rust has no way to express these right now after d16 was removed. The LLVM features expand like this: ``` vfp4 -> vfp3 + fp16 + vfp4d16 + vfp4sp vfp4d16 -> vfp3d16 + fp16 + fp64 + vfp4d16sp vfp4sp -> vfp3sp + fp16 + d32 + vfp4d16sp vfp4d16sp -> vfp3d16sp + fp16 vfp3 -> vfp2 + vfp3d16 + vfp3sp vfp3d16 -> vfp2 + fp64 + vfp3d16sp vfp3sp -> vfp2 + d32 + vfp3d16sp vfp3d16sp -> vfp2sp vfp2 -> vfp2sp + fp64 vfp2sp -> fpregs ``` `-neon` might be unnecessary too in many of these cases, but some default CPUs that Rust specifies will turn Neon on so that needs a bit more care. I can't see any LLVM cpus that enable D32. Old description: > Fixes rust-lang#149399 - this implication was likely a mistake and isn't enforced by LLVM. This is is a breaking change and any users specifying `vfp2/3/4` via `-Ctarget-features` or the `target_feature` attribute will need to add `d32` in to get the same behaviour. The target features are unstable so this is ok for Rust, and this is necessary as otherwise there's no way to specify a `vfp2-d16` configuration, for example. > > I expect these targets would have been broken by rust-lang#149173 as `-d32` would have disabled any `+vfpX` feature before it. With the removal of the implication the `-d32` went back to being unnecessary, but I've removed it anyway. > > As ``@RalfJung`` pointed out, thumbv7a-nuttx-eabihf looks to have been relying on this implication so I've added `+d32` to it's target spec.

rustbot assigned chenyukang Nov 21, 2025

bjorn3 mentioned this pull request Nov 21, 2025

target-spec-toml draft davidtwco/rfcs#5

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rustbot assigned lcnr and unassigned chenyukang Nov 22, 2025

rustbot assigned WaffleLapkin and unassigned lcnr Nov 24, 2025

rustbot assigned RalfJung and unassigned WaffleLapkin Nov 24, 2025

RalfJung requested changes Nov 25, 2025

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rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 25, 2025

bjorn3 added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Nov 25, 2025

bjorn3 mentioned this pull request Nov 25, 2025

miri ignores -Ctarget-cpu since nightly-2025-11-10 #149314

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Use rust rather than LLVM target features in the target spec

fedbccd

This works better with non-LLVM codegen backends.

bjorn3 force-pushed the target_spec_rust_features branch from 658763b to fedbccd Compare November 25, 2025 14:40

bors removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Nov 25, 2025

bors added the S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. label Nov 25, 2025

jhpratt added a commit to jhpratt/rust that referenced this pull request Nov 26, 2025

Rollup merge of rust-lang#149173 - bjorn3:target_spec_rust_features, …

e8925e2

…r=RalfJung Use rust rather than LLVM target features in the target spec This works better with non-LLVM codegen backends.

jhpratt mentioned this pull request Nov 26, 2025

Rollup of 9 pull requests #149342

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Zalathar mentioned this pull request Nov 26, 2025

Rollup of 12 pull requests #149351

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bors merged commit 3b531a1 into rust-lang:main Nov 26, 2025
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rustbot added this to the 1.93.0 milestone Nov 26, 2025

rust-timer added a commit that referenced this pull request Nov 26, 2025

Unrolled build for #149173

b85362c

Rollup merge of #149173 - bjorn3:target_spec_rust_features, r=RalfJung Use rust rather than LLVM target features in the target spec This works better with non-LLVM codegen backends.

bjorn3 deleted the target_spec_rust_features branch November 26, 2025 18:35

adamgemmell mentioned this pull request Dec 1, 2025

Fix d32 usage in Arm target specs #149512

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Use rust rather than LLVM target features in the target spec #149173

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