Compiler does not recognize LLVM supported target-features

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1

Hello, first time poster here so please bear with me.

I'm currently trying to compile a library with the target "armv7r-none-eabihf". I also need to specify some target-features as the library is supposed to integrate with some C-code on a microcontroller. The flags needed are "vfp3d16" and "strict-align" and I get the following error.

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Even though the features are clearly specified in the list when I run "rustc --target=armv7r-none-eabi --print target-features". I guess there is a difference between rustc and llvm supported features but I cannot find any information on this.

2

It's not an error, just a warning that rustc doesn't know what those mean, but it will pass it on to LLVM. Have you checked the binary?

3

Okay, so the compiler flags will be passed on to the LLVM but rustc warns that it do not recognize them? No, I have not checked the binary yet. Is there something special I should look for?

4

Rustc has a hard coded list of target features for each architecture. These are the only ones for which #[cfg(target_feature = "...")] and #[target_feature(enable = "...")] work. All other target features are still passed through to LLVM with -Ctarget-feature, but will give a warning and may change in future LLVM versions. The full list of known target features can be found at https://github.com/rust-lang/rust/blob/155a5c2862c2939aa8464456ca9f358fbb213005/compiler/rustc_codegen_ssa/src/target_features.rs

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