AArch64 target feature cfgs are being incorrectly enabled #95122

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1. Amanieu

   added

   C-bugCategory: This is a bug.Category: This is a bug.

   O-AArch64Armv8-A or later processors in AArch64 modeArmv8-A or later processors in AArch64 mode

   on Mar 19, 2022
2. workingjubilee commented on Mar 19, 2022

   

   workingjubilee

   on Mar 19, 2022

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   Commenting out the match arm in to_llvm_features for a given mapping alters the emitted features:

           // Rust ties fp and neon together. In LLVM neon implicitly enables fp,
           // but we manually enable neon when a feature only implicitly enables fp
           ("aarch64", "f32mm") => smallvec!["f32mm", "neon"],
           // ("aarch64", "f64mm") => smallvec!["f64mm", "neon"],
           ("aarch64", "fhm") => smallvec!["fp16fml", "neon"],
           // ("aarch64", "fp16") => smallvec!["fullfp16", "neon"],
           ("aarch64", "jsconv") => smallvec!["jsconv", "neon"],
           // ("aarch64", "sve") => smallvec!["sve", "neon"],
           ("aarch64", "sve2") => smallvec!["sve2", "neon"],
           // ("aarch64", "sve2-aes") => smallvec!["sve2-aes", "neon"],
           ("aarch64", "sve2-sm4") => smallvec!["sve2-sm4", "neon"],
           // ("aarch64", "sve2-sha3") => smallvec!["sve2-sha3", "neon"],
           ("aarch64", "sve2-bitperm") => smallvec!["sve2-bitperm", "neon"],
           (_, s) => smallvec![s],

   Result is:

   $ rustc +stage1 --print cfg --target aarch64-unknown-linux-gnu | grep target_feature
   '+fp16' is not a recognized feature for this target (ignoring feature)
   '+fp16' is not a recognized feature for this target (ignoring feature)
   target_feature="f32mm"
   target_feature="fhm"
   target_feature="fp16"
   target_feature="jsconv"
   target_feature="llvm14-builtins-abi"
   target_feature="neon"
   target_feature="pmuv3"
   target_feature="sve2"
   target_feature="sve2-bitperm"
   target_feature="sve2-sm4"
   
3. pnkfelix

   added

   T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

   on Mar 22, 2022
4. Dylan-DPC

   added a commit that references this issue on Mar 22, 2022

   Rollup merge of rust-lang#91608 - workingjubilee:fold-neon-fp, r=Amanieu

   ...

   This issue will close once commit e77d593 is merged into the 'master' branch.

   e77d593
5. Dylan-DPC

   added a commit that references this issue on Mar 23, 2022

   Rollup merge of rust-lang#91608 - workingjubilee:fold-neon-fp, r=nagi…

   ...

   This issue will close once commit 67d6cc6 is merged into the 'master' branch.

   67d6cc6
6. bors

   closed this as completedin 67d6cc6on Mar 23, 2022
7. pthariensflame commented on Mar 24, 2022

   

   pthariensflame

   on Mar 24, 2022

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   @workingjubilee Should I open a separate issue for the pmuv3 part?
8. workingjubilee commented on Mar 24, 2022

   

   workingjubilee

   on Mar 24, 2022

   Last edited by workingjubilee

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   That seems to have been a preexisting feature but yes, if you believe it is in error then feel free to open a new issue about it.

   EDIT: Ah, yeah, I think our target for darwin isn't "an M1", in actuality, and that's what's causing conflict.
9. pthariensflame commented on Mar 25, 2022

   

   pthariensflame

   on Mar 25, 2022

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   @workingjubilee Alright; I've opened #95319.