81b81faac1
Fix d32 usage in Arm target specs Fixes https://github.com/rust-lang/rust/issues/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 https://github.com/rust-lang/rust/issues/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 https://github.com/rust-lang/rust/pull/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. |
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| Cargo.toml | ||
| README.md | ||
rustc_target contains some very low-level details that are
specific to different compilation targets and so forth.
For more information about how rustc works, see the rustc dev guide.