-0.0 is the actual neutral additive float, not +0.0, and this matters to codegen.

This is a follow-up to rust-lang#123159, but applied to Armv8-R.

This required llvm/llvm-project#88287 to work
properly. Now that this change exists in rustc's llvm, we can fix
Armv8-R's default fpu features. In Armv8-R's case, the default features
from LLVM for floating-point are sufficient, because there is no
integer-only variant of this architecture.

…ingjubilee

Fix target-cpu fpu features on Armv8-R.

This is a follow-up to rust-lang#123159, but applied to Armv8-R.

This required llvm/llvm-project#88287 to work properly. Now that this change exists in rustc's llvm, we can fix Armv8-R's default fpu features. In Armv8-R's case, the default features from LLVM for floating-point are sufficient, because there is no integer-only variant of this architecture.

…ux, r=RalfJung,jieyouxu

Use -0.0 in `intrinsics::simd::reduce_add_unordered`

-0.0 is the actual neutral additive float, not +0.0, and this matters to codegen.

try-job: aarch64-gnu

… r=compiler-errors

Correctly account for niche-optimized tags in rustc_transmute

This is a bit hacky, but it fixes the ICE and makes it possible to run the safe transmute check on every `mem::transmute` check we instantiate. I want to write a lint that needs to do that, but this stands well on its own.

cc `@jswrenn` here's the fix I alluded to yesterday :)

Fixes rust-lang#123693