Fixes rendering of the end of the `Configure and Make` section.

Keeps MIR cleaner, `StorageLive(_: !)` makes no sense anyway.

gdb will now reliably detect the lanugage as rust even before any
code is run.

Fixes rust-lang#39957

cc rust-lang#40373

This commit adds the entry `"fma\0"` to the whitelist for the x86
target. LLVM already supports fma but rustc did not directly. Previously
rustc permitted `+fma` in the target-feature argument and enabled the use
of FMA instructions, but it did not list it in the configuration and
attributes.

fixes rust-lang#40406

Better docs of rusty parts of typeck

… r=frewsxcv

Add missing example for Display::fmt

r? @frewsxcv

Allow lints to check Bodys directly

r? @eddyb

babysteps towards fixing https://github.com/Manishearth/rust-clippy/issues/1580 (disable certain lints in const environments, since they make no sense there (yet))

…r=nikomatsakis

Disallow subtyping between T and U in T: Unsize<U>.

Because `&mut T` can be coerced to `&mut U`, `T` and `U` must be unified invariantly. Fixes rust-lang#40288.
E.g. coercing `&mut [&'a X; N]` to `&mut [&'b X]` must require `'a` be equal to `'b`, otherwise you can convert between `&'a X` and `&'b X` (in either direction), potentially unsoundly lengthening lifetimes.

Subtyping here was introduced with `Unsize` in rust-lang#24619 (landed in 1.1, original PR is rust-lang#23785).

save-analysis: cope with lack of method data after a type error

Fixes rust-lang#39957

r? @eddyb

Fix missing backtick typo

Fixes rendering of the end of the `Configure and Make` section.

Improve the LLVM IR we generate for trivial functions, especially #[naked] ones.

These two small changes fix edef1c/libfringe#68:
* Don't emit ZST allocas, such as when returning `()`
* Don't emit a branch from LLVM's entry block to MIR's `START_BLOCK` unless needed
  * That is, if a loop branches back to it, although I'm not sure that's even valid MIR

Do not bother creating StorageLive for TyNever

Keeps MIR cleaner, `StorageLive(_: !)` makes no sense anyway.

r? @eddyb

Fix UB in repr(packed) tests

r? @arielb1

cc rust-lang#37609 and rust-lang#27060

emit !align attributes on stores of operand pairs

This avoids another case of missing-align UB. cc rust-lang#40373

r? @eddyb

Update gdbr tests

gdb will now reliably detect the lanugage as rust even before any code is run.

fix rust-lang#40294 obligation cause.body_id is not always a NodeExpr

Hello!

This fixes rust-lang#40294 and moves tests related to rust-lang#38812 to a much more sensible directory.

Thanks to @nikomatsakis and @eddyb

rustc: Whitelist the FMA target feature

This commit adds the entry `"fma\0"` to the whitelist for the x86
target. LLVM already supports fma but rustc did not directly. Previously
rustc permitted `+fma` in the target-feature argument and enabled the use
of FMA instructions, but it did not list it in the configuration and
attributes.

fixes rust-lang#40406