Since LLVM <https://reviews.llvm.org/D99439> (4c7f820, "Update
@llvm.powi to handle different int sizes for the exponent"), the size of
the integer can be specified for the `powi` intrinsic. Make use of this
so it is more obvious that integer size is consistent across all float
types.

This feature is available since LLVM 13 (October 2021). Based on
bootstrap we currently support >= 17.0, so there should be no support
problems.

These already exist in the compiler. Expose them in core so we can add
their library functions.

This adds missing functions for math operations on the new float types.

Platform support is pretty spotty at this point, since even platforms
with generally good support can be missing math functions.
`std/build.rs` is updated to reflect this.

`min`, `max`, and similar functions require external math routines. Add
these under the same gates as `std` math functions (`reliable_f16_math`
and `reliable_f128_math`).

Clarify what makes some operations not safe, and correct comment in the
default branch ("not safe" -> "safe").

Due to a LLVM bug, `f128` math functions link successfully but LLVM
chooses the wrong symbols (`long double` symbols rather than those for
binary128).

Since this is a notable problem that may surprise a number of users, add
a note about it.

Link: llvm/llvm-project#44744

Everything works as before, + now bootstrap allows for individually selecting LLVM
tools (e.g., `x dist opt llvm-dis`) to include in the dist artifact.

Signed-off-by: onur-ozkan <work@onurozkan.dev>

…petrochenkov

Add `REDUNDANT_IMPORTS` lint for new redundant import detection

Defaults to Allow for now. Stacked on rust-lang#123744 to avoid merge conflict, but much easier to review all as one.

r? petrochenkov

…wjasper

match lowering: Hide `Candidate` from outside the lowering algorithm

The internals of `Candidate` are tricky and a source of confusion. This PR makes it so we don't expose `Candidate`s outside the lowering algorithm. Now:
- false edges are handled in `lower_match_tree`;
- `lower_match_tree` takes a list of patterns as input;
- `lower_match_tree` returns a flat datastructure that contains only the necessary information.

r? `@matthewjasper`

Cleanup sys module to match house style

This moves a test file out of sys as it's just testing std types. Also cleans up some assorted bits including making the `use` statements match the house style.

Update target-spec metadata for loongarch64 targets

Add `f16` and `f128` math functions

This adds intrinsics and math functions for `f16` and `f128` floating point types. Support is quite limited and some things are broken so tests don't run on many platforms, but this provides a starting point.

Add myself as VxWorks target maintainer for reference

Hi, would be working on VxWorks regularly, thus adding myself as a target maintainer.
r? `@workingjubilee`

…rly, r=albertlarsan68,Kobzol

improve bootstrap to allow selecting llvm tools individually

Everything works as before, + now bootstrap allows for individually selecting LLVM tools (e.g., `x dist opt llvm-dis`) to include in the dist artifact.