Make it explicit that the analysis direction is constant.

This also makes the value immediately available for optimizations.
Previously those functions were neither inline nor generic and so their
definition was unavailable when using data flow framework from other
crates.

In https://reviews.llvm.org/D125556 upstream changed sext() and zext()
to allow some no-op cases, which previously required use of the *OrSelf()
methods, which I assume is what was going on here. The *OrSelf() methods
got removed in https://reviews.llvm.org/D125559 after two weeks of
deprecation because they came with some bonus (probably-undesired)
behavior. Since the behavior of sext() and zext() changed slightly, I
kept the old *OrSelf() calls in LLVM 14 and earlier, and only use the
new version in LLVM 15.

r? @nikic

…rrors

Add regresion test for rust-lang#95307

Closes rust-lang#95307
r? `@compiler-errors`

…t, r=davidtwco

Remove `AlwaysLiveLocals` wrapper struct

It is just a wrapper around a `BitSet` and
doesn't have any functionality of its own.

Change `Direction::{is_forward,is_backward}` functions into constants

Make it explicit that the analysis direction is constant.

This also makes the value immediately available for optimizations.
Previously those functions were neither inline nor generic and so their
definition was unavailable when using data flow framework from other
crates.

RustWrapper: adapt to APInt API changes in LLVM 15

In https://reviews.llvm.org/D125556 upstream changed sext() and zext()
to allow some no-op cases, which previously required use of the *OrSelf()
methods, which I assume is what was going on here. The *OrSelf() methods
got removed in https://reviews.llvm.org/D125559 after two weeks of
deprecation because they came with some bonus (probably-undesired)
behavior. Since the behavior of sext() and zext() changed slightly, I
kept the old *OrSelf() calls in LLVM 14 and earlier, and only use the
new version in LLVM 15.

r? `@nikic`

Use more targeted suggestion when confusing i8 with std::i8

r? `@compiler-errors`