Fixes rust-lang/rustc_codegen_cranelift#1441

In the future the actual target features that Cranelift enables should
be returned here, but for now this works.

Fixes rust-lang/rustc_codegen_cranelift#1438

This reduces the amount of duplicated code and the chance for bugs.

I validated the new code for correctness against LLVM using the
following script. It found many bugs in the implementation until I was
finally able to get it correct and passing.

```rust
//! Test for x86 pack instructions. Prints deterministic results, use it to compare backends.
use std::arch::x86_64::{self, __m128i, __m256i};
use rand::{rngs::SmallRng, Rng, SeedableRng};
fn main() {
    let rng = &mut SmallRng::seed_from_u64(123);
    for _ in 0..100_000 {
        unsafe {
            sse_test(rng);
            avx_test(rng);
        }
    }
}
unsafe fn sse_test(rng: &mut SmallRng) {
    print_sse_8(x86_64::_mm_packus_epi16(sse16(rng), sse16(rng)));
    print_sse_8(x86_64::_mm_packs_epi16(sse16(rng), sse16(rng)));
    print_sse_16(x86_64::_mm_packus_epi32(sse32(rng), sse32(rng)));
    print_sse_16(x86_64::_mm_packs_epi32(sse32(rng), sse32(rng)));
}
unsafe fn avx_test(rng: &mut SmallRng) {
    print_avx_8(x86_64::_mm256_packs_epi16(avx16(rng), avx16(rng)));
    print_avx_8(x86_64::_mm256_packs_epi16(avx16(rng), avx16(rng)));
    print_avx_16(x86_64::_mm256_packus_epi32(avx32(rng), avx32(rng)));
    print_avx_16(x86_64::_mm256_packs_epi32(avx32(rng), avx32(rng)));
}
fn print_sse_8(t: __m128i) {
    let ints = unsafe { std::mem::transmute::<_, [i8; 16]>(t) };
    println!("{ints:?}");
}
fn print_sse_16(t: __m128i) {
    let ints = unsafe { std::mem::transmute::<_, [i16; 8]>(t) };
    println!("{ints:?}");
}
fn print_avx_8(t: __m256i) {
    let ints = unsafe { std::mem::transmute::<_, [i8; 32]>(t) };
    println!("{ints:?}");
}
fn print_avx_16(t: __m256i) {
    let ints = unsafe { std::mem::transmute::<_, [i16; 16]>(t) };
    println!("{ints:?}");
}
fn sse16(rand: &mut SmallRng) -> __m128i {
    unsafe { std::mem::transmute([(); 8].map(|()| i16(rand))) }
}
fn sse32(rand: &mut SmallRng) -> __m128i {
    unsafe { std::mem::transmute([(); 4].map(|()| i32(rand))) }
}
fn avx16(rand: &mut SmallRng) -> __m256i {
    unsafe { std::mem::transmute([(); 16].map(|()| i16(rand))) }
}
fn avx32(rand: &mut SmallRng) -> __m256i {
    unsafe { std::mem::transmute([(); 8].map(|()| i32(rand))) }
}
fn i16(rand: &mut SmallRng) -> i16 {
    if rand.gen() {
        rand.gen::<i16>()
    } else {
        rand.gen::<i8>() as i16
    }
}
fn i32(rand: &mut SmallRng) -> i32 {
    if rand.gen() {
        rand.gen::<i32>()
    } else {
        rand.gen::<i16>() as i32
    }
}
```

Restructure x86 signed pack instructions

Use `rust-analyzer.rustc.source` to get r-a working with rustc

fix a couple of clippy warnings

To avoid the use of a mutable local variable, and because it reads more
nicely.

…ebuginfo.rs, r=petrochenkov

Improved support of collapse_debuginfo attribute for macros.

Added walk_chain_collapsed function to consider collapse_debuginfo attribute in parent macros in call chain.
Fixed collapse_debuginfo attribute processing for cranelift (there was if/else branches error swap).

cc rust-lang#100758

…twco

Disallow reference to `static mut` and adding `static_mut_ref` lint

Closes rust-lang#114447

r? `@scottmcm`

The changelog can be found here:
https://docs.rs/libloading/latest/libloading/changelog/r0_8_0/index.html

cc rust-lang/rustc_codegen_cranelift#1447

To enable improved accuracy of diagnostics in upcoming commits.

…use-somewhat, r=bjorn3

Format sources into the error message when loading codegen backends

cc rust-lang/rustc_codegen_cranelift#1447
cc `@bjorn3`

…li-obk

Replacement of rust-lang#114390: Add new intrinsic `is_var_statically_known` and optimize pow for powers of two

This adds a new intrinsic `is_val_statically_known` that lowers to [``@llvm.is.constant.*`](https://llvm.org/docs/LangRef.html#llvm-is-constant-intrinsic).` It also applies the intrinsic in the int_pow methods to recognize and optimize the idiom `2isize.pow(x)`. See rust-lang#114390 for more discussion.

While I have extended the scope of the power of two optimization from rust-lang#114390, I haven't added any new uses for the intrinsic. That can be done in later pull requests.

Note: When testing or using the library, be sure to use `--stage 1` or higher. Otherwise, the intrinsic will be a noop and the doctests will be skipped. If you are trying out edits, you may be interested in [`--keep-stage 0`](https://rustc-dev-guide.rust-lang.org/building/suggested.html#faster-builds-with---keep-stage).

Fixes rust-lang#47234
Resolves rust-lang#114390
`@Centri3`

This makes it easier to patch cg_clif to be statically linked as part of
rustc.

Fixes rust-lang/rustc_codegen_cranelift#1446

This contains a fix for a recently introduced warning.

…clif-2024-01-26