Simplify intrinsic::raw_eq in MIR when possible

[scottmcm]

After #150945 things can inline enough to have this end up specific enough that we can remove it, for example changing raw_eq::<[u8; 4]>(a, b) → Transmute(a) == Transmute(b).

The LLVM backend can also do this (and in more cases too) but we might as well do it in MIR instead when we can so it applies to all backends and other MIR optimizations can apply afterwards.

[scottmcm]

r? mir-opt

[rustbot]

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

[rustbot]

r? @JohnTitor

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[oli-obk]

@bors r+

View changes since this review

[rust-bors]

📌 Commit c468ee3 has been approved by oli-obk

It is now in the queue for this repository.

[rust-bors]

💔 Test for 1991ed3 failed: CI. Failed jobs:

• auto - dist-powerpc64le-linux-gnu (web logs, enhanced plaintext logs)
• auto - i686-gnu-nopt-2 (web logs, enhanced plaintext logs)

[rust-log-analyzer]

A job failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

##[endgroup]
Image input checksum 8fe117101010f8822f8547370f0fe29b5e9aae9ec788335c3294c5971797140ca1d0dfa0c1caf38c876f669e84123f603a0e01a5ed78c9a9d623c58be2bccb86
##[group]Building docker image for dist-powerpc64le-linux-gnu
Docker version 28.0.4, build b8034c0
Error response from daemon: Get "https://ghcr.io/v2/": Get "https://ghcr.io/token?account=rust-lang&client_id=docker&offline_token=true&service=ghcr.io": context deadline exceeded (Client.Timeout exceeded while awaiting headers) (Client.Timeout exceeded while awaiting headers)
##[error]Process completed with exit code 1.
##[group]Run echo "disk usage:"
echo "disk usage:"
df -h
shell: /usr/bin/bash --noprofile --norc -e -o pipefail {0}

[scottmcm]

@bors retry (Error response from daemon: Get "https://ghcr.io/v2/": Get "https://ghcr.io/token?account=rust-lang&client_id=docker&offline_token=true&service=ghcr.io": context deadline exceeded (Client.Timeout exceeded while awaiting headers))