Auto merge of #155674 - JonathanBrouwer:rollup-NG1fnzG, r=JonathanBrouwer

Rollup of 10 pull requests

Successful merges:

 - rust-lang/rust#146544 (mir-opt: Remove the workaround in UnreachableEnumBranching)
 - rust-lang/rust#154819 (Fix ICE for inherent associated type mismatches)
 - rust-lang/rust#155265 (Improved assumptions relating to isqrt)
 - rust-lang/rust#152576 (c-variadic: use `emit_ptr_va_arg` for  mips)
 - rust-lang/rust#154481 (Mark a function only used in nightly as nightly only)
 - rust-lang/rust#155614 (c-variadic: rename `VaList::arg` to `VaList::next_arg`)
 - rust-lang/rust#155630 (Make `//@ skip-filecheck` a normal compiletest directive)
 - rust-lang/rust#155641 (Remove non-working code for "running" mir-opt tests)
 - rust-lang/rust#155652 (Expand `Path::is_empty` docs)
 - rust-lang/rust#155656 (rustc_llvm: update opt-level handling for LLVM 23)

Author: bors

src/tests/directives.md

@@ -326,6 +326,8 @@ See [Pretty-printer](compiletest.md#pretty-printer-tests).
 The following directives affect how certain command-line tools are invoked, in
 test suites that use those tools:
 
+- `skip-filecheck` avoids running LLVM's `FileCheck` tool in tests that would normally run it to check output.
+  - Used by codegen tests, assembly tests, and mir-opt tests.
 - `filecheck-flags` adds extra flags when running LLVM's `FileCheck` tool.
   - Used by [codegen tests](compiletest.md#codegen-tests),
   [assembly tests](compiletest.md#assembly-tests), and