add miri strong mode for tree borrows

[quiode]

This PR depends on #154946. It tries to address rust-lang/unsafe-code-guidelines#584 (comment). It is part of a bachelor thesis supervised by @JoJoDeveloping and @RalfJung, for more information, see: Project_Description.pdf.
In Tree Borrows, Miri now checks for spurious writes on function entry, if no_writable is not set. This means that all mutable references on function entry have to be writable, violating this is Undefined Behaviour. The compiler can then make use of this in #154949.

[quiode]

r? @RalfJung

[rustbot]

RalfJung is not on the review rotation at the moment.
They may take a while to respond.

[rust-log-analyzer]

The job aarch64-gnu-llvm-21-1 failed! Check out the build log: (web) (plain enhanced) (plain)

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

Executing "/scripts/stage_2_test_set1.sh"
+ /scripts/stage_2_test_set1.sh
PR_CI_JOB set; skipping tidy
+ '[' 1 == 1 ']'
+ echo 'PR_CI_JOB set; skipping tidy'
+ SKIP_TIDY='--skip tidy'
+ ../x.py --stage 2 test --skip tidy --skip compiler --skip src
##[group]Building bootstrap
    Finished `dev` profile [unoptimized] target(s) in 0.04s
##[endgroup]
downloading https://static.rust-lang.org/dist/2026-03-05/rustfmt-nightly-aarch64-unknown-linux-gnu.tar.xz
---
To only update this specific test, also pass `--test-args cfg/suggest-alternative-name-on-target.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/cfg/suggest-alternative-name-on-target.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2" "--target=aarch64-unknown-linux-gnu" "--check-cfg" "cfg(test,FALSE)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/cfg/suggest-alternative-name-on-target" "-A" "unused" "-W" "unused_attributes" "-A" "internal_features" "-A" "incomplete_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/aarch64-unknown-linux-gnu/native/rust-test-helpers"
stdout: none
--- stderr -------------------------------
error: unexpected `cfg` condition value: `arm`
##[error]  --> /checkout/tests/ui/cfg/suggest-alternative-name-on-target.rs:5:7
   |
---
LL | #![deny(unexpected_cfgs)]
   |         ^^^^^^^^^^^^^^^
help: `arm` is an expected value for `target_arch`
   |
LL - #[cfg(target_abi = "arm")]
LL + #[cfg(target_arch = "arm")]
   |

error: unexpected `cfg` condition value: `gnu`
##[error]  --> /checkout/tests/ui/cfg/suggest-alternative-name-on-target.rs:12:7
   |
LL | #[cfg(target_arch = "gnu")]
   |       ^^^^^^^^^^^^^^^^^^^
   |
   = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
help: `gnu` is an expected value for `target_env`
   |
LL - #[cfg(target_arch = "gnu")]
LL + #[cfg(target_env = "gnu")]
   |

error: unexpected `cfg` condition value: `openbsd`
##[error]  --> /checkout/tests/ui/cfg/suggest-alternative-name-on-target.rs:19:7
   |

[RalfJung]

Thanks!

Could you make a Miri PR that doesn't depend on #154946? It should be possible to have a flag like -Zmiri-tree-borrows-writable with all the new TB logic, without having a new attribute. Ideally that is submitted as a PR in https://github.com/rust-lang/miri.

[rust-bors]

☔ The latest upstream changes (presumably #154958) made this pull request unmergeable. Please resolve the merge conflicts.