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Add `overflow_checks` intrinsic This adds an intrinsic which allows code in a pre-built library to inherit the overflow checks option from a crate depending on it. This enables code in the standard library to explicitly change behavior based on whether `overflow_checks` are enabled, regardless of the setting used when standard library was compiled. This is very similar to the `ub_checks` intrinsic, and refactors the two to use a common mechanism. The primary use case for this is to allow the new `RangeFrom` iterator to yield the maximum element before overflowing, as requested [here](https://github.com/rust-lang/rust/issues/125687#issuecomment-2151118208). This PR includes a working `IterRangeFrom` implementation based on this new intrinsic that exhibits the desired behavior. [Prior discussion on Zulip](https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/Ability.20to.20select.20code.20based.20on.20.60overflow_checks.60.3F)
This crate is currently developed in-tree together with the compiler.
Our goal is to start publishing stable_mir into crates.io.
Until then, users will use this as any other rustc crate, by installing
the rustup component rustc-dev, and declaring stable-mir as an external crate.
See the StableMIR "Getting Started" guide for more information.
Stable MIR Design
The stable-mir will follow a similar approach to proc-macro2. Its implementation is split between two main crates:
stable_mir: Public crate, to be published on crates.io, which will contain the stable data structure as well as calls torustc_smirAPIs. The translation between stable and internal constructs will also be done in this crate, however, this is currently implemented in therustc_smircrate.1.rustc_smir: This crate implements the public APIs to the compiler. It is responsible for gathering all the information requested, and providing the data in its unstable form.
I.e.,
tools will depend on stable_mir crate,
which will invoke the compiler using APIs defined in rustc_smir.
I.e.:
┌──────────────────────────────────┐ ┌──────────────────────────────────┐
│ External Tool ┌──────────┐ │ │ ┌──────────┐ Rust Compiler │
│ │ │ │ │ │ │ │
│ │stable_mir| │ │ │rustc_smir│ │
│ │ │ ├──────────►| │ │ │
│ │ │ │◄──────────┤ │ │ │
│ │ │ │ │ │ │ │
│ │ │ │ │ │ │ │
│ └──────────┘ │ │ └──────────┘ │
└──────────────────────────────────┘ └──────────────────────────────────┘
More details can be found here: https://hackmd.io/XhnYHKKuR6-LChhobvlT-g?view
-
This is currently implemented in the
rustc_smircrate, but we are working to change that. ↩︎