nll: correctly deal with bivariance
fixes#104409
when in a bivariant context, relating stuff should always trivially succeed. Also changes the mir validator to correctly deal with higher ranked regions.
r? types cc ``@RalfJung``
Record `LocalDefId` in HIR nodes instead of a side table
This is part of an attempt to remove the `HirId -> LocalDefId` table from HIR.
This attempt is a prerequisite to creation of `LocalDefId` after HIR lowering (https://github.com/rust-lang/rust/pull/96840), by controlling how `def_id` information is accessed.
This first part adds the information to HIR nodes themselves instead of a table.
The second part is https://github.com/rust-lang/rust/pull/103902
The third part will be to make `hir::Visitor::visit_fn` take a `LocalDefId` as last parameter.
The fourth part will be to completely remove the side table.
Perform simple scalar replacement of aggregates (SROA) MIR opt
This is a re-open of https://github.com/rust-lang/rust/pull/85796
I copied the debuginfo implementation (first commit) from `@eddyb's` own SROA PR.
This pass replaces plain field accesses by simple locals when possible.
To be eligible, the replaced locals:
- must not be enums or unions;
- must not be used whole;
- must not have their address taken.
The storage and deinit statements are duplicated on each created local.
cc `@tmiasko` who reviewed the former version of this PR.
interpret: support for per-byte provenance
Also factors the provenance map into its own module.
The third commit does the same for the init mask. I can move it in a separate PR if you prefer.
Fixes https://github.com/rust-lang/miri/issues/2181
r? `@oli-obk`
Add new MIR constant propagation based on dataflow analysis
The current constant propagation in `rustc_mir_transform/src/const_prop.rs` fails to handle many cases that would be expected from a constant propagation optimization. For example:
```rust
let x = if true { 0 } else { 0 };
```
This pull request adds a new constant propagation MIR optimization pass based on the existing dataflow analysis framework. Since most of the analysis is not unique to constant propagation, a generic framework has been extracted. It works on top of the existing framework and could be reused for other optimzations.
Closes#80038. Closes#81605.
## Todo
### Essential
- [x] [Writes to inactive enum variants](https://github.com/rust-lang/rust/pull/101168#pullrequestreview-1089493974). Resolved by rejecting the registration of places with downcast projections for now. Could be improved by flooding other variants if mutable access to a variant is observed.
- [X] Handle [`StatementKind::CopyNonOverlapping`](https://github.com/rust-lang/rust/pull/101168#discussion_r957774914). Resolved by flooding the destination.
- [x] Handle `UnsafeCell` / `!Freeze` correctly.
- [X] Overflow propagation of `CheckedBinaryOp`: Decided to not propagate if overflow flag is `true` (`false` will still be propagated)
- [x] More documentation in general.
- [x] Arguments for correctness, documentation of necessary assumptions.
- [x] Better performance, or alternatively, require `-Zmir-opt-level=3` for now.
### Extra
- [x] Add explicit unreachability, i.e. upgrading the lattice from $\mathbb{P} \to \mathbb{V}$ to $\set{\bot} \cup (\mathbb{P} \to \mathbb{V})$.
- [x] Use storage statements to improve precision.
- [ ] Consider opening issue for duplicate diagnostics: https://github.com/rust-lang/rust/pull/101168#issuecomment-1276609950
- [ ] Flood moved-from places with $\bot$ (requires some changes for places with tracked projections).
- [ ] Add downcast projections back in.
- [ ] [Algebraic simplifications](https://github.com/rust-lang/rust/pull/101168#discussion_r957967878) (possibly with a shared API; done by old const prop).
- [ ] Propagation through slices / arrays.
- [ ] Find other optimizations that are done by old `const_prop.rs`, but not by this one.
