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Visit move out of `_0` when visiting `return`
Closes https://github.com/rust-lang/rust/issues/72032
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I also added test cases to make sure the optimization can fire on all of
these cases:
```rust
fn case_1(o: Option<u8>) -> Option<u8> {
match o {
Some(u) => Some(u),
None => None,
}
}
fn case2(r: Result<u8, i32>) -> Result<u8, i32> {
match r {
Ok(u) => Ok(u),
Err(i) => Err(i),
}
}
fn case3(r: Result<u8, i32>) -> Result<u8, i32> {
let u = r?;
Ok(u)
}
```
Without MIR inlining, this still does not completely optimize away the
`?` operator because the `Try::into_result()`, `From::from()` and
`Try::from_error()` calls still exist. This does move us a bit closer to
that goal though because:
- We can now run the pass on mir-opt-level=1
- We no longer depend on the copy propagation pass running which is
unlikely to stabilize anytime soon.
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Const prop aggregates even if partially or fully modified
r? @wesleywiser
cc @rust-lang/wg-mir-opt I'm moderately scared of this change, but I'm confident in having reviewed all the cases.
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Remove ast::{Ident, Name} reexports.
The reexport of `Symbol` into `Name` confused me.
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Rollup of 8 pull requests
Successful merges:
- #70834 (Add core::future::{pending,ready})
- #71839 (Make BTreeMap::new and BTreeSet::new const)
- #71890 (Simplify the error Registry methods a little)
- #71942 (Shrink `LocalDecl`)
- #71947 (Dead-code pass highlights too much of impl functions)
- #71981 (Fix `strip-priv-imports` pass name in the rustdoc documentation)
- #72018 (Fix canonicalization links)
- #72031 (Better documentation for io::Read::read() return value)
Failed merges:
r? @ghost
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Shrink `LocalDecl`
`LocalDecl` contributes 4-8% of peak heap memory usage on a range of benchmarks. This PR reduces its size from 128 bytes to 56 bytes on 64-bit, and does some clean-ups as well.
r? @matthewjasper
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Renamed "undef" -> "uninit"
1. InvalidUndefBytes -> InvalidUninitBytes
2. ScalarMaybeUndef -> ScalarMaybeUninit
3. UndefMask -> InitMask
Related issue #71193
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Use a single enum for the kind of a const context
This adds a `ConstContext` enum to the `rustc_hir` crate and method that can be called via `tcx.hir()` to get the `ConstContext` for a given body owner. This arose from discussion in #71824.
r? @oli-obk
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1. InvalidUndefBytes -> InvalidUninitBytes
2. ScalarMaybeUndef -> ScalarMaybeUninit
3. UndefMask -> InitMask
Related issue #71193
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Use the `impls` module to import pre-existing dataflow analyses
Currently, existing analyses live in the same module as the traits and types used to define new dataflow analyses. This muddles the [documentation for the `dataflow` module](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_mir/dataflow/index.html). After this PR, `dataflow::impls` will refer to concrete dataflow analyses, and `dataflow` to the generic interface.
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By boxing `local_info`.
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This commit adds some new `LocalDecl` methods:
- `with_source_info`, a most general constructor.
- `new`, a variant of `with_source_info` which represents the most
common use case.
- `internal` a modifying method (like the already present `immutable`).
It removes some old `LocalDecl` methods:
- `new_internal` and `new_local`, because they're subsumed by the new
methods.
- `new_return_place`, because it was identical to `new_temp`.
Finally, it cleans up all the use sites.
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Suggest to add missing feature when using gated const features
Fixes #71797
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Added MIR constant propagation of Scalars into function call arguments
Now for the function call arguments!
Caveats:
1. It's only being enabled at `mir-opt-2` or higher, because currently codegen gives performance regressions with this optimization.
2. Only propagates Scalars. Tuples and references (references are `Indirect`, right??) are not being propagated into as of this PR.
3. Maybe more tests would be nice?
4. I need (shamefully) to ask @wesleywiser to write in his words (or explain to me, and then I can write it down) why we want to ignore propagation into `ScalarPairs` and `Indirect` arguments.
r? @wesleywiser
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Miri: unleash all feature gates
IMO it is silly to unleash features that do not even have a feature gate yet, but not unleash features that do. The only thing this achieves is making unleashed mode annoying to use as we have to figure out the feature flags to enable (and not always do the error messages say what that flag is).
Given that the point of `-Z unleash-the-miri-inside-of-you` is to debug the Miri internals, I see no good reason for this extra hurdle. I cannot imagine a situation where we'd use that flag, realize the program also requires some feature gate, and then be like "oh I guess if this feature is unstable I will do something else". Instead, we'll always just add that flag to the code as well, so requiring the flag achieves nothing.
r? @oli-obk @ecstatic-morse
Fixes https://github.com/rust-lang/rust/issues/71630
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Use existing framework for backward dataflow analyses
This PR adds support for backward analyses to the dataflow framework and adds a new live variable analysis (based on the existing one in `librustc_mir/util/liveness.rs`). By adding these to the framework instead of having a separate API, all newly implemented backward dataflow analyses get cursors/visitors, `rustc_peek` tests, and graphviz visualizations for free. In the near-term, this makes it much easier to implement global dead-store elimination, and I believe that this will enable even more MIR optimizations in the future.
This PR makes many changes to the dataflow API, since some concepts and terminology only make sense in forward dataflow. Below is a list of the important changes.
- ~~`entry_set` -> `fixpoint` (the fixpoint for backward dataflow problems is after the block's terminator)~~
- `seek_{before,after}` -> `seek_{before,after}_primary_effect` (the unprefixed dataflow effect is now referred to as the "primary" effect instead of the "after" effect. The "before" effect remains the same, although I considered changing it to the "antecedent" effect. In both backward and forward dataflow, the "before" effect is applied prior to the "primary" effect. I feel very strongly that this is the correct choice, as it means consumers don't have to switch between `seek_before` and `seek_after` based on the direction of their analysis.
- `seek_after_assume_call_returns` is now gone. Users can use `ResultsCursor::apply_custom_effect` to emulate it.
- `visit_{statement,terminator}_exit` -> `visit_{statement,terminator}_after_primary_effect`
- `visit_{statement,terminator}` -> `visit_{statement,terminator}_before_primary_effect`
Implementing this also required refactoring the dataflow cursor implementation so it could work in both directions. This is a large percentage of the diff, since the cursor code is rather complex. The fact that the cursor is exhaustively tested in both directions should reassure whomever is unlucky enough to review this :rofl:.
In order to avoid computing the reverse CFG for forward dataflow analyses, I've added some hacks to the existing `mir::BodyAndCache` interface. I've requested changes to this interface that would let me implement this more efficiently.
r? @eddyb (feel free to reassign)
cc @rust-lang/wg-mir-opt
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Fix exceeding bitshifts not emitting for assoc. consts (properly this time, I swear!)
Fixes #69021 and fixes #71353.
As described in https://github.com/rust-lang/rust/issues/71353#issuecomment-617901923, this PR:
- adds a variant of `try_validation!` called `try_validation_pat!` that allows specific failures to be turned into validation failures (but returns the rest, unchanged), and
- allows `InvalidProgram` to be returned out of validation
r? @RalfJung
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fix rustdoc warnings
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Mark query function as must_use.
And use the `ensure()` version when the result is not needed.
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Implement RFC 2396: `#[target_feature]` 1.1
Tracking issue: #69098
r? @nikomatsakis
cc @gnzlbg @joshtriplett
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- Documented rationale of current solution
- Polished documentation
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This partially reverts commit 4b5b6cbe60a8dd1822cfa46c41cf1ad58c113e18,
reversing some changes made to 62b362472dbf8bdf43b252ac5ea53b527a8dbee3.
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also tweak InvalidDiscriminant message
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Have the per-query caches store the results on arenas
This PR leverages the cache for each query to serve as storage area for the query results.
It introduces a new cache `ArenaCache`, which moves the result to an arena,
and only stores the reference in the hash map.
This allows to remove a sizeable part of the usage of the global `TyCtxt` arena.
I only migrated queries that already used arenas before.
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Allow `Unreachable` terminators unconditionally in const-checking
If we ever actually reach an `Unreachable` terminator while executing, the MIR is ill-formed or the user's program is UB due to something like `unreachable_unchecked`. I don't think we need to forbid these in `qualify_min_const_fn`.
r? @oli-obk
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Allow `Downcast` projections unconditionally in const-checking
`ProjectionElem::Downcast` sounds scary, but it's really just the projection we use to access a particular enum variant. They usually appear in the lowering of a `match` statement, so they have been associated with control flow in const-checking, but they don't do any control flow by themselves. We already have a HIR pass that looks for `if` and `match` (even ones that have 1 or fewer reachable branches). That pass is double-checked by a MIR pass that looks for `SwitchInt`s and `FakeRead`s for match scrutinees. In my opinion, there's no need to look for `Downcast` as well.
r? @oli-obk
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