Wrap the whole LocalInfo in ClearCrossCrate.
MIR contains a lot of information about locals. The primary purpose of this information is the quality of borrowck diagnostics.
This PR aims to drop this information after MIR analyses are finished, ie. starting from post-cleanup runtime MIR.
Ensure `ptr::read` gets all the same LLVM `load` metadata that dereferencing does
I was looking into `array::IntoIter` optimization, and noticed that it wasn't annotating the loads with `noundef` for simple things like `array::IntoIter<i32, N>`. Trying to narrow it down, it seems that was because `MaybeUninit::assume_init_read` isn't marking the load as initialized (<https://rust.godbolt.org/z/Mxd8TPTnv>), which is unfortunate since that's basically its reason to exist.
The root cause is that `ptr::read` is currently implemented via the *untyped* `copy_nonoverlapping`, and thus the `load` doesn't get any type-aware metadata: no `noundef`, no `!range`. This PR solves that by lowering `ptr::read(p)` to `copy *p` in MIR, for which the backends already do the right thing.
Fortuitiously, this also improves the IR we give to LLVM for things like `mem::replace`, and fixes a couple of long-standing bugs where `ptr::read` on `Copy` types was worse than `*`ing them.
Zulip conversation: <https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/Move.20array.3A.3AIntoIter.20to.20ManuallyDrop/near/341189936>
cc `@erikdesjardins` `@JakobDegen` `@workingjubilee` `@the8472`
Fixes#106369Fixes#73258
Remove `box_syntax`
r? `@Nilstrieb`
This removes the feature `box_syntax`, which allows the use of `box <expr>` to create a Box, and finalises removing use of the feature from the compiler. `box_patterns` (allowing the use of `box <pat>` in a pattern) is unaffected.
It also removes `ast::ExprKind::Box` - the only way to create a 'box' expression now is with the rustc-internal `#[rustc_box]` attribute.
As a temporary measure to help users move away, `box <expr>` now parses the inner expression, and emits a `MachineApplicable` lint to replace it with `Box::new`
Closes#49733
Strengthen state tracking in const-prop
Some/many of the changes are replicated between both the const-prop lint and the const-prop optimization.
Behaviour changes:
- const-prop opt does not give a span to propagated values. This was useless as that span's primary purpose is to diagnose evaluation failure in codegen.
- we remove the `OnlyPropagateInto` mode. It was only used for function arguments, which are better modeled by a write before entry.
- the tracking of assignments and discriminants make clearer that we do nothing in `NoPropagation` mode or on indirect places.
Ensure value is on the on-disk cache before returning from `ensure()`.
The current logic for `ensure()` a query just checks that the node is green in the dependency graph.
However, a lot of places use `ensure()` to prevent the query from being called later. This is the case before stealing a query result.
If the query is actually green but the value is not available in the on-disk cache, `ensure` would return, but a subsequent call to the full query would run the code, and attempt to read from a stolen value.
This PR conforms the query system to the usage by checking whether the queried value is loadable from disk before returning.
Sadly, I can't manage to craft a proper test...
Should fix all instances of "attempted to read from stolen value".
Avoid unnecessary hashing
I noticed some stable hashing being done in a non-incremental build. It turns out that some of this is necessary to compute the crate hash, but some of it is not. Removing the unnecessary hashing is a perf win.
r? `@cjgillot`
I was looking into `array::IntoIter` optimization, and noticed that it wasn't annotating the loads with `noundef` for simple things like `array::IntoIter<i32, N>`.
Turned out to be a more general problem as `MaybeUninit::assume_init_read` isn't marking the load as initialized (<https://rust.godbolt.org/z/Mxd8TPTnv>), which is unfortunate since that's basically its reason to exist.
This PR lowers `ptr::read(p)` to `copy *p` in MIR, which fortuitiously also improves the IR we give to LLVM for things like `mem::replace`.
Rollup of 8 pull requests
Successful merges:
- #108754 (Retry `pred_known_to_hold_modulo_regions` with fulfillment if ambiguous)
- #108759 (1.41.1 supported 32-bit Apple targets)
- #108839 (Canonicalize root var when making response from new solver)
- #108856 (Remove DropAndReplace terminator)
- #108882 (Tweak E0740)
- #108898 (Set `LIBC_CHECK_CFG=1` when building Rust code in bootstrap)
- #108911 (Improve rustdoc-gui/tester.js code a bit)
- #108916 (Remove an unused return value in `rustc_hir_typeck`)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Do not consider `&mut *x` as mutating `x` in `CopyProp`
This PR removes an unfortunate overly cautious case from the current implementation.
Found by https://github.com/rust-lang/rust/pull/105274 cc `@saethlin`
Do not implement HashStable for HashSet (MCP 533)
This PR removes all occurrences of `HashSet` in query results, replacing it either with `FxIndexSet` or with `UnordSet`, and then removes the `HashStable` implementation of `HashSet`. This is part of implementing [MCP 533](https://github.com/rust-lang/compiler-team/issues/533), that is, removing the `HashStable` implementations of all collection types with unstable iteration order.
The changes are mostly mechanical. The only place where additional sorting is happening is in Miri's override implementation of the `exported_symbols` query.
The crate hash is needed:
- if debug assertions are enabled, or
- if incr. comp. is enabled, or
- if metadata is being generated, or
- if `-C instrumentation-coverage` is enabled.
This commit avoids computing the crate hash when these conditions are
all false, such as when doing a release build of a binary crate.
It uses `Option` to store the hashes when needed, rather than
computing them on demand, because some of them are needed in multiple
places and computing them on demand would make compilation slower.
The commit also removes `Owner::hash_without_bodies`. There is no
benefit to pre-computing that one, it can just be done in the normal
fashion.
Check for free regions in MIR validation
This turns https://github.com/rust-lang/rust/issues/108720 into a MIR validation failure that will reproduce without debug-assertions enabled.
```
error: internal compiler error: broken MIR in Item(WithOptConstParam { did: DefId(0:296 ~ futures_util[3805]::future::future::remote_handle::{impl#3}::poll), const_param_did: None }) (after pass ScalarReplacementOfAggregates) at bb0[0]:
Free regions in optimized runtime-post-cleanup MIR
--> /home/ben/.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.26/src/future/future/remote_handle.rs:96:13
|
96 | let this = self.project();
| ^^^^
```
Desugaring of drop and replace at MIR build
This commit desugars the drop and replace deriving from an
assignment at MIR build, avoiding the construction of the
`DropAndReplace` terminator (which will be removed in a following PR).
In order to retain the same error messages for replaces a new
`DesugaringKind::Replace` variant is introduced.
The changes in the borrowck are also useful for future work in moving drop elaboration
before borrowck, as no `DropAndReplace` would be present there anymore.
Notes on test diffs:
* `tests/ui/borrowck/issue-58776-borrowck-scans-children`: the assignment deriving from the desugaring kills the borrow.
* `tests/ui/async-await/async-fn-size-uninit-locals.rs`, `tests/mir-opt/issue_41110.test.ElaborateDrops.after.mir`, `tests/mir-opt/issue_41888.main.ElaborateDrops.after.mir`: drop elaboration generates (or reads from) a useless drop flag due to an issue with the dataflow analysis. Will be fixed independently by https://github.com/rust-lang/rust/pull/106430.
See https://github.com/rust-lang/rust/pull/104488 for more context
This commit desugars the drop and replace deriving from an
assignment at MIR build, avoiding the construction of the
DropAndReplace terminator (which will be removed in a followign PR)
In order to retain the same error messages for replaces a new
DesugaringKind::Replace variant is introduced.
Unify validity checks into a single query
Previously, there were two queries to check whether a type allows the 0x01 or zeroed bitpattern.
I am planning on adding a further initness to check in #100423, truly uninit for MaybeUninit, which would make this three queries. This seems overkill for such a small feature, so this PR unifies them into one.
I am not entirely happy with the naming and key type and open for improvements.
r? oli-obk
(This is a large commit. The changes to
`compiler/rustc_middle/src/ty/context.rs` are the most important ones.)
The current naming scheme is a mess, with a mix of `_intern_`, `intern_`
and `mk_` prefixes, with little consistency. In particular, in many
cases it's easy to use an iterator interner when a (preferable) slice
interner is available.
The guiding principles of the new naming system:
- No `_intern_` prefixes.
- The `intern_` prefix is for internal operations.
- The `mk_` prefix is for external operations.
- For cases where there is a slice interner and an iterator interner,
the former is `mk_foo` and the latter is `mk_foo_from_iter`.
Also, `slice_interners!` and `direct_interners!` can now be `pub` or
non-`pub`, which helps enforce the internal/external operations
division.
It's not perfect, but I think it's a clear improvement.
The following lists show everything that was renamed.
slice_interners
- const_list
- mk_const_list -> mk_const_list_from_iter
- intern_const_list -> mk_const_list
- substs
- mk_substs -> mk_substs_from_iter
- intern_substs -> mk_substs
- check_substs -> check_and_mk_substs (this is a weird one)
- canonical_var_infos
- intern_canonical_var_infos -> mk_canonical_var_infos
- poly_existential_predicates
- mk_poly_existential_predicates -> mk_poly_existential_predicates_from_iter
- intern_poly_existential_predicates -> mk_poly_existential_predicates
- _intern_poly_existential_predicates -> intern_poly_existential_predicates
- predicates
- mk_predicates -> mk_predicates_from_iter
- intern_predicates -> mk_predicates
- _intern_predicates -> intern_predicates
- projs
- intern_projs -> mk_projs
- place_elems
- mk_place_elems -> mk_place_elems_from_iter
- intern_place_elems -> mk_place_elems
- bound_variable_kinds
- mk_bound_variable_kinds -> mk_bound_variable_kinds_from_iter
- intern_bound_variable_kinds -> mk_bound_variable_kinds
direct_interners
- region
- intern_region (unchanged)
- const
- mk_const_internal -> intern_const
- const_allocation
- intern_const_alloc -> mk_const_alloc
- layout
- intern_layout -> mk_layout
- adt_def
- intern_adt_def -> mk_adt_def_from_data (unusual case, hard to avoid)
- alloc_adt_def(!) -> mk_adt_def
- external_constraints
- intern_external_constraints -> mk_external_constraints
Other
- type_list
- mk_type_list -> mk_type_list_from_iter
- intern_type_list -> mk_type_list
- tup
- mk_tup -> mk_tup_from_iter
- intern_tup -> mk_tup
Previously, there were two queries to check whether a type allows the
0x01 or zeroed bitpattern.
I am planning on adding a further initness to check, truly uninit for
MaybeUninit, which would make this three queries. This seems overkill
for such a small feature, so this PR unifies them into one.
As a part of drop elaboration, we identify dead unwinds, i.e., unwind
edges on a drop terminators which are known to be unreachable, because
there is no need to drop anything.
Previously, the data flow framework was informed about the dead unwinds,
and it assumed those edges are absent from MIR. Unfortunately, the data
flow framework wasn't consistent in maintaining this assumption.
In particular, if a block was reachable only through a dead unwind edge,
its state was propagated to other blocks still. This became an issue in
the context of change removes DropAndReplace terminator, since it
introduces initialization into cleanup blocks.
To avoid this issue, remove unreachable unwind edges before the drop
elaboration, and elaborate only blocks that remain reachable.
Correctly handle aggregates in DataflowConstProp
The previous implementation from https://github.com/rust-lang/rust/pull/107411 flooded target of an aggregate assignment with `Bottom`, corresponding to the `deinit` that the interpreter does.
As a consequence, when assigning `target = Enum::Variant#i(...)` all the `(target as Variant#j)` were at `Bottom` while they should have been `Top`.
This PR replaces that flooding with `Top`.
Aside, it corrects a second bug where the wrong place would be used to assign to enum variant fields, resulting to nothing happening.
Fixes https://github.com/rust-lang/rust/issues/108166
Enable instcombine for mutable reborrows
`instcombine` used to contain this comment, which is no longer accurate because there it is fine to copy `&mut _` in MIR:
```rust
// The dereferenced place must have type `&_`, so that we don't copy `&mut _`.
```
So let's try replacing that check with something much more permissive...
There are several `mk_foo`/`intern_foo` pairs, where the former takes an
iterator and the latter takes a slice. (This naming convention is bad,
but that's a fix for another PR.)
This commit changes several `mk_foo` occurrences into `intern_foo`,
avoiding the need for some `.iter()`/`.into_iter()` calls. Affected
cases:
- mk_type_list
- mk_tup
- mk_substs
- mk_const_list
Switch to `EarlyBinder` for `type_of` query
Part of the work to finish #105779 and implement https://github.com/rust-lang/types-team/issues/78.
Several queries `X` have a `bound_X` variant that wraps the output in `EarlyBinder`. This adds `EarlyBinder` to the return type of the `type_of` query and removes `bound_type_of`.
r? `@lcnr`
Implement partial support for non-lifetime binders
This implements support for non-lifetime binders. It's pretty useless currently, but I wanted to put this up so the implementation can be discussed.
Specifically, this piggybacks off of the late-bound lifetime collection code in `rustc_hir_typeck::collect::lifetimes`. This seems like a necessary step given the fact we don't resolve late-bound regions until this point, and binders are sometimes merged.
Q: I'm not sure if I should go along this route, or try to modify the earlier nameres code to compute the right bound var indices for type and const binders eagerly... If so, I'll need to rename all these queries to something more appropriate (I've done this for `resolve_lifetime::Region` -> `resolve_lifetime::ResolvedArg`)
cc rust-lang/types-team#81
r? `@ghost`
Rollup of 7 pull requests
Successful merges:
- #106347 (More accurate spans for arg removal suggestion)
- #108057 (Prevent some attributes from being merged with others on reexports)
- #108090 (`if $c:expr { Some($r:expr) } else { None }` =>> `$c.then(|| $r)`)
- #108092 (note issue for feature(packed_bundled_libs))
- #108099 (use chars instead of strings where applicable)
- #108115 (Do not ICE on unmet trait alias bounds)
- #108125 (Add new people to the compiletest review rotation)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Optimize `mk_region`
PR #107869 avoiding some interning under `mk_ty` by special-casing `Ty` variants with simple (integer) bodies. This PR does something similar for regions.
r? `@compiler-errors`
Don't ICE in `might_permit_raw_init` if reference is polymorphic
Emitting optimized MIR for a polymorphic function may require computing layout of a type that isn't (yet) known. This happens in the instcombine pass, for example. Let's fail gracefully in that condition.
cc `@saethlin`
fixes#107999
Handle discriminant in DataflowConstProp
cc ``@jachris``
r? ``@JakobDegen``
This PR attempts to extend the DataflowConstProp pass to handle propagation of discriminants. We handle this by adding 2 new variants to `TrackElem`: `TrackElem::Variant` for enum variants and `TrackElem::Discriminant` for the enum discriminant pseudo-place.
The difficulty is that the enum discriminant and enum variants may alias each another. This is the issue of the `Option<NonZeroUsize>` test, which is the equivalent of https://github.com/rust-lang/unsafe-code-guidelines/issues/84 with a direct write.
To handle that, we generalize the flood process to flood all the potentially aliasing places. In particular:
- any write to `(PLACE as Variant)`, either direct or through a projection, floods `(PLACE as OtherVariant)` for all other variants and `discriminant(PLACE)`;
- `SetDiscriminant(PLACE)` floods `(PLACE as Variant)` for each variant.
This implies that flooding is not hierarchical any more, and that an assignment to a non-tracked place may need to flood a tracked place. This is handled by `for_each_aliasing_place` which generalizes `preorder_invoke`.
As we deaggregate enums by putting `SetDiscriminant` last, this allows to propagate the value of the discriminant.
This refactor will allow to make https://github.com/rust-lang/rust/pull/107009 able to handle discriminants too.
Mir-Opt for copying enums with large discrepancies
I have been meaning to make this for quite a while, based off of this [hackmd](https://hackmd.io/`@ft4bxUsFT5CEUBmRKYHr7w/rJM8BBPzD).`
I'm not sure where to put this opt now that I've made it, so I'd appreciate suggestions on that!
It's also one long chain of statements, not sure if there's a more friendly format to make it.
r? `@tmiasko`
I would `r` oli but he's on leave so he suggested I `r` tmiasko or wesleywiser.
Treat Drop as a rmw operation
Previously, a Drop terminator was considered a move in MIR. This commit changes the behavior to only treat Drop as a mutable access to the dropped place.
In order for this change to be correct, we need to guarantee that
1. A dropped value won't be used again
2. Places that appear in a drop won't be used again before a
subsequent initialization.
We can ensure this to be correct at MIR construction because Drop will only be emitted when a variable goes out of scope, thus having:
* (1) as there is no way of reaching the old value. drop-elaboration
will also remove any uninitialized drop.
* (2) as the place can't be named following the end of the scope.
However, the initialization status, previously tracked by moves, should also be tied to the execution of a Drop, hence the additional logic in the dataflow analyses.
From discussion in [this thread](https://rust-lang.zulipchat.com/#narrow/stream/233931-t-compiler.2Fmajor-changes/topic/.60DROP.60.20to.20.60DROP_IF.60.20compiler-team.23558), originating from https://github.com/rust-lang/compiler-team/issues/558.
See also https://github.com/rust-lang/rust/pull/104488#discussion_r1085556010
Turn projections into copies in CopyProp.
The current implementation can leave behind projections that are moved out several times.
This PR widens the check to turn such moves into copies: a move out of a projection of a copy is equivalent to a copy of the original projection.
There is a distinction between running this on wasm and i686, even though they should be
identical. This technically is not _incorrect_, it's just an unexpected difference, which is
worth investigating, but not for correctness.
Remove both StorageLive and StorageDead in CopyProp.
Fixes https://github.com/rust-lang/rust/issues/107511https://github.com/rust-lang/rust/pull/106908 removed StorageDead without the accompanying StorageLive. In loops, execution would see repeated StorageLive, without any StorageDead, which is UB.
So when removing storage statements, we have to remove both StorageLive and StorageDead.
~I also added a MIR validation pass for StorageLive. It may be a bit overzealous.~
Currently, deriving on packed structs has some non-trivial limitations,
related to the fact that taking references on unaligned fields is UB.
The current approach to field accesses in derived code:
- Normal case: `&self.0`
- In a packed struct that derives `Copy`: `&{self.0}`
- In a packed struct that doesn't derive `Copy`: `&self.0`
Plus, we disallow deriving any builtin traits other than `Default` for any
packed generic type, because it's possible that there might be
misaligned fields. This is a fairly broad restriction.
Plus, we disallow deriving any builtin traits other than `Default` for most
packed types that don't derive `Copy`. (The exceptions are those where the
alignments inherently satisfy the packing, e.g. in a type with
`repr(packed(N))` where all the fields have alignments of `N` or less
anyway. Such types are pretty strange, because the `packed` attribute is
not having any effect.)
This commit introduces a new, simpler approach to field accesses:
- Normal case: `&self.0`
- In a packed struct: `&{self.0}`
In the latter case, this requires that all fields impl `Copy`, which is
a new restriction. This means that the following example compiles under
the old approach and doesn't compile under the new approach.
```
#[derive(Debug)]
struct NonCopy(u8);
#[derive(Debug)
#[repr(packed)]
struct MyType(NonCopy);
```
(Note that the old approach's support for cases like this was brittle.
Changing the `u8` to a `u16` would be enough to stop it working. So not
much capability is lost here.)
However, the other constraints from the old rules are removed. We can now
derive builtin traits for packed generic structs like this:
```
trait Trait { type A; }
#[derive(Hash)]
#[repr(packed)]
pub struct Foo<T: Trait>(T, T::A);
```
To allow this, we add a `T: Copy` bound in the derived impl and a `T::A:
Copy` bound in where clauses. So `T` and `T::A` must impl `Copy`.
We can now also derive builtin traits for packed structs that don't derive
`Copy`, so long as the fields impl `Copy`:
```
#[derive(Hash)]
#[repr(packed)]
pub struct Foo(u32);
```
This includes types that hand-impl `Copy` rather than deriving it, such as the
following, that show up in winapi-0.2:
```
#[derive(Clone)]
#[repr(packed)]
struct MyType(i32);
impl Copy for MyType {}
```
The new approach is simpler to understand and implement, and it avoids
the need for the `unsafe_derive_on_repr_packed` check.
One exception is required for backwards-compatibility: we allow `[u8]`
fields for now. There is a new lint for this,
`byte_slice_in_packed_struct_with_derive`.
Previously, a Drop terminator was considered a move in MIR.
This commit changes the behavior to only treat Drop as a mutable
access to the dropped place.
In order for this change to be correct, we need to guarantee that
a) A dropped value won't be used again
b) Places that appear in a drop won't be used again before a
subsequent initialization.
We can ensure this to be correct at MIR construction because Drop
will only be emitted when a variable goes out of scope,
thus having:
(a) as there is no way of reaching the old value. drop-elaboration
will also remove any uninitialized drop.
(b) as the place can't be named following the end of the scope.
However, the initialization status, previously tracked by moves,
should also be tied to the execution of a Drop, hence the
additional logic in the dataflow analyses.
Implement simple CopyPropagation based on SSA analysis
This PR extracts the "copy propagation" logic from https://github.com/rust-lang/rust/pull/106285.
MIR may produce chains of assignment between locals, like `_x = move? _y`.
This PR attempts to remove such chains by unifying locals.
The current implementation is a bit overzealous in turning moves into copies, and in removing storage statements.
Use stable metric for const eval limit instead of current terminator-based logic
This patch adds a `MirPass` that inserts a new MIR instruction `ConstEvalCounter` to any loops and function calls in the CFG. This instruction is used during Const Eval to count against the `const_eval_limit`, and emit the `StepLimitReached` error, replacing the current logic which uses Terminators only.
The new method of counting loops and function calls should be more stable across compiler versions (i.e., not cause crates that compiled successfully before, to no longer compile when changes to the MIR generation/optimization are made).
Also see: #103877
InstCombine away intrinsic validity assertions
This optimization (currently) fires 246 times on the standard library. It seems to fire hardly at all on the big crates in the benchmark suite. Interesting.
This patch adds a `MirPass` that tracks the number of back-edges and
function calls in the CFG, adds a new MIR instruction to increment a
counter every time they are encountered during Const Eval, and emit a
warning if a configured limit is breached.
There is a number of APIs that answer dominance queries. Previously they
were named either "dominates" or "is_dominated_by". Consistently use the
"dominates" form.
No functional changes.
- Eliminates all the `get_context` calls that async lowering created.
- Replace all `Local` `ResumeTy` types with `&mut Context<'_>`.
The `Local`s that have their types replaced are:
- The `resume` argument itself.
- The argument to `get_context`.
- The yielded value of a `yield`.
The `ResumeTy` hides a `&mut Context<'_>` behind an unsafe raw pointer, and the
`get_context` function is being used to convert that back to a `&mut Context<'_>`.
Ideally the async lowering would not use the `ResumeTy`/`get_context` indirection,
but rather directly use `&mut Context<'_>`, however that would currently
lead to higher-kinded lifetime errors.
See <https://github.com/rust-lang/rust/issues/105501>.
The async lowering step and the type / lifetime inference / checking are
still using the `ResumeTy` indirection for the time being, and that indirection
is removed here. After this transform, the generator body only knows about `&mut Context<'_>`.
Always permit ConstProp to exploit arithmetic identities
Fixes https://github.com/rust-lang/rust/issues/72751
Initially, I thought I would need to enable operand propagation then do something else, but actually https://github.com/rust-lang/rust/pull/74491 already has the fix for the issue in question! It looks like this optimization was put under MIR opt level 3 due to possible soundness/stability implications, then demoted further to MIR opt level 4 when MIR opt level 2 became associated with `--release`.
Perhaps in the past we were doing CTFE on optimized MIR? We aren't anymore, so this optimization has no stability implications.
r? `@oli-obk`
Improve syntax of `newtype_index`
This makes it more like proper Rust and also makes the implementation a lot simpler.
Mostly just turns weird flags in the body into proper attributes.
It should probably also be converted to an attribute macro instead of function-like, but that can be done in a future PR.
Remove the `..` from the body, only a few invocations used it and it's
inconsistent with rust syntax.
Use `;` instead of `,` between consts. As the Rust syntax gods inteded.
This removes the `custom` format functionality as its only user was
trivially migrated to using a normal format.
If a new use case for a custom formatting impl pops up, you can add it
back.
Custom MIR: Many more improvements
Commits are each atomic changes, best reviewed one at a time, with the exception that the last commit includes all the documentation.
### First commit
Unsafetyck was not correctly disabled before for `dialect = "built"` custom MIR. This is fixed and a regression test is added.
### Second commit
Implements `Discriminant`, `SetDiscriminant`, and `SwitchInt`.
### Third commit
Implements indexing, field, and variant projections.
### Fourth commit
Documents the previous commits and everything else.
There is some amount of weirdness here due to having to beat Rust syntax into cooperating with MIR concepts, but it hopefully should not be too much. All of it is documented.
r? `@oli-obk`
always check alignment during CTFE
We originally disabled alignment checks because they got in the way -- there are some things we do with the interpreter during CTFE which does not correspond to actually running user-written code, but is purely administrative, and we didn't want alignment checks there, so we just disabled them entirely. But with `-Zextra-const-ub-checks` we anyway had to figure out how to disable those alignment checks while doing checks in regular code. So now it is easy to enable CTFE alignment checking by default. Let's see what the perf consequences of that are.
r? `@oli-obk`
Various cleanups to dest prop
This makes fixing the issues identified in #105577 easier. A couple changes
- Use an enum with names instead of a bool
- Only call `remove_candidates_if` from one place instead of two. Doing it from two places is far too fragile, since any divergence in the behavior between those callsites is likely to be unsound.
- Remove `is_constant`. Right now we only merge locals, so this doesn't do anything, and the logic would be wrong if it did.
r? `@tmiasko`
Combine `ty::Projection` and `ty::Opaque` into `ty::Alias`
Implements https://github.com/rust-lang/types-team/issues/79.
This PR consolidates `ty::Projection` and `ty::Opaque` into a single `ty::Alias`, with an `AliasKind` and `AliasTy` type (renamed from `ty::ProjectionTy`, which is the inner data of `ty::Projection`) defined as so:
```
enum AliasKind {
Projection,
Opaque,
}
struct AliasTy<'tcx> {
def_id: DefId,
substs: SubstsRef<'tcx>,
}
```
Since we don't have access to `TyCtxt` in type flags computation, and because repeatedly calling `DefKind` on the def-id is expensive, these two types are distinguished with `ty::AliasKind`, conveniently glob-imported into `ty::{Projection, Opaque}`. For example:
```diff
match ty.kind() {
- ty::Opaque(..) =>
+ ty::Alias(ty::Opaque, ..) => {}
_ => {}
}
```
This PR also consolidates match arms that treated `ty::Opaque` and `ty::Projection` identically.
r? `@ghost`
Don't require owned data in `MaybeStorageLive`
Small improvement that avoids a clone. I don't expect this to have any noticeable perf effects, but better to have it than not to.
r? ``@tmiasko``
compiler: remove unnecessary imports and qualified paths
Some of these imports were necessary before Edition 2021, others were already in the prelude.
I hope it's fine that this PR is so spread-out across files :/
make retagging work even with 'unstable' places
This is based on top of https://github.com/rust-lang/rust/pull/105301. Only the last two commits are new.
While investigating https://github.com/rust-lang/unsafe-code-guidelines/issues/381 I realized that we would have caught this issue much earlier if the add_retag pass wouldn't bail out on assignments of the form `*ptr = ...`.
So this PR changes our retag strategy:
- When a new reference is created via `Rvalue::Ref` (or a raw ptr via `Rvalue::AddressOf`), we do the retagging as part of just executing that address-taking operation.
- For everything else, we still insert retags -- these retags basically serve to ensure that references stored in local variables (and their fields) are always freshly tagged, so skipping this for assignments like `*ptr = ...` is less egregious.
r? ```@oli-obk```
Re-enable removal of ZST writes to unions
This was previously disabled because Miri was lazily allocating unsized locals. But we aren't doing that anymore since https://github.com/rust-lang/rust/pull/98831, so we can have this optimization back.
feed resolver_for_lowering instead of storing it in a field
r? `@cjgillot`
opening this as
* a discussion for `no_hash` + `feedable` queries. I think we'll want those, but I don't quite understand why they are rejected beyond a double check of the stable hashes for situations where the query is fed but also read from incremental caches.
* and a discussion on removing all untracked fields from TyCtxt and setting it up so that they are fed queries instead
Disable top down MIR inlining
The current MIR inliner has exponential behavior in some cases: <https://godbolt.org/z/7jnWah4fE>. The cause of this is top-down inlining, where we repeatedly do inlining like `call_a() => { call_b(); call_b(); }`. Each decision on its own seems to make sense, but the result is exponential.
Disabling top-down inlining fundamentally prevents this. Each call site in the original, unoptimized source code is now considered for inlining exactly one time, which means that the total growth in MIR size is limited to number of call sites * inlining threshold.
Top down inlining may be worth re-introducing at some point, but it needs to be accompanied with a principled way to prevent this kind of behavior.
This fixes a number of correctness issues from the previous version. Additionally, we use a new
strategy which has much better performance charactersitics and also finds more opportunities to
apply the optimization.
Refine `instruction_set` MIR inline rules
Previously an exact match of the `instruction_set` attribute was required for an MIR inline to be considered. This change checks for an exact match *only* if the callee sets an `instruction_set` in the first place. When the callee does not declare an instruction set then it is considered to be platform agnostic code and it's allowed to be inline'd into the caller.
cc ``@oli-obk``
[Edit] Zulip Context: https://rust-lang.zulipchat.com/#narrow/stream/189540-t-compiler.2Fwg-mir-opt/topic/What.20exactly.20does.20the.20MIR.20optimizer.20do.3F
Previously an exact match of the `instruction_set` attribute was required for an MIR inline to be considered. This change checks for an exact match *only* if the callee sets an `instruction_set` in the first place. When the callee does not declare an instruction set then it is considered to be platform agnostic code and it's allowed to be inline'd into the caller.
