There are a few places were we have to construct it, though, and a few
places that are more invasive to change. To do this, we create a
constructor with a long obvious name.
Currently some `Allocation`s are interned, some are not, and it's very
hard to tell at a use point which is which.
This commit introduces `ConstAllocation` for the known-interned ones,
which makes the division much clearer. `ConstAllocation::inner()` is
used to get the underlying `Allocation`.
In some places it's natural to use an `Allocation`, in some it's natural
to use a `ConstAllocation`, and in some places there's no clear choice.
I've tried to make things look as nice as possible, while generally
favouring `ConstAllocation`, which is the type that embodies more
information. This does require quite a few calls to `inner()`.
The commit also tweaks how `PartialOrd` works for `Interned`. The
previous code was too clever by half, building on `T: Ord` to make the
code shorter. That caused problems with deriving `PartialOrd` and `Ord`
for `ConstAllocation`, so I changed it to build on `T: PartialOrd`,
which is slightly more verbose but much more standard and avoided the
problems.
Move ty::print methods to Drop-based scope guards
Primary goal is reducing codegen of the TLS access for each closure, which shaves ~3 seconds of bootstrap time over rustc as a whole.
Specifically, rename the `Const` struct as `ConstS` and re-introduce `Const` as
this:
```
pub struct Const<'tcx>(&'tcx Interned<ConstS>);
```
This now matches `Ty` and `Predicate` more closely, including using
pointer-based `eq` and `hash`.
Notable changes:
- `mk_const` now takes a `ConstS`.
- `Const` was copy, despite being 48 bytes. Now `ConstS` is not, so need a
we need separate arena for it, because we can't use the `Dropless` one any
more.
- Many `&'tcx Const<'tcx>`/`&Const<'tcx>` to `Const<'tcx>` changes
- Many `ct.ty` to `ct.ty()` and `ct.val` to `ct.val()` changes.
- Lots of tedious sigil fiddling.
Specifically, change `Ty` from this:
```
pub type Ty<'tcx> = &'tcx TyS<'tcx>;
```
to this
```
pub struct Ty<'tcx>(Interned<'tcx, TyS<'tcx>>);
```
There are two benefits to this.
- It's now a first class type, so we can define methods on it. This
means we can move a lot of methods away from `TyS`, leaving `TyS` as a
barely-used type, which is appropriate given that it's not meant to
be used directly.
- The uniqueness requirement is now explicit, via the `Interned` type.
E.g. the pointer-based `Eq` and `Hash` comes from `Interned`, rather
than via `TyS`, which wasn't obvious at all.
Much of this commit is boring churn. The interesting changes are in
these files:
- compiler/rustc_middle/src/arena.rs
- compiler/rustc_middle/src/mir/visit.rs
- compiler/rustc_middle/src/ty/context.rs
- compiler/rustc_middle/src/ty/mod.rs
Specifically:
- Most mentions of `TyS` are removed. It's very much a dumb struct now;
`Ty` has all the smarts.
- `TyS` now has `crate` visibility instead of `pub`.
- `TyS::make_for_test` is removed in favour of the static `BOOL_TY`,
which just works better with the new structure.
- The `Eq`/`Ord`/`Hash` impls are removed from `TyS`. `Interned`s impls
of `Eq`/`Hash` now suffice. `Ord` is now partly on `Interned`
(pointer-based, for the `Equal` case) and partly on `TyS`
(contents-based, for the other cases).
- There are many tedious sigil adjustments, i.e. adding or removing `*`
or `&`. They seem to be unavoidable.
Remove `NullOp::Box`
Follow up of #89030 and MCP rust-lang/compiler-team#460.
~1 month later nothing seems to be broken, apart from a small regression that #89332 (1aac85bb716c09304b313d69d30d74fe7e8e1a8e) shows could be regained by remvoing the diverging path, so it shall be safe to continue and remove `NullOp::Box` completely.
r? `@jonas-schievink`
`@rustbot` label T-compiler
polymorphization: shims and predicates
Supersedes #75737 and #75414. This pull request includes up some changes to polymorphization which hadn't landed previously and gets stage2 bootstrapping and the test suite passing when polymorphization is enabled. There are still issues with `type_id` and polymorphization to investigate but this should get polymorphization in a reasonable state to work on.
- #75737 and #75414 both worked but were blocked on having the rest of the test suite pass (with polymorphization enabled) with and without the PRs. It makes more sense to just land these so that the changes are in.
- #75737's changes remove the restriction of `InstanceDef::Item` on polymorphization, so that shims can now be polymorphized. This won't have much of an effect until polymorphization's analysis is more advanced, but it doesn't hurt.
- #75414's changes remove all logic which marks parameters as used based on their presence in predicates - given #75675, this will enable more polymorphization and avoid the symbol clashes that predicate logic previously sidestepped.
- Polymorphization now explicitly checks (and skips) foreign items, this is necessary for stage2 bootstrapping to work when polymorphization is enabled.
- The conditional determining the emission of a note adding context to a post-monomorphization error has been modified. Polymorphization results in `optimized_mir` running for shims during collection where that wouldn't happen previously, some errors are emitted during `optimized_mir` and these were considered post-monomorphization errors with the existing logic (more errors and shims have a `DefId` coming from the std crate, not the local crate), adding a note that resulted in tests failing. It isn't particularly feasible to change where polymorphization runs or prevent it from using `optimized_mir`, so it seemed more reasonable to not change the conditional.
- `characteristic_def_id_of_type` was being invoked during partitioning for self types of impl blocks which had projections that depended on the value of unused generic parameters of a function - this caused a ICE in a debuginfo test. If partitioning is enabled and the instance needs substitution then this is skipped. That test still fails for me locally, but not with an ICE, but it fails in a fresh checkout too, so 🤷♂️.
r? `@lcnr`
This commit removes the restriction of `InstanceDef::Item` on
polymorphization, so that shims can now be polymorphized.
Signed-off-by: David Wood <david.wood@huawei.com>
rustc adds notes to errors which happen post-monomorphization to
provide the user with helpful context (as these errors may rely on the
specific instantiations). To prevent this note being added where it is
not appropriate, the node is checked to originate outwith the current
crate. However, when polymorphization is enabled, this can result in
some errors (produced by `optimized_mir`) to occur earlier in
compilation than they normally would, during the collection of shims.
Some shims have ids that originate in the standard library, but these
should not receive the PME note, so instances for compiler-generated
functions no longer receive this note.
Signed-off-by: David Wood <david.wood@huawei.com>
