It existed only to bridge the divide between `rustc_query_system` and
`rustc_query_impl`. But enough pieces have been moved from the former to
the latter that the trait is no longer needed. Less indirection and
abstraction makes the code easier to understand.
It takes an `is_anon` argument, but it's now generic over `QueryFlags`,
which contains the same `is_anon` field. So the argument is no longer
necessary.
It's always `SemiDynamicQueryDispatcher`, so we can just use that type
directly. (This requires adding some explicit generic params to
`QueryDispatcherUnerased`.) Less indirection makes the code clearer, and
this is a prerequisite for the next commit, which is a much bigger
simplification.
Query keys must be stably hashable. Currently this requirement is
expressed as a where-clause on `impl QueryDispatcher for
SemiDynamicQueryDispatcher` and a where-clause on
`create_deferred_query_stack_frame`.
This commit removes those where-clause bounds and adds a single bound to
`QueryCache::Key`, which already has some other bounds. I.e. it
consolidates the bounds. It also gives them a name (`QueryCacheKey`) to
avoid repeating them. There is also a related `Key` trait in
`rustc_middle`; it should probably be merged with `QueryCacheKey` in the
future, but not today.
This cleanup helps with the next two commits, which do bigger
rearrangements, and where the where-clauses caused me some difficulties.
The previous commit moved some code from `rustc_query_system`, which
doesn't have access to `TyCtxt` and `QueryCtxt`, to `rustc_query_impl`,
which does. We can now remove quite a bit of indirection.
- Three methods in `trait QueryContext` are no longer needed
(`next_job_id`, `current_query_job`, `start_query`). As a result,
`QueryCtxt`'s trait impls of these methods are changed to inherent
methods.
- `qcx: Q::Qcx` parameters are simplified to `qcx: QueryCtxt<'tcx>`.
- `*qcx.dep_context()` occurrences are simplified to `qcx.tcx`, and
things like `qcx.dep_context().profiler()` become `qcx.tcx.prof`.
- `DepGraphData<<Q::Qcx as HasDepContext>::Deps>` becomes
`DepGraphData<DepsType>`.
In short, various layers of indirection and abstraction are cut away.
The resulting code is simpler, more concrete, and easier to understand.
It's a good demonstration of the benefits of eliminating
`rustc_query_system`, and there will be more to come.
[Note: this commit conceptually moves 75% of a file to another location,
and leaves 25% of it behind. It's impossible to preserve all the git
history. To preserve git history of the moved 75%, in this commit we
rename the file and remove the 25% from it, leaving the code in an
incomplete (uncompilable) state. In the next commit we add back the
25% in the old location.]
We are in the process of eliminating `rustc_query_system`. Chunks of it
are unused by `rustc_middle`, and so can be moved into
`rustc_query_impl`. This commit does some of that.
Mostly it's just moving code from one file to a new file. There are a
couple of non-trivial changes.
- `QueryState` and `ActiveKeyStatus` must remain in `rustc_query_system`
because they are used by `rustc_middle`. But their inherent methods
are not used by `rustc_middle`. So these methods are moved and
converted to free functions.
- The visibility of some things must increase. This includes `DepGraphData`
and some of its methods, which are now used in `rustc_query_impl`.
This is a bit annoying but seems hard to avoid.
What little is left behind in
`compiler/rustc_query_system/src/query/plumbing.rs` will be able to
moved into `rustc_query_impl` or `rustc_middle` in the future.
Incorporate query description functions into `QueryVTable`
Putting a `desc` function in each query vtable reduces the amount of parameter juggling required when creating query stack frames, because almost all of the necessary information can be found in the vtable.
There should be no change to compiler output.
Some `rustc_query_system` cleanups
Small improvements I found while looking closely at `rustc_query_system`. Best reviewed one commit at a time.
r? @cjgillot
Rename trait `DepNodeParams` to `DepNodeKey`
In query system plumbing, we usually refer to a query's explicit argument value as a “key”.
The first few commits do some preliminary cleanup that would conflict with the rename; the rename itself is in the final commit.
r? nnethercote (or compiler)
They are defined in `rustc_query_system` but used in `rustc_query_impl`.
This is very much *not* how things are supposed to be done; I suspect
someone got lazy and took a shortcut at some point.
This commit moves the errors into `rustc_query_impl`. This requires more
lines of code to give `rustc_query_impl` an errors module, but it's
worthwhile to do things in the normal way instead of a weird exceptional
way.
It's a tiny module with one trait and a default impl. It's not used in
`rustc_query_system`; all uses and non-default impls are in
`rustc_middle` and `rustc_query_impl`.
This commit moves it into `rustc_middle`, which makes things simpler
overall.
If we make sure that `compute_fn` in the query's vtable is actually named
`__rust_begin_short_backtrace`, we can avoid the need for some additional
intermediate functions and stack frames.
This is similar to how the `get_query_incr` and `get_query_non_incr` functions
are actually named `__rust_end_short_backtrace`.
Move the query list into a new `rustc_middle::queries` module
This moves the query list from `rustc_middle::query` into a new `rustc_middle::queries` module. This splits up the use of the query system from the remaining implementation of it in `rustc_middle::query`, which conceptually belong to `rustc_query_system`.
The goal is to let rustc crates define queries with their own `queries` module, and this makes `rustc_middle` also fit this pattern.
The inner `queries` module used by the macros are renamed to `query_info`, so it doesn't conflict with the new outer name.
Various `QueryStackFrame` variables are called `query`; `frame` is a
better name. And various `QueryInfo` variables are called `frame`;
`info` is a better name.
This eliminates some confusing `query.query()` occurrences, which is a
good sign, and some `frame.query` occurrences become `info.frame`.
`QueryStackFrame<I>` is a generic type, and the `I` parameter leaks out
to many other related types. However, it only has two instantiations in
practice:
- `QueryStackFrame<QueryStackFrameExtra>`
- `QueryStackFrame<QueryStackDeferred<'tcx>>`
And most of the places that currently use `QueryStackFrame<I>` are
actually specific to one of the instantiations. This commit removes the
unneeded genericity.
The following types are only ever used with `QueryStackDeferred<'tcx>`:
- QueryMap
- QueryJobInfo
- QueryJob
- QueryWaiter
- QueryLatchInfo
- QueryLatch
- QueryState
- QueryResult
and their `<I>` parameter is changed to `<'tcx>`.
Also, the `QueryContext::QueryInfo` associated type is removed.
`CycleError<I>` and `QueryInfo<I>` are still generic over type, because
they are used with both instantiations.
This required also adding a `<'tcx>` parameter to the traits
`QueryDispatcher` and `QueryContext`, which is annoying but I can't see
how to avoid it.
Reintroduce `QueryStackFrame` split.
I tried removing it in rust-lang/rust#151203, to replace it with something simpler. But a couple of fuzzing failures have come up and I don't have a clear picture on how to fix them. So I'm reverting the main part of rust-lang/rust#151203.
This commit also adds the two fuzzing tests.
Fixesrust-lang/rust#151226, rust-lang/rust#151358.
r? @oli-obk
I tried removing it in #151203, to replace it with something simpler.
But a couple of fuzzing failures have come up and I don't have a clear
picture on how to fix them. So I'm reverting the main part of #151203.
This commit also adds the two fuzzing tests.
Fixes#151226, #151358.
PR #138672 introduced a complex and invasive split of `QueryStackFrame`
to avoid a query cycle. This commit reverts that change because there is
a much simpler change that fixes the problem, which will be in the next
commit.
