coverage: Clarify some parts of coverage counter creation
This is a series of semi-related changes that are trying to make the `counters` module easier to read, understand, and modify.
For example, the existing code happens to avoid ever using the count for a `TerminatorKind::Yield` node as the count for its sole out-edge (since doing so would be incorrect), but doesn't do so explicitly, so seemingly-innocent changes can result in baffling test failures.
This PR also takes the opportunity to simplify some debug-logging code that was making its surrounding code disproportionately hard to read.
There should be no changes to the resulting coverage instrumentation/mappings, as demonstrated by the absence of changes to the coverage test suite.
Given that we directly access the graph predecessors/successors in so many
other places, and sometimes must do so to satisfy the borrow checker, there is
little value in having this trivial helper method.
- Look up the node's predecessors only once
- Get rid of some overly verbose logging
- Explain why some nodes need physical counters
- Extract a helper method to create and set a physical node counter
Simplify the canonical clone method and the copy-like forms to copy
Fixes#128081.
The optimized clone method ends up as the following MIR:
```
_2 = copy ((*_1).0: i32);
_3 = copy ((*_1).1: u64);
_4 = copy ((*_1).2: [i8; 3]);
_0 = Foo { a: move _2, b: move _3, c: move _4 };
```
We can transform this to:
```
_0 = copy (*_1);
```
r? `@cjgillot`
Don't call closure_by_move_body_def_id on FnOnce async closures in MIR validation
Refactors the check in #129847 to not unncessarily call the `closure_by_move_body_def_id` query for async closures that don't *need* a by-move body.
Fixes#130167
- Replace non-standard names like 's, 'p, 'rg, 'ck, 'parent, 'this, and
'me with vanilla 'a. These are cases where the original name isn't
really any more informative than 'a.
- Replace names like 'cx, 'mir, and 'body with vanilla 'a when the lifetime
applies to multiple fields and so the original lifetime name isn't
really accurate.
- Put 'tcx last in lifetime lists, and 'a before 'b.
coverage: Simplify creation of sum counters
A small and self-contained improvement, extracted from some larger changes that I'm still working on.
Ultimately I want to avoid creating these sum counter-expressions in some cases (in favour of just adding physical counters directly to the nodes we care about), so a good incremental move towards that is splitting the “gather edge counters” step out from the ”build a sum of those counters” step.
Creating an extra intermediate vector should have negligible cost (and coverage isn't exercised by the benchmark suite anyway). The removed logging is redundant with the `#[instrument(..)]` logging we already have on the underlying method calls.
some const cleanup: remove unnecessary attributes, add const-hack indications
I learned that we use `FIXME(const-hack)` on top of the "const-hack" label. That seems much better since it marks the right place in the code and moves around with the code. So I went through the PRs with that label and added appropriate FIXMEs in the code. IMO this means we can then remove the label -- Cc ``@rust-lang/wg-const-eval.``
I also noticed some const stability attributes that don't do anything useful, and removed them.
r? ``@fee1-dead``
coverage: Clean up terminology in counter creation
Some of the terminology in this module is confusing, or has drifted out of sync with other parts of the coverage code.
This PR therefore renames some variables and methods, and adjusts comments and debug logging statements, to make things clearer and more consistent.
No functional changes, other than some small tweaks to debug logging.
In all cases the struct can own the relevant thing instead of having a
reference to it. This makes the code simpler, and in some cases removes
a struct lifetime.
These are all functions with a single callsite, where having a separate
function does nothing to help with readability. These changes make the
code a little shorter and easier to read.
There are four related dataflow structs: `MaybeInitializedPlaces`,
`MaybeUninitializedPlaces`, and `EverInitializedPlaces`,
`DefinitelyInitializedPlaces`. They all have a `&Body` and a
`&MoveData<'tcx>` field. The first three use different lifetimes for the
two fields, but the last one uses the same lifetime for both.
This commit changes the first three to use the same lifetime, removing
the need for one of the lifetimes. Other structs that also lose a
lifetime as a result of this are `LivenessContext`, `LivenessResults`,
`InitializationData`.
It then does similar things in various other structs.
Currently it constructs two vectors `calls_to_terminated` and
`cleanups_to_remove` in the main loop, and then processes them after the
main loop. But the processing can be done in the main loop, avoiding the
need for the vectors.
