Since the value of `InitialFlow` defines the semantics of the `join`
operation, there's no reason to have seperate traits for each. We can
add a default impl of `join` which branches based on `BOTTOM_VALUE`.
This should get optimized away.
This commit makes `sets.on_entry` inaccessible in
`{before_,}{statement,terminator}_effect`. This field was meant to allow
implementors of `BitDenotation` to access the initial state for each
block (optionally with the effect of all previous statements applied via
`accumulates_intrablock_state`) while defining transfer functions.
However, the ability to set the initial value for the entry set of each
basic block (except for START_BLOCK) no longer exists. As a result, this
functionality is mostly useless, and when it *was* used it was used
erroneously (see #62007).
Since `on_entry` is now useless, we can also remove `BlockSets`, which
held the `gen`, `kill`, and `on_entry` bitvectors and replace it with a
`GenKill` struct. Variables of this type are called `trans` since they
represent a transfer function. `GenKill`s are stored contiguously in
`AllSets`, which reduces the number of bounds checks and may improve
cache performance: one is almost never accessed without the other.
Replacing `BlockSets` with `GenKill` allows us to define some new helper
functions which streamline dataflow iteration and the
dataflow-at-location APIs. Notably, `state_for_location` used a subtle
side-effect of the `kill`/`kill_all` setters to apply the transfer
function, and could be incorrect if a transfer function depended on
effects of previous statements in the block on `gen_set`.
Resolves#62007.
Due to a bug, the previous version of this check did not actually kill
any conflicting borrows unless the borrowed place had no projections.
Specifically, `entry_set` will always be empty when `statement_effect`
is called. It does not contain the set of borrows which are live at this
point in the program.
The commit should have changed comments as well.
At the time of writting, it passes the tidy and check tool.
Revisions asked by eddyb :
- Renamed of all the occurences of {visit/super}_mir
- Renamed test structures `CachedMir` to `Cached`
Fixing the missing import on `AggregateKind`
Use normal newtype_index macro for MIR dataflows
* Makes the definition of these structs contain `struct IndexName`
* Avoids having an offset by removing high values, rather than 0
* Implements some traits for us.
This avoids all sorts of confusing issues with using both `dest_place`
and `self` in the `propagate_call_return` function in the
`BitDenotation` implementation for `Borrows`.
This commit extends previous work to kill borrows from a local after
assignment into that local to kill borrows from a projection after
assignment into a prefix of that place.
As suggested in the feedback for #55244.
When I replaced the macro with a function, rustc started complaining
that there were two unused functions so I also removed those.
