Nate Chandler 2163269f88 [SemanticARCOpts] Check uses in moved load range. ...

In https://github.com/apple/swift/pull/65417 , support for promoting
moved-from `load [copy]`s was added.  At that time, the existing logic
was generalized so that the check for whether writes the loaded-from
address occurred: rather than checking whether the writes occurred in
the live-range of the `load [copy]`, it was generalized to check whether
writes occurred in the live range of the "original" value which was
either the `load [copy]` or the `move_value`.  That opened a hole for
writes that occurred between the `load [copy]` and the `move_value`:

```
%v = load [copy] %a
%u = load [take] %a
%m = move_value %v
```

Here, this is fixed by checking both the live-range of the "original"
and also (supposing the original is different from the `load [copy]`)
also the live range of the `load [copy]`.

This required changing the list of consuming uses passed to the
`LinearLifetimeChecker::usesNotContainedWithinLifetime` to include not
just the `destroy_value`s but also the "unknown" consuming uses (i.e.
those that are not forwarding).

This change only affects arguments (and specifically only `@inout`
arguments since promotion for `@in` arguments isn't supported) because a
totally different code path is followed for `alloc_stack`s which regards
`load [take]`s as an "init" of the address (concretely,
`getSingleInitAllocStackUse` returns `truea for the above example if `%a` is
an `alloc_stack`).

rdar://108745323

2023-05-01 18:30:22 -07:00

8.0 KiB

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