Michael Gottesman bd472b12be [region-isolation] Make store_borrow a store operation that does not require. ...

TLDR:

The reason why I am doing this is it ensures that temporary store_borrow that we
create when materializing a value before were treated as uses. So we would error
on this:

```swift
@MainActor func transferToMain<T>(_ t: T) async {}

func test() async {
  let x = NonSendableKlass()
  await transferToMain(x)
  await transferToMain(x)
}
```

----

store_borrow is an instruction intended to be used to initialize temporary
alloc_stack with borrows. Since it is a temporary, we do not want to error on
the temporaries initialization... instead, we want to error on the use of the
temporary parameter.

This is achieved by making it so that store_borrow still performs an
assign/merge, but does not require that src/dest be alive. So the regions still
merge (yielding diagnostics for later uses).

It also required me to make it so that PartitionOp::{Assign,Merge} do not
require by default. Instead, we want the individual operations to always emit a
PartitionOp::Require explicitly (which they already did).

One thing to be aware of is that when it comes to diagnostics, we already know
how to find a temporaries original value and how to handle that. So this is the
last part of making store_borrow behave nicely.

rdar://129237675

2024-06-12 15:01:38 -07:00

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