Nate Chandler 482e18b90f [SILCombine] Fix apply(convert_func(@guaranteed)). ...

The operands to the original apply are cast via an ownership forwarding
instruction to the appropriate type for the rewritten apply.

```
%converted = convert_function %original to $(NewTy) -> ()
apply %converted(%operand)
```
->
```
%cast = cast %operand to $OriginalTy
apply %original(%cast)
```

Previously, when an original operand is owned but the new apply does not
consume that operand, the newly added cast would consume the original
operand (an owned value)--something the original code being replaced did
not do.

```
%converted = convert_function %original to $(NewTy) -> ()
apply %converted(%operand : @guaranteed)
// %operand remains available
```
->
```
%cast = cast %operand to $OriginalTy // consumes %operand!
apply %original(%cast : @guaranteed)
// %operand is not available!
```

This is incorrect for the complementary reasons that the result of the
cast is leaked and any uses of the original operand subsequent to the
new apply are uses-after-consume.

Here, this is fixed by borrowing the original operand before casting in
this case.

rdar://142570727

2025-01-08 20:33:49 -08:00

68 KiB

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