Add _withUnsafeGuaranteedRef to Unmanaged #1890
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@swift-ci Please smoke test |
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Please add an execution test. |
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These builtins can be used to denote a scope over which the parameter passed to unsafeGuaranteed can be assume to be @guaranteed: That is there is another reference that keeps the value alive. // Scope begin strong_retain %0 : $Foo %2 = builtin "unsafeGuaranteed"<Foo>(%0 : $Foo) : $(Foo, Builtin.Int8) %3 = tuple_extract %2 : $(Foo, Builtin.Int8), 0 %4 = tuple_extract %2 : $(Foo, Builtin.Int8), 1 %5 = class_method %3 : $Foo, #Foo.beep!1 : (Foo) -> () -> () %6 = apply %5(%3) : $@convention(method) (@guaranteed Foo) -> () strong_release %3 : $Foo %8 = builtin "unsafeGuaranteedEnd"(%4 : $Builtin.Int8) : $( // Scope end is semantically equivalent to: sil @guaranteed_lifetime : $@convention(method) (@guaranteed Foo) -> () { bb(%3: $Foo): %5 = class_method %3 : $Foo, #Foo.beep!1 : (Foo) -> () -> () %6 = apply %5(%3) : $@convention(method) (@guaranteed Foo) -> () } ... // Scope begin apply @guaranteed_lifetime(%0) // Scope end
We can remove the retain/release pair preceeding the builtins based on the knowledge that the lifetime of the reference is guaranteed by someone hanging on to the reference elsewhere.
This is an internal method that will go away in the future.
Get the value of the unmanaged referenced as a managed reference without
consuming an unbalanced retain of it and pass it to the closure. Asserts
that there is some other reference ('the owning reference') to the
unmanaged reference that guarantees the lifetime of the unmanaged reference
for the duration of the '_withUnsafeGuaranteedRef' call.
var owningReference = Instance()
...
withExtendedLifetime(owningReference) {
let u = Unmanaged.passUnretained(owningReference)
for i in 0 ..< 100 {
// Assert that the reference in 'u' is kept alive by another storage
// location or value that holds the same reference.
u._withUnsafeGuaranteedRef {
$0.doSomething()
}
}
} // owningReference's lifetime (reference count > 0) is guaranteed
// for this scope.
rdar://25129935
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MaxDesiatov
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Oct 13, 2020
[pull] swiftwasm-release/5.3 from release/5.3
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What's in this pull request?
This is an internal method that will go away in the future.
Get the value of the unmanaged referenced as a managed reference without
consuming an unbalanced retain of it and pass it to the closure. Asserts
that there is some other reference ('the owning reference') to the
unmanaged reference that guarantees the lifetime of the unmanaged reference
for the duration of the '_withUnsafeGuaranteedRef' call.