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After https://github.com/apple/swift/pull/40793, alloc_boxes all have their lifetimes protected by a lexical borrow scope. In that PR, DI had been updated to see through begin_borrow instructions from a project_box to a mark_uninitialized. It did not, however, correct the end_borrow instructions when destroy_values of mark_uninitializeds were replaced with destroy_addrs of project_boxes. That is done here. In a bit more detail, in the following context %box = alloc_box %mark_uninit = mark_uninitialized %box %lifetime = begin_borrow [lexical] %mark_uninit %proj_box = project_box %lifetime When it is not statically known whether a field is initialized, we are replacing the instruction // before destroy_value %mark_uninit // after with the following diamond // before %initialized = load cond_br %initialized, yes, no yes: destroy_addr %proj_box br bottom no: br bottom bottom: dealloc_box %box br keep_going keep_going: // after Doing so is problematic, though, because by SILGen construction the destroy_value is always preceded by an end_borrow: end_borrow %lifetime destroy_value %mark_uninit Previously, that end_borrow remained above the %initialized = load instruction in the above. That was invalid because the the newly introduced destroy_addr %proj_box was a use of the borrow scope (%proj_box is a projection of the begin_borrow) and consequently must be within the borrow scope. Note also that it would not be sufficient to simply emit the diamond before the end_borrow. The end_borrow must come before the destruction of the value whose lifetime it is protecting (%box), and the diamond contains the instruction to destroy that value (dealloc_box) in its bottom block. To resolve this issue, just move the end_borrow instruction from where it was to before the dealloc box. (This is actually done by moving it to the top of the diamond's "continue" block prior to the emission of that dealloc_box instruction.) rdar://89984216
22 lines
335 B
Swift
22 lines
335 B
Swift
// RUN: %target-swift-frontend -emit-sil %s -o /dev/null
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// For OSLogTestHelper.
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// REQUIRES: VENDOR=apple
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import OSLogTestHelper
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struct Thing {
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let guts: AnyObject
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}
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func getThings() -> [Thing] { [] }
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func run() {
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var things: [Thing]
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while(true) {
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things = getThings()
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OSLogMessage("count: \(things.count)")
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}
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}
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