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5bc036661c
It lowers let property accesses of classes.
Lowering consists of two tasks:
* In class initializers, insert `end_init_let_ref` instructions at places where all let-fields are initialized.
This strictly separates the life-range of the class into a region where let fields are still written during
initialization and a region where let fields are truly immutable.
* Add the `[immutable]` flag to all `ref_element_addr` instructions (for let-fields) which are in the "immutable"
region. This includes the region after an inserted `end_init_let_ref` in an class initializer, but also all
let-field accesses in other functions than the initializer and the destructor.
This pass should run after DefiniteInitialization but before RawSILInstLowering (because it relies on `mark_uninitialized` still present in the class initializer).
Note that it's not mandatory to run this pass. If it doesn't run, SIL is still correct.
Simplified example (after lowering):
bb0(%0 : @owned C): // = self of the class initializer
%1 = mark_uninitialized %0
%2 = ref_element_addr %1, #C.l // a let-field
store %init_value to %2
%3 = end_init_let_ref %1 // inserted by lowering
%4 = ref_element_addr [immutable] %3, #C.l // set to immutable by lowering
%5 = load %4
55 lines
1.6 KiB
Swift
55 lines
1.6 KiB
Swift
// RUN: %target-swift-frontend -O %s -parse-as-library -emit-sil -enforce-exclusivity=none -Xllvm -sil-disable-pass=function-signature-opts | %FileCheck %s
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// REQUIRES: swift_in_compiler
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// Test ARC optimizations on source level tests that have been
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// miscompiled and crash (e.g. because of use-after-free).
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// -----------------------------------------------------------------------------
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// rdar://74469299 (ARC miscompile: EscapeAnalysis::mayReleaseContent;
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// potential use-after-free)
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// -----------------------------------------------------------------------------
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public class Base {
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var i = 3
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init() {}
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}
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public class Node : Base {
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var node: Base
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@inline(never)
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init(node: Base) { self.node = node }
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}
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struct Queue {
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var node: Node
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}
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@inline(never)
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func useQueue(q: __owned Queue) {}
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@inline(never)
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func useNode(n: Base) -> Int {
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return n.i
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}
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// CHECK-LABEL: sil [noinline] @$s9arc_crash14testMayReleaseAA4BaseCyF : $@convention(thin) () -> @owned Base {
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// CHECK: [[BASE:%.*]] = alloc_ref $Base
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// CHECK: [[EI:%.*]] = end_init_let_ref [[BASE]]
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// CHECK: strong_retain [[EI]] : $Base
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// CHECK: apply %{{.*}} : $@convention(thin) (@owned Queue) -> ()
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// CHECK-LABEL: } // end sil function '$s9arc_crash14testMayReleaseAA4BaseCyF'
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@inline(never)
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public func testMayRelease() -> Base {
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let n2 = Base()
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let n1 = Node(node: n2)
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let q = Queue(node: n1)
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// n2 must not be release before useQueue.
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useQueue(q: q)
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return n2
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}
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// This crashes when testMayRelease releases the object too early.
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// print("Object:")
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// print(testMayRelease())
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// -----------------------------------------------------------------------------
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