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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
41 lines
1.8 KiB
Swift
41 lines
1.8 KiB
Swift
// RUN: %empty-directory(%t)
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// RUN: %target-swift-frontend %s -emit-sil | %FileCheck %s
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// RUN: %target-swift-frontend %s -emit-sil -O | %FileCheck -check-prefix=OPT %s
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// REQUIRES: optimized_stdlib
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// REQUIRES: swift_in_compiler
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// Make sure that when we invoke Unmanaged._withUnsafeGuaranteedRef, we do not
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// have any ref count overhead.
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public class Klass {}
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public class KlassContainer {
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let k = Klass()
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}
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@inline(never)
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public func myPrint(_ k: Klass) { print(k) }
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// Check the codegen of _withUnsafeGuaranteedRef
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//
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// CHECK-LABEL: sil public_external [transparent] @$ss9UnmanagedV24_withUnsafeGuaranteedRefyqd__qd__xKXEKlF :
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// CHECK: bb0([[RESULT:%.*]] : $*Result, [[FUNC:%.*]] : $@noescape @callee_guaranteed @substituted <τ_0_0, τ_0_1 where τ_0_0 : AnyObject> (@guaranteed τ_0_0) -> (@out τ_0_1, @error any Error) for <Instance, Result>, [[UNMANAGED:%.*]] : $Unmanaged<Instance>):
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// CHECK: [[UNMANAGED_REF:%.*]] = struct_extract [[UNMANAGED]]
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// CHECK: [[REF:%.*]] = unmanaged_to_ref [[UNMANAGED_REF]]
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// CHECK: try_apply {{%.*}}([[RESULT]], [[REF]]) :
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// CHECK-NOT: destroy_value
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// CHECK: } // end sil function '$ss9UnmanagedV24_withUnsafeGuaranteedRefyqd__qd__xKXEKlF'
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// OPT-LABEL: sil @$s12unmanaged_rc12useUnmanagedyys0D0VyAA14KlassContainerCGF : $@convention(thin) (Unmanaged<KlassContainer>) -> () {
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// OPT: bb0([[UNMANAGED:%.*]] :
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// OPT: [[UNMANAGED_REF:%.*]] = struct_extract [[UNMANAGED]]
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// OPT: [[REF:%.*]] = unmanaged_to_ref [[UNMANAGED_REF]]
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// OPT: [[REF_ELT_ADDR:%.*]] = ref_element_addr [immutable] [[REF]] : $KlassContainer, #KlassContainer.k
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// OPT: [[VALUE:%.*]] = load [[REF_ELT_ADDR]]
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// OPT: apply {{%.*}}([[VALUE]])
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// OPT: } // end sil function '$s12unmanaged_rc12useUnmanagedyys0D0VyAA14KlassContainerCGF'
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public func useUnmanaged(_ u: Unmanaged<KlassContainer>) {
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u._withUnsafeGuaranteedRef {
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myPrint($0.k)
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}
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}
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