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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
28 lines
692 B
Swift
28 lines
692 B
Swift
// RUN: %target-swift-frontend -parse-as-library -module-name test %s -O -emit-sil | %FileCheck %s
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// REQUIRES: swift_in_compiler
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public final class C {
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let i: Int
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init(i: Int) {
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self.i = i
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}
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}
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// CHECK-LABEL: sil @$s4test0A8LetField_1fSi_SitAA1CC_yyXEtF :
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// CHECK: [[A:%.*]] = ref_element_addr [immutable] %0 : $C, #C.i
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// CHECK: [[L:%.*]] = load [[A]]
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// CHECK: apply
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// CHECK-NOT: load
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// CHECK: tuple ([[L]] : $Int, [[L]] : $Int)
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// CHECK: } // end sil function '$s4test0A8LetField_1fSi_SitAA1CC_yyXEtF'
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public func testLetField(_ c: C, f: () -> ()) -> (Int, Int) {
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let a = c.i
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f()
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let b = c.i
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return (a, b)
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}
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