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A @_fixed_layout protocol exposes its witness table layout to clients, which prevents re-ordering of requirements or adding new requiremenst with a default. When library evolution is enabled, we still emit method descriptors even for @_fixed_layout protocols; this allows a previously-resilient protocol to become @_fixed_layout as long as the published layout matches the resilient layout in all previously-shipped versions of the library.
53 lines
2.4 KiB
Swift
53 lines
2.4 KiB
Swift
// RUN: %empty-directory(%t)
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// RUN: %target-swift-frontend -emit-module -enable-library-evolution -emit-module-path=%t/resilient_protocol.swiftmodule -module-name=resilient_protocol %S/../Inputs/resilient_protocol.swift
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// RUN: %target-swift-frontend -I %t -emit-ir -enable-library-evolution %s | %FileCheck %s -DINT=i%target-ptrsize
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// RUN: %target-swift-frontend -I %t -emit-ir -enable-library-evolution -O %s
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import resilient_protocol
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@_fixed_layout public protocol FrozenProtocol {
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func protocolMethod()
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}
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public func callOtherProtocolMethod<T : OtherFrozenProtocol>(_ t: T) {
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t.protocolMethod()
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}
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public struct ConformsToFrozenProtocol : FrozenProtocol {
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public func protocolMethod() {}
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}
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// CHECK-LABEL: @"$s16frozen_protocols24ConformsToFrozenProtocolVAA0eF0AAMc" = {{(dllexport )?}}{{(protected )?}}constant %swift.protocol_conformance_descriptor
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// -- the protocol
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// CHECK-SAME: @"$s16frozen_protocols14FrozenProtocolMp"
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// -- the conforming type
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// CHECK-SAME: @"$s16frozen_protocols24ConformsToFrozenProtocolVMn"
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// -- the witness table
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// CHECK-SAME: @"$s16frozen_protocols24ConformsToFrozenProtocolVAA0eF0AAWP"
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// -- flags
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// CHECK-SAME: i32 0
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// CHECK-SAME: }
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// @_fixed_layout protocols still emit protocol requirement descriptors though,
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// which allows for a protocol to be retroactively declared as @_fixed_layout
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// CHECK-LABEL: @"$s16frozen_protocols14FrozenProtocolP14protocolMethodyyFTq" = {{(dllexport )?}}{{(protected )?}}alias %swift.protocol_requirement
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// Requirements in @_fixed_layout protocols are called by direct witness
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// table lookup
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// CHECK-LABEL: define{{( dllexport)?}}{{( protected)?}} swiftcc void @"$s16frozen_protocols23callOtherProtocolMethodyyx18resilient_protocol0d6FrozenE0RzlF"(%swift.opaque* noalias nocapture %0, %swift.type* %T, i8** %T.OtherFrozenProtocol)
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// CHECK: [[ADDR:%.*]] = getelementptr inbounds i8*, i8** %T.OtherFrozenProtocol, i32 1
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// CHECK: [[FN:%.*]] = load i8*, i8** [[ADDR]]
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// CHECK: [[CAST:%.*]] = bitcast i8* [[FN]] to void (%swift.opaque*, %swift.type*, i8**)*
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// CHECK: call swiftcc void %3(%swift.opaque* noalias nocapture swiftself %0, %swift.type* %T, i8** %T.OtherFrozenProtocol)
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// CHECK: ret void
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// @_fixed_layout protocols still emit method dispatch thunks though, which
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// allows for a protocol to be retroactively declared as @_fixed_layout
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// CHECK-LABEL: define{{( dllexport)?}}{{( protected)?}} swiftcc void @"$s16frozen_protocols14FrozenProtocolP14protocolMethodyyFTj"(
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