Swift Actor መ࡞୳ࡧ John Lin (@johnlinvc)

᮫ԙզ • John Lin • Twitter: @johnlinvc • Senior Solution Architect, DevOps 
 @ West Pharmaceutical Service (୆ᖯҖ๏෰຿) • Swift Taipei meetup ओ㭎ਓ

Swift Taipei Meetup • https://swift.taipei • 㑌݄ୈҰݸᜌ፨ೋᎯ㭎ɻ • ౼࿦ Swift ૬᮫తࢿ㘤ɼ৽஌ɼመ࡞౳౳ɻ • ݱ৔༗ఏڙ᫊৯࿨ञਫ਼ᢛඇञਫ਼ҿྉɻ • ᓣܴိ٣׃⇭ᡅɻ

େߝ • Actor model • Swift actor • Swift actor መ຿ൣྫ • Swift ฤᩄྲྀఔ • Swift actor ฤᩄྲྀఔ

Actor model • Actor: ԋһ • model: ໛ܕɼయൣɻ

֌٢ཁࡏ৽ిӨཫԋ֌٢

Actor model • Ұݸ༻ိ႔ཧฒߦӡࢉతఔࣜ໛ܕ • 1973 ೥༝ Carl Hewitt, Peter Bishop & Richard Steiger ఏग़ɻ • ༝ၷେ෦෼૊੒ Actor & message • ෆधཁ೚Կಛผత async featureɼ
 ՄҎࡏၚ౷త blocking ؀ڥதመ࡞ɻ

Actor • ఔࣜӡࢉతᄸݩɻ༗ࣗݾᘐཱతهԱᱪ࿨ӡࢉೳྗɻ • ༗ᘐಛత໊ࢠʢ஍ᅿʣ • ՄҎ၏Լ໘ز݅ࣄɻ • ઀Ꮕ㘤ଉ • 㗞ੜ৽త actorɻ • ૹ㘤ଉڅଖଞ actorɻ • վᏓࣗݾతهԱᱪʢվᏓߦҝʣ

Message • Actor ೭ؒޓ૬ߏ௨తػ੍ɻ • Actor ՄҎૹmessageڅଖଞత actorɻ • ୠੋ୞ೳᏅࣗݾత messageɻ • Obj-C message send ༗ 87% ૾

actor model ӡ࡞

Swift

Swift

Swift • 2011 ೥༝ LLVM ࡞ऀ Chris Lattner ։ᚙత৽ੈ୅ఔࣜޠݴ • 2015 ೥։ݯɼओཁߩᘔऀҝ Apple • ࢧԉ Linux, macOS, iOS & Windowsɻ • ࠷৽൛ຊҝ 5.5ɻ

Swift ಛ৭ • Objective-C without C • ಉ࣌ࢧԉ OOP & FPɻ • ࢧԉ Value Type & Reference Typeɻ • ABI stableɼ޲ԼࢧԉલҰ൛తޠ๏ɻ • Generic, Protocol ɻ • 㚎ݐ Package managerɻ

Swift Async / Await • Swift 5.5 త৽ޭೳ func fetch() async -> Int {...} let x = await fetch() async let y = fetch() await y

Swift Actor • SE-0306 Actors መ࡞ྃ Actorɻୠੋ࿨ Actor model ฒෆ׬શ૬ಉɻ • ༻ىိ૾ੋ㚎ݐྃ mutex త classɻॴ༗త var/method ౎ඃ mutex อޢɻ actor Counter { 
 var count:Int = 0 
 func inc() async { 
 self.count += 1 
 } 
 }

Swift actor message passing • ᔒ༗ message passingɼ୞༗ typed async method callɻ • ୞༗ࡏࣗݾతmethod ཫ࠽ೳ௚઀मվ varɻࡏଖଞ஍ํधཁ࢖༻ async/ awaitɻ actor Counter { 
 var count:Int = 0 
 func inc() async { 
 self.count += 1 
 } 
 }

Swift Actor vs Actor model Local Value Message passing Mailbox Reply Swift Yes Static, Compiler invoke methods No, compiler invoke methods Automatic, Typed Classic Actor Yes Dynamic Send anything Yes Manual, Need to know sender

Swift Actor መ຿ൣྫ • iOS 15 UIKit Framework ࢖༻ actor ိආ໔ࡏଖଞ thread मվ UI private func loadUser() { async { do { let user = try await loader.loadUser() nameLabel.text = user.name biographyLabel.text = user.biography } catch { showError(error) } } }

ಹኄੋዎኄ၏ग़ိత䏆ʁ

Swift ฤᩄྲྀఔ Lexer / Parser Semantic analysis SIL generation SIL guaranteed transformations SIL Optimizations LLVM IR Generation LLVM Source Code AST AST SIL SIL SIL LLVM IR

Lexer / Parser • ሡ७จࣈతఔࣜᛰ᫚׵੒ந৅ޠ๏थ(AST, abstract syntax tree)ɻ • ෛ੹ᒾҰࣈ໘্తޠ๏ੋ൱ਖ਼֬ɻ

Semantic analysis • ෼ੳޠ๏थɻ • ᒾҰྨผੋ൱ਖ਼֬ɻ • ॏഉӡࢉࢠ༏ઌᒟɻ • 㢨ఔࣜิ্༬ઃతመ࡞ɻ

SIL generation • ሡޠ๏थ᫚׵੒ SIL ( Swift Intermediate Language )ɻ • SIL ੋ SSA Form త Platform agnostic IRɻሢҝ Swift ઃܭతɻ • ༗Ұࠣ࠷ՂԽࡏ IR ൺ Tree ޷၏ɻॴҎ༗ྃ SILɻ

SIL guaranteed transformations • ਐߦҰࠣඞཁత IR ᫚׵ɻෆ؅༗ᔒ༗։࠷ՂԽ (-O) ౎။䋯 • return analysis • memory promotion

SIL Optimizations • ਐߦ IR త࠷ՂԽɻ᮫ᎃ࠷ՂԽ (-Onone) త࿩ब။௓ա • Inline, Specialization, Devirtualization ౳౳ɻ

LLVM IR Generation • ೺ SIL ᫚׵੒ LLVM IR (Intermediate Representationɼதհදࣔ)ɻ

Actor ฤᩄྲྀఔ Lexer / Parser Semantic analysis SIL generation SIL guaranteed transformations SIL Optimizations LLVM IR Generation LLVM Source Code AST AST SIL SIL SIL LLVM IR

Swift Actor ൣྫ actor Counter { 
 var count:Int = 0 
 func inc() async { 
 self.count += 1 
 } 
 }

ၷେॏᴍ • Async : ೗Կ֬อಉ࣌୞။༗Ұݸ actor method ӡߦɻ • State Isolation : ೗Կ֬อᏓᏐෆ။ඃଖଞ஍ํଘऔɻ

Lexer / Parser • መࡍ্ੋᙛ੒ class ိ parse • lib/Parse/ParseDecl.cpp line 7532 ParserResult Parser::parseDeclClass(ParseDeclOptions Flags, DeclAttributes &Attributes) { bool isExplicitActorDecl = 
 Tok.isContextualKeyword("actor");

Semantic analysis • ᒾҰ state isolationɻ lib/sema/TypeCheckConcurrency.cpp line 2256 bool checkMemberReference( Expr *base, ConcreteDeclRef memberRef, SourceLoc memberLoc, Optional partialApply = None, Expr *context = nullptr) { { switch (auto isolation = ActorIsolationRestriction::forDeclaration( memberRef, getDeclContext())) { case ActorIsolationRestriction::CrossActorSelf: { return diagnoseNonConcurrentTypesInReference(memberRef, getDeclContext()->getParentModule(), memberLoc, ConcurrentReferenceKind::CrossActor); }

㗞ੜ SIL • swiftc -emit-sil counter.swift

ฤᩄޙత SIL • sil_stage canonical • import Builtin • import Swift • import SwiftShims • import Foundation • actor Counter { • @_hasStorage @_hasInitialValue var count: Int { get set } • func inc() async • @objc deinit • init() • } • @_hasStorage @_hasInitialValue let task: Task<(), Never> { get } • // task • sil_global hidden [let] @$s7counter4tasks4TaskVyyts5NeverOGvp : $Task<(), Never> • // main • sil @main : $@convention(c) (Int32, UnsafeMutablePointer>>) -> Int32 { • bb0(%0 : $Int32, %1 : $UnsafeMutablePointer>>): • alloc_global @$s7counter4tasks4TaskVyyts5NeverOGvp // id: %2 • %3 = global_addr @$s7counter4tasks4TaskVyyts5NeverOGvp : $*Task<(), Never> // user: %13 • %4 = metatype $@thin Task<(), Never>.Type // user: %13 • %5 = alloc_stack $Optional // users: %15, %14, %13, %6 • inject_enum_addr %5 : $*Optional, #Optional.none!enumelt // id: %6 • // function_ref closure #1 in • %7 = function_ref @$s7counteryyYaYbcfU_ : $@convention(thin) @Sendable @async () -> () // user: %8 • %8 = thin_to_thick_function %7 : $@convention(thin) @Sendable @async () -> () to $@Sendable @async @callee_guaranteed () -> () // user: %10 • // function_ref thunk for @escaping @callee_guaranteed @Sendable @async () -> () • %9 = function_ref @$sIeghH_ytIeghHr_TR : $@convention(thin) @Sendable @async (@guaranteed @Sendable @async @callee_guaranteed () -> ()) -> @out () // user: %10 • %10 = partial_apply [callee_guaranteed] %9(%8) : $@convention(thin) @Sendable @async (@guaranteed @Sendable @async @callee_guaranteed () -> ()) -> @out () // user: %11 • %11 = convert_function %10 : $@Sendable @async @callee_guaranteed () -> @out () to $@Sendable @async @callee_guaranteed @substituted <τ_0_0> () -> @out τ_0_0 for <()> // user: %13 • // function_ref static Task<>.detached(priority:operation:) • %12 = function_ref @$ss4TaskVss5NeverORs_rlE8detached8priority9operationAByxADGs0A8PriorityVSg_xyYaYbcntFZ : $@convention(method) <τ_0_0, τ_0_1 where τ_0_1 == Never> (@in_guaranteed Optional, @owned @Sendable @async @callee_guaranteed @substituted <τ_0_0> () -> @out τ_0_0 for <τ_0_0>, @thin Task<τ_0_0, Never>.Type) -> @out Task<τ_0_0, Never> // user: %13 • %13 = apply %12<(), Never>(%3, %5, %11, %4) : $@convention(method) <τ_0_0, τ_0_1 where τ_0_1 == Never> (@in_guaranteed Optional, @owned @Sendable @async @callee_guaranteed @substituted <τ_0_0> () -> @out τ_0_0 for <τ_0_0>, @thin Task<τ_0_0, Never>.Type) -> @out Task<τ_0_0, Never> • destroy_addr %5 : $*Optional // id: %14 • dealloc_stack %5 : $*Optional // id: %15 • %16 = integer_literal $Builtin.Int32, 1 // user: %17 • %17 = struct $UInt32 (%16 : $Builtin.Int32) // user: %19 • // function_ref _sleep • %18 = function_ref @_sleep : $@convention(c) (UInt32) -> UInt32 // user: %19 • %19 = apply %18(%17) : $@convention(c) (UInt32) -> UInt32 • %20 = integer_literal $Builtin.Int32, 0 // user: %21 • %21 = struct $Int32 (%20 : $Builtin.Int32) // user: %22 • return %21 : $Int32 // id: %22 • } // end sil function 'main' • // variable initialization expression of Counter.count • sil hidden [transparent] @$s7counter7CounterC5countSivpfi : $@convention(thin) () -> Int { • bb0: • %0 = integer_literal $Builtin.Int64, 0 // user: %1 • %1 = struct $Int (%0 : $Builtin.Int64) // user: %2 • return %1 : $Int // id: %2 • } // end sil function '$s7counter7CounterC5countSivpfi' • // Int.init(_builtinIntegerLiteral:) • sil public_external [transparent] @$sSi22_builtinIntegerLiteralSiBI_tcfC : $@convention(method) (Builtin.IntLiteral, @thin Int.Type) -> Int { • // %0 // user: %2 • bb0(%0 : $Builtin.IntLiteral, %1 : $@thin Int.Type): • %2 = builtin "s_to_s_checked_trunc_IntLiteral_Int64"(%0 : $Builtin.IntLiteral) : $(Builtin.Int64, Builtin.Int1) // user: %3 • %3 = tuple_extract %2 : $(Builtin.Int64, Builtin.Int1), 0 // user: %4 • %4 = struct $Int (%3 : $Builtin.Int64) // user: %5 • return %4 : $Int // id: %5 • } // end sil function '$sSi22_builtinIntegerLiteralSiBI_tcfC' • // Counter.count.getter • sil hidden [transparent] @$s7counter7CounterC5countSivg : $@convention(method) (@guaranteed Counter) -> Int { • // %0 "self" // users: %2, %1 • bb0(%0 : $Counter): • debug_value %0 : $Counter, let, name "self", argno 1 // id: %1 • %2 = ref_element_addr %0 : $Counter, #Counter.count // user: %3 • %3 = begin_access [read] [dynamic] %2 : $*Int // users: %4, %5 • %4 = load %3 : $*Int // user: %6 • end_access %3 : $*Int // id: %5 • return %4 : $Int // id: %6 • } // end sil function '$s7counter7CounterC5countSivg' • // Counter.count.setter • sil hidden [transparent] @$s7counter7CounterC5countSivs : $@convention(method) (Int, @guaranteed Counter) -> () { • // %0 "value" // users: %6, %2 • // %1 "self" // users: %4, %3 • bb0(%0 : $Int, %1 : $Counter): • debug_value %0 : $Int, let, name "value", argno 1 // id: %2 • debug_value %1 : $Counter, let, name "self", argno 2 // id: %3 • %4 = ref_element_addr %1 : $Counter, #Counter.count // user: %5 • %5 = begin_access [modify] [dynamic] %4 : $*Int // users: %6, %7 • store %0 to %5 : $*Int // id: %6 • end_access %5 : $*Int // id: %7 • %8 = tuple () // user: %9 • return %8 : $() // id: %9 • } // end sil function '$s7counter7CounterC5countSivs' • // Counter.count.modify • sil hidden [transparent] @$s7counter7CounterC5countSivM : $@yield_once @convention(method) (@guaranteed Counter) -> @yields @inout Int { • // %0 "self" // users: %2, %1 • bb0(%0 : $Counter): • debug_value %0 : $Counter, let, name "self", argno 1 // id: %1 • %2 = ref_element_addr %0 : $Counter, #Counter.count // user: %3 • %3 = begin_access [modify] [dynamic] %2 : $*Int // users: %5, %8, %4 • yield %3 : $*Int, resume bb1, unwind bb2 // id: %4 • bb1: // Preds: bb0 • end_access %3 : $*Int // id: %5 • %6 = tuple () // user: %7 • return %6 : $() // id: %7 • bb2: // Preds: bb0 • end_access %3 : $*Int // id: %8 • unwind // id: %9 • } // end sil function '$s7counter7CounterC5countSivM' • // Counter.inc() • sil hidden @$s7counter7CounterC3incyyYaF : $@convention(method) @async (@guaranteed Counter) -> () { • // %0 "self" // users: %5, %4, %2, %1 • bb0(%0 : $Counter): • debug_value %0 : $Counter, let, name "self", argno 1 // id: %1 • hop_to_executor %0 : $Counter // id: %2 • %3 = integer_literal $Builtin.Int64, 1 // user: %10 • %4 = class_method %0 : $Counter, #Counter.count!modify : (Counter) -> () -> (), $@yield_once @convention(method) (@guaranteed Counter) -> @yields @inout Int // user: %5 • (%5, %6) = begin_apply %4(%0) : $@yield_once @convention(method) (@guaranteed Counter) -> @yields @inout Int // users: %15, %7, %17 • %7 = struct_element_addr %5 : $*Int, #Int._value // user: %8 • %8 = load %7 : $*Builtin.Int64 // user: %10 • %9 = integer_literal $Builtin.Int1, -1 // user: %10 • %10 = builtin "sadd_with_overflow_Int64"(%8 : $Builtin.Int64, %3 : $Builtin.Int64, %9 : $Builtin.Int1) : $(Builtin.Int64, Builtin.Int1) // users: %12, %11 • %11 = tuple_extract %10 : $(Builtin.Int64, Builtin.Int1), 0 // user: %14 • %12 = tuple_extract %10 : $(Builtin.Int64, Builtin.Int1), 1 // user: %13 • cond_fail %12 : $Builtin.Int1, "arithmetic overflow" // id: %13 • %14 = struct $Int (%11 : $Builtin.Int64) // user: %15 • store %14 to %5 : $*Int // id: %15 • %16 = tuple () • end_apply %6 // id: %17 • %18 = tuple () // user: %19 • return %18 : $() // id: %19 • } // end sil function '$s7counter7CounterC3incyyYaF' • // static Int.+= infix(_:_:) • sil public_external [transparent] @$sSi2peoiyySiz_SitFZ : $@convention(method) (@inout Int, Int, @thin Int.Type) -> () { • // %0 // users: %12, %3 • // %1 // user: %5 • bb0(%0 : $*Int, %1 : $Int, %2 : $@thin Int.Type): • %3 = struct_element_addr %0 : $*Int, #Int._value // user: %4 • %4 = load %3 : $*Builtin.Int64 // user: %7 • %5 = struct_extract %1 : $Int, #Int._value // user: %7 • %6 = integer_literal $Builtin.Int1, -1 // user: %7 • %7 = builtin "sadd_with_overflow_Int64"(%4 : $Builtin.Int64, %5 : $Builtin.Int64, %6 : $Builtin.Int1) : $(Builtin.Int64, Builtin.Int1) // users: %9, %8 • %8 = tuple_extract %7 : $(Builtin.Int64, Builtin.Int1), 0 // user: %11 • %9 = tuple_extract %7 : $(Builtin.Int64, Builtin.Int1), 1 // user: %10 • cond_fail %9 : $Builtin.Int1, "arithmetic overflow" // id: %10 • %11 = struct $Int (%8 : $Builtin.Int64) // user: %12 • store %11 to %0 : $*Int // id: %12 • %13 = tuple () // user: %14 • return %13 : $() // id: %14 • } // end sil function '$sSi2peoiyySiz_SitFZ' • // Counter.deinit • sil hidden @$s7counter7CounterCfd : $@convention(method) (@guaranteed Counter) -> @owned Builtin.NativeObject { • // %0 "self" // users: %3, %2, %1 • bb0(%0 : $Counter): • debug_value %0 : $Counter, let, name "self", argno 1 // id: %1 • %2 = builtin "destroyDefaultActor"(%0 : $Counter) : $() • %3 = unchecked_ref_cast %0 : $Counter to $Builtin.NativeObject // user: %4 • return %3 : $Builtin.NativeObject // id: %4 • } // end sil function '$s7counter7CounterCfd' • // Counter.__deallocating_deinit • sil hidden @$s7counter7CounterCfD : $@convention(method) (@owned Counter) -> () { • // %0 "self" // users: %3, %1 • bb0(%0 : $Counter): • debug_value %0 : $Counter, let, name "self", argno 1 // id: %1 • // function_ref Counter.deinit • %2 = function_ref @$s7counter7CounterCfd : $@convention(method) (@guaranteed Counter) -> @owned Builtin.NativeObject // user: %3 • %3 = apply %2(%0) : $@convention(method) (@guaranteed Counter) -> @owned Builtin.NativeObject // user: %4 • %4 = unchecked_ref_cast %3 : $Builtin.NativeObject to $Counter // user: %5 • dealloc_ref %4 : $Counter // id: %5 • %6 = tuple () // user: %7 • return %6 : $() // id: %7 • } // end sil function '$s7counter7CounterCfD' 360 ߦ

SIL ॏᴍઅ㑚 inc // Counter.inc() sil hidden @$s7counter7CounterC3incyyYaF : $@convention(method) @async (@guaranteed Counter) -> () { // %0 "self" // users: %5, %4, %2, %1 bb0(%0 : $Counter): debug_value %0 : $Counter, let, name "self", argno 1 // id: %1 hop_to_executor %0 : $Counter // id: %2 ... %10 = builtin "sadd_with_overflow_Int64"(%8 : $Builtin.Int64, %3 : $Builtin.Int64, %9 : $Builtin.Int1) : $(Builtin.Int64, Builtin.Int1) // users: %12, %11 ... }

SIL generation • ೺ actor ᙛ੒ class ိgenerate SILɻୠੋಛผ㗞ੜ hop_to_executor ɻ • lib/SILGen/SILGenProlog.cpp Line 407 void SILGenFunction::emitProlog(CaptureInfo captureInfo, ...) { switch (actorIsolation.getKind()) { ... case ActorIsolation::ActorInstance: { if (F.isAsync() || (wantDataRaceChecks && funcDecl->isLocalCapture())) { auto loc = RegularLocation::getAutoGeneratedLocation(F.getLocation()); ManagedValue selfArg = ManagedValue::forUnmanaged(F.getSelfArgument()); ExpectedExecutor = emitLoadActorExecutor(loc, selfArg); } break; }

SIL generation • ೺ actor ᙛ੒ class ိgenerate SILɻୠੋಛผ㗞ੜ hop_to_executor ɻ • lib/SILGen/SILGenProlog.cpp Line 569 void SILGenFunction::emitProlog(CaptureInfo captureInfo, ...) { ... // Jump to the expected executor. if (ExpectedExecutor) { if (F.isAsync()) { // For an async function, hop to the executor. B.createHopToExecutor( RegularLocation::getAutoGeneratedLocation(F.getLocation()), ExpectedExecutor, /*mandatory*/ false);

SIL ॏᴍઅ㑚 count getter // Counter.count.getter sil hidden [transparent] @$s7counter7CounterC5countSivg : $@convention(method) (@guaranteed Counter) -> Int { // %0 "self" // users: %2, %1 bb0(%0 : $Counter): debug_value %0 : $Counter, let, name "self", argno 1 // id: %1 %2 = ref_element_addr %0 : $Counter, #Counter.count // user: %3 %3 = begin_access [read] [dynamic] %2 : $*Int // users: %4, %5 %4 = load %3 : $*Int // user: %6 end_access %3 : $*Int // id: %5 return %4 : $Int // id: %6 } // end sil function '$s7counter7CounterC5countSivg'

SIL ॏᴍઅ㑚 count setter // Counter.count.setter sil hidden [transparent] @$s7counter7CounterC5countSivs : $@convention(method) (Int, @guaranteed Counter) -> () { // %0 "value" // users: %6, %2 // %1 "self" // users: %4, %3 bb0(%0 : $Int, %1 : $Counter): ... %4 = ref_element_addr %1 : $Counter, #Counter.count // user: %5 %5 = begin_access [modify] [dynamic] %4 : $*Int // users: %6, %7 store %0 to %5 : $*Int // id: %6 end_access %5 : $*Int // id: %7 %8 = tuple () // user: %9 return %8 : $() // id: %9 } // end sil function '$s7counter7CounterC5countSivs'

SIL generation • ࡏଘऔత࣌ީ။؃ੋෆੋࡏ actor ཫɼੋత࿩ब။Ճ্ beginAccess • lib/SILGen/SILGenLValue.cpp Line 615 SILValue UnenforcedAccess::beginAccess(SILGenFunction &SGF, SILLocation loc, SILValue address, SILAccessKind kind) { if (!SGF.getOptions().VerifyExclusivity) return address; ... auto BAI = SGF.B.createBeginAccess(loc, address, kind, SILAccessEnforcement::Unsafe, /*hasNoNestedConflict=*/false, /*fromBuiltin=*/false); return BAI; }

SIL generation • ޙ໘໵။Ճ্ሣጯత endAccess • lib/SILGen/SILGenLValue.cpp Line 639 void UnenforcedAccess::emitEndAccess(SILGenFunction &SGF) { if (!beginAccessPtr) return; SGF.B.createEndAccess(beginAccessPtr->getLoc(), beginAccessPtr.get(), /*abort*/ false); }

㗞ੜ LLVM IR • swiftc -emit-ir counter.swift

ฤᩄޙత LLVM IR ; ModuleID = '' source_filename = "" target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128" target triple = "x86_64-unknown-linux-gnu" module asm ".section .swift1_autolink_entries,\220x80000000\22" %TScT = type <{ %swift.refcounted* }> %swift.refcounted = type { %swift.type*, i64 } %swift.type = type { i64 } %swift.async_func_pointer = type <{ i32, i32 }> %swift.full_boxmetadata = type { void (%swift.refcounted*)*, i8**, %swift.type, i32, i8* } %swift.full_type = type { i8**, %swift.type } %swift.protocol = type { i8*, i8*, i8*, i8*, i8*, i8*, i8*, i8*, i32, i32, i32, i32, i32, i32 } %swift.method_descriptor = type { i32, i32 } %T7counter7CounterC = type <{ %swift.refcounted, %swift.defaultactor, %TSi }> %swift.defaultactor = type { [12 x i8*] } %TSi = type <{ i64 }> %swift.type_metadata_record = type { i32 } %swift.vwtable = type { i8*, i8*, i8*, i8*, i8*, i8*, i8*, i8*, i64, i64, i32, i32 } %TScPSg = type <{}> %swift.opaque = type opaque %swift.metadata_response = type { %swift.type*, i64 } %swift.function = type { i8*, %swift.refcounted* } %swift.type_descriptor = type opaque %"$s7counter7CounterC5countSivM.Frame" = type { [24 x i8] } %swift.context = type { %swift.context*, void (%swift.context*)*, i64 } %"$s7counter7CounterC3incyyYaF.Frame" = type { %swift.context*, %T7counter7CounterC*, %T7counter7CounterC* } %"$s7counteryyYaYbcfU_.Frame" = type { %swift.context*, %T7counter7CounterC*, i64, %T7counter7CounterC*, i8*, i64, i64, i64 } %swift.executor = type { i64, i64 } %Ts28__ContiguousArrayStorageBaseC = type opaque %Any = type { [24 x i8], %swift.type* } %swift.bridge = type opaque %TSa = type <{ %Ts22_ContiguousArrayBufferV }> %Ts22_ContiguousArrayBufferV = type <{ %Ts28__ContiguousArrayStorageBaseC* }> %"$sIeghH_ytIeghHr_TR.Frame" = type { %swift.context*, i8* } %"$sIeghH_ytIeghHr_TRTA.Frame" = type { %swift.context*, i8* } %swift.async_task_and_context = type { %swift.task*, %swift.context* } %swift.task = type { %swift.refcounted, i8*, i8*, i32, i32, i8*, i8*, i8*, %swift.context*, i64 } %"$sxIeghHr_xs5Error_pIegHrzo_s5NeverORs_r0_lTR.Frame" = type { %swift.context*, i8* } %swift.error = type opaque %"$sxIeghHr_xs5Error_pIegHrzo_s5NeverORs_r0_lTRTA.Frame" = type { %swift.context*, i8* } @"$s7counter4taskScTyyts5NeverOGvp" = hidden global %TScT zeroinitializer, align 8 @"symbolic ScPSg" = linkonce_odr hidden constant <{ [5 x i8], i8 }> <{ [5 x i8] c"ScPSg", i8 0 }>, section "swift5_typeref", align 2 @"$sScPSgMD" = linkonce_odr hidden global { i32, i32 } { i32 trunc (i64 sub (i64 ptrtoint (<{ [5 x i8], i8 }>* @"symbolic ScPSg" to i64), i64 ptrtoint ({ i32, i32 }* @"$sScPSgMD" to i64)) to i32), i32 -5 }, align 8 @"$s7counteryyYaYbcfU_Tu" = internal global %swift.async_func_pointer <{ i32 trunc (i64 sub (i64 ptrtoint (void (%swift.context*)* @"$s7counteryyYaYbcfU_" to i64), i64 ptrtoint (%swift.async_func_pointer* @"$s7counteryyYaYbcfU_Tu" to i64)) to i32), i32 96 }>, section ".rodata", align 8 @"$sIeghH_ytIeghHr_TRTu" = linkonce_odr hidden global %swift.async_func_pointer <{ i32 trunc (i64 sub (i64 ptrtoint (void (%swift.opaque*, %swift.context*, i8*, %swift.refcounted*)* @"$sIeghH_ytIeghHr_TR" to i64), i64 ptrtoint (%swift.async_func_pointer* @"$sIeghH_ytIeghHr_TRTu" to i64)) to i32), i32 48 }>, section ".rodata", align 8 @"symbolic IeghH_" = linkonce_odr hidden constant <{ [6 x i8], i8 }> <{ [6 x i8] c"IeghH_", i8 0 }>, section "swift5_typeref", align 2 @"\01l__swift5_reflection_descriptor" = private constant { i32, i32, i32, i32 } { i32 1, i32 0, i32 0, i32 trunc (i64 sub (i64 ptrtoint (<{ [6 x i8], i8 }>* @"symbolic IeghH_" to i64), i64 ptrtoint (i32* getelementptr inbounds ({ i32, i32, i32, i32 }, { i32, i32, i32, i32 }* @"\01l__swift5_reflection_descriptor", i32 0, i32 3) to i64)) to i32) }, section "swift5_capture", align 4 @metadata = private constant %swift.full_boxmetadata { void (%swift.refcounted*)* @objectdestroy, i8** null, %swift.type { i64 1024 }, i32 16, i8* bitcast ({ i32, i32, i32, i32 }* @"\01l__swift5_reflection_descriptor" to i8*) }, align 8 @"$sIeghH_ytIeghHr_TRTATu" = internal global %swift.async_func_pointer <{ i32 trunc (i64 sub (i64 ptrtoint (void (%swift.opaque*, %swift.context*, %swift.refcounted*)* @"$sIeghH_ytIeghHr_TRTA" to i64), i64 ptrtoint (%swift.async_func_pointer* @"$sIeghH_ytIeghHr_TRTATu" to i64)) to i32), i32 48 }>, section ".rodata", align 8 @"$sytN" = external global %swift.full_type @"$s7counter7CounterC3incyyYaFTu" = hidden global %swift.async_func_pointer <{ i32 trunc (i64 sub (i64 ptrtoint (void (%swift.context*, %T7counter7CounterC*)* @"$s7counter7CounterC3incyyYaF" to i64), i64 ptrtoint (%swift.async_func_pointer* @"$s7counter7CounterC3incyyYaFTu" to i64)) to i32), i32 48 }>, section ".rodata", align 8 @"$sScAMp" = external global %swift.protocol, align 4 @"got.$sScAMp" = private unnamed_addr constant %swift.protocol* @"$sScAMp" @"$sScA15unownedExecutorScevgTq" = external global %swift.method_descriptor, align 4 @"got.$sScA15unownedExecutorScevgTq" = private unnamed_addr constant %swift.method_descriptor* @"$sScA15unownedExecutorScevgTq" @"$s7counter7CounterCScAAAMcMK" = internal global [16 x i8*] zeroinitializer @"$s7counter7CounterCScAAAMc" = hidden constant { i32, i32, i32, i32, i32, i32, i32, i16, i16, i32, i32 } { i32 add (i32 trunc (i64 sub (i64 ptrtoint (%swift.protocol** @"got.$sScAMp" to i64), i64 ptrtoint ({ i32, i32, i32, i32, i32, i32, i32, i16, i16, i32, i32 }* @"$s7counter7CounterCScAAAMc" to i64)) to i32), i32 1), i32 trunc (i64 sub (i64 ptrtoint (<{ i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, %swift.method_descriptor, %swift.method_descriptor, %swift.method_descriptor, %swift.method_descriptor, %swift.method_descriptor }>* @"$s7counter7CounterCMn" to i64), i64 ptrtoint (i32* getelementptr inbounds ({ i32, i32, i32, i32, i32, i32, i32, i16, i16, i32, i32 }, { i32, i32, i32, i32, i32, i32, i32, i16, i16, i32, i32 }* @"$s7counter7CounterCScAAAMc", i32 0, i32 1) to i64)) to i32), i32 0, i32 196608, i32 1, i32 add (i32 trunc (i64 sub (i64 ptrtoint (%swift.method_descriptor** @"got.$sScA15unownedExecutorScevgTq" to i64), i64 ptrtoint (i32* getelementptr inbounds ({ i32, i32, i32, i32, i32, i32, i32, i16, i16, i32, i32 }, { i32, i32, i32, i32, i32, i32, i32, i16, i16, i32, i32 }* @"$s7counter7CounterCScAAAMc", i32 0, i32 5) to i64)) to i32), i32 1), i32 trunc (i64 sub (i64 ptrtoint ({ i64, i64 } (%T7counter7CounterC*, %swift.type*, i8**)* @"$s7counter7CounterCScAAAScA15unownedExecutorScevgTW" to i64), i64 ptrtoint (i32* getelementptr inbounds ({ i32, i32, i32, i32, i32, i32, i32, i16, i16, i32, i32 }, { i32, i32, i32, i32, i32, i32, i32, i16, i16, i32, i32 }* @"$s7counter7CounterCScAAAMc", i32 0, i32 6) to i64)) to i32), i16 0, i16 1, i32 0, i32 trunc (i64 sub (i64 ptrtoint ([16 x i8*]* @"$s7counter7CounterCScAAAMcMK" to i64), i64 ptrtoint (i32* getelementptr inbounds ({ i32, i32, i32, i32, i32, i32, i32, i16, i16, i32, i32 }, { i32, i32, i32, i32, i32, i32, i32, i16, i16, i32, i32 }* @"$s7counter7CounterCScAAAMc", i32 0, i32 10) to i64)) to i32) }, section ".rodata", align 4 @"\01l_entry_point" = private constant { i32 } { i32 trunc (i64 sub (i64 ptrtoint (i32 (i32, i8**)* @main to i64), i64 ptrtoint ({ i32 }* @"\01l_entry_point" to i64)) to i32) }, section "swift5_entry", align 4 @"$s7counter7CounterC5countSivpWvd" = hidden constant i64 112, align 8 @"$sBoWV" = external global i8*, align 8 @0 = private constant [8 x i8] c"counter\00" @"$s7counterMXM" = linkonce_odr hidden constant <{ i32, i32, i32 }> <{ i32 0, i32 0, i32 trunc (i64 sub (i64 ptrtoint ([8 x i8]* @0 to i64), i64 ptrtoint (i32* getelementptr inbounds (<{ i32, i32, i32 }>, <{ i32, i32, i32 }>* @"$s7counterMXM", i32 0, i32 2) to i64)) to i32) }>, section ".rodata", align 4 @1 = private constant [8 x i8] c"Counter\00" 1357 ߦ

LLVM IR inc ॏᴍઅ㑚 define hidden swifttailcc void @"$s7counter7CounterC3incyyYaF"(%swift.context* swiftasync %0, %T7counter7CounterC* swiftself %1) #0 { entry: ... musttail call swifttailcc void @swift_task_switch(%swift.context* swiftasync %6, i8* bitcast (void (i8*)* @"$s7counter7CounterC3incyyYaFTY0_" to i8*), i64 %5, i64 0) #7 ret void }

LLVM IR inc ॏᴍઅ㑚 define internal swifttailcc void @"$s7counter7CounterC3incyyYaFTY0_"(i8* swiftasync %0) #0 { entryresume.0: %async.ctx.frameptr1 = getelementptr inbounds i8, i8* %0, i32 24 %FramePtr = bitcast i8* %async.ctx.frameptr1 to %"$s7counter7CounterC3incyyYaF.Frame"* ... %15 = call { i64, i1 } @llvm.sadd.with.overflow.i64(i64 %14, i64 1) ... }

LLVM IR Generation • lib/IRGen/IRGenSIL.cpp Line 6173 void IRGenSILFunction::visitHopToExecutorInst(HopToExecutorInst *i) { assert(i->getTargetExecutor()->getType().getOptionalObjectType() .is()); llvm::Value *resumeFn = Builder.CreateIntrinsicCall( llvm::Intrinsic::coro_async_resume, {}); Explosion executor; getLoweredExplosion(i->getOperand(), executor); emitSuspensionPoint(executor, resumeFn); }

LLVM IR Generation • lib/IRGen/GenFunc.cpp Line 2402 void IRGenFunction::emitSuspensionPoint(Explosion &toExecutor, llvm::Value *asyncResume) { // Setup the suspend point. ... llvm::Function *suspendFn = createAsyncSuspendFn(); ... }

LLVM IR Generation • lib/IRGen/GenFunc.cpp Line 2438 llvm::Function *IRGenFunction::createAsyncSuspendFn() { ... auto *suspendCall = Builder.CreateCall( IGM.getTaskSwitchFuncFn(), { context, resumeFunction, targetExecutorFirst, targetExecutorSecond });

LLVM IR Generation • include/swift/Runtime/RuntimeFunctions.def Line 1569 FUNCTION(TaskSwitchFunc, swift_task_switch, SwiftAsyncCC, ConcurrencyAvailability, RETURNS(VoidTy), ARGS(SwiftContextPtrTy, Int8PtrTy, ExecutorFirstTy, ExecutorSecondTy), ATTRS(NoUnwind))

LLVM IR count getter ॏᴍઅ㑚 define hidden swiftcc i64 @"$s7counter7CounterC5countSivg"(%T7counter7CounterC* swiftself %0) #0 { entry: ... call void @swift_beginAccess(i8* %3, [24 x i8]* %access-scratch, i64 32, i8* null) #7 %._value = getelementptr inbounds %TSi, %TSi* %1, i32 0, i32 0 %4 = load i64, i64* %._value, align 16 call void @swift_endAccess([24 x i8]* %access-scratch) #7 ... ret i64 %4 }

LLVM IR count setter ॏᴍઅ㑚 define hidden swiftcc void @"$s7counter7CounterC5countSivs"(i64 %0, %T7counter7CounterC* swiftself %1) #0 { entry: ... call void @swift_beginAccess(i8* %4, [24 x i8]* %access-scratch, i64 33, i8* null) #7 %._value = getelementptr inbounds %TSi, %TSi* %2, i32 0, i32 0 store i64 %0, i64* %._value, align 16 call void @swift_endAccess([24 x i8]* %access-scratch) #7 ... }

Async : ೗Կ֬อಉ࣌୞။༗Ұݸ actor method ӡߦ • ࡏ semantic analysis త࣌ީ䔪ᎃᔒ༗ async తݺڣɻ • ೺ method ຊᱪ แࡏҰݸ async helper ཫɻ • ࡏ async helper औಘ actor త thread(Executor)ɻ • ࡏ async helper ೺ method ຊᱪഉਐ actor thread 
 త task queueɻ • ༻task queue ိࣥߦ method ຊᱪɻ

State Isolation : ೗Կ֬อᏓᏐෆ။ඃଖଞ஍ํଘऔ • ࡏ semantic analysis త࣌ީ䔪ᎃଖଞ஍ํతଘऔ • ೺ଘऔ౎༻ getter/setter method แىိɻ • ࡏ getter/setter ཫ࢖༻ swift_beginAccess/swift_endAccess 
 ိ࠯ఆᏓᏐ

݁࿦ • actor ੋඃᙛ੒Ұछ conform to Actor Protocol త Class ိ႔ཧɻ • State isolation ੋ༻ type check enforceɻ • State access ။༻ begin_access & end_access ࠯ఆɻ • ॴ༗త actor method call ౎༗Ճ্ hop_to_executor SIL • hop_to_executor ။Ꮣ੒ swift_task_switch IRɼࡏ task queue
 ཫংྻࣥߦɻ

References • https://swift.org/swift-compiler/#compiler-architecture • https://github.com/apple/swift • https://www.swiftbysundell.com/articles/the-main-actor-attribute/ • https://llvm.org/docs/Coroutines.html#switched-resume-lowering •

Q&A John Lin Twitter: @johnlinvc ౤Өย QR code ໢ᅿɿ
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