コンパイラから紐解くSwift method dispatch

Transcript

1. ίϯύΠϥ͔Βඥղ͘
   4XJGU
   NFUIPE
   EJTQBUDI !LBUFJOPJHBLVLVO

2. ࣗݾ঺հ w !LBUFJOPJHBLVLVO
   w ૣҴాେֶߴ౳ֶӃ̏೥

3. ͍͖ͳΓͰ͕͢

4. ΫΠζͰ͢
   

5. class Cat { func bark() -> String { return "ʹΌΜ"

   } } class Dog { func bark() -> String { return "ΘΜ" } } let cat = Cat() let dog = unsafeBitCast(cat, to: Dog.self) print(dog.bark()) 2
   Կ͕ग़ྗ͞ΕΔͰ͠ΐ͏ʁ ʹΌΜ
   PS
   ΘΜ

6. class Cat { func bark() -> String { return "ʹΌΜ"

   } } class Dog { func bark() -> String { return "ΘΜ" } } let cat = Cat() let dog = unsafeBitCast(cat, to: Dog.self) print(dog.bark()) 2
   Կ͕ग़ྗ͞ΕΔͰ͠ΐ͏ʁ "
   ΘΜ

7. ʮΘΜʯ

8. ࠓ೔࿩͢͜ͱ w .FUIPE
   %JTQBUDIͷ࢓૊Έ
   w ࠷దԽͷ࢓૊Έ
   w ύϑΥʔϚϯε

9. 2
   .FUIPE
   EJTQBUDIͱ͸ʁ

10. 2
    .FUIPE
    EJTQBUDIͱ͸ʁ "
    ϝιου͕ݺͼग़͞ΕΔ࣌ʹɺ
 ࣮ࡍʹͲͷϝιουΛ࣮ߦ͢Δ͔ΛܾΊΔػߏ

11. None

12. class Animal { func bark() { print("ΞχϚϧͰ͢") } } class

    Cat: Animal { override func bark() { print("ʹΌΜ") } } func callAnimalBark(_ animal: Animal) { animal.bark() }

13. class Animal { func bark() { print("ΞχϚϧͰ͢") } } class

    Cat: Animal { override func bark() { print("ʹΌΜ") } } func callAnimalBark(_ animal: Animal) { animal.bark() // ΞχϚϧͰ͢ or ʹΌΜ }

14. class Animal { func bark() { print("ΞχϚϧͰ͢") } } class

    Cat: Animal { override func bark() { print("ʹΌΜ") } } func callAnimalBark(_ animal: Animal) { animal.bark() // ΞχϚϧͰ͢ or ʹΌΜ } ࣮ߦ͞ΕΔϝιου͸Ͳͬͪʁʁ

15. .FUIPE
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    %JTQBUDI
    w ݺͼग़͢ϝιουΛίϯύΠϧ࣌ʹܾΊΔ
    w %ZOBNJD
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    w ݺͼग़͢ϝιουΛ࣮ߦ࣌ʹܾΊΔ

16. 4UBUJD
    %JTQBUDI w ؔ਺
    w ஋ܕͷϝιου
    w FYUFOTJPOʹॻ͍ͨϝιου
    w pOBMͳϝιου struct

    S { func foo() {} } let s = S() s.foo()

17. 4UBUJD
    %JTQBUDI struct S { func foo() {} } let s

    = S() s.foo() ಉ͡γάωνϟͷϝιου͕ଘࡏ͠ͳ͍ w ؔ਺
    w ஋ܕͷϝιου
    w FYUFOTJPOʹॻ͍ͨϝιου
    w pOBMͳϝιου

18. %ZOBNJD
    %JTQBUDI w $MBTTͷϝιου
    w 1SPUPDPMͷϝιου protocol Animal { func foo()

    } struct Cat: Animal { func foo() {} } func callFoo<T: Animal>(_ animal: T) { animal.foo() }

19. w $MBTTͷϝιου
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    ΦʔόʔϥΠυ
    w 1SPUPDPMͷϝιου
    
    
    
    
    
    
    
    
    
    
    ෳ਺ͷܕ͕४ڌ %ZOBNJD
    %JTQBUDI protocol Animal { func foo()

    } struct Cat: Animal { func foo() {} } func callFoo<T: Animal>(_ animal: T) { animal.foo() } ಉ͡γάωνϟͷϝιου͕ෳ਺ଘࡏ͢Δ

20. .FUIPE
    %JTQBUDIͷύλʔϯ w 4UBUJD
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    w ݺͼग़͢ϝιουΛίϯύΠϧ࣌ʹܾΊΔ
    w %ZOBNJD
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    w ݺͼग़͢ϝιουΛ࣮ߦ࣌ʹܾΊΔ

21. .FUIPE
    %JTQBUDIͷύλʔϯ w 4UBUJD
    %JTQBUDI
    w ݺͼग़͢ϝιουΛίϯύΠϧ࣌ʹܾΊΔ
    w %ZOBNJD
    %JTQBUDI
    w ݺͼग़͢ϝιουΛ࣮ߦ࣌ʹܾΊΔ
    w

    75BCMF
    w 8JUOFTT
    5BCMF

22. 75BCMF w Ծ૝ؔ਺ςʔϒϧ͔ΒϝιουΛ୳ࡧ͢Δ%JTQBUDIํࣜ
    w ΫϥεͷϝιουΛݺͼग़࣌͢ʹ࢖͏
    w ΠϯελϯεͷϝλσʔλʹຒΊࠐ·ΕΔ

23. func Animal.bark() *Animal.bark 75BCMF
    GPS
    "OJNBM class Animal { func bark() {}

    }

24. func Animal.bark() *Animal.bark 75BCMF
    GPS
    $BU *Animal.bark 75BCMF
    GPS
    "OJNBM class Animal { func

    bark() {} } class Cat: Animal { }

25. func Cat.foo() func Animal.bark() *Animal.bark *Animal.bark *Cat.foo 75BCMF
    GPS
    "OJNBM 75BCMF
    GPS
    $BU class

    Animal { func bark() {} } class Cat: Animal { func foo() {} }

26. class Animal { func bark() {} } class Cat: Animal

    { override func bark() {} func foo() {} } 75BCMF
    GPS
    $BU func Animal.bark() 75BCMF
    GPS
    "OJNBM *Animal.bark *Animal.bark *Cat.foo func Cat.bark() func Cat.foo()

27. 8JUOFTT
    5BCMF w Ծ૝ؔ਺ςʔϒϧ͔ΒϝιουΛ୳ࡧ͢Δ%JTQBUDIํࣜ
    w ϓϩτίϧͷϝιουΛݺͼग़࣌͢ʹ࢖͏
    w ϓϩτίϧ΁ͷ४ڌ͝ͱʹఆٛ͞ΕΔ

28. protocol Animal { func bark() }

29. protocol Animal { func bark() } struct Dog: Animal {

    func bark() {} } 8JUOFTT
    5BCMF
    GPS
    "OJNBM
    JO
    DPOGPSNBODF
    %PH
    *Animal.bark func Animal.bark(dog) { Dog.bark(dog) } 8JUOFTT
    NFUIPE
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    DPOGPSNBODF
    %PH

30. ʮΘΜʯ໰୊

31. class Cat { func bark() -> String { return "ʹΌΜ"

    } } class Dog { func bark() -> String { return “ΘΜ" } } let cat = Cat() let dog = unsafeBitCast(cat, to: Dog.self) print(dog.bark()) ϝϞϦϨΠΞ΢τ͸มߋ͞Εͳ͍ ࢀর͢ΔVTable΋มΘΒͳ͍ Catͷςʔϒϧ͕ࢀর͞ΕΔ ʮʹΌΜʯ͕ग़ྗ͞ΕΔ͸ͣʂ

32. ͔͠͠ɺ

33. class Cat { func bark() -> String { return "ʹΌΜ"

    } } class Dog { func bark() -> String { return "ΘΜ" } } let cat = Cat() let dog = unsafeBitCast(cat, to: Dog.self) print(dog.bark()) // ΘΜ ʮΘΜʯ
34. None

35. ࠷దԽΛΦϑʹͯ͠ΈΔ

36. $ swiftc -frontend -c -primary-file animal.swift $ swiftc animal.o $

    ./animal ʹΌΜ ʮʹΌΜʯ

37. ࠷దԽͷաఔʹԿ͔͋Γͦ͏

38. %FWJSUVBMJ[F

39. %FWJSUVBMJ[F w 4*-0QUJNJ[FSͷ࠷దԽύε
    w %ZOBNJD
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    %JTQBUDIʹ࠷దԽ͢Δ
    w ίϯύΠϧ࣌ͷܕ৘ใ͔ΒϝιουΛ̍ͭʹܾΊΔ

40. 75BCMFͷ࠷దԽ

41. USZ%FWJSUVBMJ[F"QQMZ auto &M = FAS.getModule(); auto Instance = stripUpCasts(CMI->getOperand()); auto

    ClassType = Instance->getType(); ... if (isEffectivelyFinalMethod(FAS, ClassType, CD, CHA)) return tryDevirtualizeClassMethod(FAS, Instance, ORE, true /*isEffectivelyFinalMethod*/); if (auto Instance = getInstanceWithExactDynamicType(CMI->getOperand(), CMI->getModule(), CHA)) return tryDevirtualizeClassMethod(FAS, Instance, ORE); if (auto ExactTy = getExactDynamicType(CMI->getOperand(), CMI->getModule(), CHA)) { if (ExactTy == CMI->getOperand()->getType()) return tryDevirtualizeClassMethod(FAS, CMI->getOperand(), ORE); } MJC4*-0QUJNJ[FS6UJMT%FWJSUVBMJ[FDQQ

42. USZ%FWJSUVBMJ[F"QQMZ auto &M = FAS.getModule(); auto Instance = stripUpCasts(CMI->getOperand()); auto

    ClassType = Instance->getType(); ... if (isEffectivelyFinalMethod(FAS, ClassType, CD, CHA)) return tryDevirtualizeClassMethod(FAS, Instance, ORE, true /*isEffectivelyFinalMethod*/); if (auto Instance = getInstanceWithExactDynamicType(CMI->getOperand(), CMI->getModule(), CHA)) return tryDevirtualizeClassMethod(FAS, Instance, ORE); if (auto ExactTy = getExactDynamicType(CMI->getOperand(), CMI->getModule(), CHA)) { if (ExactTy == CMI->getOperand()->getType()) return tryDevirtualizeClassMethod(FAS, CMI->getOperand(), ORE); } Πϯελϯεͷ࣮ߦ࣌ͷܕ͕੩తʹܾఆͰ͖Δύλʔϯ MJC4*-0QUJNJ[FS6UJMT%FWJSUVBMJ[FDQQ

43. %FWJSUVBMJ[F
    GPS
    75BCMF class Animal { func bark() {} } class Cat:

    Animal { override func bark() {} } let animal: Animal = Cat() // ΠχγϟϥΠβ͔Β࡞ͬͯΔͷͰCatܕ animal.bark() Πϯελϯεͷ࣮ߦ࣌ͷܕ͕੩తʹܾఆͰ͖Δύλʔϯ

44. USZ%FWJSUVBMJ[F"QQMZ auto &M = FAS.getModule(); auto Instance = stripUpCasts(CMI->getOperand()); auto

    ClassType = Instance->getType(); ... if (isEffectivelyFinalMethod(FAS, ClassType, CD, CHA)) return tryDevirtualizeClassMethod(FAS, Instance, ORE, true /*isEffectivelyFinalMethod*/); if (auto Instance = getInstanceWithExactDynamicType(CMI->getOperand(), CMI->getModule(), CHA)) return tryDevirtualizeClassMethod(FAS, Instance, ORE); if (auto ExactTy = getExactDynamicType(CMI->getOperand(), CMI->getModule(), CHA)) { if (ExactTy == CMI->getOperand()->getType()) return tryDevirtualizeClassMethod(FAS, CMI->getOperand(), ORE); } ϝιου͕
    z࣮࣭pOBMzͳύλʔϯ MJC4*-0QUJNJ[FS6UJMT%FWJSUVBMJ[FDQQ

45. JT&⒎FDUJWFMZ'JOBM.FUIPE static bool isEffectivelyFinalMethod(FullApplySite AI, SILType ClassType, ClassDecl *CD, ClassHierarchyAnalysis

    *CHA) { if (CD && CD->isFinal()) return true; const DeclContext *DC = AI.getModule().getAssociatedContext(); auto *CMI = cast<MethodInst>(AI.getCallee()); if (!calleesAreStaticallyKnowable(AI.getModule(), CMI->getMember())) return false; auto *Method = CMI->getMember().getAbstractFunctionDecl(); if (!Method->isOverridden()) return true; ... return true; } ϝιου͕
    z࣮࣭pOBMzͳύλʔϯ MJC4*-0QUJNJ[FS6UJMT%FWJSUVBMJ[FDQQ

46. JT&⒎FDUJWFMZ'JOBM.FUIPE static bool isEffectivelyFinalMethod(FullApplySite AI, SILType ClassType, ClassDecl *CD, ClassHierarchyAnalysis

    *CHA) { if (CD && CD->isFinal()) return true; const DeclContext *DC = AI.getModule().getAssociatedContext(); auto *CMI = cast<MethodInst>(AI.getCallee()); if (!calleesAreStaticallyKnowable(AI.getModule(), CMI->getMember())) return false; auto *Method = CMI->getMember().getAbstractFunctionDecl(); if (!Method->isOverridden()) return true; ... return true; } ϝιου͕
    z࣮࣭pOBMzͳύλʔϯ MJC4*-0QUJNJ[FS6UJMT%FWJSUVBMJ[FDQQ

47. JT&⒎FDUJWFMZ'JOBM.FUIPE static bool isEffectivelyFinalMethod(FullApplySite AI, SILType ClassType, ClassDecl *CD, ClassHierarchyAnalysis

    *CHA) { if (CD && CD->isFinal()) return true; const DeclContext *DC = AI.getModule().getAssociatedContext(); auto *CMI = cast<MethodInst>(AI.getCallee()); if (!calleesAreStaticallyKnowable(AI.getModule(), CMI->getMember())) return false; auto *Method = CMI->getMember().getAbstractFunctionDecl(); if (!Method->isOverridden()) return true; ... return true; } ϝιου͕
    z࣮࣭pOBMzͳύλʔϯ MJC4*-0QUJNJ[FS6UJMT%FWJSUVBMJ[FDQQ

48. DBMMFFT"SF4UBUJDBMMZ,OPXBCMF bool swift::calleesAreStaticallyKnowable(SILModule &M, SILDeclRef Decl) { ... switch (AFD->getEffectiveAccess())

    { case AccessLevel::Open: return false; case AccessLevel::Public: if (isa<ConstructorDecl>(AFD)) { auto *ND = AFD->getDeclContext()->getSelfNominalTypeDecl(); if (ND->getEffectiveAccess() == AccessLevel::Open) return false; } case AccessLevel::Internal: return M.isWholeModule(); case AccessLevel::FilePrivate: case AccessLevel::Private: return true; } } ϝιουΛ੩తʹܾఆͰ͖Δύλʔϯ MJC4*-0QUJNJ[FS6UJMT-PDBMDQQ

49. JT&⒎FDUJWFMZ'JOBM.FUIPE static bool isEffectivelyFinalMethod(FullApplySite AI, SILType ClassType, ClassDecl *CD, ClassHierarchyAnalysis

    *CHA) { if (CD && CD->isFinal()) return true; const DeclContext *DC = AI.getModule().getAssociatedContext(); auto *CMI = cast<MethodInst>(AI.getCallee()); if (!calleesAreStaticallyKnowable(AI.getModule(), CMI->getMember())) return false; auto *Method = CMI->getMember().getAbstractFunctionDecl(); if (!Method->isOverridden()) return true; ... return true; } ϝιου͕
    z࣮࣭pOBMzͳύλʔϯ MJC4*-0QUJNJ[FS6UJMT%FWJSUVBMJ[FDQQ

50. JT&⒎FDUJWFMZ'JOBM.FUIPE static bool isEffectivelyFinalMethod(FullApplySite AI, SILType ClassType, ClassDecl *CD, ClassHierarchyAnalysis

    *CHA) { ... if (!Method->isOverridden()) return true; ClassHierarchyAnalysis::ClassList Subs; getAllSubclasses(CHA, CD, ClassType, AI.getModule(), Subs); auto *ImplMethod = CD->findImplementingMethod(Method); for (auto S : Subs) { auto *ImplFD = S->findImplementingMethod(Method); if (ImplFD != ImplMethod) return false; } return true; } ϝιου͕
    z࣮࣭pOBMzͳύλʔϯ MJC4*-0QUJNJ[FS6UJMT%FWJSUVBMJ[FDQQ

51. JT&⒎FDUJWFMZ'JOBM.FUIPE static bool isEffectivelyFinalMethod(FullApplySite AI, SILType ClassType, ClassDecl *CD, ClassHierarchyAnalysis

    *CHA) { ... if (!Method->isOverridden()) return true; ClassHierarchyAnalysis::ClassList Subs; getAllSubclasses(CHA, CD, ClassType, AI.getModule(), Subs); auto *ImplMethod = CD->findImplementingMethod(Method); for (auto S : Subs) { auto *ImplFD = S->findImplementingMethod(Method); if (ImplFD != ImplMethod) return false; } return true; } ϝιου͕
    z࣮࣭pOBMzͳύλʔϯ MJC4*-0QUJNJ[FS6UJMT%FWJSUVBMJ[FDQQ

52. JT&⒎FDUJWFMZ'JOBM.FUIPE static bool isEffectivelyFinalMethod(FullApplySite AI, SILType ClassType, ClassDecl *CD, ClassHierarchyAnalysis

    *CHA) { ... if (!Method->isOverridden()) return true; ClassHierarchyAnalysis::ClassList Subs; getAllSubclasses(CHA, CD, ClassType, AI.getModule(), Subs); auto *ImplMethod = CD->findImplementingMethod(Method); for (auto S : Subs) { auto *ImplFD = S->findImplementingMethod(Method); if (ImplFD != ImplMethod) return false; } return true; } ϝιου͕
    z࣮࣭pOBMzͳύλʔϯ MJC4*-0QUJNJ[FS6UJMT%FWJSUVBMJ[FDQQ

53. 0WFSSJEF͞ΕͭͭΠϯελϯε͕
    ͦͷαϒΫϥεʹͳΓಘͳ͍৔߹ class Cat<Name> { func bark() {} } enum

    Tama {} enum Kuro {} class TamaCat: Cat<Tama> { override func bark() {} } func callBark(cat: Cat<Kuro>) { cat.bark() }

54. class Cat<Name> { func bark() {} } enum Tama {}

    enum Kuro {} // Cat<Kuro>ͷαϒλΠϓͰ͸ͳ͍ class TamaCat: Cat<Tama> { override func bark() {} } func callBark(cat: Cat<Kuro>) { cat.bark() } 0WFSSJEF͞ΕͭͭΠϯελϯε͕
    ͦͷαϒΫϥεʹͳΓಘͳ͍৔߹

55. JT&⒎FDUJWFMZ'JOBM.FUIPE ϝιου͕
    z࣮࣭pOBMzͳύλʔϯ

56. ʮΘΜʯ໰୊

57. class Cat { func bark() -> String { return “ʹΌΜ"

    } } class Dog { func bark() -> String { return "ΘΜ" } } let cat = Cat() let dog = unsafeBitCast(cat, to: Dog.self) print(dog.bark()) // ΘΜ ࠷దԽ͋Γͷ৔߹ Dog.barkϝιου͸non-final ΦʔόʔϥΠυ͞Ε͍ͯͳ͍ͷͰ”࣮࣭final” dog.bark()͕Static Dispatchʹ࠷దԽ͞ΕΔ

58. ࠷దԽͳ͠ͷ৔߹ class Cat { func bark() -> String { return

    “ʹΌΜ" } } class Dog { func bark() -> String { return "ΘΜ" } } let cat = Cat() let dog = unsafeBitCast(cat, to: Dog.self) print(dog.bark()) // ʹΌΜ Whole Module࠷దԽ͕Φϑ Ϟδϡʔϧ಺ͰΦʔόʔϥΠυ͞ΕΔՄೳੑ͕͋Δ ΠϯελϯεͷϝλσʔλͷVTable͔Β Dynamic Dispatch͢Δ

59. %JTQBUDI
    1FSGPSNBODF

60. LBUFJOPJHBLVLVO%JTQBUDI#FODINBSL

61. 3VOUJNF
    1FSGPSNBODF /VNCFS
    PG
    EJTQBUDI $16
    5JNF

62. ·ͱΊ w %ZOBNJD
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    w ίϯύΠϥΛಡΊ͹4XJGUͷڍಈ͕෼͔͓ͬͯ΋͠Ζ͍

63. w IUUQTHJUIVCDPNBQQMFTXJGUCMPCNBTUFSEPDT4*-STU
    w IUUQTHJUIVCDPNBQQMFTXJGUCMPCNBTUFSEPDT 0QUJNJ[BUJPO5JQTSTUSFEVDJOHEZOBNJDEJTQBUDI
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