Keynote from JAX 2012

1. invokedynamic
You Ain’t Seen Nothin’ Yet

2. Me

6. @headius

7. JRuby Guy

8. JVM Guy

9. I KNOW
π

11. What is
invokedynamic?

12. Invoke?

13. Invoke?
That’s one use, but there are many others

14. Dynamic?

15. Dynamic?
Dynamic typing is a common reason,
but there are many others

16. User-defined Data
Endpoint

17. User-defined Data
Endpoint
Hä
?!

18. JVM 101

19. JVM 101
200 opcodes

20. JVM 101
200 opcodes
Ten (or 16) “data endpoints”

21. JVM 101
200 opcodes
Ten (or 16) “data endpoints”
Invocation
invokevirtual
invokeinterface
invokestatic
invokespecial

22. JVM 101
200 opcodes
Ten (or 16) “data endpoints”
Invocation Field Access
invokevirtual getfield
invokeinterface setfield
invokestatic getstatic
invokespecial setstatic

23. JVM 101
200 opcodes
Ten (or 16) “data endpoints”
Invocation Field Access Array Access
invokevirtual getfield *aload
invokeinterface setfield *astore
invokestatic getstatic b,s,c,i,l,d,f,a
invokespecial setstatic

24. JVM 101
200 opcodes
Ten (or 16) “data endpoints”
Invocation Field Access Array Access
invokevirtual getfield *aload
invokeinterface setfield *astore
invokestatic getstatic b,s,c,i,l,d,f,a
invokespecial setstatic
All Java code revolves around these endpoints
Remaining ops are stack, local vars, flow control
allocation, and math/boolean/bit operations

25. JVM
Opcodes

26. JVM
Opcodes
Invocation Field Access Array Access
invokevirtual getfield
*aload
invokeinterface setfield
*astore
invokestatic getstatic
b,s,c,i,l,d,f,a
invokespecial setstatic

27. JVM
Opcodes
Invocation Field Access Array Access
invokevirtual getfield
*aload
invokeinterface setfield
*astore
invokestatic getstatic
b,s,c,i,l,d,f,a
invokespecial setstatic
Stack Local Vars
Flow Control
Allocation
Boolean and Numeric

28. JVM
Opcodes
Invocation Field Access Array Access
invokevirtual getfield
*aload
invokeinterface setfield
*astore
invokestatic getstatic
b,s,c,i,l,d,f,a
invokespecial setstatic
Stack Local Vars
Flow Control
Allocation
Boolean and Numeric

29. JVM
Opcodes
Invocation Field Access Array Access
invokevirtual getfield
*aload
invokeinterface setfield
*astore
invokestatic getstatic
b,s,c,i,l,d,f,a
invokespecial setstatic
Stack Local Vars
Flow Control
Allocation
Boolean and Numeric

32. Invocation

33. Invocation

34. Invocation
Call Site VM Operations

35. Invocation
Call Site VM Operations
Method Name
Signature
Target + Args

36. Invocation
Call Site VM Operations
Method Name Method Lookup
Signature Type Checking
Target + Args Branch
Method Cache

37. Invocation
Target
Object
instanceof
obj.foo() JVM
Object’s
Class
void foo()
static void bar()

38. Invocation
VM Operations
Target
Object
instanceof
obj.foo() JVM
Object’s
Class
Call Site void foo()
static void bar()

39. Invocation
VM Operations
Target
Object
instanceof
obj.foo() JVM
Object’s
Class
Call Site void foo()
static void bar()

40. Invocation
VM Operations
Method Lookup
Target
Object
instanceof
obj.foo() JVM
Object’s
Class
Call Site void foo()
void foo()
static void bar()

41. Invocation
VM Operations
Method Lookup
Type Checking Target
Object
instanceof
obj.foo() JVM
Object’s
Class
Call Site void foo()
void foo()
static void bar()

42. Invocation
VM Operations
Method Lookup
Type Checking Target
Branch Object
instanceof
obj.foo() JVM
Object’s
Class
Call Site void foo()
void foo()
static void bar()

43. Invocation
VM Operations
Method Lookup
Type Checking Target
Branch Object
Method Cache
instanceof
obj.foo() JVM
Object’s
Class
void foo()
Call Site void foo()
static void bar()

44. Invocation

45. Invocation
Virtual Interface
Method Lookup Method Lookup
Type Checking Type Checking
Branch Branch
Method Cache Method Cache

46. Invocation
Virtual Interface
Method Lookup Method Lookup
Type Checking Type Checking
Branch Branch
Method Cache Method Cache
Static
Method Lookup
Branch
Method Cache

47. Invocation
Virtual Interface
Method Lookup Method Lookup
Type Checking Type Checking
Branch Branch
Method Cache Method Cache
Static Special
Method Lookup
Method Lookup
Access Checking
Branch
Branch
Method Cache
Method Cache

48. Field Access

49. Field Access
Call Site
Field Name
Signature
Target [+ Value]

50. Field Access
Call Site VM Operations
Field Name Get Field Offset
Signature Type Check
Target [+ Value] Access Field

51. Array Access

52. Array Access
Call Site
Target + Offset [+ Value]

53. Array Access
Call Site VM Operations
Target + Offset [+ Value] Type Check
Access Element

54. Deja Vu?
• Similar call site
• Similar VM operations
• Why can’t we compose our own?

56. invokedynamic

57. Call Site
invokedynamic

58. Call Site VM Operations
invokedynamic

59. bytecode + Site
Call bootstrap Method Handles
VM Operations
invokedynamic

60. bytecode

61. bytecode
• invokedynamic
• like invokevirtual, invokestatic, etc
• Name and signature, like the others
• Additional bootstrap method
• JVM defers to you

62. Method Handles
• Function/field/array pointers
• Argument manipulation
• Flow control
• Optimizable by the JVM
• This is very important

64. invokedynamic bytecode

65. invokedynamic bytecode
bo
ot
stra
p
m
et
ho
d

66. invokedynamic bytecode
bo
ot
stra
p
m
et
ho
d method handles

67. invokedynamic bytecode
target method
bo
ot
stra
p
m
et
ho
d method handles

68. invokedynamic bytecode
target method
bo
ot
stra
p
m
et
ho
d method handles

69. invokedynamic bytecode
target method
bo
ot
stra
p
m
et
ho
d method handles

70. You Decide
How to reach some data endpoint

71. You Decide
What transformations to perform on arguments

72. You Decide
When and why the endpoint should change

73. You Decide
How to make the JVM work for you!

74. Use Cases

75. Dynamic Invocation
• The obvious one
• Method lookup based on runtime types
• Potentially mutable types
• Type check specific to language

76. Dynamic Invocation
Target
Object
associated with
obj.foo() JVM
Method
Table
def foo ...
def bar ...

77. Dynamic Invocation
VM Operations
Target
Object
associated with
obj.foo() JVM
Method
Table
Call Site def foo ...
def bar ...

78. Dynamic Invocation
VM Operations
Target
Object
associated with
obj.foo() JVM
Method
Table
Call Site def foo ...
def bar ...

79. Dynamic Invocation
VM Operations
Method Lookup Target
Object
associated with
obj.foo() JVM
Method
Table
Call Site def foo ...
def foo ...
def bar ...

80. Dynamic Invocation
VM Operations
Method Lookup Target
Branch
Object
associated with
obj.foo() JVM
Method
Table
Call Site def foo ...
def foo ...
def bar ...

81. Dynamic Invocation
VM Operations
Method Lookup Target
Branch
Method Cache Object
associated with
obj.foo() JVM
def foo ...
Method
Table
Call Site def foo ...
def bar ...

82. Lazy Constants
• Call site just produces a value
• Value calculated once
• Subsequent access is direct, optimizable

83. Lazy Constant
JVM Lazy
LAZY_CONST
Computation
Call Site

84. Lazy Constant
VM Operations
JVM Lazy
LAZY_CONST
Computation
Call Site

85. Lazy Constant
VM Operations
JVM Lazy
LAZY_CONST
Computation
Call Site

86. Lazy Constant
VM Operations
Calculate Value
JVM Lazy
LAZY_CONST
Computation
value
Call Site

87. Lazy Constant
VM Operations
Calculate Value
Bind Permanently
JVM Lazy
LAZY_CONST
value Computation
Call Site

88. Delegates
• Arbitrary function pointers
• No anon inner classes
• No bridge methods
• Java 8 “Lambda” will do this

89. Lambda Expression
Surrounding
String s -> JVM Class
toString() lambda
body
Call Site

90. Lambda Expression
VM Operations
Surrounding
String s -> JVM Class
toString() lambda
body
Call Site

91. Lambda Expression
VM Operations
Surrounding
String s -> JVM Class
toString() lambda
body
Call Site

92. Lambda Expression
VM Operations
Retrieve Lambda Obj
Surrounding
String s ->
lambda JVM Class
body
toString()
Call Site

93. Lambda Expression
VM Operations
Retrieve Lambda Obj
Bind and Invoke
Surrounding
String s ->
lambda JVM Class
body
toString()
Call Site

94. Multi-dispatch
• Dispatch based on runtime types
• Java is single-dispatch
• Call site looks like normal invoke
• VM side examines target, args
• Multiple targets cached with branches

95. How Do You Benefit?

96. Future
• New language impls
• JavaScript: Dyn.js and Nashorn
• Redline Smalltalk
• Improved language performance
• JRuby, Groovy, Jython, Clojure, Scala
• Java features too!

97. JRuby/Java 6 JRuby/Java 7

98. JRuby/Java 6 JRuby/Java 7
Times Faster than Ruby 1.9.3
5
3.75
2.5
1.25
0
base64 richards neural redblack

99. JRuby/Java 6 JRuby/Java 7
Times Faster than Ruby 1.9.3
5
3.75
2.5
1.914
1.538 1.565
1.25 1.346
0
base64 richards neural redblack

100. JRuby/Java 6 JRuby/Java 7
Times Faster than Ruby 1.9.3
5
4.32
3.75
3.66
3.44
2.5 2.658
1.914
1.538 1.565
1.25 1.346
0
base64 richards neural redblack

101. invokedynamic
is the future of Java!

102. Thank You!
• @headius
• blog.headius.com
• invokedynamic post coming soon
• headius@headius.com
• Come to my deep dive at 16:00
• Have fun with invokedynamic!