InvokeDynamic - You Ain't Seen Nothin Yet

invokedynamic You Ain’t Seen Nothin’ Yet

@headius

JRuby Guy

JVM Guy

I KNOW π

What isinvokedynamic?

Invoke?

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

Dynamic?

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

User-deﬁned Data Endpoint

User-deﬁned Data Endpoint Hä ?!

JVM 101

JVM 101200 opcodes

JVM 101 200 opcodesTen (or 16) “data endpoints”

JVM 101 200 opcodes Ten (or 16) “data endpoints” Invocation invokevirtualinvokeinterface invokestatic invokespecial

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

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

JVM 101 200 opcodes Ten (or 16) “data endpoints” Invocation Field Access Array Access invokevirtual getfield *aloadinvokeinterface 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

JVMOpcodes

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

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

Invocation

InvocationCall Site VM Operations

Invocation Call Site VM OperationsMethod Name SignatureTarget + Args

Invocation Call Site VM OperationsMethod Name Method Lookup Signature Type CheckingTarget + Args Branch Method Cache

Invocation Target Object instanceofobj.foo() JVM Object’s Class void foo() static void bar()

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

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

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

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

InvocationVM 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()

Invocation

Invocation Virtual InterfaceMethod Lookup Method LookupType Checking Type Checking Branch BranchMethod Cache Method Cache

Invocation Virtual InterfaceMethod Lookup Method LookupType Checking Type Checking Branch BranchMethod Cache Method Cache StaticMethod Lookup BranchMethod Cache

Invocation Virtual InterfaceMethod Lookup Method LookupType Checking Type Checking Branch BranchMethod Cache Method Cache Static Special Method LookupMethod Lookup Access Checking Branch BranchMethod Cache Method Cache

Field Access

Field Access Call Site Field Name SignatureTarget [+ Value]

Field Access Call Site VM Operations Field Name Get Field Offset Signature Type CheckTarget [+ Value] Access Field

Array Access

Array Access Call SiteTarget + Offset [+ Value]

Array Access Call Site VM OperationsTarget + Offset [+ Value] Type Check Access Element

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

invokedynamic

Call Siteinvokedynamic

Call Site VM Operationsinvokedynamic

bytecode + Site Call bootstrap Method Handles VM Operationsinvokedynamic

bytecode

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

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

invokedynamic bytecode

invokedynamic bytecodebo ot stra p m et ho d

invokedynamic bytecodebo ot stra p m et ho d method handles

invokedynamic bytecode target methodbo ot stra p m et ho d method handles

You DecideHow to reach some data endpoint

You DecideWhat transformations to perform on arguments

You DecideWhen and why the endpoint should change

You DecideHow to make the JVM work for you!

Use Cases

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

Dynamic Invocation Target Object associated withobj.foo() JVM Method Table def foo ... def bar ...

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

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

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

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

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

Lazy Constant JVM LazyLAZY_CONST Computation Call Site

Lazy ConstantVM Operations JVM LazyLAZY_CONST Computation Call Site

Lazy ConstantVM Operations Calculate Value JVM LazyLAZY_CONST Computation value Call Site

Lazy ConstantVM Operations Calculate Value Bind Permanently JVM LazyLAZY_CONST value Computation Call Site

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

Lambda Expression SurroundingString s -> JVM ClasstoString() lambda body Call Site

Lambda ExpressionVM Operations Surrounding String s -> JVM Class toString() lambda body Call Site

Lambda ExpressionVM OperationsRetrieve Lambda Obj Surrounding String s -> lambda JVM Class body toString() Call Site

Lambda ExpressionVM OperationsRetrieve Lambda Obj Bind and Invoke Surrounding String s -> lambda JVM Class body toString() Call Site

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

How Do You Beneﬁt?

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

JRuby/Java 6 JRuby/Java 7

JRuby/Java 6 JRuby/Java 7 Times Faster than Ruby 1.9.3 53.75 2.51.25 0 base64 richards neural redblack

JRuby/Java 6 JRuby/Java 7 Times Faster than Ruby 1.9.3 53.75 2.5 1.914 1.538 1.5651.25 1.346 0 base64 richards neural redblack

JRuby/Java 6 JRuby/Java 7 Times Faster than Ruby 1.9.3 5 4.323.75 3.66 3.44 2.5 2.658 1.914 1.538 1.5651.25 1.346 0 base64 richards neural redblack

invokedynamicis the future of Java!

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!

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InvokeDynamic - You Ain't Seen Nothin Yet

by Charles Nutter

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