JavaOne 2015: From Java Code to Machine Code

143
© 2015 IBM Corporation Java Code to Machine Code How to write highly optimizeable Java code

Transcript of JavaOne 2015: From Java Code to Machine Code

Page 1: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation

Java Code to Machine CodeHow to write highly optimizeable Java code

Page 2: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation

Important Disclaimers

THE INFORMATION CONTAINED IN THIS PRESENTATION IS PROVIDED FOR INFORMATIONAL PURPOSES ONLY.

WHILST EFFORTS WERE MADE TO VERIFY THE COMPLETENESS AND ACCURACY OF THE INFORMATION CONTAINED IN THIS PRESENTATION, IT IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED.

ALL PERFORMANCE DATA INCLUDED IN THIS PRESENTATION HAVE BEEN GATHERED IN A CONTROLLED ENVIRONMENT. YOUR OWN TEST RESULTS MAY VARY BASED ON HARDWARE, SOFTWARE OR INFRASTRUCTURE DIFFERENCES.

ALL DATA INCLUDED IN THIS PRESENTATION ARE MEANT TO BE USED ONLY AS A GUIDE.

IN ADDITION, THE INFORMATION CONTAINED IN THIS PRESENTATION IS BASED ON IBM’S CURRENT PRODUCT PLANS AND STRATEGY, WHICH ARE SUBJECT TO CHANGE BY IBM, WITHOUT NOTICE.

IBM AND ITS AFFILIATED COMPANIES SHALL NOT BE RESPONSIBLE FOR ANY DAMAGES ARISING OUT OF THE USE OF, OR OTHERWISE RELATED TO, THIS PRESENTATION OR ANY OTHER DOCUMENTATION.

NOTHING CONTAINED IN THIS PRESENTATION IS INTENDED TO, OR SHALL HAVE THE EFFECT OF:

- CREATING ANY WARRANT OR REPRESENTATION FROM IBM, ITS AFFILIATED COMPANIES OR ITS OR THEIR SUPPLIERS AND/OR LICENSORS

2

Page 3: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation3 3

Monitoring and Diagnostics Architect

@Chris__Bailey

@seabaylea

Page 4: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation4

Goals of the talk

Look at how Java code is executed

Look at how Java code is optimized

Learn how to enable optimizations to occur

Page 5: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation5

> javac

Page 6: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation6

Anatomy of a Java Class Filestruct Class_File_Format { u4 magic_number; u2 minor_version; u2 major_version;

u2 constant_pool_count; cp_info constant_pool[constant_pool_count – 1];

u2 access_flags; u2 this_class; u2 super_class;

u2 interfaces_count; u2 interfaces[interfaces_count]; u2 fields_count; field_info fields[fields_count]; u2 methods_count; method_info methods[methods_count];

u2 attributes_count; attribute_info attributes[attributes_count];}

Page 7: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation7

Anatomy of a Java Class File

public class MyObject() { public int myField = 48;

public MyObject() { }}

Page 8: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation8

Anatomy of a Java Class Filepublic class MyObject() { public int myField = 48;

public MyObject() { }}

flags: ACC_PUBLIC, ACC_SUPERConstant pool: #1 = Class #2 #2 = Utf8 MyObject #3 = Class #4 #4 = Utf8 java/lang/Object #5 = Utf8 myField #6 = Utf8 I #7 = Utf8 <init> #8 = Utf8 ()V #9 = Utf8 Code #10 = Methodref #4.#11 #11 = NameAndType #7:#8 #12 = Fieldref #1.#13 #13 = NameAndType #5:#6 #14 = Utf8 LineNumberTable #15 = Utf8 LocalVariableTable #16 = Utf8 this #17 = Utf8 LmyObject; #18 = Utf8 SourceFile #19 = Utf8 MyObject.java

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

Page 9: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation9

Anatomy of a Java Class File

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

public class MyObject() { public int myField = 48;

public MyObject() { }}

Page 10: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation10

Anatomy of a Java Class File

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

Constant Pool

#2 MyObject #4 java/lang/Object

myField I <init> ()V

Code #3.#11 #7.#8 #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

Page 11: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation11

Anatomy of a Java Class File

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

Local Variables

Constant Pool

#2 MyObject #4 java/lang/Object

myField I <init> ()V

Code #3.#11 #7.#8 #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

Page 12: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation12

Anatomy of a Java Class File

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

Local Variables

Operand Stack

Constant Pool

#2 MyObject #4 java/lang/Object

myField I <init> ()V

Code #3.#11 #7.#8 #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

Page 13: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation13

Anatomy of a Java Class File

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

Local Variables

Operand Stack

Constant Pool

Java Heap

#2 MyObject #4 java/lang/Object

myField I <init> ()V

Code #3.#11 #7.#8 #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

Page 14: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation14

Executing Bytecode

Page 15: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation15

Executing Bytecodes

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

Local Variables

Operand Stack

Constant Pool

Java Heap

#2 MyObject #4 java/lang/Object

myField I <init> ()V

Code #3.#11 #7.#8 #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

Page 16: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation16

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

Operand Stack

Constant Pool

Java Heap

#2 MyObject #4 java/lang/Object

myField I <init> ()V

Code #3.#11 #7.#8 #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

Executing Bytecodes

Page 17: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation17

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject #4 java/lang/Object

myField I <init> ()V

Code #3.#11 #7.#8 #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

push

Executing Bytecodes

Page 18: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation18

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject #4 java/lang/Object

myField I <init> ()V

Code #3.#11 #7.#8 #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

Executing Bytecodes

Page 19: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation19

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject #4 java/lang/Object

myField I <init> ()V

Code #3.#11 #7.#8 #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

Executing Bytecodes

Page 20: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation20

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject #4 java/lang/Object

myField I <init> ()V

Code #3.#11 #7.#8 #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

Executing Bytecodes

Page 21: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation21

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code #3.#11 #7.#8 #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

Executing Bytecodes

Page 22: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation22

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code #3.#11 #7.#8 #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

Executing Bytecodes

Page 23: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation23

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.#11 #7.#8 #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

Executing Bytecodes

Page 24: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation24

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.#11 #7.#8 #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

Executing Bytecodes

Page 25: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation25

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.#11 #7.#8 #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

Executing Bytecodes

Page 26: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation26

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.#11 <init>.#8 #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

Executing Bytecodes

Page 27: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation27

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.#11 <init>.#8 #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

Executing Bytecodes

Page 28: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation28

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.#11 <init>.()V #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

Executing Bytecodes

Page 29: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation29

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.#11 <init>.()V #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

Executing Bytecodes

Page 30: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation30

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

Executing Bytecodes

Page 31: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation31

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #10 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

Executing Bytecodes

Page 32: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation32

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

Executing Bytecodes

Page 33: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation33

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

Local Variables

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

MyObject

Executing Bytecodes

Page 34: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation34

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

Local Variables

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

Executing Bytecodes

Page 35: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation35

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

Executing Bytecodes

Page 36: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation36

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

pushMyObject

Executing Bytecodes

Page 37: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation37

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

Executing Bytecodes

Page 38: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation38

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

pushMyObject

Executing Bytecodes

Page 39: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation39

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

Executing Bytecodes

Page 40: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation40

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

Executing Bytecodes

Page 41: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation41

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

Executing Bytecodes

Page 42: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation42

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

#2 MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

Executing Bytecodes

Page 43: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation43

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

MyObject MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

Executing Bytecodes

Page 44: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation44

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

MyObject MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V #1.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

Executing Bytecodes

Page 45: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation45

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

MyObject MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V MyObject.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

Executing Bytecodes

Page 46: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation46

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

MyObject MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V MyObject.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

Executing Bytecodes

Page 47: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation47

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

MyObject MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V MyObject.#13

#5.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

Executing Bytecodes

Page 48: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation48

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

MyObject MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V MyObject.#13

myField.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

Executing Bytecodes

Page 49: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation49

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

MyObject MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V MyObject.#13

myField.#6 LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

Executing Bytecodes

Page 50: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation50

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

MyObject MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V MyObject.#13

myField.I LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

Executing Bytecodes

Page 51: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation51

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

MyObject MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V MyObject.#13

myField.I LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

Executing Bytecodes

Page 52: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation52

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

MyObject MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V MyObject.myField.I

myField.I LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

Executing Bytecodes

Page 53: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation53

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield #12 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

MyObject MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V MyObject.myField.I

myField.I LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

Executing Bytecodes

Page 54: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation54

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield MyObject.myField.I 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

MyObject MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V MyObject.myField.I

myField.I LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

Executing Bytecodes

Page 55: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation55

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield MyObject.myField.I 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

MyObject MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V MyObject.myField.I

myField.I LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

pop

Executing Bytecodes

Page 56: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation56

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield MyObject.myField.I 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

MyObject MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V MyObject.myField.I

myField.I LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

>

MyObject

48pop

Executing Bytecodes

Page 57: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation57

public int myField; flags: ACC_PUBLIC

public MyObject(); flags: ACC_PUBLIC Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial Object.<init>.()V 4: aload_0 5: bipush 48 7: putfield MyObject.myField.I 10: return LineNumberTable: line 4: 0 line 2: 4 line 5: 10 LocalVariableTable: 0 11 0 this LmyObject;

thisLocal Variables

48

this

Operand Stack

Constant Pool

Java Heap

MyObject MyObject java/lang/Object java/lang/Object

myField I <init> ()V

Code Object.<init>.()V <init>.()V MyObject.myField.I

myField.I LineNumberTable LocalVariableTable this

LmyObject SourceFile MyObject.java

public class MyObject() { public int myField = 48;

public MyObject() { }}

> MyObject

48

Executing Bytecodes

Page 58: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation58

Local Variables

Operand Stack

Constant Pool

Java Heap

MyObject

48

Executing Bytecodes

Page 59: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation59

Machine Code

Page 60: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation60

Machine Codepublic synchronized int sync1(){ return intArr[0];}

Page 61: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation61

Machine Codepublic synchronized int sync1(){ return intArr[0];}

public int sync2(){ synchronized (this){ return intArr[0]; }}

Page 62: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation62

public synchronized int sync1(){ return intArr[0];}

public synchronized int sync1(); descriptor: ()I flags: ACC_PUBLIC, ACC_SYNCHRONIZED Code: stack=2, locals=1, args_size=1 0: aload_0 1: getfield #12 4: iconst_0 5: iaload 6: ireturn

public int sync2(){ synchronized (this){ return intArr[0]; }}

Machine Code

Page 63: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation63

public synchronized int sync1(){ return intArr[0];}

public synchronized int sync1(); descriptor: ()I flags: ACC_PUBLIC, ACC_SYNCHRONIZED Code: stack=2, locals=1, args_size=1 0: aload_0 1: getfield #12 4: iconst_0 5: iaload 6: ireturn

public int sync2(); descriptor: ()I flags: ACC_PUBLIC Code: stack=2, locals=2, args_size=1 0: aload_0 1: dup 2: astore_1 3: monitorenter 4: aload_0 5: getfield #12 // Field intArr:[I 8: iconst_0 9: iaload 10: aload_1 11: monitorexit 12: ireturn 13: aload_1 14: monitorexit 15: athrow Exception table: from to target type 4 12 13 any 13 15 13 any StackMapTable: number_of_entries = 1 frame_type = 255 /* full_frame */ offset_delta = 13 locals = [ class test/SyncClass, class test/SyncClass ] stack = [ class java/lang/Throwable ]

public int sync2(){ synchronized (this){ return intArr[0]; }}

Machine Code

Page 64: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation64

JIT Optimizations

Page 65: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation65

JIT Generated Code

public static int multiply(int a, int b){ return a * b;}

public static int multiply(int, int); descriptor: (II)I flags: ACC_PUBLIC, ACC_STATIC Code: stack=2, locals=2, args_size=2 0: iload_0 1: iload_1 2: imul 3: ireturn LineNumberTable: line 14: 0 LocalVariableTable: Start Length Slot Name Signature 0 4 0 a I 0 4 1 b I

# {method} {0x000000000d4408e0} 'multiply' '(II)I'# parm0: rdx = int# parm1: r8 = int# [sp+0x40] (sp of caller)0x000000000f121560: mov dword ptr0x000000000f121567: push rbp0x000000000f121568: sub rsp,30h ;*iload_00x000000000f12156c: imul edx,r8d0x000000000f121570: mov rax,rdx0x000000000f121573: add rsp,30h0x000000000f121577: pop rbp0x000000000f121578: test dword ptr0x000000000f12157e: ret

Page 66: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation66

public static int multiply(int a, int b){ return a * b;}

public static int multiply(int, int); descriptor: (II)I flags: ACC_PUBLIC, ACC_STATIC Code: stack=2, locals=2, args_size=2 0: iload_0 1: iload_1 2: imul 3: ireturn LineNumberTable: line 14: 0 LocalVariableTable: Start Length Slot Name Signature 0 4 0 a I 0 4 1 b I

# {method} {0x000000000d4408e0} 'multiply' '(II)I'# parm0: rdx = int# parm1: r8 = int# [sp+0x40] (sp of caller)0x000000000f121560: mov dword ptr0x000000000f121567: push rbp0x000000000f121568: sub rsp,30h0x000000000f12156c: imul edx,r8d0x000000000f121570: mov rax,rdx0x000000000f121573: add rsp,30h0x000000000f121577: pop rbp0x000000000f121578: test dword ptr0x000000000f12157e: ret

JIT Generated Code

Page 67: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation67

public static int multiply(int a, int b){ return a * b;}

public static int multiply(int, int); descriptor: (II)I flags: ACC_PUBLIC, ACC_STATIC Code: stack=2, locals=2, args_size=2 0: iload_0 1: iload_1 2: imul 3: ireturn LineNumberTable: line 14: 0 LocalVariableTable: Start Length Slot Name Signature 0 4 0 a I 0 4 1 b I

# {method} {0x000000000d4408e0} 'multiply' '(II)I'# parm0: rdx = int# parm1: r8 = int# [sp+0x40] (sp of caller)0x000000000f121560: mov dword ptr0x000000000f121567: push rbp0x000000000f121568: sub rsp,30h0x000000000f12156c: imul edx,r8d0x000000000f121570: mov rax,rdx0x000000000f121573: add rsp,30h0x000000000f121577: pop rbp0x000000000f121578: test dword ptr0x000000000f12157e: ret

JIT Generated Code

Page 68: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation68

JIT Generated Code

public static int multiply(int a, int b){ return a * b;}

public static int multiply(int, int); descriptor: (II)I flags: ACC_PUBLIC, ACC_STATIC Code: stack=2, locals=2, args_size=2 0: iload_0 1: iload_1 2: imul 3: ireturn LineNumberTable: line 14: 0 LocalVariableTable: Start Length Slot Name Signature 0 4 0 a I 0 4 1 b I

# {method} {0x000000000d4408e0} 'multiply' '(II)I'# parm0: rdx = int# parm1: r8 = int# [sp+0x40] (sp of caller)0x000000000f121560: mov dword ptr0x000000000f121567: push rbp0x000000000f121568: sub rsp,30h0x000000000f12156c: imul rdx,r8d0x000000000f121570: mov rax,rdx0x000000000f121573: add rsp,30h0x000000000f121577: pop rbp0x000000000f121578: test dword ptr0x000000000f12157e: ret

Page 69: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation69

JIT Generated Code

public static int multiply(int a, int b){ return a * b;}

public static int multiply(int, int); descriptor: (II)I flags: ACC_PUBLIC, ACC_STATIC Code: stack=2, locals=2, args_size=2 0: iload_0 1: iload_1 2: imul 3: ireturn LineNumberTable: line 14: 0 LocalVariableTable: Start Length Slot Name Signature 0 4 0 a I 0 4 1 b I

# {method} {0x000000000d4408e0} 'multiply' '(II)I'# parm0: rdx = int# parm1: r8 = int# [sp+0x40] (sp of caller)0x000000000f121560: mov dword ptr0x000000000f121567: push rbp0x000000000f121568: sub rsp,30h0x000000000f12156c: imul rdx,r8d0x000000000f121570: mov rax,rdx0x000000000f121573: add rsp,30h0x000000000f121577: pop rbp0x000000000f121578: test dword ptr0x000000000f12157e: ret

Page 70: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation70

JIT Generated Code

public static int multiply(int a, int b){ return a * b;}

public static int multiply(int, int); descriptor: (II)I flags: ACC_PUBLIC, ACC_STATIC Code: stack=2, locals=2, args_size=2 0: iload_0 1: iload_1 2: imul 3: ireturn LineNumberTable: line 14: 0 LocalVariableTable: Start Length Slot Name Signature 0 4 0 a I 0 4 1 b I

# {method} {0x000000000d4408e0} 'multiply' '(II)I'# parm0: rdx = int# parm1: r8 = int# [sp+0x40] (sp of caller)0x000000000f121560: mov dword ptr0x000000000f121567: push rbp0x000000000f121568: sub rsp,30h0x000000000f12156c: imul rdx,r8d0x000000000f121570: mov rax,rdx0x000000000f121573: add rsp,30h0x000000000f121577: pop rbp0x000000000f121578: test dword ptr0x000000000f12157e: ret

Page 71: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation71

Inlining

Page 72: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation72

Inlining

public static int factorial(int num) { int factorial = 1; for (int i = 1; i <= num; i++) { factorial = multiply(factorial, i); } return factorial;}

public static int multiply(int a, int b){ return a * b;}

Page 73: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation73

Inlining

public static int factorial(int num) { int factorial = 1; for (int i = 1; i <= num; i++) { factorial = multiply(factorial, i); } return factorial;}

public static int multiply(int a, int b){ return a * b;}

36 instructions

Page 74: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation74

Inlining

public static int factorial(int num) { int factorial = 1; for (int i = 1; i <= num; i++) { factorial = multiply(factorial, i); } return factorial;}

public static int multiply(int a, int b){ return a * b;}

36 instructions

9 instructions

Page 75: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation75

Inlining

public static int factorial(int num) { int factorial = 1; for (int i = 1; i <= num; i++) { factorial = multiply(factorial, i); } return factorial;}

public static int multiply(int a, int b){ return a * b;}

36 instructions

9 instructions

Page 76: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation76

Inlining

public static int factorial(int num) { int factorial = 1; for (int i = 1; i <= num; i++) { factorial = } return factorial;}

public static int multiply(int a, int b){ return a * b;}

36 instructions

9 instructions

Page 77: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation77

Inlining

public static int factorial(int num) { int factorial = 1; for (int i = 1; i <= num; i++) { factorial = } return factorial;}

public static int multiply(int a, int b){ return a * b;}

inline

36 instructions

9 instructions

Page 78: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation78

Inlining

public static int factorial(int num) { int factorial = 1; for (int i = 1; i <= num; i++) { factorial = factorial * i; } return factorial;}

public static int multiply(int a, int b){ return a * b;}

inline

36 instructions

9 instructions

Page 79: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation79

Inlining

public static int factorial(int num) { int factorial = 1; for (int i = 1; i <= num; i++) { factorial = factorial * i; } return factorial;}

public static int multiply(int a, int b){ return a * b;}

9 instructions

36 instructions

Page 80: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation80

Inlining

public static int factorial(int num) { int factorial = 1; for (int i = 1; i <= num; i++) { factorial = factorial * i; } return factorial;}

public static int multiply(int a, int b){ return a * b;}

29 instructions

9 instructions

36 instructions

Page 81: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation81

Inlining

public static int factorial(int num) { int factorial = 1; for (int i = 1; i <= num; i++) { factorial = factorial * i; } return factorial;}

public static int multiply(int a, int b){ return a * b;}

29 instructions

9 instructions

36 instructions

Inlining increases performance by:● Removing Prologue and Epilogue● Removing need to set up arguments

Page 82: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation82

Enabling Inlining

Inlining increases performance by removing cost of calling conventions– Prologue, Eplilogue, Setting up parameters

Inlining benefits from certainty:– private, static and final methods are more easily inlined– public methods can be, depending on morphism

Inlining benefits from simplicity:– Must be small: thresholds at ≤35 bytecodes and ≤325 bytecodes– Simple is faster than complex

Page 83: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation83

Example of Enabling Inliningpublic void transformData () { for (int i = 0; i < dataSet.length; i ++) { dataSet[i] = transformEntry(dataSet[i]); }}

private int transformEntry(int data){ int val = data.getValue(); if (val == Integer.MAX_VALUE) { StringBuffer sb = new StringBuffer(); Date date = Calendar.getInstance().getTime(); sb.append(new SimpleDateFormat("yyyyMMdd_HHmmss").format(date)); sb.append(" Error as value at MAX_VALUE "); data.setErrorMessage(sb.toString()); return data; } data.setValue(val + 1); return data;}

Too Large

Page 84: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation84

Example of Enabling Inliningpublic void transformData () { for (int i = 0; i < dataSet.length; i ++) { dataSet[i] = transformEntry(dataSet[i]); }}

private int transformEntry(int data){ int val = data.getValue(); if (val == Integer.MAX_VALUE) { StringBuffer sb = new StringBuffer(); Date date = Calendar.getInstance().getTime(); sb.append(new SimpleDateFormat("yyyyMMdd_HHmmss").format(date)); sb.append(" Error as value at MAX_VALUE "); data.setErrorMessage(sb.toString()); return data; } data.setValue(val + 1); return data;}

Too Large

Exceptional condition check

Page 85: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation85

Example of Enabling Inliningpublic void transformData () { for (int i = 0; i < dataSet.length; i ++) { dataSet[i] = transformEntry(dataSet[i]); }}

private int transformEntry(int data){ int val = data.getValue(); if (val == Integer.MAX_VALUE) { handleError(data); return data;

} data.setValue(val + 1); return data;}

Replace withmethod call

Page 86: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation86

Example of Enabling Inliningpublic void transformData () { for (int i = 0; i < dataSet.length; i ++) { dataSet[i] = transformEntry(dataSet[i]); }}

private int transformEntry(int data){ int val = data.getValue(); if (val == Integer.MAX_VALUE) { handleError(data); return data; } data.setValue(val + 1); return data;}

Page 87: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation87

Example of Enabling Inliningpublic void transformData () { for (int i = 0; i < dataSet.length; i ++) { dataSet[i] = transformEntry(dataSet[i]); }}

private int transformEntry(int data){ int val = data.getValue(); if (val == Integer.MAX_VALUE) { handleError(data); return data; } data.setValue(val + 1); return data;}

Inline

Page 88: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation88

Example of Enabling Inliningpublic void transformData () { for (int i = 0; i < dataSet.length; i ++) { int val = dataSet[i].getValue(); if (val == Integer.MAX_VALUE) { handleError(dataSet[i]); } dataSet[i] .setValue(val + 1); }}

private int transformEntry(int data){ int val = data.getValue(); if (val == Integer.MAX_VALUE) { handleError(data); return data; } data.setValue(val + 1); return data;}

Not inlined

Page 89: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation89

Loop Unrolling

Page 90: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation90

Loop Unrolling

private static final String[] numbers = {"0", "1", "2", "3", "4"};

public static int total() { int result = 0;

for (String num : numbers) { result += parse(num); } return result;}

private static int parse(String num) { return Integer.parseInt(num);}

Page 91: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation91

Loop Unrolling

private static final String[] numbers = {"0", "1", "2", "3", "4"};

public static int total() { int result = 0;

for (String num : numbers) { result += parse(num); } return result;}

private static int parse(String num) { return Integer.parseInt(num);}

inline

Page 92: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation92

Loop Unrolling

private static final String[] numbers = {"0", "1", "2", "3", "4"};

public static int total() { int result = 0;

for (String num : numbers) { result += Integer.parseInt(num); } return result;}

private static int parse(String num) { return Integer.parseInt(num);}

inline

Page 93: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation93

Loop Unrolling

private static final String[] numbers = {"0", "1", "2", "3", "4"};

public static int total() { int result = 0;

for (String num : numbers) { result += Integer.parseInt(num); } return result;}

private static int parse(String num) { return Integer.parseInt(num);}

Page 94: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation94

Loop Unrolling

private static final String[] numbers = {"0", "1", "2", "3", "4"};

public static int total() { int result = 0;

for (String num : numbers) { result += Integer.parseInt(num); } return result;}

private static int parse(String num) { return Integer.parseInt(num);}

unroll

Page 95: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation95

Loop Unrolling

private static final String[] numbers = {"0", "1", "2", "3", "4"};

public static int total() { int result = 0;

result += Integer.parseInt("0"); result += Integer.parseInt("1"); result += Integer.parseInt("2"); result += Integer.parseInt("3"); result += Integer.parseInt("4");

return result;}

private static int parse(String num) { return Integer.parseInt(num);}

Page 96: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation96

Loop Unrolling

private static final String[] numbers = {"0", "1", "2", "3", "4"};

public static int total() { int result = 0;

result += Integer.parseInt("0"); result += Integer.parseInt("1"); result += Integer.parseInt("2"); result += Integer.parseInt("3"); result += Integer.parseInt("4");

return result;}

private static int parse(String num) { return Integer.parseInt(num);}

Possible because collection is final

Page 97: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation97

Enabling LoopUnrolling

Loop unrolling increases performance by removing cost of:– Iterating around loop– Bounds checking

Loop unrolling benefits from certainty:– Know the size of the loop

Loop unrolling benefits from simplicity:– Loop must be inlinable

Page 98: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation98

Synchronization

Page 99: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation99

Synchronization approaches

public int[] intArr = {0, 1, 2};

public int sync2(){ synchronized (this){ return intArr[0]; }}

Page 100: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation100

Synchronization approaches

public int[] intArr = {0, 1, 2};

public synchronized int sync1(){ return intArr[0];}

Page 101: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation101

Lock Coarsening

public int[] intArr = {0, 1, 2}; public int arrayCount() { int result = 0;

for (int i = 0; i < intArr.length; i++) { result += getEntry(i); }

return result;}

public synchronized int getEntry(int entry){ return intArr[entry];}

Page 102: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation102

Lock Coarsening

public int[] intArr = {0, 1, 2}; public int arrayCount() { int result = 0;

for (int i = 0; i < intArr.length; i++) { result += getEntry(i); }

return result;}

public synchronized int getEntry(int entry){ return intArr[entry];}

inline

Page 103: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation103

Lock Coarsening

public int[] intArr = {0, 1, 2}; public int arrayCount() { int result = 0;

for (int i = 0; i < intArr.length; i++) { result += intArr[entry]; }

return result;}

public synchronized int getEntry(int entry){ return intArr[entry];}

inline

Page 104: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation104

Lock Coarsening

public int[] intArr = {0, 1, 2}; public int arrayCount() { int result = 0;

for (int i = 0; i < intArr.length; i++) { result += intArr[entry]; }

return result;}

public synchronized int getEntry(int entry){ return intArr[entry];}

Page 105: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation105

Lock Coarsening

public int[] intArr = {0, 1, 2}; public int arrayCount() { int result = 0; for (int i = 0; i < intArr.length; i++) { result += intArr[entry]; } return result;}

public synchronized int getEntry(int entry){ return intArr[entry];}

Page 106: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation106

Lock Coarsening

public int[] intArr = {0, 1, 2}; public int arrayCount() { int result = 0; synchronized { for (int i = 0; i < intArr.length; i++) { result += intArr[entry]; } } return result;}

public synchronized int getEntry(int entry){ return intArr[entry];}

Lock coarsen

Page 107: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation107

Lock Elision

public String walkLockedList() { List syncdList = new ArrayList(); synchronized (syncdList) { for (int i = 0; i < 10; i++) { syncdList.add(i); } return syncdList.toString(); }}

Page 108: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation108

Lock Elision

public String walkLockedList() { List syncdList = new ArrayList(); synchronized (syncdList) { for (int i = 0; i < 10; i++) { syncdList.add(i); } return syncdList.toString(); }}

Page 109: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation109

Lock Elision

public String walkLockedList() { List syncdList = new ArrayList(); synchronized (syncdList) { for (int i = 0; i < 10; i++) { syncdList.add(i); } return syncdList.toString(); }}

Page 110: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation110

Lock Elision

public String walkLockedList() { List syncdList = new ArrayList(); synchronized (syncdList) { for (int i = 0; i < 10; i++) { syncdList.add(i); } return syncdList.toString(); }}

Page 111: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation111

Lock Elision

public String walkLockedList() { List syncdList = new ArrayList(); synchronized (syncdList) { for (int i = 0; i < 10; i++) { syncdList.add(i); } return syncdList.toString(); }}

Page 112: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation112

Lock Elision

public String walkLockedList() { List syncdList = new ArrayList(); for (int i = 0; i < 10; i++) { syncdList.add(i); } return syncdList.toString(); }

Lock elision

Page 113: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation113

Enabling Synchronization optimizations

Synchronization optimizations increases performance by removing cost of:– Unnecessary synchronization– Repeated synchronization

Synchronization optimizations from certainty:– Scope of the object being locked

Loop unrolling benefits from simplicity:– Inlining enables removal of locks

Page 114: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation114

Field Optimizations

Page 115: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation115

Accessing Fieldspublic static int test = 10;public static int getTest() { return test;}

private static int test = 10;public static int getTest() { return test;}

private final static int test = 10;public static int getTest() { return test;}

public static int getTest() { return 10;}

public int test = 10;public int getTest() { return test;}

private int test = 10;public int getTest() { return test;}

public final int test = 10;public int getTest() { return test;}

public int getTest() { return 10;}

Page 116: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation116

Static Final fields

public static final int test = 10;

public int getTest() { return test;}

Page 117: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation117

Static Final fields

public static final int test = 10;

public int getTest() { return test;}

Page 118: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation118

Static Final fields

public static final int test = 10;

public int getTest() { return test;}

inline

Page 119: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation119

Static Final fields

public static final int test = 10;

public int getTest() { return 10;}

inline

Page 120: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation120

Static Final fields

public static final int test;

static { test = new Random().nextInt();}

public int getTest() { return test;}

Page 121: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation121

Static Final fields

public static final int test;

static { test = 7;}

public int getTest() { return test;}

Page 122: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation122

Static Final fields

public static final int test = 7;

static { test = 7;}

public int getTest() { return test;}

Page 123: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation123

Static Final fields

public static final int test = 7;

public int getTest() { return test;}

Page 124: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation124

Static Final fields

public static final int test = 7;

public int getTest() { return test;}

inline

Page 125: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation125

Static Final fields

public static final int test = 7;

public int getTest() { return 7;}

inline

Page 126: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation126

Instance Final fields

public final int test = 10;

public FieldTest() {

}

public int getTest() { return test;}

Page 127: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation127

Instance Final fields

public final int test = 10;

public FieldTest() {

}

public int getTest() { return test;}

inline

Page 128: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation128

Instance Final fields

public final int test = 10;

public FieldTest() {

}

public int getTest() { return 10;}

inline

Page 129: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation129

Instance Final fields

public final int test;

public FieldTest(int val) { this.test = val;}

public int getTest() { return test;}

Page 130: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation130

Instance Final fields

public final int test = val;

public FieldTest(int val) { this.test = val;}

public int getTest() { return test;}

Page 131: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation131

Instance Final fields

public final int test = val;

public FieldTest(int val) { this.test = val;}

public int getTest() { return test;}

Not possible

Page 132: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation132

Enabling Field optimizations

Field optimizations increases performance by:– Enabling other optimizations

Optimizations result from certainty:– Constants (final) are faster than variables– Locals (parameters and variables) are faster than fields–private can be faster than public

Page 133: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation133

Coding Guidelines

Page 134: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation134

Coding Guidelines

Follow good programming practices!– Fields that can be final, should be final– Fields that can be private, should be private– Data that can be passed as a parameter, should be passed as a parameter

Follow good object orientated design!– If function can be delegated to another method, it should be delegated

This results in short methods and well described data, allowing optimizations.

Page 135: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation135

Defaulting to final and private

Default all fields/variables to final:– Compile time error:

Default all fields/variables to private:– Compile time error:

FieldTest2.java:14: error: cannot assign a value to final variable value this.value = val;

FieldLauncher.java:14: error: test3 has private access in FieldTest fieldTest.test3 = 10;

Page 136: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation136

Analyzing the JIT

Page 137: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation137

Digging into the generated assembler

HotSpot JIT provides options to look at JIT behaviour:– -XX:+UnlockDiagnosticVMOptions– -XX:+TraceClassLoading– -XX:+LogCompilation– -XX:+PrintAssembly

-XX:+PrintAssembly requires additional hdis library– Installed into jre/bin/server

Generates output to console and hotspot_pid<pid>.log file

Page 138: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation138

Visualizing with JITWatch

Open source JITWatch tool provides visualization of data:

“Journal” tells you what optimizations have been applied, and which couldn't be

Also attempts to make optimization suggestions

Page 139: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation139

Summary

Page 140: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation140

Certainty

Locals are faster than globals– Fields and statics are slow; parameters and locals are fast

Constants are faster than variables– final is your friend, especially final static

private can be faster than public– protected and package are always just as slow as public

Small methods (≤100 bytecodes) are good

Simple is faster than complex

Page 141: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation141

Questions?

Page 142: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation142

IBM Developer Kits for Javahttp://www.ibm.com/java/jdk

IBM Developer Kits for Node.jshttp://ibm.co/ibmnodejs

WebShere Liberty Profilehttp://wasdev.net

IBM Bluemixhttp://www.ibm.com/bluemix

http://www.ibm.com/java/jdk
http://ibm.co/ibmnodejs
http://wasdev.net/
http://www.ibm.com/bluemix
Page 143: JavaOne 2015: From Java Code to Machine Code

© 2015 IBM Corporation143

Copyright and Trademarks

© IBM Corporation 2015. All Rights Reserved.

IBM, the IBM logo, and ibm.com are trademarks or registered trademarks of International Business Machines Corp., and registered in many jurisdictions worldwide.

Other product and service names might be trademarks of IBM or other companies.

A current list of IBM trademarks is available on the Web – see the IBM “Copyright and trademark information” page at URL: www.ibm.com/legal/copytrade.shtml

http://www.ibm.com/legal/copytrade.shtml

JavaOne 2015 Java Mixed-Mode Flame Graphs

JavaOne 2015 Java Mixed-Mode Flame Graphs

FRONT Join Java Community Process (JCP) at JavaOne 2011

FRONT Join Java Community Process (JCP) at JavaOne 2011

JavaOne 2016: Kubernetes introduction for Java Developers

JavaOne 2016: Kubernetes introduction for Java Developers

10 Tips for Java EE 7 with PrimeFaces - JavaOne 2013

10 Tips for Java EE 7 with PrimeFaces - JavaOne 2013

Introduciton to Apache Cassandra for Java Developers (JavaOne)

Introduciton to Apache Cassandra for Java Developers (JavaOne)

JavaONE 2012 Using Java with HTML5 and CSS3

JavaONE 2012 Using Java with HTML5 and CSS3

JavaOne 2015 Event Demographics - Oracle...Title JavaOne 2015 Event Demographics Author Oracle Corporation Subject JavaOne 2015 Event Demographics Keywords "Java, Java FY15, PowerPoint

JavaOne 2015 Event Demographics - Oracle...Title JavaOne 2015 Event Demographics Author Oracle Corporation Subject JavaOne 2015 Event Demographics Keywords "Java, Java FY15, PowerPoint

JavaOne 2013 Java SE Update

JavaOne 2013 Java SE Update

JavaOne LATAM 2016 - Combinando AngularJS com Java EE

JavaOne LATAM 2016 - Combinando AngularJS com Java EE

JavaOne 2016 "Java, Microservices, Cloud and Containers"

JavaOne 2016 "Java, Microservices, Cloud and Containers"

JavaOne Report - Java SE Update

JavaOne Report - Java SE Update

JavaOne - A Sip Of Java - RJ Auburn

JavaOne - A Sip Of Java - RJ Auburn

Java EE Next - BeJUG JavaOne Afterglow 2016

Java EE Next - BeJUG JavaOne Afterglow 2016

Java Movement in Indonesia - Javaone Beijing 2010 - JUG Meeting

Java Movement in Indonesia - Javaone Beijing 2010 - JUG Meeting

Java Community Process (JCP) Program Activities · Java Community Process (JCP) Program Activities. 2 Agenda ... DevoxxUK, JavaOne Latin America, Java Mexico Day, JavaOne San Francisco.

Java Community Process (JCP) Program Activities · Java Community Process (JCP) Program Activities. 2 Agenda ... DevoxxUK, JavaOne Latin America, Java Mexico Day, JavaOne San Francisco.

Java EE Technical Keynote at JavaOne Latin America 2011

Java EE Technical Keynote at JavaOne Latin America 2011

2011 JavaOne Apache TomEE Java EE 6 Web Profile

2011 JavaOne Apache TomEE Java EE 6 Web Profile

JavaOne 2011 - Going Mobile With Java Based Technologies Today

JavaOne 2011 - Going Mobile With Java Based Technologies Today

Experion Presentation at JavaOne 2011: Memory optimizing Java ME applications

Experion Presentation at JavaOne 2011: Memory optimizing Java ME applications

JavaOne 2014: Java vs JavaScript

JavaOne 2014: Java vs JavaScript