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JavaOne 2015: From Java Code to Machine Code

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Chris Bailey

The document provides an informational presentation on optimizing Java code, including its execution and how to enable optimizations. It delves into the anatomy of Java class files, demonstrating with examples of bytecode and highlighting important flags and structures. The content is offered without warranty and is an overview of IBM's current product strategy.

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© 2015 IBM Corporation Java Code to Machine Code How to write highly optimizeable Java 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
© 2015 IBM Corporation3 3 Monitoring and Diagnostics Architect @Chris__Bailey @seabaylea
© 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
© 2015 IBM Corporation5 > javac
© 2015 IBM Corporation6 Anatomy of a Java Class File struct 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]; }
© 2015 IBM Corporation7 Anatomy of a Java Class File public class MyObject() { public int myField = 48; public MyObject() { } }
© 2015 IBM Corporation8 Anatomy of a Java Class File public class MyObject() { public int myField = 48; public MyObject() { } } flags: ACC_PUBLIC, ACC_SUPER Constant 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;
© 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() { } }
© 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() { } }
© 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() { } }
© 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() { } }
© 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() { } }
© 2015 IBM Corporation14 Executing Bytecode
© 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() { } }
© 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; this 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() { } } > Executing Bytecodes
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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
© 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
© 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; this 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
© 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; this Local 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() { } } > push MyObject Executing Bytecodes
© 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; this Local 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
© 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; this Local 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() { } } > push MyObject Executing Bytecodes
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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
© 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; this Local 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 pop Executing Bytecodes
© 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; this Local 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
© 2015 IBM Corporation58 Local Variables Operand Stack Constant Pool Java Heap MyObject 48 Executing Bytecodes
© 2015 IBM Corporation59 Machine Code
© 2015 IBM Corporation60 Machine Code public synchronized int sync1(){ return intArr[0]; }
© 2015 IBM Corporation61 Machine Code public synchronized int sync1(){ return intArr[0]; } public int sync2(){ synchronized (this){ return intArr[0]; } }
© 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
© 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
© 2015 IBM Corporation64 JIT Optimizations
© 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 ptr 0x000000000f121567: push rbp 0x000000000f121568: sub rsp,30h ;*iload_0 0x000000000f12156c: imul edx,r8d 0x000000000f121570: mov rax,rdx 0x000000000f121573: add rsp,30h 0x000000000f121577: pop rbp 0x000000000f121578: test dword ptr 0x000000000f12157e: ret
© 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 ptr 0x000000000f121567: push rbp 0x000000000f121568: sub rsp,30h 0x000000000f12156c: imul edx,r8d 0x000000000f121570: mov rax,rdx 0x000000000f121573: add rsp,30h 0x000000000f121577: pop rbp 0x000000000f121578: test dword ptr 0x000000000f12157e: ret JIT Generated 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 ptr 0x000000000f121567: push rbp 0x000000000f121568: sub rsp,30h 0x000000000f12156c: imul edx,r8d 0x000000000f121570: mov rax,rdx 0x000000000f121573: add rsp,30h 0x000000000f121577: pop rbp 0x000000000f121578: test dword ptr 0x000000000f12157e: ret JIT Generated 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 ptr 0x000000000f121567: push rbp 0x000000000f121568: sub rsp,30h 0x000000000f12156c: imul rdx,r8d 0x000000000f121570: mov rax,rdx 0x000000000f121573: add rsp,30h 0x000000000f121577: pop rbp 0x000000000f121578: test dword ptr 0x000000000f12157e: ret
© 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 ptr 0x000000000f121567: push rbp 0x000000000f121568: sub rsp,30h 0x000000000f12156c: imul rdx,r8d 0x000000000f121570: mov rax,rdx 0x000000000f121573: add rsp,30h 0x000000000f121577: pop rbp 0x000000000f121578: test dword ptr 0x000000000f12157e: ret
© 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 ptr 0x000000000f121567: push rbp 0x000000000f121568: sub rsp,30h 0x000000000f12156c: imul rdx,r8d 0x000000000f121570: mov rax,rdx 0x000000000f121573: add rsp,30h 0x000000000f121577: pop rbp 0x000000000f121578: test dword ptr 0x000000000f12157e: ret
© 2015 IBM Corporation71 Inlining
© 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; }
© 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
© 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
© 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
© 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
© 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
© 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
© 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
© 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
© 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
© 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
© 2015 IBM Corporation83 Example of Enabling Inlining public 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
© 2015 IBM Corporation84 Example of Enabling Inlining public 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
© 2015 IBM Corporation85 Example of Enabling Inlining public 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 with method call
© 2015 IBM Corporation86 Example of Enabling Inlining public 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; }
© 2015 IBM Corporation87 Example of Enabling Inlining public 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
© 2015 IBM Corporation88 Example of Enabling Inlining public 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
© 2015 IBM Corporation89 Loop Unrolling
© 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); }
© 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
© 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
© 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); }
© 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
© 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); }
© 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
© 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
© 2015 IBM Corporation98 Synchronization
© 2015 IBM Corporation99 Synchronization approaches public int[] intArr = {0, 1, 2}; public int sync2(){ synchronized (this){ return intArr[0]; } }
© 2015 IBM Corporation100 Synchronization approaches public int[] intArr = {0, 1, 2}; public synchronized int sync1(){ return intArr[0]; }
© 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]; }
© 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
© 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
© 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]; }
© 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]; }
© 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
© 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(); } }
© 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(); } }
© 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(); } }
© 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(); } }
© 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(); } }
© 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
© 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
© 2015 IBM Corporation114 Field Optimizations
© 2015 IBM Corporation115 Accessing Fields public 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; }
© 2015 IBM Corporation116 Static Final fields public static final int test = 10; public int getTest() { return test; }
© 2015 IBM Corporation117 Static Final fields public static final int test = 10; public int getTest() { return test; }
© 2015 IBM Corporation118 Static Final fields public static final int test = 10; public int getTest() { return test; } inline
© 2015 IBM Corporation119 Static Final fields public static final int test = 10; public int getTest() { return 10; } inline
© 2015 IBM Corporation120 Static Final fields public static final int test; static { test = new Random().nextInt(); } public int getTest() { return test; }
© 2015 IBM Corporation121 Static Final fields public static final int test; static { test = 7; } public int getTest() { return test; }
© 2015 IBM Corporation122 Static Final fields public static final int test = 7; static { test = 7; } public int getTest() { return test; }
© 2015 IBM Corporation123 Static Final fields public static final int test = 7; public int getTest() { return test; }
© 2015 IBM Corporation124 Static Final fields public static final int test = 7; public int getTest() { return test; } inline
© 2015 IBM Corporation125 Static Final fields public static final int test = 7; public int getTest() { return 7; } inline
© 2015 IBM Corporation126 Instance Final fields public final int test = 10; public FieldTest() { } public int getTest() { return test; }
© 2015 IBM Corporation127 Instance Final fields public final int test = 10; public FieldTest() { } public int getTest() { return test; } inline
© 2015 IBM Corporation128 Instance Final fields public final int test = 10; public FieldTest() { } public int getTest() { return 10; } inline
© 2015 IBM Corporation129 Instance Final fields public final int test; public FieldTest(int val) { this.test = val; } public int getTest() { return test; }
© 2015 IBM Corporation130 Instance Final fields public final int test = val; public FieldTest(int val) { this.test = val; } public int getTest() { return test; }
© 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
© 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
© 2015 IBM Corporation133 Coding Guidelines
© 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.
© 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;
© 2015 IBM Corporation136 Analyzing the JIT
© 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
© 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
© 2015 IBM Corporation139 Summary
© 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
© 2015 IBM Corporation141 Questions?
© 2015 IBM Corporation142 IBM Developer Kits for Java http://www.ibm.com/java/jdk IBM Developer Kits for Node.js http://ibm.co/ibmnodejs WebShere Liberty Profile http://wasdev.net IBM Bluemix http://www.ibm.com/bluemix
© 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

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JavaOne 2015: From Java Code to Machine Code

  • 1. © 2015 IBM Corporation Java Code to Machine Code How to write highly optimizeable Java code
  • 2. © 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
  • 3. © 2015 IBM Corporation3 3 Monitoring and Diagnostics Architect @Chris__Bailey @seabaylea
  • 4. © 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
  • 5. © 2015 IBM Corporation5 > javac
  • 6. © 2015 IBM Corporation6 Anatomy of a Java Class File struct 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]; }
  • 7. © 2015 IBM Corporation7 Anatomy of a Java Class File public class MyObject() { public int myField = 48; public MyObject() { } }
  • 8. © 2015 IBM Corporation8 Anatomy of a Java Class File public class MyObject() { public int myField = 48; public MyObject() { } } flags: ACC_PUBLIC, ACC_SUPER Constant 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;
  • 9. © 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() { } }
  • 10. © 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() { } }
  • 11. © 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() { } }
  • 12. © 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() { } }
  • 13. © 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() { } }
  • 14. © 2015 IBM Corporation14 Executing Bytecode
  • 15. © 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() { } }
  • 16. © 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; this 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() { } } > Executing Bytecodes
  • 17. © 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; this Local 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
  • 18. © 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; this Local 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
  • 19. © 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; this Local 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
  • 20. © 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; this Local 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
  • 21. © 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; this Local 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
  • 22. © 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; this Local 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
  • 23. © 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; this Local 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
  • 24. © 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; this Local 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
  • 25. © 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; this Local 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
  • 26. © 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; this Local 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
  • 27. © 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; this Local 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
  • 28. © 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; this Local 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
  • 29. © 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; this Local 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
  • 30. © 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; this Local 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
  • 31. © 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; this Local 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
  • 32. © 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; this Local 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
  • 33. © 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
  • 34. © 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
  • 35. © 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; this 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
  • 36. © 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; this Local 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() { } } > push MyObject Executing Bytecodes
  • 37. © 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; this Local 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
  • 38. © 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; this Local 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() { } } > push MyObject Executing Bytecodes
  • 39. © 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; this Local 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
  • 40. © 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; this Local 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
  • 41. © 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; this Local 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
  • 42. © 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; this Local 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
  • 43. © 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; this Local 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
  • 44. © 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; this Local 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
  • 45. © 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; this Local 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
  • 46. © 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; this Local 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
  • 47. © 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; this Local 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
  • 48. © 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; this Local 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
  • 49. © 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; this Local 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
  • 50. © 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; this Local 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
  • 51. © 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; this Local 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
  • 52. © 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; this Local 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
  • 53. © 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; this Local 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
  • 54. © 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; this Local 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
  • 55. © 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; this Local 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
  • 56. © 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; this Local 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 pop Executing Bytecodes
  • 57. © 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; this Local 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
  • 58. © 2015 IBM Corporation58 Local Variables Operand Stack Constant Pool Java Heap MyObject 48 Executing Bytecodes
  • 59. © 2015 IBM Corporation59 Machine Code
  • 60. © 2015 IBM Corporation60 Machine Code public synchronized int sync1(){ return intArr[0]; }
  • 61. © 2015 IBM Corporation61 Machine Code public synchronized int sync1(){ return intArr[0]; } public int sync2(){ synchronized (this){ return intArr[0]; } }
  • 62. © 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
  • 63. © 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
  • 64. © 2015 IBM Corporation64 JIT Optimizations
  • 65. © 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 ptr 0x000000000f121567: push rbp 0x000000000f121568: sub rsp,30h ;*iload_0 0x000000000f12156c: imul edx,r8d 0x000000000f121570: mov rax,rdx 0x000000000f121573: add rsp,30h 0x000000000f121577: pop rbp 0x000000000f121578: test dword ptr 0x000000000f12157e: ret
  • 66. © 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 ptr 0x000000000f121567: push rbp 0x000000000f121568: sub rsp,30h 0x000000000f12156c: imul edx,r8d 0x000000000f121570: mov rax,rdx 0x000000000f121573: add rsp,30h 0x000000000f121577: pop rbp 0x000000000f121578: test dword ptr 0x000000000f12157e: ret JIT Generated Code
  • 67. © 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 ptr 0x000000000f121567: push rbp 0x000000000f121568: sub rsp,30h 0x000000000f12156c: imul edx,r8d 0x000000000f121570: mov rax,rdx 0x000000000f121573: add rsp,30h 0x000000000f121577: pop rbp 0x000000000f121578: test dword ptr 0x000000000f12157e: ret JIT Generated Code
  • 68. © 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 ptr 0x000000000f121567: push rbp 0x000000000f121568: sub rsp,30h 0x000000000f12156c: imul rdx,r8d 0x000000000f121570: mov rax,rdx 0x000000000f121573: add rsp,30h 0x000000000f121577: pop rbp 0x000000000f121578: test dword ptr 0x000000000f12157e: ret
  • 69. © 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 ptr 0x000000000f121567: push rbp 0x000000000f121568: sub rsp,30h 0x000000000f12156c: imul rdx,r8d 0x000000000f121570: mov rax,rdx 0x000000000f121573: add rsp,30h 0x000000000f121577: pop rbp 0x000000000f121578: test dword ptr 0x000000000f12157e: ret
  • 70. © 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 ptr 0x000000000f121567: push rbp 0x000000000f121568: sub rsp,30h 0x000000000f12156c: imul rdx,r8d 0x000000000f121570: mov rax,rdx 0x000000000f121573: add rsp,30h 0x000000000f121577: pop rbp 0x000000000f121578: test dword ptr 0x000000000f12157e: ret
  • 71. © 2015 IBM Corporation71 Inlining
  • 72. © 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; }
  • 73. © 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
  • 74. © 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
  • 75. © 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
  • 76. © 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
  • 77. © 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
  • 78. © 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
  • 79. © 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
  • 80. © 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
  • 81. © 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
  • 82. © 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
  • 83. © 2015 IBM Corporation83 Example of Enabling Inlining public 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
  • 84. © 2015 IBM Corporation84 Example of Enabling Inlining public 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
  • 85. © 2015 IBM Corporation85 Example of Enabling Inlining public 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 with method call
  • 86. © 2015 IBM Corporation86 Example of Enabling Inlining public 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; }
  • 87. © 2015 IBM Corporation87 Example of Enabling Inlining public 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
  • 88. © 2015 IBM Corporation88 Example of Enabling Inlining public 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
  • 89. © 2015 IBM Corporation89 Loop Unrolling
  • 90. © 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); }
  • 91. © 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
  • 92. © 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
  • 93. © 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); }
  • 94. © 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
  • 95. © 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); }
  • 96. © 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
  • 97. © 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
  • 98. © 2015 IBM Corporation98 Synchronization
  • 99. © 2015 IBM Corporation99 Synchronization approaches public int[] intArr = {0, 1, 2}; public int sync2(){ synchronized (this){ return intArr[0]; } }
  • 100. © 2015 IBM Corporation100 Synchronization approaches public int[] intArr = {0, 1, 2}; public synchronized int sync1(){ return intArr[0]; }
  • 101. © 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]; }
  • 102. © 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
  • 103. © 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
  • 104. © 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]; }
  • 105. © 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]; }
  • 106. © 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
  • 107. © 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(); } }
  • 108. © 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(); } }
  • 109. © 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(); } }
  • 110. © 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(); } }
  • 111. © 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(); } }
  • 112. © 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
  • 113. © 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
  • 114. © 2015 IBM Corporation114 Field Optimizations
  • 115. © 2015 IBM Corporation115 Accessing Fields public 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; }
  • 116. © 2015 IBM Corporation116 Static Final fields public static final int test = 10; public int getTest() { return test; }
  • 117. © 2015 IBM Corporation117 Static Final fields public static final int test = 10; public int getTest() { return test; }
  • 118. © 2015 IBM Corporation118 Static Final fields public static final int test = 10; public int getTest() { return test; } inline
  • 119. © 2015 IBM Corporation119 Static Final fields public static final int test = 10; public int getTest() { return 10; } inline
  • 120. © 2015 IBM Corporation120 Static Final fields public static final int test; static { test = new Random().nextInt(); } public int getTest() { return test; }
  • 121. © 2015 IBM Corporation121 Static Final fields public static final int test; static { test = 7; } public int getTest() { return test; }
  • 122. © 2015 IBM Corporation122 Static Final fields public static final int test = 7; static { test = 7; } public int getTest() { return test; }
  • 123. © 2015 IBM Corporation123 Static Final fields public static final int test = 7; public int getTest() { return test; }
  • 124. © 2015 IBM Corporation124 Static Final fields public static final int test = 7; public int getTest() { return test; } inline
  • 125. © 2015 IBM Corporation125 Static Final fields public static final int test = 7; public int getTest() { return 7; } inline
  • 126. © 2015 IBM Corporation126 Instance Final fields public final int test = 10; public FieldTest() { } public int getTest() { return test; }
  • 127. © 2015 IBM Corporation127 Instance Final fields public final int test = 10; public FieldTest() { } public int getTest() { return test; } inline
  • 128. © 2015 IBM Corporation128 Instance Final fields public final int test = 10; public FieldTest() { } public int getTest() { return 10; } inline
  • 129. © 2015 IBM Corporation129 Instance Final fields public final int test; public FieldTest(int val) { this.test = val; } public int getTest() { return test; }
  • 130. © 2015 IBM Corporation130 Instance Final fields public final int test = val; public FieldTest(int val) { this.test = val; } public int getTest() { return test; }
  • 131. © 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
  • 132. © 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
  • 133. © 2015 IBM Corporation133 Coding Guidelines
  • 134. © 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.
  • 135. © 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;
  • 136. © 2015 IBM Corporation136 Analyzing the JIT
  • 137. © 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
  • 138. © 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
  • 139. © 2015 IBM Corporation139 Summary
  • 140. © 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
  • 141. © 2015 IBM Corporation141 Questions?
  • 142. © 2015 IBM Corporation142 IBM Developer Kits for Java http://www.ibm.com/java/jdk IBM Developer Kits for Node.js http://ibm.co/ibmnodejs WebShere Liberty Profile http://wasdev.net IBM Bluemix http://www.ibm.com/bluemix
  • 143. © 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