Let s make some Marc R. Hoffmann Eclipse Summit Europe

Transcription

1 Let s make some Marc R. Hoffmann Eclipse Summit Europe

2 public class WhatIsFaster { int i; void inc1() { i = i + 1; } void inc2() { i += 1; } void inc3() { i++; } }

3 Why? Compilers Scrip;ng Engines Sta;c Analysis Dynamic Analysis Reverse Engineering Read Write

4 ca fe ba be c a f 6c 61 6e 67 2f 4f 62 6a c 69 6e e f a b 0c f 4c 69 6e 65 4e 75 6d c c 6f c c c e 4c b e 63 31

5 Versions The JVM Spec First Edi;on The JVM Spec Second Edi;on The JVM Spec Java 7 SE Edi;on

6 Class File Naming java/lang/string.class java/util/map$entry.class Java/util/Collections$1.class

7 JVM Type Nota<on Base Types Z C B S I J F D V Object Types Ljava/lang/String; Array Types: [C [[Z [Ljava/lang/String;

8 ClassFile { u4 magic; u2 minor_version; u2 major_version; u2 constant_pool_count; cp_info constant_pool[]; u2 access_flags; u2 this_class; u2 super_class; u2 interfaces_count; u2 interfaces[]; u2 fields_count; field_info fields[]; u2 methods_count; method_info methods[]; u2 attributes_count; attribute_info attributes[]; }

9 Class File Anatomy Class Constant Pool Fields ASributes Methods ASributes ASributes

10 Constant Pool Idx Idx Idx Idx Idx Idx Idx Idx u1 tag; u1[] info u1 tag; u1[] info u1 tag; u1[] info u1 tag; u1[] info u1 tag; u1[] info u1 tag; u1[] info u1 tag; u1[] info u1 tag; u1[] info Constant Pool Fields Methods

11 Constant Pool FieldRef MethodRef IntfMethRef String Class NameAndType 2 Utf8 Integer Float Long Double Constant Pool Fields Methods MethodHandle, MethodType, InvokeDynamic

12 Fields field_info { u2 access_flags; u2 name_index; Utf8 u2 descriptor_index; Utf8 u2 attributes_count; attribute_info attributes[]; } Constant Pool Fields Methods

13 ConstantValue AAribute Contant Pool int, short, char, byte, boolean float long double java.lang.string Integer Float Long Double String Constant Pool Fields Methods

14 Methods method_info { u2 access_flags; Utf8 u2 name_index; u2 descriptor_index; Utf8 u2 attributes_count; attribute_info attributes[]; } Where is the Code? getvalue run <init> <clinit> ()I ()V (LFoo;)V (II)I; Constant Pool Fields Methods

15 Code AAribute Code_attribute { u2 attribute_name_index; u4 attribute_length; u2 max_stack; u2 max_locals; u4 code_length; u1 code[]; u2 exception_table_length; { u2 start_pc; u2 end_pc; u2 handler_pc; u2 catch_type; } exception_table[]; u2 attributes_count; attribute_info attributes[]; }

16 void inc1() { i = i + 1; } ALOAD 0 59 DUP B4 nn nn GETFIELD WhatIsFaster.i 04 ICONST_1 60 IADD B5 nn nn PUTFIELD WhatIsFaster.i B1 RETURN

17 Data Operand Stack Local Variables this Methods Args Local Vars References get/put field invoke new

18 Operand Stack ALOAD 0 DUP GETFIELD WhatIsFaster.i ICONST_1 IADD PUTFIELD WhatIsFaster.i RETURN

19 Operand Stack ALOAD 0 DUP GETFIELD WhatIsFaster.i ICONST_1 IADD PUTFIELD WhatIsFaster.i RETURN this

20 Operand Stack ALOAD 0 DUP GETFIELD WhatIsFaster.i ICONST_1 IADD PUTFIELD WhatIsFaster.i RETURN this this

21 Operand Stack ALOAD 0 DUP GETFIELD WhatIsFaster.i ICONST_1 IADD PUTFIELD WhatIsFaster.i RETURN i this

22 Operand Stack ALOAD 0 DUP GETFIELD WhatIsFaster.i ICONST_1 IADD PUTFIELD WhatIsFaster.i RETURN 1 i this

23 Operand Stack ALOAD 0 DUP GETFIELD WhatIsFaster.i ICONST_1 IADD PUTFIELD WhatIsFaster.i RETURN i+1 this

24 Operand Stack ALOAD 0 DUP GETFIELD WhatIsFaster.i ICONST_1 IADD PUTFIELD WhatIsFaster.i RETURN

25 Stack Frame Max Locals Max Stack 1 i this

26 205 Opcodes I Constants NOP ACONST_NULL ICONST_n LCONST_n FCONST_n DCONST_n BIPUSH SIPUSH LDC LDC_W LDC2_W Loads ILOAD LLOAD FLOAD DLOAD ALOAD IALOAD LALOAD FALOAD DALOAD AALOAD BALOAD Stores ISTORE LSTORE FSTORE DSTORE ASTORE IASTORE LASTORE FASTORE DASTORE AASTORE BASTORE

27 205 Opcodes II References GETSTATIC PUTSTATIC GETFIELD PUTFIELD INVOKExxx NEWARRAY ANEWARRAY ATHROW CHECKCAST INSTANCEOF MONITORENTER MONITOREXIT Control GOTO TABLESWITCH LOOKUPSWITCH xreturn IFEQ IFNE IFLT IFGE IFGT IFLE IFNULL IFNONNULL Comparison LCMP FCMPL FCMPG DCMPL DCMPG

28 Byte Code Tools javap Byte Code Outline Plug- in asm.objectweb.org

29 JVM Data Types top oneword twoword int float reference long double uninitialized Object Java Class Hierachy

30 Stack Map Frames L0: ILOAD 3 ISTORE 4 ILOAD 1 IFEQ L1 ILOAD 3 ICONST_2 IMUL ISTORE 3 L1: ILOAD 2 IFEQ L2 IINC 3 L2: ILOAD 4 IRETURN Locals Stack

31 Debug AAributes Class SourceFile Methods LineNumberTable LocalVariableTable LocalVariableTypeTable

32 What is Faster? void inc1() { } i = i + 1; void inc2() { } i += 1; void inc3() { } i++; ALOAD 0 DUP GETFIELD WhatIsFaster.i ICONST_1 IADD PUTFIELD WhatIsFaster.i RETURN ALOAD 0 DUP GETFIELD WhatIsFaster.i ICONST_1 IADD PUTFIELD WhatIsFaster.i RETURN ALOAD 0 DUP GETFIELD WhatIsFaster.i ICONST_1 IADD PUTFIELD WhatIsFaster.i RETURN

33 Thank You! Ques<ons? Please Vote! Marc R. Hoffmann Eclipse Summit Europe