1 / 25

Java Virtual Machine: Instruction Set

Java Virtual Machine: Instruction Set. Cheng-Chia Chen. Java Program. class SumI { public static void main (String[] args) { int count=10; int sum =0; for (int index=1;index<count;index++) sum=sum+index; } // method main } // class SumI. 2. Java ByteCode.

ray
Download Presentation

Java Virtual Machine: Instruction Set

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Java Virtual Machine: Instruction Set Cheng-Chia Chen

  2. Java Program class SumI { public static void main (String[] args) { int count=10; int sum =0; for (int index=1;index<count;index++) sum=sum+index; } // method main } // class SumI 2

  3. Java ByteCode Method void main(java.lang.String[]) 0 bipush 10 // byte push 10 to stack (0x10) 2 istore_1 // load 10 (top of stack) to count 3 iconst_0 // push 0 to stack 4 istore_2 // load 0 (top of stack to sum 5 iconst_1 // push 1 to stack 6 istore_3 // load 1 (top of stack) to index 7 goto 17 // go to 17 3

  4. Java ByteCode 10 iload_2 // load sum to stack 11 iload_3 // load index to stack 12 iadd // add 13 istore_2 // store “top of stack” to sum 14 iinc 3 1 // index ++ 17 iload_3 // load index to stack 18 iload_1 // load count to stack 19 if_icmplt 10 // if index < count goto 10 22 return 3

  5. import java.io.*; class ReadFile { public static void main (String[] args) { try { FileInputStream in = new FileInputStream(args[0]); int c; while((c = in.read()) != -1) System.out.println(c); in.close(); } catch(Exception e) { e.printStackTrace(); } } // method main } // class ReadFile

  6. JVM Instruction Sets • Stack and Local Variable Operations • Type Conversion • Integer Arithmetic • Logic and Bit manipulation • Floating Point Arithmetic • Objects and Arrays • Control Flow • Exceptions • Finally Clauses • Method Invocation and Return • Thread Synchronization

  7. Menmonics for instruction type • i for an int operation, • l for long, • s for short, • b for byte, • c for char, • f for float, • d for double, and • a for reference/array. • EX: iload, lload, fload, dload, aload,…

  8. Load and Store Instructions • transfer values between the local variables and the operand stack • load: localVar  Stack • store: Stack  localVar • [i | l | f | d | a]load u8,// or wide load u16 • [i | l | f | d | a]load_<n>, // n=0..3 • [i | l | f | d | a]store u8, // or wide load u16 • [i | l | f | d | a]store_<n>, // n=0..3

  9. Push Constants onto stack • iconst_x • x=m1..5; push int x onto stack. • fconst_x • x=0..2; push float x onto stack. • lconst_x ; dconst_x : • x=0 or 1; push long (or double) x onto stack • aconst_null: push null onto stack. • bipush s8;sipush s16, • push (int) s8 [or (int) s16] onto stack

  10. Push Constants onto stack • ldc u8;ldc_w u16, ldc2_w u16, • push single word (or double worlds for ldc2) from constant_pool entry u8 (or u16) • ldc/ldc_w can be used to push byte/short/char/int/float/String constants.

  11. Generic Stack Operations • nop // do nothing • pop, pop2, // pop top (two) words • dup, dup2, // duplicate top (two) words • swap. // swap top two words • dup_x1, dup_x2 • duplicate top words and put 1 ( 2 ) down • w3, w2, w1 => w3,w1,w2,w1 or (w1,w3,w2,w1) • dup2_x1, dup2_x2, • w4, w3, w2, w1 =>w4, w2,w1, w3,w2,w1 or (w2,w1,w4,w3,w2,w1)

  12. Integer and floating pointArithmetic Instructions • Add: iadd, ladd, fadd, dadd. • Subtract: isub, lsub, fsub, dsub. • Multiply: imul, lmul, fmul, dmul. • Divide: idiv, ldiv, fdiv, ddiv. • Remainder: irem, lrem, frem, drem. • Negate: ineg, lneg, fneg, dneg. • Local variable increment: • iinc u8 s8 // add s8 to lcalvar[u8]. • wide iinc u16 s16 // add s16 to local var at u16

  13. Shift and Bitwise operations • Shift: ishl, ishr, iushr, lshl, lshr, lushr. • ishl : … int2, int1 => … , int2<<(int1 & 0x001f) • lushr: … long2, int1=> … , long2 >>> (int1 & 0x003f) • Bitwise OR: ior, lor. • Bitwise AND: iand, land. • Bitwise exclusive OR: ixor, lxor.

  14. Comparison operations • dcmpg, dcmpl, • …d1,d2=>… int; (d1 < d2 =>-1; d2=d1=> 0; d1>d2 =>1 ) or NaN=>(g =>1; l=>-1) • fcmpg, fcmpl, // like above • lcmp. • … long1, long2 => … int k where • k = -1, 0 or 1 depending on long1 <, = or > long2.

  15. Type Conversion Instructions • widening conversions: • int  long  float  double : • i2l, i2f, i2d, l2f, l2d, f2d. • // sign extension+round-to-nearest mode • Narrowing conversions: • double  float  long  int : • d2f, d2l, d2i, f2l, f2i, l2i // truncate+ sign extension+ rtn mode • int  short, byte, char: • i2s, i2c, i2b // truncate+ sign extension • Note: byte, short, char  int are done automaticaly.

  16. Object Creation and Field Access • new • Create a new class instance on the heap, • and push a reference: • Field access: • getfield fieldRefIndex;putfield fieldRefIndex, • … objRef  … value; …objRef, value … • getstaticfieldRefIndexputstatic fieldRefIndex • …  value; …value  … • Type Checking: • instanceof class_index : … objRef  … RltVal • checkcast class_index: …obj1  … obj1 if obj1 can be casted to class type, o/w throw CastException

  17. Array Creation • newarray aType: • pop length, allocate new primitive array of type given by atype, push the reference. • aType : (z,c,f,d,b,s,i,l) ->(4,5,6,7,8,9,10,11) • … u16 -> arrayRef • anewarray Class_index, • pop length, allocate new array of type given by class_index, push the reference • multianewarray type_index dim:u8. • pop dim number of array lengths, allocate multi-dimensional array of type class_index, pop reference. • new int[10][20] ==> p10, p20, multianewarray [[i 2.

  18. Array Component Access • array component  stack : • baload, caload, saload, iaload, • … arrayRef, index:s32  … (int) array[index] • laload, faload, daload, aaload. • stack  array component • bastore, castore, sastore, iastore, • … arrayRef, index:s32, val  … • lastore, fastore, dastore, aastore. • Get the length of array:arraylength • … arrayRef  … (int)array.length

  19. Control flow Instructions1. Conditional Branches • Conditional branch: • unary comparsions • ifeq, iflt, ifle, ifne, ifgt, ifge, // =0?, <0?,… • ifnull, ifnonnull, // null or not null • binary comparisons • if_icmpeq, if_icmpne, if_icmplt, if_icmpgt, if_icmple, if_icmpge, • if_acmpeq, if_acmpne. // compare reference • For comparison of long, double and float • use dcmpg, dcmpl, fcmpg, fcmpl, lcmp and • unary comparisons on int.

  20. Control flow Instructions :2.Compound Conditional Branches • lookupswitch <0-3bytepads for word alignment> defaultOffset#pairs {caseoffset}#pairs: • all (blue) fields are int32 values • case must be in ascending order • e.g.: lookupswitch lab0 3 2 lab1 10 lab2 13 lab3 • tableswitch <0-3pads> defOffset lowCase highCase offset high-low+1. • goto offset[top-low+1] iff low ≤ top ≤ high • else goto defOffset. • e.g.: tableswitch lab0 11 14 lab11 lab12 lab13 lab14.

  21. Control flow Instructions: Unconditional branches • goto s16;goto_w s32 • pc = pc + s16 (or s32). // for implementing finally clauses // intraMethod subroutine call • jsr s16,jsr_w s32, • push return addr and jumpToSubroutine pc+s16 for a finally block • …  … returnAddr • ret u8; widen ret u16, • return to addr given by localVar u8 or u16 .

  22. Method Invocation and Return Instructions • invokevirtual : for normal methods • invokeInterface: • for interface methods // search of implementation is needed • invokespecial: • for private method, superclass method and instance initialization (constructors) methods • invokestatic : for static methods • format: opcode u16// methodRefIndex • return : • ireturn, lreturn, freturn, dreturn, areturn • return : for void, instance, class (or interface) initialization methods

  23. Exceptions related Instructions • Throw Exception: • athrow • can also be thrown by other instructions if abnormal condition detected. • … ExcObj  … • Implementing finally • jsr s16,jsr_w s32, • jumpToSubroutine pc+s16 for a finally block • ret u8; widen ret u16, • return to addr given by localVar u8 or u16 .

  24. Synchronization • via monitor construct: • monitorenter, monitorexit • monitorenter • pop objectref, acquire the lock associated with the object. • … ObjRef  … • monitorexit • pop objectref, release the lock associate with objectref • … ObjRef  …

  25. Classes needing special support of JVM • Reflection: • java.lang.reflect.* and java.lang.Class. • Loading and creation of a class or interface. • ClassLoader. • Linking and initialization of a class or interface. • Security: • java.security.** and other classes such as SecurityManager. • Multithreading, such as the class Thread. • Weak references: java.lang.ref.* • …

More Related