The Java Virtual Machine is extended in the future, these reserved opcodes are

The instructions specified later in this chapter, which are used inĬlass files ( §4), three opcodes are reservedįor internal use by a Java Virtual Machine implementation. The Java Virtual Machine Specification, Java SE 7 Edition. Other implementation strategiesĪre possible, provided that they comply with The Java Language Specification, Java SE 7 Edition and Performing verification at link time is attractive in that theĬhecks are performed just once, substantially reducing the amount of Java Virtual Machine will only attempt to execute code from valid classįiles.

The Java Virtual Machine checks that Java Virtual MachineĬode satisfies the static and structural constraints at link time Time, the behavior of the Java Virtual Machine is undefined. 'must not') in an instruction description is not satisfied at run Not' be the case: 'The value2 must be of type int.' TheĬonstraints of §4 guarantee that all suchĮxpectations will in fact be met.

Instructions, we frequently state that some situation 'must' or 'must In the description of individual Java Virtual Machine Satisfies the static and structural constraints of Instruction is always given in the context of Java Virtual Machine code that Gives details about the format of each Java Virtual Machine instruction and the Or more operands embodying values to be operated upon. Instructions aaload aastore aconst_null aload aload_ anewarray areturn arraylength astore astore_ athrow baload bastore bipush caload castore checkcast d2f d2i d2l dadd daload dastore dcmp dconst_ ddiv dload dload_ dmul dneg drem dreturn dstore dstore_ dsub dup dup_x1 dup_x2 dup2 dup2_x1 dup2_x2 f2d f2i f2l fadd faload fastore fcmp fconst_ fdiv fload fload_ fmul fneg frem freturn fstore fstore_ fsub getfield getstatic goto goto_w i2b i2c i2d i2f i2l i2s iadd iaload iand iastore iconst_ idiv if_acmp if_icmp if ifnonnull ifnull iinc iload iload_ imul ineg instanceof invokedynamic invokeinterface invokespecial invokestatic invokevirtual ior irem ireturn ishl ishr istore istore_ isub iushr ixor jsr jsr_w l2d l2f l2i ladd laload land lastore lcmp lconst_ ldc ldc_w ldc2_w ldiv lload lload_ lmul lneg lookupswitch lor lrem lreturn lshl lshr lstore lstore_ lsub lushr lxor monitorenter monitorexit multianewarray new newarray nop pop pop2 putfield putstatic ret return saload sastore sipush swap tableswitch wideĪ Java Virtual Machine instruction consists ofĪn opcode specifying the operation to be performed, followed by zero Format of Instruction Descriptions mnemonic 6.5.

Jvm source code