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package jdk.nashorn.internal.codegen.types;

import jdk.internal.org.objectweb.asm.MethodVisitor;



Interface for byte code generation for all runtime types. Each
type implements this interface and provides the type specific
operations to do the generic things described herein.
The bytecode ops are coupled to a MethodVisitor from ASM for
byte code generation. They know nothing about our MethodGenerator,
which is the abstraction for working with Nashorn JS types
For example, anything like "two or one slots" for a type, which
is represented in bytecode and ASM, is abstracted away in the
MethodGenerator. There you just say "dup" or "store".

See Also:
/**
 * Interface for byte code generation for all runtime types. Each
 * type implements this interface and provides the type specific
 * operations to do the generic things described herein.
 *
 * The bytecode ops are coupled to a MethodVisitor from ASM for
 * byte code generation. They know nothing about our MethodGenerator,
 * which is the abstraction for working with Nashorn JS types
 * For example, anything like "two or one slots" for a type, which
 * is represented in bytecode and ASM, is abstracted away in the
 * MethodGenerator. There you just say "dup" or "store".
 *
 * @see Type
 * @see MethodVisitor
 */
interface BytecodeOps {

    
Duplicate top entry of stack. If a too large depth is
given, so that there are no possible bytecode instructions
available to generate the dup sequence, null is returned.

Params:
  • method –  method visitor
  • depth –   how far should the copy be pushed down
Returns:       the type at the top of the stack or null
/**
     * Duplicate top entry of stack. If a too large depth is
     * given, so that there are no possible bytecode instructions
     * available to generate the dup sequence, null is returned.
     *
     * @param method  method visitor
     * @param depth   how far should the copy be pushed down
     *
     * @return        the type at the top of the stack or null
     */
    Type dup(MethodVisitor method, int depth);

    
Pop an entry of this type from the top of the bytecode
stack. This works regardless of what category this type
is

Params:
  • method –  method visitor
Returns:the popped type
/**
     * Pop an entry of this type from the top of the bytecode
     * stack. This works regardless of what category this type
     * is
     *
     * @param method  method visitor
     *
     * @return the popped type
     */
    Type pop(MethodVisitor method);

    
Swap this type with the bytecode stack with the one below
Generate appropriate code no matter the categories of the
two types

Params:
  • method –  method visitor
  • other –   the type below this one on the stack
Returns:       the other type
/**
     * Swap this type with the bytecode stack with the one below
     * Generate appropriate code no matter the categories of the
     * two types
     *
     * @param method  method visitor
     * @param other   the type below this one on the stack
     *
     * @return        the other type
     */
    Type swap(MethodVisitor method, Type other);

    
Pop two values on top of the stack and add the
first to the second, pushing the result on the stack

Params:
  • method –  method visitor
  • programPoint – program point id
Returns:result type
/**
     * Pop two values on top of the stack and add the
     * first to the second, pushing the result on the stack
     *
     * @param method  method visitor
     * @param programPoint program point id
     * @return result type
     */
    Type add(MethodVisitor method, int programPoint);

    
Load a variable from a local slot to the stack

Params:
  • method – method visitor
  • slot –   the slot to load
Returns:      the type that was loaded
/**
     * Load a variable from a local slot to the stack
     *
     * @param method method visitor
     * @param slot   the slot to load
     *
     * @return       the type that was loaded
     */
    Type load(MethodVisitor method, int slot);

    
Store a variable from the stack to a local slot

Params:
  • method –  method visitor
  • slot –    the slot to store to
/**
     * Store a variable from the stack to a local slot
     *
     * @param method  method visitor
     * @param slot    the slot to store to
     */
    void store(MethodVisitor method, int slot);

    
Load a constant to the stack.

Params:
  • method –  method visitor
  • c –       the value of the constant
Returns:       the type at the top of the stack after load
/**
     * Load a constant to the stack.
     *
     * @param method  method visitor
     * @param c       the value of the constant
     *
     * @return        the type at the top of the stack after load
     */
    Type ldc(MethodVisitor method, Object c);

    
Load the "undefined" value to the stack. Note that
there may be different representations of this for
e.g. doubles and objects. Abstraction removes this

Params:
  • method –  method visitor.
Returns:the undefined type at the top of the stack
/**
     * Load the "undefined" value to the stack. Note that
     * there may be different representations of this for
     * e.g. doubles and objects. Abstraction removes this
     *
     * @param  method  method visitor.
     *
     * @return the undefined type at the top of the stack
     */
    Type loadUndefined(MethodVisitor method);

    
Load the "forced initializer" value to the stack, used to ensure that a local variable has a value when it is
read by the unwarranted optimism catch block.

Params:
  • method –  method visitor.
Returns:the forced initialization type at the top of the stack
/**
     * Load the "forced initializer" value to the stack, used to ensure that a local variable has a value when it is
     * read by the unwarranted optimism catch block.
     *
     * @param  method  method visitor.
     *
     * @return the forced initialization type at the top of the stack
     */
    Type loadForcedInitializer(MethodVisitor method);


    
Load the "empty" value to the stack.

Params:
  • method –  method visitor.
Returns:the undefined type at the top of the stack
/**
     * Load the "empty" value to the stack.
     *
     * @param  method  method visitor.
     * @return the undefined type at the top of the stack
     */
    Type loadEmpty(MethodVisitor method);

    
Generate code that pops and casts the element on top of the
stack to another type, given as parameter

Params:
  • method –  method visitor
  • to –      the type to cast to
Returns:the to type
/**
     * Generate code that pops and casts the element on top of the
     * stack to another type, given as parameter
     *
     * @param method  method visitor
     * @param to      the type to cast to
     *
     * @return the to type
     */
    Type convert(MethodVisitor method, Type to);

    
Return the parameter on top of the stack
from a method

Params:
  • method – the method visitor
/**
     * Return the parameter on top of the stack
     * from a method
     *
     * @param method the method visitor
     */
    void _return(MethodVisitor method);

}