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/*
* Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
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 exmaple, 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.
*
* @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
*
* @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
*
* @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
*
* @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
*
* @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
*
* @param method method visitor
* @param slot the slot to store to
*/
void store(MethodVisitor method, int slot);
/**
* 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
*
* @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.
*
* @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.
*
* @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
*
* @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
*
* @param method the method visitor
*/
void _return(MethodVisitor method);
}
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