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package com.oracle.truffle.js.builtins.helper;

import static com.oracle.truffle.api.CompilerDirectives.CompilationFinal;

import com.oracle.truffle.api.Assumption;
import com.oracle.truffle.api.dsl.Cached;
import com.oracle.truffle.api.dsl.Specialization;
import com.oracle.truffle.api.nodes.Node;
import com.oracle.truffle.api.object.DynamicObject;
import com.oracle.truffle.api.object.Shape;
import com.oracle.truffle.js.builtins.RegExpPrototypeBuiltins;
import com.oracle.truffle.js.nodes.access.GetPrototypeNode;
import com.oracle.truffle.js.runtime.JSContext;
import com.oracle.truffle.js.runtime.Symbol;
import com.oracle.truffle.js.runtime.builtins.JSClass;
import com.oracle.truffle.js.runtime.builtins.JSProxy;
import com.oracle.truffle.js.runtime.builtins.JSRegExp;

Helper node for optimization of built-in functions. Some built-in functions, like
RegExp.prototype.[@@replace], are suboptimal when implemented in full conformance to the
ECMAScript spec. We want to replace those functions with faster, non-spec-conforming variants
whenever possible. One of the prerequisites for doing so is that running the spec-conforming
variant must be side-effect-free, which can only be guaranteed when all properties and functions
used by the built-in function are known/built-in as well. Therefore, we define a "pristine"
property for built-in objects: 

An object is considered "pristine" in respect to a given class and list of properties if and only
if:

The object is an instance of the given class
The object's prototype's shape has never been changed
None of the given properties have been overwritten in the prototype or the object

/**
 * Helper node for optimization of built-in functions. Some built-in functions, like
 * RegExp.prototype.[@@replace], are suboptimal when implemented in full conformance to the
 * ECMAScript spec. We want to replace those functions with faster, non-spec-conforming variants
 * whenever possible. One of the prerequisites for doing so is that running the spec-conforming
 * variant must be side-effect-free, which can only be guaranteed when all properties and functions
 * used by the built-in function are known/built-in as well. Therefore, we define a "pristine"
 * property for built-in objects: <br/>
 * An object is considered "pristine" in respect to a given class and list of properties if and only
 * if:
 * <ul>
 * <li>The object is an instance of the given class</li>
 * <li>The object's prototype's shape has never been changed</li>
 * <li>None of the given properties have been overwritten in the prototype or the object</li>
 * </ul>
 */
public abstract class IsPristineObjectNode extends Node {

    private final JSClass jsClass;
    private final Shape initialPrototypeShape;
    @CompilationFinal(dimensions = 1) private final Object[] propertyKeys;
    @CompilationFinal(dimensions = 1) private final Assumption[] propertyFinalAssumptions;
    @Child private GetPrototypeNode getPrototypeNode = GetPrototypeNode.create();

    IsPristineObjectNode(JSClass jsClass, Shape initialPrototypeShape, Object... propertyKeys) {
        assert jsClass != JSProxy.INSTANCE : "not supported because getting the prototype of proxy objects can have side effects";
        this.jsClass = jsClass;
        this.initialPrototypeShape = initialPrototypeShape;
        this.propertyKeys = propertyKeys;
        propertyFinalAssumptions = new Assumption[propertyKeys.length];
        for (int i = 0; i < propertyKeys.length; i++) {
            propertyFinalAssumptions[i] = initialPrototypeShape.getProperty(propertyKeys[i]).getLocation().getFinalAssumption();
        }
    }

    public static IsPristineObjectNode create(JSClass jsClass, Shape initialPrototypeShape, Object... propertyKeys) {
        return IsPristineObjectNodeGen.create(jsClass, initialPrototypeShape, propertyKeys);
    }

    public static IsPristineObjectNode createRegExpExecAndMatch(JSContext context) {
        assert context.getEcmaScriptVersion() >= 6;
        return IsPristineObjectNode.create(JSRegExp.INSTANCE, context.getRealm().getInitialRegExpPrototypeShape(),
                        Symbol.SYMBOL_MATCH,
                        RegExpPrototypeBuiltins.RegExpPrototype.exec.getKey(),
                        JSRegExp.FLAGS,
                        JSRegExp.GLOBAL,
                        JSRegExp.UNICODE,
                        JSRegExp.STICKY);
    }

    public abstract boolean execute(DynamicObject object);

    @Specialization(guards = {"cachedShape.check(object)"}, assumptions = "getPropertyFinalAssumptions()")
    boolean doCached(@SuppressWarnings("unused") DynamicObject object,
                    @Cached("object.getShape()") @SuppressWarnings("unused") Shape cachedShape,
                    @Cached("isInstanceAndDoesNotOverwriteProps(cachedShape)") boolean isInstanceAndDoesNotOverwriteProps) {
        return isInstanceAndDoesNotOverwriteProps && prototypeShapeUnchanged(object);
    }

    @Specialization(assumptions = "getPropertyFinalAssumptions()", replaces = "doCached")
    boolean doDynamic(DynamicObject object) {
        return isInstanceAndDoesNotOverwriteProps(object.getShape()) && prototypeShapeUnchanged(object);
    }

    @Specialization
    boolean doAssumptionsInvalid(@SuppressWarnings("unused") DynamicObject object) {
        return false;
    }

    Assumption[] getPropertyFinalAssumptions() {
        return propertyFinalAssumptions;
    }

    private boolean prototypeShapeUnchanged(DynamicObject object) {
        return getPrototypeNode.executeJSObject(object).getShape() == initialPrototypeShape;
    }

    boolean isInstanceAndDoesNotOverwriteProps(Shape objectShape) {
        if (objectShape.getDynamicType() != jsClass) {
            return false;
        }
        for (Object key : propertyKeys) {
            if (objectShape.hasProperty(key)) {
                return false;
            }
        }
        return true;
    }
}