gecko/js/src/jsinterpinlines.h

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
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 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is SpiderMonkey code.
 *
 * The Initial Developer of the Original Code is
 * Mozilla Corporation.
 * Portions created by the Initial Developer are Copyright (C) 2010
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Luke Wagner <lw@mozilla.com>
 *
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 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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 * ***** END LICENSE BLOCK ***** */

#ifndef jsinterpinlines_h__
#define jsinterpinlines_h__

#include "jsapi.h"
#include "jsbool.h"
#include "jscompartment.h"
#include "jsinterp.h"
#include "jsnum.h"
#include "jsprobes.h"
#include "jsstr.h"
#include "methodjit/MethodJIT.h"

#include "jsfuninlines.h"

#include "vm/Stack-inl.h"

namespace js {

class AutoPreserveEnumerators {
    JSContext *cx;
    JSObject *enumerators;

  public:
    AutoPreserveEnumerators(JSContext *cx) : cx(cx), enumerators(cx->enumerators)
    {
    }

    ~AutoPreserveEnumerators()
    {
        cx->enumerators = enumerators;
    }
};

/*
 * Compute the implicit |this| parameter for a call expression where the callee
 * funval was resolved from an unqualified name reference to a property on obj
 * (an object on the scope chain).
 *
 * We can avoid computing |this| eagerly and push the implicit callee-coerced
 * |this| value, undefined, if any of these conditions hold:
 *
 * 1. The callee funval is not an object.
 *
 * 2. The nominal |this|, obj, is a global object.
 *
 * 3. The nominal |this|, obj, has one of Block, Call, or DeclEnv class (this
 *    is what IsCacheableNonGlobalScope tests). Such objects-as-scopes must be
 *    censored with undefined.
 *
 * Only if funval is an object and obj is neither a declarative scope object to
 * be censored, nor a global object, do we bind |this| to obj->thisObject().
 * Only |with| statements and embedding-specific scope objects fall into this
 * last ditch.
 *
 * If funval is a strict mode function, then code implementing JSOP_THIS in the
 * interpreter and JITs will leave undefined as |this|. If funval is a function
 * not in strict mode, JSOP_THIS code replaces undefined with funval's global.
 *
 * We set *vp to undefined early to reduce code size and bias this code for the
 * common and future-friendly cases.
 */
inline bool
ComputeImplicitThis(JSContext *cx, JSObject *obj, const Value &funval, Value *vp)
{
    vp->setUndefined();

    if (!funval.isObject())
        return true;

    if (obj->isGlobal())
        return true;

    if (IsCacheableNonGlobalScope(obj))
        return true;

    obj = obj->thisObject(cx);
    if (!obj)
        return false;

    vp->setObject(*obj);
    return true;
}

inline bool
ComputeThis(JSContext *cx, StackFrame *fp)
{
    Value &thisv = fp->thisValue();
    if (thisv.isObject())
        return true;
    if (fp->isFunctionFrame()) {
        if (fp->fun()->inStrictMode())
            return true;
        /*
         * Eval function frames have their own |this| slot, which is a copy of the function's
         * |this| slot. If we lazily wrap a primitive |this| in an eval function frame, the
         * eval's frame will get the wrapper, but the function's frame will not. To prevent
         * this, we always wrap a function's |this| before pushing an eval frame, and should
         * thus never see an unwrapped primitive in a non-strict eval function frame.
         */
        JS_ASSERT(!fp->isEvalFrame());
    }
    return BoxNonStrictThis(cx, fp->callReceiver());
}

/*
 * Return an object on which we should look for the properties of |value|.
 * This helps us implement the custom [[Get]] method that ES5's GetValue
 * algorithm uses for primitive values, without actually constructing the
 * temporary object that the specification does.
 * 
 * For objects, return the object itself. For string, boolean, and number
 * primitive values, return the appropriate constructor's prototype. For
 * undefined and null, throw an error and return NULL, attributing the
 * problem to the value at |spindex| on the stack.
 */
JS_ALWAYS_INLINE JSObject *
ValuePropertyBearer(JSContext *cx, const Value &v, int spindex)
{
    if (v.isObject())
        return &v.toObject();

    JSProtoKey protoKey;
    if (v.isString()) {
        protoKey = JSProto_String;
    } else if (v.isNumber()) {
        protoKey = JSProto_Number;
    } else if (v.isBoolean()) {
        protoKey = JSProto_Boolean;
    } else {
        JS_ASSERT(v.isNull() || v.isUndefined());
        js_ReportIsNullOrUndefined(cx, spindex, v, NULL);
        return NULL;
    }

    JSObject *pobj;
    if (!js_GetClassPrototype(cx, NULL, protoKey, &pobj))
        return NULL;
    return pobj;
}

inline bool
FunctionNeedsPrologue(JSContext *cx, JSFunction *fun)
{
    /* Heavyweight functions need call objects created. */
    if (fun->isHeavyweight())
        return true;

    /* Outer and inner functions need to preserve nesting invariants. */
    if (cx->typeInferenceEnabled() && fun->script()->nesting())
        return true;

    return false;
}

inline bool
ScriptPrologue(JSContext *cx, StackFrame *fp, bool newType)
{
    JS_ASSERT_IF(fp->isNonEvalFunctionFrame() && fp->fun()->isHeavyweight(), fp->hasCallObj());

    if (fp->isConstructing()) {
        JSObject *obj = js_CreateThisForFunction(cx, &fp->callee(), newType);
        if (!obj)
            return false;
        fp->functionThis().setObject(*obj);
    }

    Probes::enterJSFun(cx, fp->maybeFun(), fp->script());
    if (cx->compartment->debugMode())
        ScriptDebugPrologue(cx, fp);

    return true;
}

inline bool
ScriptEpilogue(JSContext *cx, StackFrame *fp, bool ok)
{
    Probes::exitJSFun(cx, fp->maybeFun(), fp->script());
    if (cx->compartment->debugMode())
        ok = ScriptDebugEpilogue(cx, fp, ok);

    /*
     * If inline-constructing, replace primitive rval with the new object
     * passed in via |this|, and instrument this constructor invocation.
     */
    if (fp->isConstructing() && ok) {
        if (fp->returnValue().isPrimitive())
            fp->setReturnValue(ObjectValue(fp->constructorThis()));
    }

    return ok;
}

inline bool
ScriptPrologueOrGeneratorResume(JSContext *cx, StackFrame *fp, bool newType)
{
    if (!fp->isGeneratorFrame())
        return ScriptPrologue(cx, fp, newType);
    if (cx->compartment->debugMode())
        ScriptDebugPrologue(cx, fp);
    return true;
}

inline bool
ScriptEpilogueOrGeneratorYield(JSContext *cx, StackFrame *fp, bool ok)
{
    if (!fp->isYielding())
        return ScriptEpilogue(cx, fp, ok);
    if (cx->compartment->debugMode())
        return ScriptDebugEpilogue(cx, fp, ok);
    return ok;
}

}  /* namespace js */

#endif /* jsinterpinlines_h__ */