diff --git a/js/src/frontend/Parser.cpp b/js/src/frontend/Parser.cpp
index 8fc7b4552ab1..da6991091047 100644
--- a/js/src/frontend/Parser.cpp
+++ b/js/src/frontend/Parser.cpp
@@ -2069,9 +2069,9 @@ Parser<SyntaxParseHandler>::finishFunctionDefinition(Node pn, FunctionBox *funbo
     size_t numInnerFunctions = pc->innerFunctions.length();
 
     RootedFunction fun(context, funbox->function());
-    LazyScript *lazy = LazyScript::Create(context, fun, numFreeVariables, numInnerFunctions, versionNumber(),
-                                          funbox->bufStart, funbox->bufEnd,
-                                          funbox->startLine, funbox->startColumn);
+    LazyScript *lazy = LazyScript::CreateRaw(context, fun, numFreeVariables, numInnerFunctions,
+                                             versionNumber(), funbox->bufStart, funbox->bufEnd,
+                                             funbox->startLine, funbox->startColumn);
     if (!lazy)
         return false;
 
diff --git a/js/src/jsfun.cpp b/js/src/jsfun.cpp
index e6fffff38e90..984db5e5bd75 100644
--- a/js/src/jsfun.cpp
+++ b/js/src/jsfun.cpp
@@ -357,8 +357,9 @@ js::XDRInterpretedFunction(XDRState<mode> *xdr, HandleObject enclosingScope, Han
                            MutableHandleObject objp)
 {
     enum FirstWordFlag {
-        HasAtom = 0x1,
-        IsStarGenerator = 0x2
+        HasAtom             = 0x1,
+        IsStarGenerator     = 0x2,
+        IsLazy              = 0x4
     };
 
     /* NB: Keep this in sync with CloneFunctionAndScript. */
@@ -369,6 +370,8 @@ js::XDRInterpretedFunction(XDRState<mode> *xdr, HandleObject enclosingScope, Han
     JSContext *cx = xdr->cx();
     RootedFunction fun(cx);
     RootedScript script(cx);
+    Rooted<LazyScript *> lazy(cx);
+
     if (mode == XDR_ENCODE) {
         fun = &objp->as<JSFunction>();
         if (!fun->isInterpreted()) {
@@ -379,13 +382,27 @@ js::XDRInterpretedFunction(XDRState<mode> *xdr, HandleObject enclosingScope, Han
             }
             return false;
         }
+
         if (fun->atom() || fun->hasGuessedAtom())
             firstword |= HasAtom;
+
         if (fun->isStarGenerator())
             firstword |= IsStarGenerator;
-        script = fun->getOrCreateScript(cx);
-        if (!script)
-            return false;
+
+        if (fun->isInterpretedLazy()) {
+            // This can only happen for re-lazified cloned functions, so this
+            // does not apply to any JSFunction produced by the parser, only to
+            // JSFunction created by the runtime.
+            JS_ASSERT(!fun->lazyScript()->maybeScript());
+
+            // Encode a lazy script.
+            firstword |= IsLazy;
+            lazy = fun->lazyScript();
+        } else {
+            // Encode the script.
+            script = fun->nonLazyScript();
+        }
+
         atom = fun->displayAtom();
         flagsword = (fun->nargs() << 16) | fun->flags();
     }
@@ -414,18 +431,29 @@ js::XDRInterpretedFunction(XDRState<mode> *xdr, HandleObject enclosingScope, Han
     if (!xdr->codeUint32(&flagsword))
         return false;
 
-    if (!XDRScript(xdr, enclosingScope, enclosingScript, fun, &script))
-        return false;
+    if (firstword & IsLazy) {
+        if (!XDRLazyScript(xdr, enclosingScope, enclosingScript, fun, &lazy))
+            return false;
+    } else {
+        if (!XDRScript(xdr, enclosingScope, enclosingScript, fun, &script))
+            return false;
+    }
 
     if (mode == XDR_DECODE) {
         fun->setArgCount(flagsword >> 16);
         fun->setFlags(uint16_t(flagsword));
         fun->initAtom(atom);
-        fun->initScript(script);
-        script->setFunction(fun);
+        if (firstword & IsLazy) {
+            fun->initLazyScript(lazy);
+        } else {
+            fun->initScript(script);
+            script->setFunction(fun);
+            JS_ASSERT(fun->nargs() == script->bindings.numArgs());
+        }
+
+
         if (!JSFunction::setTypeForScriptedFunction(cx, fun))
             return false;
-        JS_ASSERT(fun->nargs() == fun->nonLazyScript()->bindings.numArgs());
         objp.set(fun);
     }
 
diff --git a/js/src/jsscript.cpp b/js/src/jsscript.cpp
index 309804f46618..a9e26ec6c071 100644
--- a/js/src/jsscript.cpp
+++ b/js/src/jsscript.cpp
@@ -414,6 +414,75 @@ js::XDRScriptConst(XDRState<XDR_ENCODE> *, MutableHandleValue);
 template bool
 js::XDRScriptConst(XDRState<XDR_DECODE> *, MutableHandleValue);
 
+// Code LazyScript's free variables.
+template<XDRMode mode>
+static bool
+XDRLazyFreeVariables(XDRState<mode> *xdr, MutableHandle<LazyScript *> lazy)
+{
+    JSContext *cx = xdr->cx();
+    RootedAtom atom(cx);
+    HeapPtrAtom *freeVariables = lazy->freeVariables();
+    size_t numFreeVariables = lazy->numFreeVariables();
+    for (size_t i = 0; i < numFreeVariables; i++) {
+        if (mode == XDR_ENCODE)
+            atom = freeVariables[i];
+
+        if (!XDRAtom(xdr, &atom))
+            return false;
+
+        if (mode == XDR_DECODE)
+            freeVariables[i] = atom;
+    }
+
+    return true;
+}
+
+// Code the missing part needed to re-create a LazyScript from a JSScript.
+template<XDRMode mode>
+static bool
+XDRRelazificationInfo(XDRState<mode> *xdr, HandleFunction fun, HandleScript script,
+                      MutableHandle<LazyScript *> lazy)
+{
+    MOZ_ASSERT_IF(mode == XDR_ENCODE, script->isRelazifiable() && script->maybeLazyScript());
+    MOZ_ASSERT_IF(mode == XDR_ENCODE, !lazy->numInnerFunctions());
+
+    JSContext *cx = xdr->cx();
+
+    uint64_t packedFields;
+    {
+        uint32_t begin = script->sourceStart();
+        uint32_t end = script->sourceEnd();
+        uint32_t lineno = script->lineno();
+        uint32_t column = script->column();
+
+        if (mode == XDR_ENCODE) {
+            packedFields = lazy->packedFields();
+            MOZ_ASSERT(begin == lazy->begin());
+            MOZ_ASSERT(end == lazy->end());
+            MOZ_ASSERT(lineno == lazy->lineno());
+            MOZ_ASSERT(column == lazy->column());
+        }
+
+        if (!xdr->codeUint64(&packedFields))
+            return false;
+
+        if (mode == XDR_DECODE) {
+            lazy.set(LazyScript::Create(cx, fun, packedFields, begin, end, lineno, column));
+
+            // As opposed to XDRLazyScript, we need to restore the runtime bits
+            // of the script, as we are trying to match the fact this function
+            // has already been parsed and that it would need to be re-lazified.
+            lazy->initRuntimeFields(packedFields);
+        }
+    }
+
+    // Code free variables.
+    if (!XDRLazyFreeVariables(xdr, lazy))
+        return false;
+
+    return true;
+}
+
 static inline uint32_t
 FindScopeObjectIndex(JSScript *script, NestedScopeObject &scope)
 {
@@ -463,7 +532,8 @@ js::XDRScript(XDRState<mode> *xdr, HandleObject enclosingScope, HandleScript enc
         SelfHosted,
         IsCompileAndGo,
         HasSingleton,
-        TreatAsRunOnce
+        TreatAsRunOnce,
+        HasLazyScript
     };
 
     uint32_t length, lineno, column, nslots;
@@ -561,6 +631,8 @@ js::XDRScript(XDRState<mode> *xdr, HandleObject enclosingScope, HandleScript enc
             scriptBits |= (1 << HasSingleton);
         if (script->treatAsRunOnce())
             scriptBits |= (1 << TreatAsRunOnce);
+        if (script->isRelazifiable())
+            scriptBits |= (1 << HasLazyScript);
     }
 
     if (!xdr->codeUint32(&prologLength))
@@ -821,12 +893,16 @@ js::XDRScript(XDRState<mode> *xdr, HandleObject enclosingScope, HandleScript enc
           case CK_JSFunction: {
             /* Code the nested function's enclosing scope. */
             uint32_t funEnclosingScopeIndex = 0;
+            RootedObject funEnclosingScope(cx);
             if (mode == XDR_ENCODE) {
-                JSScript *innerScript = (*objp)->as<JSFunction>().getOrCreateScript(cx);
-                if (!innerScript)
-                    return false;
-                RootedObject staticScope(cx, innerScript->enclosingStaticScope());
-                StaticScopeIter<NoGC> ssi(staticScope);
+                RootedFunction function(cx, &(*objp)->as<JSFunction>());
+
+                if (function->isInterpretedLazy())
+                    funEnclosingScope = function->lazyScript()->enclosingScope();
+                else
+                    funEnclosingScope = function->nonLazyScript()->enclosingStaticScope();
+
+                StaticScopeIter<NoGC> ssi(funEnclosingScope);
                 if (ssi.done() || ssi.type() == StaticScopeIter<NoGC>::FUNCTION) {
                     JS_ASSERT(ssi.done() == !fun);
                     funEnclosingScopeIndex = UINT32_MAX;
@@ -835,9 +911,10 @@ js::XDRScript(XDRState<mode> *xdr, HandleObject enclosingScope, HandleScript enc
                     JS_ASSERT(funEnclosingScopeIndex < i);
                 }
             }
+
             if (!xdr->codeUint32(&funEnclosingScopeIndex))
                 return false;
-            Rooted<JSObject*> funEnclosingScope(cx);
+
             if (mode == XDR_DECODE) {
                 if (funEnclosingScopeIndex == UINT32_MAX) {
                     funEnclosingScope = fun;
@@ -847,6 +924,7 @@ js::XDRScript(XDRState<mode> *xdr, HandleObject enclosingScope, HandleScript enc
                 }
             }
 
+            // Code nested function and script.
             RootedObject tmp(cx, *objp);
             if (!XDRInterpretedFunction(xdr, funEnclosingScope, script, &tmp))
                 return false;
@@ -901,6 +979,18 @@ js::XDRScript(XDRState<mode> *xdr, HandleObject enclosingScope, HandleScript enc
         }
     }
 
+    if (scriptBits & (1 << HasLazyScript)) {
+        Rooted<LazyScript *> lazy(cx);
+        if (mode == XDR_ENCODE)
+            lazy = script->maybeLazyScript();
+
+        if (!XDRRelazificationInfo(xdr, fun, script, &lazy))
+            return false;
+
+        if (mode == XDR_DECODE)
+            script->setLazyScript(lazy);
+    }
+
     if (mode == XDR_DECODE) {
         scriptp.set(script);
 
@@ -923,6 +1013,83 @@ template bool
 js::XDRScript(XDRState<XDR_DECODE> *, HandleObject, HandleScript, HandleFunction,
               MutableHandleScript);
 
+template<XDRMode mode>
+bool
+js::XDRLazyScript(XDRState<mode> *xdr, HandleObject enclosingScope, HandleScript enclosingScript,
+                  HandleFunction fun, MutableHandle<LazyScript *> lazy)
+{
+    JSContext *cx = xdr->cx();
+
+    {
+        uint32_t begin;
+        uint32_t end;
+        uint32_t lineno;
+        uint32_t column;
+        uint64_t packedFields;
+
+        if (mode == XDR_ENCODE) {
+            MOZ_ASSERT(!lazy->maybeScript());
+            MOZ_ASSERT(fun == lazy->functionNonDelazifying());
+
+            begin = lazy->begin();
+            end = lazy->end();
+            lineno = lazy->lineno();
+            column = lazy->column();
+            packedFields = lazy->packedFields();
+        }
+
+        if (!xdr->codeUint32(&begin) || !xdr->codeUint32(&end) ||
+            !xdr->codeUint32(&lineno) || !xdr->codeUint32(&column) ||
+            !xdr->codeUint64(&packedFields))
+        {
+            return false;
+        }
+
+        if (mode == XDR_DECODE)
+            lazy.set(LazyScript::Create(cx, fun, packedFields, begin, end, lineno, column));
+    }
+
+    // Code free variables.
+    if (!XDRLazyFreeVariables(xdr, lazy))
+        return false;
+
+    // Code inner functions.
+    {
+        RootedObject func(cx);
+        HeapPtrFunction *innerFunctions = lazy->innerFunctions();
+        size_t numInnerFunctions = lazy->numInnerFunctions();
+        for (size_t i = 0; i < numInnerFunctions; i++) {
+            if (mode == XDR_ENCODE)
+                func = innerFunctions[i];
+
+            if (!XDRInterpretedFunction(xdr, fun, enclosingScript, &func))
+                return false;
+
+            if (mode == XDR_DECODE)
+                innerFunctions[i] = &func->as<JSFunction>();
+        }
+    }
+
+    if (mode == XDR_DECODE) {
+        JS_ASSERT(!lazy->sourceObject());
+        ScriptSourceObject *sourceObject = &enclosingScript->scriptSourceUnwrap();
+
+        // Set the enclosing scope of the lazy function, this would later be
+        // used to define the environment when the function would be used.
+        lazy->setParent(enclosingScope, sourceObject);
+    }
+
+    return true;
+}
+
+template bool
+js::XDRLazyScript(XDRState<XDR_ENCODE> *, HandleObject, HandleScript,
+                  HandleFunction, MutableHandle<LazyScript *>);
+
+template bool
+js::XDRLazyScript(XDRState<XDR_DECODE> *, HandleObject, HandleScript,
+                  HandleFunction, MutableHandle<LazyScript *>);
+
 void
 JSScript::setSourceObject(JSObject *object)
 {
@@ -930,9 +1097,14 @@ JSScript::setSourceObject(JSObject *object)
     sourceObject_ = object;
 }
 
+js::ScriptSourceObject &
+JSScript::scriptSourceUnwrap() const {
+    return UncheckedUnwrap(sourceObject())->as<ScriptSourceObject>();
+}
+
 js::ScriptSource *
 JSScript::scriptSource() const {
-    return UncheckedUnwrap(sourceObject())->as<ScriptSourceObject>().source();
+    return scriptSourceUnwrap().source();
 }
 
 bool
@@ -3242,30 +3414,18 @@ JSScript::formalLivesInArgumentsObject(unsigned argSlot)
     return argsObjAliasesFormals() && !formalIsAliased(argSlot);
 }
 
-LazyScript::LazyScript(JSFunction *fun, void *table, uint32_t numFreeVariables, uint32_t numInnerFunctions,
-                       JSVersion version, uint32_t begin, uint32_t end, uint32_t lineno, uint32_t column)
+LazyScript::LazyScript(JSFunction *fun, void *table, uint64_t packedFields, uint32_t begin, uint32_t end, uint32_t lineno, uint32_t column)
   : script_(nullptr),
     function_(fun),
     enclosingScope_(nullptr),
     sourceObject_(nullptr),
     table_(table),
-    version_(version),
-    numFreeVariables_(numFreeVariables),
-    numInnerFunctions_(numInnerFunctions),
-    generatorKindBits_(GeneratorKindAsBits(NotGenerator)),
-    strict_(false),
-    bindingsAccessedDynamically_(false),
-    hasDebuggerStatement_(false),
-    directlyInsideEval_(false),
-    usesArgumentsAndApply_(false),
-    hasBeenCloned_(false),
-    treatAsRunOnce_(false),
+    packedFields_(packedFields),
     begin_(begin),
     end_(end),
     lineno_(lineno),
     column_(column)
 {
-    JS_ASSERT(this->version() == version);
     JS_ASSERT(begin <= end);
 }
 
@@ -3301,14 +3461,23 @@ LazyScript::sourceObject() const
 }
 
 /* static */ LazyScript *
-LazyScript::Create(ExclusiveContext *cx, HandleFunction fun,
-                   uint32_t numFreeVariables, uint32_t numInnerFunctions, JSVersion version,
-                   uint32_t begin, uint32_t end, uint32_t lineno, uint32_t column)
+LazyScript::CreateRaw(ExclusiveContext *cx, HandleFunction fun,
+                      uint64_t packedFields, uint32_t begin, uint32_t end,
+                      uint32_t lineno, uint32_t column)
 {
-    JS_ASSERT(begin <= end);
+    union {
+        PackedView p;
+        uint64_t packed;
+    };
 
-    size_t bytes = (numFreeVariables * sizeof(HeapPtrAtom))
-                 + (numInnerFunctions * sizeof(HeapPtrFunction));
+    packed = packedFields;
+
+    // Reset runtime flags to obtain a fresh LazyScript.
+    p.hasBeenCloned = false;
+    p.treatAsRunOnce = false;
+
+    size_t bytes = (p.numFreeVariables * sizeof(HeapPtrAtom))
+                 + (p.numInnerFunctions * sizeof(HeapPtrFunction));
 
     void *table = nullptr;
     if (bytes) {
@@ -3323,8 +3492,75 @@ LazyScript::Create(ExclusiveContext *cx, HandleFunction fun,
 
     cx->compartment()->scheduleDelazificationForDebugMode();
 
-    return new (res) LazyScript(fun, table, numFreeVariables, numInnerFunctions, version,
-                                begin, end, lineno, column);
+    return new (res) LazyScript(fun, table, packed, begin, end, lineno, column);
+}
+
+/* static */ LazyScript *
+LazyScript::CreateRaw(ExclusiveContext *cx, HandleFunction fun,
+                      uint32_t numFreeVariables, uint32_t numInnerFunctions, JSVersion version,
+                      uint32_t begin, uint32_t end, uint32_t lineno, uint32_t column)
+{
+    union {
+        PackedView p;
+        uint64_t packedFields;
+    };
+
+    p.version = version;
+    p.numFreeVariables = numFreeVariables;
+    p.numInnerFunctions = numInnerFunctions;
+    p.generatorKindBits = GeneratorKindAsBits(NotGenerator);
+    p.strict = false;
+    p.bindingsAccessedDynamically = false;
+    p.hasDebuggerStatement = false;
+    p.directlyInsideEval = false;
+    p.usesArgumentsAndApply = false;
+
+    LazyScript *res = LazyScript::CreateRaw(cx, fun, packedFields, begin, end, lineno, column);
+    JS_ASSERT(res->version() == version);
+    return res;
+}
+
+/* static */ LazyScript *
+LazyScript::Create(ExclusiveContext *cx, HandleFunction fun,
+                   uint64_t packedFields, uint32_t begin, uint32_t end,
+                   uint32_t lineno, uint32_t column)
+{
+    // Dummy atom which is not a valid property name.
+    RootedAtom dummyAtom(cx, cx->names().comma);
+
+    // Dummy function which is not a valid function as this is the one which is
+    // holding this lazy script.
+    HandleFunction dummyFun = fun;
+
+    LazyScript *res = LazyScript::CreateRaw(cx, fun, packedFields, begin, end, lineno, column);
+    if (!res)
+        return nullptr;
+
+    // Fill with dummies, to be GC-safe after the initialization of the free
+    // variables and inner functions.
+    size_t i, num;
+    HeapPtrAtom *variables = res->freeVariables();
+    for (i = 0, num = res->numFreeVariables(); i < num; i++)
+        variables[i].init(dummyAtom);
+
+    HeapPtrFunction *functions = res->innerFunctions();
+    for (i = 0, num = res->numInnerFunctions(); i < num; i++)
+        functions[i].init(dummyFun);
+
+    return res;
+}
+
+void
+LazyScript::initRuntimeFields(uint64_t packedFields)
+{
+    union {
+        PackedView p;
+        uint64_t packed;
+    };
+
+    packed = packedFields;
+    p_.hasBeenCloned = p.hasBeenCloned;
+    p_.treatAsRunOnce = p.treatAsRunOnce;
 }
 
 uint32_t
diff --git a/js/src/jsscript.h b/js/src/jsscript.h
index d7954220ae0a..5eb375266d6c 100644
--- a/js/src/jsscript.h
+++ b/js/src/jsscript.h
@@ -595,6 +595,11 @@ JSScript *
 CloneScript(JSContext *cx, HandleObject enclosingScope, HandleFunction fun, HandleScript script,
             NewObjectKind newKind = GenericObject);
 
+template<XDRMode mode>
+bool
+XDRLazyScript(XDRState<mode> *xdr, HandleObject enclosingScope, HandleScript enclosingScript,
+              HandleFunction fun, MutableHandle<LazyScript *> lazy);
+
 /*
  * Code any constant value.
  */
@@ -1240,6 +1245,7 @@ class JSScript : public js::gc::BarrieredCell<JSScript>
     JSObject *sourceObject() const {
         return sourceObject_;
     }
+    js::ScriptSourceObject &scriptSourceUnwrap() const;
     js::ScriptSource *scriptSource() const;
     JSPrincipals *originPrincipals() const { return scriptSource()->originPrincipals(); }
     const char *filename() const { return scriptSource()->filename(); }
@@ -1607,22 +1613,29 @@ class LazyScript : public gc::BarrieredCell<LazyScript>
     uint32_t padding;
 #endif
 
-    // Assorted bits that should really be in ScriptSourceObject.
-    uint32_t version_ : 8;
+    struct PackedView {
+        // Assorted bits that should really be in ScriptSourceObject.
+        uint32_t version : 8;
 
-    uint32_t numFreeVariables_ : 24;
-    uint32_t numInnerFunctions_ : 23;
+        uint32_t numFreeVariables : 24;
+        uint32_t numInnerFunctions : 23;
 
-    uint32_t generatorKindBits_:2;
+        uint32_t generatorKindBits : 2;
 
-    // N.B. These are booleans but need to be uint32_t to pack correctly on MSVC.
-    uint32_t strict_ : 1;
-    uint32_t bindingsAccessedDynamically_ : 1;
-    uint32_t hasDebuggerStatement_ : 1;
-    uint32_t directlyInsideEval_:1;
-    uint32_t usesArgumentsAndApply_:1;
-    uint32_t hasBeenCloned_:1;
-    uint32_t treatAsRunOnce_:1;
+        // N.B. These are booleans but need to be uint32_t to pack correctly on MSVC.
+        uint32_t strict : 1;
+        uint32_t bindingsAccessedDynamically : 1;
+        uint32_t hasDebuggerStatement : 1;
+        uint32_t directlyInsideEval : 1;
+        uint32_t usesArgumentsAndApply : 1;
+        uint32_t hasBeenCloned : 1;
+        uint32_t treatAsRunOnce : 1;
+    };
+
+    union {
+        PackedView p_;
+        uint64_t packedFields_;
+    };
 
     // Source location for the script.
     uint32_t begin_;
@@ -1630,16 +1643,34 @@ class LazyScript : public gc::BarrieredCell<LazyScript>
     uint32_t lineno_;
     uint32_t column_;
 
-    LazyScript(JSFunction *fun, void *table,
-               uint32_t numFreeVariables, uint32_t numInnerFunctions, JSVersion version,
+    LazyScript(JSFunction *fun, void *table, uint64_t packedFields,
                uint32_t begin, uint32_t end, uint32_t lineno, uint32_t column);
 
+    // Create a LazyScript without initializing the freeVariables and the
+    // innerFunctions. To be GC-safe, the caller must initialize both vectors
+    // with valid atoms and functions.
+    static LazyScript *CreateRaw(ExclusiveContext *cx, HandleFunction fun,
+                                 uint64_t packedData, uint32_t begin, uint32_t end,
+                                 uint32_t lineno, uint32_t column);
+
   public:
+    // Create a LazyScript without initializing the freeVariables and the
+    // innerFunctions. To be GC-safe, the caller must initialize both vectors
+    // with valid atoms and functions.
+    static LazyScript *CreateRaw(ExclusiveContext *cx, HandleFunction fun,
+                                 uint32_t numFreeVariables, uint32_t numInnerFunctions,
+                                 JSVersion version, uint32_t begin, uint32_t end,
+                                 uint32_t lineno, uint32_t column);
+
+    // Create a LazyScript and initialize the freeVariables and the
+    // innerFunctions with dummy values to be replaced in a later initialization
+    // phase.
     static LazyScript *Create(ExclusiveContext *cx, HandleFunction fun,
-                              uint32_t numFreeVariables, uint32_t numInnerFunctions,
-                              JSVersion version, uint32_t begin, uint32_t end,
+                              uint64_t packedData, uint32_t begin, uint32_t end,
                               uint32_t lineno, uint32_t column);
 
+    void initRuntimeFields(uint64_t packedFields);
+
     inline JSFunction *functionDelazifying(JSContext *cx) const;
     JSFunction *functionNonDelazifying() const {
         return function_;
@@ -1663,26 +1694,26 @@ class LazyScript : public gc::BarrieredCell<LazyScript>
     }
     JSVersion version() const {
         JS_STATIC_ASSERT(JSVERSION_UNKNOWN == -1);
-        return (version_ == JS_BIT(8) - 1) ? JSVERSION_UNKNOWN : JSVersion(version_);
+        return (p_.version == JS_BIT(8) - 1) ? JSVERSION_UNKNOWN : JSVersion(p_.version);
     }
 
     void setParent(JSObject *enclosingScope, ScriptSourceObject *sourceObject);
 
     uint32_t numFreeVariables() const {
-        return numFreeVariables_;
+        return p_.numFreeVariables;
     }
     HeapPtrAtom *freeVariables() {
         return (HeapPtrAtom *)table_;
     }
 
     uint32_t numInnerFunctions() const {
-        return numInnerFunctions_;
+        return p_.numInnerFunctions;
     }
     HeapPtrFunction *innerFunctions() {
         return (HeapPtrFunction *)&freeVariables()[numFreeVariables()];
     }
 
-    GeneratorKind generatorKind() const { return GeneratorKindFromBits(generatorKindBits_); }
+    GeneratorKind generatorKind() const { return GeneratorKindFromBits(p_.generatorKindBits); }
 
     bool isGenerator() const { return generatorKind() != NotGenerator; }
 
@@ -1696,56 +1727,56 @@ class LazyScript : public gc::BarrieredCell<LazyScript>
         JS_ASSERT(!isGenerator());
         // Legacy generators cannot currently be lazy.
         JS_ASSERT(kind != LegacyGenerator);
-        generatorKindBits_ = GeneratorKindAsBits(kind);
+        p_.generatorKindBits = GeneratorKindAsBits(kind);
     }
 
     bool strict() const {
-        return strict_;
+        return p_.strict;
     }
     void setStrict() {
-        strict_ = true;
+        p_.strict = true;
     }
 
     bool bindingsAccessedDynamically() const {
-        return bindingsAccessedDynamically_;
+        return p_.bindingsAccessedDynamically;
     }
     void setBindingsAccessedDynamically() {
-        bindingsAccessedDynamically_ = true;
+        p_.bindingsAccessedDynamically = true;
     }
 
     bool hasDebuggerStatement() const {
-        return hasDebuggerStatement_;
+        return p_.hasDebuggerStatement;
     }
     void setHasDebuggerStatement() {
-        hasDebuggerStatement_ = true;
+        p_.hasDebuggerStatement = true;
     }
 
     bool directlyInsideEval() const {
-        return directlyInsideEval_;
+        return p_.directlyInsideEval;
     }
     void setDirectlyInsideEval() {
-        directlyInsideEval_ = true;
+        p_.directlyInsideEval = true;
     }
 
     bool usesArgumentsAndApply() const {
-        return usesArgumentsAndApply_;
+        return p_.usesArgumentsAndApply;
     }
     void setUsesArgumentsAndApply() {
-        usesArgumentsAndApply_ = true;
+        p_.usesArgumentsAndApply = true;
     }
 
     bool hasBeenCloned() const {
-        return hasBeenCloned_;
+        return p_.hasBeenCloned;
     }
     void setHasBeenCloned() {
-        hasBeenCloned_ = true;
+        p_.hasBeenCloned = true;
     }
 
     bool treatAsRunOnce() const {
-        return treatAsRunOnce_;
+        return p_.treatAsRunOnce;
     }
     void setTreatAsRunOnce() {
-        treatAsRunOnce_ = true;
+        p_.treatAsRunOnce = true;
     }
 
     ScriptSource *source() const {
@@ -1775,6 +1806,10 @@ class LazyScript : public gc::BarrieredCell<LazyScript>
     {
         return mallocSizeOf(table_);
     }
+
+    uint64_t packedFields() const {
+        return packedFields_;
+    }
 };
 
 /* If this fails, add/remove padding within LazyScript. */