JavaScriptCore-7601.1.46.3.tar.gz

[apple/javascriptcore.git] / runtime / JSString.cpp

diff --git a/runtime/JSString.cpp b/runtime/JSString.cpp
index 904cc4d3e51fa4d91f5681a8d02de042b78d1d73..eb046ed2df98c52e6d29c57b42ca0e9b73cb009c 100644 (file)
--- a/runtime/JSString.cpp
+++ b/runtime/JSString.cpp
@@ -26,31 +26,47 @@
 #include "JSGlobalObject.h"
 #include "JSGlobalObjectFunctions.h"
 #include "JSObject.h"
 #include "JSGlobalObject.h"
 #include "JSGlobalObjectFunctions.h"
 #include "JSObject.h"

-#include "Operations.h"
+#include "JSCInlines.h"

 #include "StringObject.h"
 #include "StringPrototype.h"
 #include "StringObject.h"
 #include "StringPrototype.h"

+#include "StrongInlines.h"

 
 namespace JSC {
     
 
 namespace JSC {
     

-static const unsigned substringFromRopeCutoff = 4;
-
-const ClassInfo JSString::s_info = { "string", 0, 0, 0, CREATE_METHOD_TABLE(JSString) };
+const ClassInfo JSString::s_info = { "string", 0, 0, CREATE_METHOD_TABLE(JSString) };

 
 void JSRopeString::RopeBuilder::expand()
 {
     ASSERT(m_index == JSRopeString::s_maxInternalRopeLength);
     JSString* jsString = m_jsString;
 
 void JSRopeString::RopeBuilder::expand()
 {
     ASSERT(m_index == JSRopeString::s_maxInternalRopeLength);
     JSString* jsString = m_jsString;

-    m_jsString = jsStringBuilder(&m_globalData);
+    RELEASE_ASSERT(jsString);
+    m_jsString = jsStringBuilder(&m_vm);

     m_index = 0;
     append(jsString);
 }
 
 void JSString::destroy(JSCell* cell)
 {
     m_index = 0;
     append(jsString);
 }
 
 void JSString::destroy(JSCell* cell)
 {

-    JSString* thisObject = jsCast<JSString*>(cell);
+    JSString* thisObject = static_cast<JSString*>(cell);

     thisObject->JSString::~JSString();
 }
 
     thisObject->JSString::~JSString();
 }
 

+void JSString::dumpToStream(const JSCell* cell, PrintStream& out)
+{
+    const JSString* thisObject = jsCast<const JSString*>(cell);
+    out.printf("<%p, %s, [%u], ", thisObject, thisObject->className(), thisObject->length());
+    if (thisObject->isRope())
+        out.printf("[rope]");
+    else {
+        WTF::StringImpl* ourImpl = thisObject->m_value.impl();
+        if (ourImpl->is8Bit())
+            out.printf("[8 %p]", ourImpl->characters8());
+        else
+            out.printf("[16 %p]", ourImpl->characters16());
+    }
+    out.printf(">");
+}
+

 void JSString::visitChildren(JSCell* cell, SlotVisitor& visitor)
 {
     JSString* thisObject = jsCast<JSString*>(cell);
 void JSString::visitChildren(JSCell* cell, SlotVisitor& visitor)
 {
     JSString* thisObject = jsCast<JSString*>(cell);


@@ -58,75 +74,200 @@ void JSString::visitChildren(JSCell* cell, SlotVisitor& visitor)
     
     if (thisObject->isRope())
         static_cast<JSRopeString*>(thisObject)->visitFibers(visitor);
     
     if (thisObject->isRope())
         static_cast<JSRopeString*>(thisObject)->visitFibers(visitor);

+    else {
+        StringImpl* impl = thisObject->m_value.impl();
+        ASSERT(impl);
+        visitor.reportExtraMemoryVisited(thisObject, impl->costDuringGC());
+    }

 }
 
 void JSRopeString::visitFibers(SlotVisitor& visitor)
 {
 }
 
 void JSRopeString::visitFibers(SlotVisitor& visitor)
 {

-    for (size_t i = 0; i < s_maxInternalRopeLength && m_fibers[i]; ++i)
-        visitor.append(&m_fibers[i]);
+    if (isSubstring()) {
+        visitor.append(&substringBase());
+        return;
+    }
+    for (size_t i = 0; i < s_maxInternalRopeLength && fiber(i); ++i)
+        visitor.append(&fiber(i));
+}
+
+static const unsigned maxLengthForOnStackResolve = 2048;
+
+void JSRopeString::resolveRopeInternal8(LChar* buffer) const
+{
+    if (isSubstring()) {
+        StringImpl::copyChars(
+            buffer, substringBase()->m_value.characters8() + substringOffset(), m_length);
+        return;
+    }
+    
+    resolveRopeInternal8NoSubstring(buffer);
+}
+
+void JSRopeString::resolveRopeInternal8NoSubstring(LChar* buffer) const
+{
+    for (size_t i = 0; i < s_maxInternalRopeLength && fiber(i); ++i) {
+        if (fiber(i)->isRope()) {
+            resolveRopeSlowCase8(buffer);
+            return;
+        }
+    }
+
+    LChar* position = buffer;
+    for (size_t i = 0; i < s_maxInternalRopeLength && fiber(i); ++i) {
+        const StringImpl& fiberString = *fiber(i)->m_value.impl();
+        unsigned length = fiberString.length();
+        StringImpl::copyChars(position, fiberString.characters8(), length);
+        position += length;
+    }
+    ASSERT((buffer + m_length) == position);
+}
+
+void JSRopeString::resolveRopeInternal16(UChar* buffer) const
+{
+    if (isSubstring()) {
+        StringImpl::copyChars(
+            buffer, substringBase()->m_value.characters16() + substringOffset(), m_length);
+        return;
+    }
+    
+    resolveRopeInternal16NoSubstring(buffer);
+}
+
+void JSRopeString::resolveRopeInternal16NoSubstring(UChar* buffer) const
+{
+    for (size_t i = 0; i < s_maxInternalRopeLength && fiber(i); ++i) {
+        if (fiber(i)->isRope()) {
+            resolveRopeSlowCase(buffer);
+            return;
+        }
+    }
+
+    UChar* position = buffer;
+    for (size_t i = 0; i < s_maxInternalRopeLength && fiber(i); ++i) {
+        const StringImpl& fiberString = *fiber(i)->m_value.impl();
+        unsigned length = fiberString.length();
+        if (fiberString.is8Bit())
+            StringImpl::copyChars(position, fiberString.characters8(), length);
+        else
+            StringImpl::copyChars(position, fiberString.characters16(), length);
+        position += length;
+    }
+    ASSERT((buffer + m_length) == position);
+}
+
+void JSRopeString::resolveRopeToAtomicString(ExecState* exec) const
+{
+    if (m_length > maxLengthForOnStackResolve) {
+        resolveRope(exec);
+        m_value = AtomicString(m_value);
+        setIs8Bit(m_value.impl()->is8Bit());
+        return;
+    }
+
+    if (is8Bit()) {
+        LChar buffer[maxLengthForOnStackResolve];
+        resolveRopeInternal8(buffer);
+        m_value = AtomicString(buffer, m_length);
+        setIs8Bit(m_value.impl()->is8Bit());
+    } else {
+        UChar buffer[maxLengthForOnStackResolve];
+        resolveRopeInternal16(buffer);
+        m_value = AtomicString(buffer, m_length);
+        setIs8Bit(m_value.impl()->is8Bit());
+    }
+
+    clearFibers();
+
+    // If we resolved a string that didn't previously exist, notify the heap that we've grown.
+    if (m_value.impl()->hasOneRef())
+        Heap::heap(this)->reportExtraMemoryAllocated(m_value.impl()->cost());
+}
+
+void JSRopeString::clearFibers() const
+{
+    for (size_t i = 0; i < s_maxInternalRopeLength; ++i)
+        u[i].number = 0;
+}
+
+RefPtr<AtomicStringImpl> JSRopeString::resolveRopeToExistingAtomicString(ExecState* exec) const
+{
+    if (m_length > maxLengthForOnStackResolve) {
+        resolveRope(exec);
+        if (RefPtr<AtomicStringImpl> existingAtomicString = AtomicStringImpl::lookUp(m_value.impl())) {
+            m_value = *existingAtomicString;
+            setIs8Bit(m_value.impl()->is8Bit());
+            clearFibers();
+            return existingAtomicString;
+        }
+        return nullptr;
+    }
+    
+    if (is8Bit()) {
+        LChar buffer[maxLengthForOnStackResolve];
+        resolveRopeInternal8(buffer);
+        if (RefPtr<AtomicStringImpl> existingAtomicString = AtomicStringImpl::lookUp(buffer, m_length)) {
+            m_value = *existingAtomicString;
+            setIs8Bit(m_value.impl()->is8Bit());
+            clearFibers();
+            return existingAtomicString;
+        }
+    } else {
+        UChar buffer[maxLengthForOnStackResolve];
+        resolveRopeInternal16(buffer);
+        if (RefPtr<AtomicStringImpl> existingAtomicString = AtomicStringImpl::lookUp(buffer, m_length)) {
+            m_value = *existingAtomicString;
+            setIs8Bit(m_value.impl()->is8Bit());
+            clearFibers();
+            return existingAtomicString;
+        }
+    }
+
+    return nullptr;

 }
 
 void JSRopeString::resolveRope(ExecState* exec) const
 {
     ASSERT(isRope());
 }
 
 void JSRopeString::resolveRope(ExecState* exec) const
 {
     ASSERT(isRope());

-
+    
+    if (isSubstring()) {
+        ASSERT(!substringBase()->isRope());
+        m_value = substringBase()->m_value.substring(substringOffset(), m_length);
+        substringBase().clear();
+        return;
+    }
+    

     if (is8Bit()) {
         LChar* buffer;
         if (RefPtr<StringImpl> newImpl = StringImpl::tryCreateUninitialized(m_length, buffer)) {
     if (is8Bit()) {
         LChar* buffer;
         if (RefPtr<StringImpl> newImpl = StringImpl::tryCreateUninitialized(m_length, buffer)) {

-            Heap::heap(this)->reportExtraMemoryCost(newImpl->cost());
+            Heap::heap(this)->reportExtraMemoryAllocated(newImpl->cost());

             m_value = newImpl.release();
         } else {
             outOfMemory(exec);
             return;
         }
             m_value = newImpl.release();
         } else {
             outOfMemory(exec);
             return;
         }

-
-        for (size_t i = 0; i < s_maxInternalRopeLength && m_fibers[i]; ++i) {
-            if (m_fibers[i]->isRope())
-                return resolveRopeSlowCase8(buffer);
-        }
-
-        LChar* position = buffer;
-        for (size_t i = 0; i < s_maxInternalRopeLength && m_fibers[i]; ++i) {
-            StringImpl* string = m_fibers[i]->m_value.impl();
-            unsigned length = string->length();
-            StringImpl::copyChars(position, string->characters8(), length);
-            position += length;
-            m_fibers[i].clear();
-        }
-        ASSERT((buffer + m_length) == position);
+        resolveRopeInternal8NoSubstring(buffer);
+        clearFibers();

         ASSERT(!isRope());
         ASSERT(!isRope());

-

         return;
     }
 
     UChar* buffer;
     if (RefPtr<StringImpl> newImpl = StringImpl::tryCreateUninitialized(m_length, buffer)) {
         return;
     }
 
     UChar* buffer;
     if (RefPtr<StringImpl> newImpl = StringImpl::tryCreateUninitialized(m_length, buffer)) {

-        Heap::heap(this)->reportExtraMemoryCost(newImpl->cost());
+        Heap::heap(this)->reportExtraMemoryAllocated(newImpl->cost());

         m_value = newImpl.release();
     } else {
         outOfMemory(exec);
         return;
     }
 
         m_value = newImpl.release();
     } else {
         outOfMemory(exec);
         return;
     }
 

-    for (size_t i = 0; i < s_maxInternalRopeLength && m_fibers[i]; ++i) {
-        if (m_fibers[i]->isRope())
-            return resolveRopeSlowCase(buffer);
-    }
-
-    UChar* position = buffer;
-    for (size_t i = 0; i < s_maxInternalRopeLength && m_fibers[i]; ++i) {
-        StringImpl* string = m_fibers[i]->m_value.impl();
-        unsigned length = string->length();
-        StringImpl::copyChars(position, string->characters(), length);
-        position += length;
-        m_fibers[i].clear();
-    }
-    ASSERT((buffer + m_length) == position);
+    resolveRopeInternal16NoSubstring(buffer);
+    clearFibers();

     ASSERT(!isRope());
 }
 
 // Overview: These functions convert a JSString from holding a string in rope form
     ASSERT(!isRope());
 }
 
 // Overview: These functions convert a JSString from holding a string in rope form

-// down to a simple UString representation.  It does so by building up the string
+// down to a simple String representation. It does so by building up the string

 // backwards, since we want to avoid recursion, we expect that the tree structure
 // representing the rope is likely imbalanced with more nodes down the left side
 // (since appending to the string is likely more common) - and as such resolving
 // backwards, since we want to avoid recursion, we expect that the tree structure
 // representing the rope is likely imbalanced with more nodes down the left side
 // (since appending to the string is likely more common) - and as such resolving


@@ -138,42 +279,46 @@ void JSRopeString::resolveRope(ExecState* exec) const
 void JSRopeString::resolveRopeSlowCase8(LChar* buffer) const
 {
     LChar* position = buffer + m_length; // We will be working backwards over the rope.
 void JSRopeString::resolveRopeSlowCase8(LChar* buffer) const
 {
     LChar* position = buffer + m_length; // We will be working backwards over the rope.

-    Vector<JSString*, 32> workQueue; // Putting strings into a Vector is only OK because there are no GC points in this method.
+    Vector<JSString*, 32, UnsafeVectorOverflow> workQueue; // Putting strings into a Vector is only OK because there are no GC points in this method.

     
     

-    for (size_t i = 0; i < s_maxInternalRopeLength && m_fibers[i]; ++i) {
-        workQueue.append(m_fibers[i].get());
-        // Clearing here works only because there are no GC points in this method.
-        m_fibers[i].clear();
-    }
+    for (size_t i = 0; i < s_maxInternalRopeLength && fiber(i); ++i)
+        workQueue.append(fiber(i).get());

 
     while (!workQueue.isEmpty()) {
         JSString* currentFiber = workQueue.last();
         workQueue.removeLast();
 
 
     while (!workQueue.isEmpty()) {
         JSString* currentFiber = workQueue.last();
         workQueue.removeLast();
 

+        const LChar* characters;
+        

         if (currentFiber->isRope()) {
             JSRopeString* currentFiberAsRope = static_cast<JSRopeString*>(currentFiber);
         if (currentFiber->isRope()) {
             JSRopeString* currentFiberAsRope = static_cast<JSRopeString*>(currentFiber);

-            for (size_t i = 0; i < s_maxInternalRopeLength && currentFiberAsRope->m_fibers[i]; ++i)
-                workQueue.append(currentFiberAsRope->m_fibers[i].get());
-            continue;
-        }
-
-        StringImpl* string = static_cast<StringImpl*>(currentFiber->m_value.impl());
-        unsigned length = string->length();
+            if (!currentFiberAsRope->isSubstring()) {
+                for (size_t i = 0; i < s_maxInternalRopeLength && currentFiberAsRope->fiber(i); ++i)
+                    workQueue.append(currentFiberAsRope->fiber(i).get());
+                continue;
+            }
+            ASSERT(!currentFiberAsRope->substringBase()->isRope());
+            characters =
+                currentFiberAsRope->substringBase()->m_value.characters8() +
+                currentFiberAsRope->substringOffset();
+        } else
+            characters = currentFiber->m_value.characters8();
+        
+        unsigned length = currentFiber->length();

         position -= length;
         position -= length;

-        StringImpl::copyChars(position, string->characters8(), length);
+        StringImpl::copyChars(position, characters, length);

     }
 
     ASSERT(buffer == position);
     }
 
     ASSERT(buffer == position);

-    ASSERT(!isRope());

 }
 
 void JSRopeString::resolveRopeSlowCase(UChar* buffer) const
 {
     UChar* position = buffer + m_length; // We will be working backwards over the rope.
 }
 
 void JSRopeString::resolveRopeSlowCase(UChar* buffer) const
 {
     UChar* position = buffer + m_length; // We will be working backwards over the rope.

-    Vector<JSString*, 32> workQueue; // These strings are kept alive by the parent rope, so using a Vector is OK.
+    Vector<JSString*, 32, UnsafeVectorOverflow> workQueue; // These strings are kept alive by the parent rope, so using a Vector is OK.

 
 

-    for (size_t i = 0; i < s_maxInternalRopeLength && m_fibers[i]; ++i)
-        workQueue.append(m_fibers[i].get());
+    for (size_t i = 0; i < s_maxInternalRopeLength && fiber(i); ++i)
+        workQueue.append(fiber(i).get());

 
     while (!workQueue.isEmpty()) {
         JSString* currentFiber = workQueue.last();
 
     while (!workQueue.isEmpty()) {
         JSString* currentFiber = workQueue.last();


@@ -181,43 +326,45 @@ void JSRopeString::resolveRopeSlowCase(UChar* buffer) const
 
         if (currentFiber->isRope()) {
             JSRopeString* currentFiberAsRope = static_cast<JSRopeString*>(currentFiber);
 
         if (currentFiber->isRope()) {
             JSRopeString* currentFiberAsRope = static_cast<JSRopeString*>(currentFiber);

-            for (size_t i = 0; i < s_maxInternalRopeLength && currentFiberAsRope->m_fibers[i]; ++i)
-                workQueue.append(currentFiberAsRope->m_fibers[i].get());
+            if (currentFiberAsRope->isSubstring()) {
+                ASSERT(!currentFiberAsRope->substringBase()->isRope());
+                StringImpl* string = static_cast<StringImpl*>(
+                    currentFiberAsRope->substringBase()->m_value.impl());
+                unsigned offset = currentFiberAsRope->substringOffset();
+                unsigned length = currentFiberAsRope->length();
+                position -= length;
+                if (string->is8Bit())
+                    StringImpl::copyChars(position, string->characters8() + offset, length);
+                else
+                    StringImpl::copyChars(position, string->characters16() + offset, length);
+                continue;
+            }
+            for (size_t i = 0; i < s_maxInternalRopeLength && currentFiberAsRope->fiber(i); ++i)
+                workQueue.append(currentFiberAsRope->fiber(i).get());

             continue;
         }
 
         StringImpl* string = static_cast<StringImpl*>(currentFiber->m_value.impl());
         unsigned length = string->length();
         position -= length;
             continue;
         }
 
         StringImpl* string = static_cast<StringImpl*>(currentFiber->m_value.impl());
         unsigned length = string->length();
         position -= length;

-        StringImpl::copyChars(position, string->characters(), length);
+        if (string->is8Bit())
+            StringImpl::copyChars(position, string->characters8(), length);
+        else
+            StringImpl::copyChars(position, string->characters16(), length);

     }
 
     ASSERT(buffer == position);
     }
 
     ASSERT(buffer == position);

-    ASSERT(!isRope());

 }
 
 void JSRopeString::outOfMemory(ExecState* exec) const
 {
 }
 
 void JSRopeString::outOfMemory(ExecState* exec) const
 {

-    for (size_t i = 0; i < s_maxInternalRopeLength && m_fibers[i]; ++i)
-        m_fibers[i].clear();
+    clearFibers();

     ASSERT(isRope());
     ASSERT(isRope());

-    ASSERT(m_value == UString());
+    ASSERT(m_value.isNull());

     if (exec)
         throwOutOfMemoryError(exec);
 }
 
     if (exec)
         throwOutOfMemoryError(exec);
 }
 

-JSString* JSRopeString::getIndexSlowCase(ExecState* exec, unsigned i)
-{
-    ASSERT(isRope());
-    resolveRope(exec);
-    // Return a safe no-value result, this should never be used, since the excetion will be thrown.
-    if (exec->exception())
-        return jsString(exec, "");
-    ASSERT(!isRope());
-    ASSERT(i < m_value.length());
-    return jsSingleCharacterSubstring(exec, m_value, i);
-}
-

 JSValue JSString::toPrimitive(ExecState*, PreferredPrimitiveType) const
 {
     return const_cast<JSString*>(this);
 JSValue JSString::toPrimitive(ExecState*, PreferredPrimitiveType) const
 {
     return const_cast<JSString*>(this);


@@ -226,80 +373,58 @@ JSValue JSString::toPrimitive(ExecState*, PreferredPrimitiveType) const
 bool JSString::getPrimitiveNumber(ExecState* exec, double& number, JSValue& result) const
 {
     result = this;
 bool JSString::getPrimitiveNumber(ExecState* exec, double& number, JSValue& result) const
 {
     result = this;

-    number = jsToNumber(value(exec));
+    number = jsToNumber(view(exec));

     return false;
 }
 
     return false;
 }
 

-bool JSString::toBoolean(ExecState*) const
-{
-    return m_length;
-}
-

 double JSString::toNumber(ExecState* exec) const
 {
 double JSString::toNumber(ExecState* exec) const
 {

-    return jsToNumber(value(exec));
+    return jsToNumber(view(exec));

 }
 
 }
 

-inline StringObject* StringObject::create(ExecState* exec, JSGlobalObject* globalObject, JSString* string)
+inline StringObject* StringObject::create(VM& vm, JSGlobalObject* globalObject, JSString* string)

 {
 {

-    StringObject* object = new (NotNull, allocateCell<StringObject>(*exec->heap())) StringObject(exec->globalData(), globalObject->stringObjectStructure());
-    object->finishCreation(exec->globalData(), string);
+    StringObject* object = new (NotNull, allocateCell<StringObject>(vm.heap)) StringObject(vm, globalObject->stringObjectStructure());
+    object->finishCreation(vm, string);

     return object;
 }
 
 JSObject* JSString::toObject(ExecState* exec, JSGlobalObject* globalObject) const
 {
     return object;
 }
 
 JSObject* JSString::toObject(ExecState* exec, JSGlobalObject* globalObject) const
 {

-    return StringObject::create(exec, globalObject, const_cast<JSString*>(this));
-}
-
-JSObject* JSString::toThisObject(JSCell* cell, ExecState* exec)
-{
-    return StringObject::create(exec, exec->lexicalGlobalObject(), jsCast<JSString*>(cell));
+    return StringObject::create(exec->vm(), globalObject, const_cast<JSString*>(this));

 }
 
 }
 

-bool JSString::getOwnPropertySlot(JSCell* cell, ExecState* exec, const Identifier& propertyName, PropertySlot& slot)
+JSValue JSString::toThis(JSCell* cell, ExecState* exec, ECMAMode ecmaMode)

 {
 {

-    JSString* thisObject = jsCast<JSString*>(cell);
-    // The semantics here are really getPropertySlot, not getOwnPropertySlot.
-    // This function should only be called by JSValue::get.
-    if (thisObject->getStringPropertySlot(exec, propertyName, slot))
-        return true;
-    slot.setBase(thisObject);
-    JSObject* object;
-    for (JSValue prototype = exec->lexicalGlobalObject()->stringPrototype(); !prototype.isNull(); prototype = object->prototype()) {
-        object = asObject(prototype);
-        if (object->methodTable()->getOwnPropertySlot(object, exec, propertyName, slot))
-            return true;
-    }
-    slot.setUndefined();
-    return true;
+    if (ecmaMode == StrictMode)
+        return cell;
+    return StringObject::create(exec->vm(), exec->lexicalGlobalObject(), jsCast<JSString*>(cell));

 }
 
 }
 

-bool JSString::getStringPropertyDescriptor(ExecState* exec, const Identifier& propertyName, PropertyDescriptor& descriptor)
+bool JSString::getStringPropertyDescriptor(ExecState* exec, PropertyName propertyName, PropertyDescriptor& descriptor)

 {
     if (propertyName == exec->propertyNames().length) {
         descriptor.setDescriptor(jsNumber(m_length), DontEnum | DontDelete | ReadOnly);
         return true;
     }
     
 {
     if (propertyName == exec->propertyNames().length) {
         descriptor.setDescriptor(jsNumber(m_length), DontEnum | DontDelete | ReadOnly);
         return true;
     }
     

-    bool isStrictUInt32;
-    unsigned i = propertyName.toUInt32(isStrictUInt32);
-    if (isStrictUInt32 && i < m_length) {
-        descriptor.setDescriptor(getIndex(exec, i), DontDelete | ReadOnly);
+    Optional<uint32_t> index = parseIndex(propertyName);
+    if (index && index.value() < m_length) {
+        descriptor.setDescriptor(getIndex(exec, index.value()), DontDelete | ReadOnly);

         return true;
     }
     
     return false;
 }
 
         return true;
     }
     
     return false;
 }
 

-bool JSString::getOwnPropertySlotByIndex(JSCell* cell, ExecState* exec, unsigned propertyName, PropertySlot& slot)
+JSString* jsStringWithCacheSlowCase(VM& vm, StringImpl& stringImpl)

 {
 {

-    JSString* thisObject = jsCast<JSString*>(cell);
-    // The semantics here are really getPropertySlot, not getOwnPropertySlot.
-    // This function should only be called by JSValue::get.
-    if (thisObject->getStringPropertySlot(exec, propertyName, slot))
-        return true;
-    return JSString::getOwnPropertySlot(thisObject, exec, Identifier::from(exec, propertyName), slot);
+    if (JSString* string = vm.stringCache.get(&stringImpl))
+        return string;
+
+    JSString* string = jsString(&vm, String(stringImpl));
+    vm.lastCachedString.set(vm, string);
+    return string;

 }
 
 } // namespace JSC
 }
 
 } // namespace JSC