diff --git a/content/canvas/src/CustomQS_WebGL.h b/content/canvas/src/CustomQS_WebGL.h
index 24252374e4b..09d27c57973 100644
--- a/content/canvas/src/CustomQS_WebGL.h
+++ b/content/canvas/src/CustomQS_WebGL.h
@@ -768,298 +768,3 @@ nsICanvasRenderingContextWebGL_VertexAttrib4fv(JSContext *cx, uintN argc, jsval
 {
     return helper_nsICanvasRenderingContextWebGL_VertexAttrib_x_fv(cx, argc, vp, 4);
 }
-
-#ifdef JS_TRACER
-
-static inline jsval FASTCALL
-helper_nsICanvasRenderingContextWebGL_Uniform_x_iv_tn(JSContext *cx, JSObject *obj, JSObject *locationobj,
-                                                      JSObject *arg, int nElements)
-{
-    XPC_QS_ASSERT_CONTEXT_OK(cx);
-
-    nsICanvasRenderingContextWebGL *self;
-    xpc_qsSelfRef selfref;
-    xpc_qsArgValArray<3> vp(cx);
-    if (!xpc_qsUnwrapThis(cx, obj, nsnull, &self, &selfref.ptr, &vp.array[0], nsnull)) {
-        js_SetTraceableNativeFailed(cx);
-        return JSVAL_VOID;
-    }
-
-    js::AutoValueRooter obj_tvr(cx);
-
-    nsIWebGLUniformLocation *location;
-    xpc_qsSelfRef location_selfref;
-    nsresult rv_convert_arg0
-        = xpc_qsUnwrapThis(cx, locationobj, nsnull, &location, &location_selfref.ptr, &vp.array[1], nsnull);
-    if (NS_FAILED(rv_convert_arg0)) {
-        js_SetTraceableNativeFailed(cx);
-        return JSVAL_VOID;
-    }
-
-    js::TypedArray *wa = 0;
-
-    if (helper_isInt32Array(arg)) {
-        wa = js::TypedArray::fromJSObject(arg);
-    }  else if (JS_IsArrayObject(cx, arg)) {
-        JSObject *nobj = js_CreateTypedArrayWithArray(cx, js::TypedArray::TYPE_INT32, arg);
-        if (!nobj) {
-            // XXX this will likely return a strange error message if it goes wrong
-            js_SetTraceableNativeFailed(cx);
-            return JSVAL_VOID;
-        }
-
-        *obj_tvr.jsval_addr() = OBJECT_TO_JSVAL(nobj);
-        wa = js::TypedArray::fromJSObject(nobj);
-    } else {
-        xpc_qsThrowMethodFailedWithDetails(cx, NS_ERROR_FAILURE, "nsICanvasRenderingContextWebGL", "uniformNiv");
-        js_SetTraceableNativeFailed(cx);
-        return JSVAL_VOID;
-    }
-
-    nsresult rv;
-
-    if (nElements == 1) {
-        rv = self->Uniform1iv_array(location, wa);
-    } else if (nElements == 2) {
-        rv = self->Uniform2iv_array(location, wa);
-    } else if (nElements == 3) {
-        rv = self->Uniform3iv_array(location, wa);
-    } else if (nElements == 4) {
-        rv = self->Uniform4iv_array(location, wa);
-    }
-
-    if (NS_FAILED(rv)) {
-        xpc_qsThrowMethodFailedWithDetails(cx, rv, "nsICanvasRenderingContextWebGL", "uniformNiv");
-        js_SetTraceableNativeFailed(cx);
-    }
-
-    return JSVAL_VOID;
-}
-
-static inline jsval FASTCALL
-helper_nsICanvasRenderingContextWebGL_Uniform_x_fv_tn(JSContext *cx, JSObject *obj, JSObject *locationobj,
-                                                      JSObject *arg, int nElements)
-{
-    XPC_QS_ASSERT_CONTEXT_OK(cx);
-
-    nsICanvasRenderingContextWebGL *self;
-    xpc_qsSelfRef selfref;
-    xpc_qsArgValArray<3> vp(cx);
-    if (!xpc_qsUnwrapThis(cx, obj, nsnull, &self, &selfref.ptr, &vp.array[0], nsnull)) {
-        js_SetTraceableNativeFailed(cx);
-        return JSVAL_VOID;
-    }
-
-    js::AutoValueRooter obj_tvr(cx);
-
-    nsIWebGLUniformLocation *location;
-    xpc_qsSelfRef location_selfref;
-    nsresult rv_convert_arg0
-        = xpc_qsUnwrapThis(cx, locationobj, nsnull, &location, &location_selfref.ptr, &vp.array[1], nsnull);
-    if (NS_FAILED(rv_convert_arg0)) {
-        js_SetTraceableNativeFailed(cx);
-        return JSVAL_VOID;
-    }
-
-    js::TypedArray *wa = 0;
-
-    if (helper_isFloat32Array(arg)) {
-        wa = js::TypedArray::fromJSObject(arg);
-    }  else if (JS_IsArrayObject(cx, arg)) {
-        JSObject *nobj = js_CreateTypedArrayWithArray(cx, js::TypedArray::TYPE_FLOAT32, arg);
-        if (!nobj) {
-            // XXX this will likely return a strange error message if it goes wrong
-            js_SetTraceableNativeFailed(cx);
-            return JSVAL_VOID;
-        }
-
-        *obj_tvr.jsval_addr() = OBJECT_TO_JSVAL(nobj);
-        wa = js::TypedArray::fromJSObject(nobj);
-    } else {
-        xpc_qsThrowMethodFailedWithDetails(cx, NS_ERROR_FAILURE, "nsICanvasRenderingContextWebGL", "uniformNfv");
-        js_SetTraceableNativeFailed(cx);
-        return JSVAL_VOID;
-    }
-
-    nsresult rv;
-
-    if (nElements == 1) {
-        rv = self->Uniform1fv_array(location, wa);
-    } else if (nElements == 2) {
-        rv = self->Uniform2fv_array(location, wa);
-    } else if (nElements == 3) {
-        rv = self->Uniform3fv_array(location, wa);
-    } else if (nElements == 4) {
-        rv = self->Uniform4fv_array(location, wa);
-    }
-
-    if (NS_FAILED(rv)) {
-        xpc_qsThrowMethodFailedWithDetails(cx, rv, "nsICanvasRenderingContextWebGL", "uniformNfv");
-        js_SetTraceableNativeFailed(cx);
-    }
-
-    return JSVAL_VOID;
-}
-
-static inline jsval FASTCALL
-helper_nsICanvasRenderingContextWebGL_UniformMatrix_x_fv_tn(JSContext *cx, JSObject *obj, JSObject *locationobj,
-                                                            JSBool transpose, JSObject *arg, int nElements)
-{
-    XPC_QS_ASSERT_CONTEXT_OK(cx);
-
-    nsICanvasRenderingContextWebGL *self;
-    xpc_qsSelfRef selfref;
-    xpc_qsArgValArray<4> vp(cx);
-    if (!xpc_qsUnwrapThis(cx, obj, nsnull, &self, &selfref.ptr, &vp.array[0], nsnull)) {
-        js_SetTraceableNativeFailed(cx);
-        return JSVAL_VOID;
-    }
-
-    js::AutoValueRooter obj_tvr(cx);
-
-    nsIWebGLUniformLocation *location;
-    xpc_qsSelfRef location_selfref;
-    nsresult rv_convert_arg0
-        = xpc_qsUnwrapThis(cx, locationobj, nsnull, &location, &location_selfref.ptr, &vp.array[1], nsnull);
-    if (NS_FAILED(rv_convert_arg0)) {
-        js_SetTraceableNativeFailed(cx);
-        return JSVAL_VOID;
-    }
-
-    js::TypedArray *wa = 0;
-
-    if (helper_isFloat32Array(arg)) {
-        wa = js::TypedArray::fromJSObject(arg);
-    }  else if (JS_IsArrayObject(cx, arg)) {
-        JSObject *nobj = js_CreateTypedArrayWithArray(cx, js::TypedArray::TYPE_FLOAT32, arg);
-        if (!nobj) {
-            // XXX this will likely return a strange error message if it goes wrong
-            js_SetTraceableNativeFailed(cx);
-            return JSVAL_VOID;
-        }
-
-        *obj_tvr.jsval_addr() = OBJECT_TO_JSVAL(nobj);
-        wa = js::TypedArray::fromJSObject(nobj);
-    } else {
-        xpc_qsThrowMethodFailedWithDetails(cx, NS_ERROR_FAILURE, "nsICanvasRenderingContextWebGL", "uniformMatrixNfv");
-        js_SetTraceableNativeFailed(cx);
-        return JSVAL_VOID;
-    }
-
-    nsresult rv;
-    if (nElements == 2) {
-        rv = self->UniformMatrix2fv_array(location, transpose, wa);
-    } else if (nElements == 3) {
-        rv = self->UniformMatrix3fv_array(location, transpose, wa);
-    } else if (nElements == 4) {
-        rv = self->UniformMatrix4fv_array(location, transpose, wa);
-    }
-
-    if (NS_FAILED(rv)) {
-        xpc_qsThrowMethodFailedWithDetails(cx, rv, "nsICanvasRenderingContextWebGL", "uniformMatrixNfv");
-        js_SetTraceableNativeFailed(cx);
-    }
-
-    return JSVAL_VOID;
-}
-
-static jsval FASTCALL
-nsICanvasRenderingContextWebGL_Uniform1iv_tn(JSContext *cx, JSObject *obj, JSObject *location, JSObject *arg)
-{
-    return helper_nsICanvasRenderingContextWebGL_Uniform_x_iv_tn(cx, obj, location, arg, 1);
-}
-
-JS_DEFINE_TRCINFO_1(nsICanvasRenderingContextWebGL_Uniform1iv,
-    (4, (static, JSVAL_FAIL, nsICanvasRenderingContextWebGL_Uniform1iv_tn, CONTEXT, THIS, OBJECT, OBJECT, 0, nanojit::ACC_STORE_ANY)))
-
-static jsval FASTCALL
-nsICanvasRenderingContextWebGL_Uniform2iv_tn(JSContext *cx, JSObject *obj, JSObject *location, JSObject *arg)
-{
-    return helper_nsICanvasRenderingContextWebGL_Uniform_x_iv_tn(cx, obj, location, arg, 2);
-}
-
-JS_DEFINE_TRCINFO_1(nsICanvasRenderingContextWebGL_Uniform2iv,
-    (4, (static, JSVAL_FAIL, nsICanvasRenderingContextWebGL_Uniform2iv_tn, CONTEXT, THIS, OBJECT, OBJECT, 0, nanojit::ACC_STORE_ANY)))
-
-static jsval FASTCALL
-nsICanvasRenderingContextWebGL_Uniform3iv_tn(JSContext *cx, JSObject *obj, JSObject *location, JSObject *arg)
-{
-    return helper_nsICanvasRenderingContextWebGL_Uniform_x_iv_tn(cx, obj, location, arg, 3);
-}
-
-JS_DEFINE_TRCINFO_1(nsICanvasRenderingContextWebGL_Uniform3iv,
-    (4, (static, JSVAL_FAIL, nsICanvasRenderingContextWebGL_Uniform3iv_tn, CONTEXT, THIS, OBJECT, OBJECT, 0, nanojit::ACC_STORE_ANY)))
-
-static jsval FASTCALL
-nsICanvasRenderingContextWebGL_Uniform4iv_tn(JSContext *cx, JSObject *obj, JSObject *location, JSObject *arg)
-{
-    return helper_nsICanvasRenderingContextWebGL_Uniform_x_iv_tn(cx, obj, location, arg, 4);
-}
-
-JS_DEFINE_TRCINFO_1(nsICanvasRenderingContextWebGL_Uniform4iv,
-    (4, (static, JSVAL_FAIL, nsICanvasRenderingContextWebGL_Uniform4iv_tn, CONTEXT, THIS, OBJECT, OBJECT, 0, nanojit::ACC_STORE_ANY)))
-
-static jsval FASTCALL
-nsICanvasRenderingContextWebGL_Uniform1fv_tn(JSContext *cx, JSObject *obj, JSObject *location, JSObject *arg)
-{
-    return helper_nsICanvasRenderingContextWebGL_Uniform_x_fv_tn(cx, obj, location, arg, 1);
-}
-
-JS_DEFINE_TRCINFO_1(nsICanvasRenderingContextWebGL_Uniform1fv,
-    (4, (static, JSVAL_FAIL, nsICanvasRenderingContextWebGL_Uniform1fv_tn, CONTEXT, THIS, OBJECT, OBJECT, 0, nanojit::ACC_STORE_ANY)))
-
-static jsval FASTCALL
-nsICanvasRenderingContextWebGL_Uniform2fv_tn(JSContext *cx, JSObject *obj, JSObject *location, JSObject *arg)
-{
-    return helper_nsICanvasRenderingContextWebGL_Uniform_x_fv_tn(cx, obj, location, arg, 2);
-}
-
-JS_DEFINE_TRCINFO_1(nsICanvasRenderingContextWebGL_Uniform2fv,
-    (4, (static, JSVAL_FAIL, nsICanvasRenderingContextWebGL_Uniform2fv_tn, CONTEXT, THIS, OBJECT, OBJECT, 0, nanojit::ACC_STORE_ANY)))
-
-static jsval FASTCALL
-nsICanvasRenderingContextWebGL_Uniform3fv_tn(JSContext *cx, JSObject *obj, JSObject *location, JSObject *arg)
-{
-    return helper_nsICanvasRenderingContextWebGL_Uniform_x_fv_tn(cx, obj, location, arg, 3);
-}
-
-JS_DEFINE_TRCINFO_1(nsICanvasRenderingContextWebGL_Uniform3fv,
-    (4, (static, JSVAL_FAIL, nsICanvasRenderingContextWebGL_Uniform3fv_tn, CONTEXT, THIS, OBJECT, OBJECT, 0, nanojit::ACC_STORE_ANY)))
-
-static jsval FASTCALL
-nsICanvasRenderingContextWebGL_Uniform4fv_tn(JSContext *cx, JSObject *obj, JSObject *location, JSObject *arg)
-{
-    return helper_nsICanvasRenderingContextWebGL_Uniform_x_fv_tn(cx, obj, location, arg, 4);
-}
-
-JS_DEFINE_TRCINFO_1(nsICanvasRenderingContextWebGL_Uniform4fv,
-    (4, (static, JSVAL_FAIL, nsICanvasRenderingContextWebGL_Uniform4fv_tn, CONTEXT, THIS, OBJECT, OBJECT, 0, nanojit::ACC_STORE_ANY)))
-
-static jsval FASTCALL
-nsICanvasRenderingContextWebGL_UniformMatrix2fv_tn(JSContext *cx, JSObject *obj, JSObject *loc, JSBool transpose, JSObject *arg)
-{
-    return helper_nsICanvasRenderingContextWebGL_UniformMatrix_x_fv_tn(cx, obj, loc, transpose, arg, 2);
-}
-
-JS_DEFINE_TRCINFO_1(nsICanvasRenderingContextWebGL_UniformMatrix2fv,
-    (5, (static, JSVAL_FAIL, nsICanvasRenderingContextWebGL_UniformMatrix2fv_tn, CONTEXT, THIS, OBJECT, BOOL, OBJECT, 0, nanojit::ACC_STORE_ANY)))
-
-static jsval FASTCALL
-nsICanvasRenderingContextWebGL_UniformMatrix3fv_tn(JSContext *cx, JSObject *obj, JSObject *loc, JSBool transpose, JSObject *arg)
-{
-    return helper_nsICanvasRenderingContextWebGL_UniformMatrix_x_fv_tn(cx, obj, loc, transpose, arg, 3);
-}
-
-JS_DEFINE_TRCINFO_1(nsICanvasRenderingContextWebGL_UniformMatrix3fv,
-    (5, (static, JSVAL_FAIL, nsICanvasRenderingContextWebGL_UniformMatrix3fv_tn, CONTEXT, THIS, OBJECT, BOOL, OBJECT, 0, nanojit::ACC_STORE_ANY)))
-
-static jsval FASTCALL
-nsICanvasRenderingContextWebGL_UniformMatrix4fv_tn(JSContext *cx, JSObject *obj, JSObject *loc, JSBool transpose, JSObject *arg)
-{
-    return helper_nsICanvasRenderingContextWebGL_UniformMatrix_x_fv_tn(cx, obj, loc, transpose, arg, 4);
-}
-
-JS_DEFINE_TRCINFO_1(nsICanvasRenderingContextWebGL_UniformMatrix4fv,
-    (5, (static, JSVAL_FAIL, nsICanvasRenderingContextWebGL_UniformMatrix4fv_tn, CONTEXT, THIS, OBJECT, BOOL, OBJECT, 0, nanojit::ACC_STORE_ANY)))
-
-#endif /* JS_TRACER */
diff --git a/dom/base/nsDOMClassInfo.cpp b/dom/base/nsDOMClassInfo.cpp
index faccb2b706e..bccb3ae8faf 100644
--- a/dom/base/nsDOMClassInfo.cpp
+++ b/dom/base/nsDOMClassInfo.cpp
@@ -9119,7 +9119,6 @@ nsHTMLDocumentSH::NewResolve(nsIXPConnectWrappedNative *wrapper, JSContext *cx,
         // If we have (or just created) a helper, pass the resolve flags
         // to the helper as its private data.
         // TODO: fix
-        JS_ASSERT(false && "Relying on dirty private = int details");
         if (helper && !::JS_SetPrivate(cx, helper, FlagsToPrivate(flags))) {
           nsDOMClassInfo::ThrowJSException(cx, NS_ERROR_UNEXPECTED);
 
diff --git a/js/src/jsapi.h b/js/src/jsapi.h
index 7d66f26a0ba..20fba0c61ba 100644
--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -268,6 +268,12 @@ JSVAL_IS_UNDERLYING_TYPE_OF_PRIVATE(jsval v)
     return JSVAL_IS_UNDERLYING_TYPE_OF_PRIVATE_IMPL(l);
 }
 
+static JS_ALWAYS_INLINE JSBool
+JSVAL_MAY_BE_PRIVATE(jsval v)
+{
+    return JSVAL_IS_UNDERLYING_TYPE_OF_PRIVATE(v);
+}
+
 /* Lock and unlock the GC thing held by a jsval. */
 #define JSVAL_LOCK(cx,v)        (JSVAL_IS_GCTHING(v)                          \
                                  ? JS_LockGCThing(cx, JSVAL_TO_GCTHING(v))    \
@@ -3031,6 +3037,7 @@ class Value
      * uses of public jsval members in jsapi.h/jspubtd.h.
      */
     friend class PrimitiveValue;
+    friend jsdouble UnboxDoubleHelper(uint32 mask, uint32 payload);
 
   protected:
     /* Type masks */
diff --git a/js/src/jsarray.cpp b/js/src/jsarray.cpp
index 495522c487a..01978b900c0 100644
--- a/js/src/jsarray.cpp
+++ b/js/src/jsarray.cpp
@@ -353,8 +353,9 @@ JSObject::resizeDenseArrayElements(JSContext *cx, uint32 oldcap, uint32 newcap,
     setDenseArrayCapacity(newcap);
 
     if (initializeAllSlots) {
-        for (uint32 i = oldcap; i < newcap; i++)
-            setDenseArrayElement(i, JS_ARRAY_HOLE);
+        Value *base = addressOfDenseArrayElement(0);
+        for (Value *vp = base + oldcap, *end = base + newcap; vp < end; ++vp)
+            vp->setMagic(JS_ARRAY_HOLE);
     }
 
     return true;
@@ -900,7 +901,7 @@ js_PrototypeHasIndexedProperties(JSContext *cx, JSObject *obj)
 
 #ifdef JS_TRACER
 
-static inline JSBool FASTCALL
+static JS_ALWAYS_INLINE JSBool FASTCALL
 dense_grow(JSContext* cx, JSObject* obj, jsint i, const Value &v)
 {
     /*
diff --git a/js/src/jsbuiltins.cpp b/js/src/jsbuiltins.cpp
index ea0e55915c2..fc5128601c2 100644
--- a/js/src/jsbuiltins.cpp
+++ b/js/src/jsbuiltins.cpp
@@ -103,13 +103,29 @@ js_imod(int32 a, int32 b)
 }
 JS_DEFINE_CALLINFO_2(extern, INT32, js_imod, INT32, INT32, 1, ACC_NONE)
 
+namespace js {
+
+jsdouble JS_ALWAYS_INLINE
+UnboxDoubleHelper(uint32 mask, uint32 payload)
+{
+    if (mask == JSVAL_MASK32_INT32) {
+        return int32(payload);
+    } else {
+        Value v;
+        v.data.s.u.mask32 = mask;
+        v.data.s.payload.u32 = payload;
+        return v.asDouble();
+    }
+}
+
+}
 
 jsdouble FASTCALL
-js_UnboxDouble(Value *v)
+js_UnboxDouble(uint32 mask, uint32 payload)
 {
-    return v->asNumber();
+    return UnboxDoubleHelper(mask, payload);
 }
-JS_DEFINE_CALLINFO_1(extern, DOUBLE, js_UnboxDouble, VALUEPTR, 1, ACC_NONE)
+JS_DEFINE_CALLINFO_2(extern, DOUBLE, js_UnboxDouble, UINT32, UINT32, 1, ACC_NONE)
 
 int32 FASTCALL
 js_UnboxInt32(Value *v)
@@ -259,7 +275,11 @@ HasProperty(JSContext* cx, JSObject* obj, jsid id)
 JSBool FASTCALL
 js_HasNamedProperty(JSContext* cx, JSObject* obj, JSString* idstr)
 {
-    return HasProperty(cx, obj, ATOM_TO_JSID(idstr));
+    jsid id;
+    if (!js_ValueToStringId(cx, StringTag(idstr), &id))
+        return JS_NEITHER;
+
+    return HasProperty(cx, obj, id);
 }
 JS_DEFINE_CALLINFO_3(extern, BOOL, js_HasNamedProperty, CONTEXT, OBJECT, STRING, 0, ACC_STORE_ANY)
 
diff --git a/js/src/jscntxt.cpp b/js/src/jscntxt.cpp
index d879cb6bc38..b85ed790aa1 100644
--- a/js/src/jscntxt.cpp
+++ b/js/src/jscntxt.cpp
@@ -48,7 +48,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-#define __STDC_LIMIT_MACROS
 #include "jsstdint.h"
 
 #include "jstypes.h"
diff --git a/js/src/jsnum.cpp b/js/src/jsnum.cpp
index 24be87108c7..1bbacf6bc73 100644
--- a/js/src/jsnum.cpp
+++ b/js/src/jsnum.cpp
@@ -877,7 +877,7 @@ js_NumberValueToCharBuffer(JSContext *cx, const Value &v, JSCharBuffer &cb)
     size_t cstrlen = strlen(cstr);
     JS_ASSERT(cstrlen < arrSize);
     size_t sizeBefore = cb.length();
-    if (!cb.growBy(cstrlen))
+    if (!cb.growByUninitialized(cstrlen))
         return JS_FALSE;
     jschar *appendBegin = cb.begin() + sizeBefore;
 #ifdef DEBUG
diff --git a/js/src/jspubtd.h b/js/src/jspubtd.h
index 3d30105275c..b986f8cb785 100644
--- a/js/src/jspubtd.h
+++ b/js/src/jspubtd.h
@@ -162,10 +162,11 @@ typedef struct JSCompartment     JSCompartment;
  * TODO: explain boxing strategy
  */
 
+#if defined(__cplusplus) || !defined(_MSC_VER)
 typedef enum JSValueMask16 
-#if defined(_MSC_VER)
+# if defined(_MSC_VER)
                            : uint16
-#endif
+# endif
 {
     JSVAL_MASK16_NULL      = (uint16)0x0001,
     JSVAL_MASK16_UNDEFINED = (uint16)0x0002,
@@ -188,10 +189,30 @@ typedef enum JSValueMask16
      */
     JSVAL_NANBOX_PATTERN   = ((uint16)0xFFFF)
 }
-#if defined(__GNUC__)
+# if defined(__GNUC__)
 __attribute__((packed))
-#endif
+# endif
 JSValueMask16;
+#else  /* defined(__cplusplus) || !defined(_MSC_VER) */
+// We need this C API for MSVC, because MSVC doesn't allow us to
+// make a 16-bit enum in C.
+typedef uint16 JSValueMask16;
+
+#define JSVAL_MASK16_NULL      ((uint16)0x0001)
+#define JSVAL_MASK16_UNDEFINED ((uint16)0x0002)
+#define JSVAL_MASK16_INT32     ((uint16)0x0004)
+#define JSVAL_MASK16_STRING    ((uint16)0x0008)
+#define JSVAL_MASK16_NONFUNOBJ ((uint16)0x0010)
+#define JSVAL_MASK16_FUNOBJ    ((uint16)0x0020)
+#define JSVAL_MASK16_BOOLEAN   ((uint16)0x0040)
+#define JSVAL_MASK16_MAGIC     ((uint16)0x0080)
+#define JSVAL_MASK16_SINGLETON (JSVAL_MASK16_NULL | JSVAL_MASK16_UNDEFINED)
+#define JSVAL_MASK16_OBJECT    (JSVAL_MASK16_NONFUNOBJ | JSVAL_MASK16_FUNOBJ)
+#define JSVAL_MASK16_OBJORNULL (JSVAL_MASK16_OBJECT | JSVAL_MASK16_NULL)
+#define JSVAL_MASK16_GCTHING   (JSVAL_MASK16_OBJECT | JSVAL_MASK16_STRING)
+#define JSVAL_NANBOX_PATTERN   ((uint16)0xFFFF)
+
+#endif /* defined(__cplusplus) || !defined(_MSC_VER) */
 
 #define JSVAL_MASK32_CLEAR      ((uint32)0xFFFF0000)
 
@@ -1116,15 +1137,15 @@ static inline JSEqualityOp     Jsvalify(EqualityOp f);      /* Same type as HasI
 }  /* namespace js */
 
 typedef js::Class JSFunctionClassType;
+extern "C" JS_FRIEND_DATA(JSFunctionClassType) js_FunctionClass;
 
 #else  /* !defined(__cplusplus) */
 
 typedef JSClass JSFunctionClassType;
+extern JS_FRIEND_DATA(JSFunctionClassType) js_FunctionClass;
 
 #endif /* __cplusplus */
 
-extern JS_FRIEND_DATA(JSFunctionClassType) js_FunctionClass;
-
 typedef struct JSPretendObject
 {
     void                *_;
diff --git a/js/src/jsrecursion.cpp b/js/src/jsrecursion.cpp
index 2abc98f4b17..8fef7e7a96c 100644
--- a/js/src/jsrecursion.cpp
+++ b/js/src/jsrecursion.cpp
@@ -731,17 +731,8 @@ TraceRecorder::slurpInt32Slot(LIns* addr_ins, ptrdiff_t offset, Value* vp, VMSid
 {
     LIns *mask_ins = lir->insLoad(LIR_ldi, addr_ins, offset + offsetof(jsval_layout, s.u.mask32), 
                                   ACC_OTHER);
-    guard(false,
-          lir->insEqI_0(lir->ins2(LIR_ori,
-                                  lir->ins2(LIR_eqi, mask_ins, INS_CONST(JSVAL_MASK32_INT32)),
-                                  lir->ins2(LIR_ltui, mask_ins, INS_CONST(JSVAL_MASK32_CLEAR)))),
-          exit);
-    LIns* space = lir->insAlloc(sizeof(int32));
-    LIns* args[] = { space, lir->ins2(LIR_addp, addr_ins, INS_CONST(offset)) };
-    LIns* result = lir->insCall(&js_TryUnboxInt32_ci, args);
-    guard(false, lir->insEqI_0(result), exit);
-    LIns* int32_ins = lir->insLoad(LIR_ldi, space, 0, ACC_OTHER);
-    return int32_ins;
+    guard(true, lir->ins2(LIR_eqi, mask_ins, INS_CONST(JSVAL_MASK32_INT32)), exit);
+    return lir->insLoad(LIR_ldi, addr_ins, offset + offsetof(jsval_layout, s.payload), ACC_OTHER);
 }
 
 JS_REQUIRES_STACK LIns*
@@ -749,13 +740,8 @@ TraceRecorder::slurpDoubleSlot(LIns* addr_ins, ptrdiff_t offset, Value* vp, VMSi
 {
     LIns *mask_ins = lir->insLoad(LIR_ldi, addr_ins, offset + offsetof(jsval_layout, s.u.mask32), 
                                   ACC_OTHER);
-    guard(false,
-          lir->insEqI_0(lir->ins2(LIR_ori,
-                                  lir->ins2(LIR_eqi, mask_ins, INS_CONST(JSVAL_MASK32_INT32)),
-                                  lir->ins2(LIR_ltui, mask_ins, INS_CONST(JSVAL_MASK32_CLEAR)))),
-          exit);
-    LIns* args[] = { lir->ins2(LIR_addp, addr_ins, INS_CONST(offset)) };
-    return lir->insCall(&js_UnboxDouble_ci, args);
+    guard(true, lir->ins2(LIR_ltui, mask_ins, INS_CONST(JSVAL_MASK32_CLEAR)), exit);
+    return lir->insLoad(LIR_ldd, addr_ins, offset + offsetof(jsval_layout, s.payload), ACC_OTHER);
 }
 
 JS_REQUIRES_STACK LIns*
diff --git a/js/src/jsstr.cpp b/js/src/jsstr.cpp
index d93995b7934..ab5b5e58204 100644
--- a/js/src/jsstr.cpp
+++ b/js/src/jsstr.cpp
@@ -1901,7 +1901,7 @@ ReplaceCallback(JSContext *cx, size_t count, void *p)
         return false;
 
     size_t growth = leftlen + replen;
-    if (!rdata.cb.growBy(growth))
+    if (!rdata.cb.growByUninitialized(growth))
         return false;
 
     jschar *chars = rdata.cb.begin() + rdata.index;
diff --git a/js/src/jstracer.cpp b/js/src/jstracer.cpp
index 789fa78d247..10ab4b739ec 100644
--- a/js/src/jstracer.cpp
+++ b/js/src/jstracer.cpp
@@ -5844,7 +5844,7 @@ JS_REQUIRES_STACK MonitorResult
 TraceRecorder::recordLoopEdge(JSContext* cx, TraceRecorder* r, uintN& inlineCallCount)
 {
 #ifdef JS_THREADSAFE
-    if (cx->fp->scopeChain->getGlobal()->scope()->title.ownercx != cx) {
+    if (cx->fp->scopeChainObj()->getGlobal()->scope()->title.ownercx != cx) {
         AbortRecording(cx, "Global object not owned by this context");
         return MONITOR_NOT_RECORDING; /* we stay away from shared global objects */
     }
@@ -8226,6 +8226,13 @@ TraceRecorder::d2i(LIns* f, bool resultCanBeImpreciseIfFractional)
     }
     if (f->isCall()) {
         const CallInfo* ci = f->callInfo();
+        if (ci == &js_UnboxDouble_ci) {
+            LIns *boxed = lir->insAlloc(sizeof(Value));
+            lir->insStore(fcallarg(f, 1), boxed, 0, ACC_OTHER);
+            lir->insStore(fcallarg(f, 0), boxed, sizeof(uint32), ACC_OTHER);
+            LIns* args[] = { boxed };
+            return lir->insCall(&js_UnboxInt32_ci, args);
+        }
         if (ci == &js_StringToNumber_ci) {
             LIns* args[] = { fcallarg(f, 1), fcallarg(f, 0) };
             return lir->insCall(&js_StringToInt32_ci, args);
@@ -9350,23 +9357,35 @@ TraceRecorder::stobj_get_slot(LIns* obj_ins, unsigned slot, LIns*& dslots_ins)
 }
 
 JS_REQUIRES_STACK LIns*
-TraceRecorder::unbox_value(const Value &v, LIns *vaddr_ins, ptrdiff_t offset, VMSideExit *exit)
+TraceRecorder::unbox_value(const Value &v, LIns *vaddr_ins, ptrdiff_t offset, VMSideExit *exit,
+                           bool force_double)
 {
     AccSet accSet = vaddr_ins == lirbuf->sp ? ACC_STACK : ACC_OTHER;
     LIns *mask_ins = lir->insLoad(LIR_ldi, vaddr_ins, offset + offsetof(jsval_layout, s.u.mask32), 
                                   accSet);
-    if (v.isNumber()) {
+    if (v.isNumber() && force_double) {
         guard(false,
               lir->insEqI_0(lir->ins2(LIR_ori,
                                       lir->ins2(LIR_eqi, mask_ins, INS_CONST(JSVAL_MASK32_INT32)),
                                       lir->ins2(LIR_ltui, mask_ins, INS_CONST(JSVAL_MASK32_CLEAR)))),
               exit);
-        LIns* args[] = { lir->ins2(LIR_addp, vaddr_ins, INS_CONST(offset)) };
+        LIns *val_ins = lir->insLoad(LIR_ldi, vaddr_ins, offset + offsetof(jsval_layout, s.payload),
+                                     accSet);
+        LIns* args[] = { val_ins, mask_ins };
         return lir->insCall(&js_UnboxDouble_ci, args);
     }
 
-    LIns *val_ins = lir->insLoad(LIR_ldi, vaddr_ins, offset + offsetof(jsval_layout, s.payload),
-                                 accSet);
+    if (v.isInt32()) {
+        guard(true, lir->ins2(LIR_eqi, mask_ins, INS_CONST(JSVAL_MASK32_INT32)), exit);
+        return i2d(lir->insLoad(LIR_ldi, vaddr_ins, offset + offsetof(jsval_layout, s.payload), accSet));
+    }
+
+    if (v.isDouble()) {
+        guard(true, lir->ins2(LIR_ltui, mask_ins, INS_CONST(JSVAL_MASK32_CLEAR)), exit);
+        return lir->insLoad(LIR_ldd, vaddr_ins, offset + offsetof(jsval_layout, s.payload), accSet);
+    }
+
+    LIns *val_ins = NULL;
     uint32 mask;
     if (v.isUndefined()) {
         mask = JSVAL_MASK32_UNDEFINED;
@@ -9387,6 +9406,9 @@ TraceRecorder::unbox_value(const Value &v, LIns *vaddr_ins, ptrdiff_t offset, VM
     } else {
         JS_NOT_REACHED("bad type");
     }
+    if (!val_ins)
+        val_ins = lir->insLoad(LIR_ldi, vaddr_ins, offset + offsetof(jsval_layout, s.payload), 
+                               accSet);
     
     guard(true, lir->ins2(LIR_eqi, mask_ins, INS_CONST(mask)), exit);
     return val_ins;
@@ -12374,7 +12396,13 @@ TraceRecorder::setElem(int lval_spindex, int idx_spindex, int v_spindex)
         LIns* res_ins;
         LIns* args[] = { NULL, idx_ins, obj_ins, cx_ins };
         if (v.isNumber()) {
-            if (isPromoteInt(v_ins)) {
+            if (fcallinfo(v_ins) == &js_UnboxDouble_ci) {
+                LIns *boxed = lir->insAlloc(sizeof(Value));
+                lir->insStore(fcallarg(v_ins, 1), boxed, 0, ACC_OTHER);
+                lir->insStore(fcallarg(v_ins, 0), boxed, sizeof(uint32), ACC_OTHER);
+                args[0] = boxed;
+                res_ins = lir->insCall(&js_Array_dense_setelem_ci, args);
+            } else if (isPromoteInt(v_ins)) {
                 args[0] = demote(lir, v_ins);
                 res_ins = lir->insCall(&js_Array_dense_setelem_int_ci, args);
             } else {
@@ -13239,7 +13267,7 @@ TraceRecorder::denseArrayElement(Value& oval, Value& ival, Value*& vp, LIns*& v_
 	JS_ASSERT(sizeof(Value) == 8); // The |3| in the following statement requires this.
     addr_ins = lir->ins2(LIR_addp, dslots_ins,
                          lir->ins2ImmI(LIR_lshp, pidx_ins, 3));
-    v_ins = unbox_value(*vp, addr_ins, 0, exit);
+    v_ins = unbox_value(*vp, addr_ins, 0, exit, true);
 
     /* Don't let the hole value escape. Turn it into an undefined. */
     if (vp->isMagic()) {
diff --git a/js/src/jstracer.h b/js/src/jstracer.h
index e93a83c7c2e..bdec64b9cde 100644
--- a/js/src/jstracer.h
+++ b/js/src/jstracer.h
@@ -1328,7 +1328,8 @@ class TraceRecorder
                                                        int v_spindex);
 
     JS_REQUIRES_STACK nanojit::LIns* unbox_value(const Value &v, nanojit::LIns *vaddr_ins, 
-                                                 ptrdiff_t offset, VMSideExit *exit);
+                                                 ptrdiff_t offset, VMSideExit *exit,
+                                                 bool force_double=false);
     JS_REQUIRES_STACK nanojit::LIns* unbox_value_load(const Value &v, nanojit::LIns *vload_ins,
                                                       VMSideExit *exit);
     JS_REQUIRES_STACK nanojit::LIns* unbox_int(const Value &v, nanojit::LIns *vaddr_ins, 
diff --git a/js/src/jsvector.h b/js/src/jsvector.h
index c0a3a9eb8f3..156400c7113 100644
--- a/js/src/jsvector.h
+++ b/js/src/jsvector.h
@@ -190,6 +190,8 @@ class Vector : AllocPolicy
     bool growHeapStorageBy(size_t lengthInc);
     bool convertToHeapStorage(size_t lengthInc);
 
+    template <bool InitNewElems> inline bool growByImpl(size_t inc);
+
     /* magic constants */
 
     static const int sMaxInlineBytes = 1024;
@@ -371,6 +373,9 @@ class Vector : AllocPolicy
     /* Call shrinkBy or growBy based on whether newSize > length(). */
     bool resize(size_t newLength);
 
+    /* Leave new elements as uninitialized memory. */
+    bool growByUninitialized(size_t incr);
+
     void clear();
 
     bool append(const T &t);
@@ -546,15 +551,17 @@ Vector<T,N,AP>::shrinkBy(size_t incr)
 }
 
 template <class T, size_t N, class AP>
-inline bool
-Vector<T,N,AP>::growBy(size_t incr)
+template <bool InitNewElems>
+JS_ALWAYS_INLINE bool
+Vector<T,N,AP>::growByImpl(size_t incr)
 {
     ReentrancyGuard g(*this);
     if (usingInlineStorage()) {
         size_t freespace = sInlineCapacity - inlineLength();
         if (incr <= freespace) {
             T *newend = inlineEnd() + incr;
-            Impl::initialize(inlineEnd(), newend);
+            if (InitNewElems)
+                Impl::initialize(inlineEnd(), newend);
             inlineLength() += incr;
             JS_ASSERT(usingInlineStorage());
             return true;
@@ -574,11 +581,26 @@ Vector<T,N,AP>::growBy(size_t incr)
     /* We are !usingInlineStorage(). Initialize new elements. */
     JS_ASSERT(heapCapacity() - heapLength() >= incr);
     T *newend = heapEnd() + incr;
-    Impl::initialize(heapEnd(), newend);
+    if (InitNewElems)
+        Impl::initialize(heapEnd(), newend);
     heapEnd() = newend;
     return true;
 }
 
+template <class T, size_t N, class AP>
+inline bool
+Vector<T,N,AP>::growBy(size_t incr)
+{
+    return growByImpl<true>(incr);
+}
+
+template <class T, size_t N, class AP>
+inline bool
+Vector<T,N,AP>::growByUninitialized(size_t incr)
+{
+    return growByImpl<false>(incr);
+}
+
 template <class T, size_t N, class AP>
 inline bool
 Vector<T,N,AP>::resize(size_t newLength)
diff --git a/js/src/trace-test/tests/basic/bug569651.js b/js/src/trace-test/tests/basic/bug569651.js
new file mode 100644
index 00000000000..58f9c136267
--- /dev/null
+++ b/js/src/trace-test/tests/basic/bug569651.js
@@ -0,0 +1,3 @@
+// don't crash or assert
+
++Function("switch(\"\"){case 1:case 8:}");
\ No newline at end of file
diff --git a/js/src/trace-test/tests/basic/bug572229.js b/js/src/trace-test/tests/basic/bug572229.js
new file mode 100644
index 00000000000..c45cea0b6c1
--- /dev/null
+++ b/js/src/trace-test/tests/basic/bug572229.js
@@ -0,0 +1,12 @@
+// Don't crash
+
+function f(o, s) {
+    var k = s.substr(0, 1);
+    var c;
+    for (var i = 0; i < 10; ++i) {
+	c = k in o;
+    }
+    return c;
+}
+
+assertEq(f({ a: 66 }, 'abc'), true);
diff --git a/js/src/xpconnect/src/Makefile.in b/js/src/xpconnect/src/Makefile.in
index 99977d462d4..da2fcb93a7a 100644
--- a/js/src/xpconnect/src/Makefile.in
+++ b/js/src/xpconnect/src/Makefile.in
@@ -159,7 +159,10 @@ DEFINES += \
   $(addprefix -D,$(filter AVMPLUS%,$(CONFIG))) \
   $(NULL)
 
-ENABLE_TRACEABLE_FLAGS = --enable-traceables
+# Disable traceable natives because (a) many of them return jsvals, which is
+# hard to support now, and (b) we can call the basic versions from trace now
+# anyway.
+ENABLE_TRACEABLE_FLAGS =
 
 endif # ENABLE_JIT
 
diff --git a/js/src/xpconnect/src/XPCDispConvert.cpp b/js/src/xpconnect/src/XPCDispConvert.cpp
index 87b9464b1e0..726eb0de802 100644
--- a/js/src/xpconnect/src/XPCDispConvert.cpp
+++ b/js/src/xpconnect/src/XPCDispConvert.cpp
@@ -309,7 +309,7 @@ JSBool XPCDispConvert::JSToCOM(XPCCallContext& ccx,
         case VT_R8:
         {
             varDest->vt = VT_R8;
-            varDest->dblVal = *JSVAL_TO_DOUBLE(src);
+            varDest->dblVal = JSVAL_TO_DOUBLE(src);
         }
         break;
         case VT_EMPTY:
diff --git a/js/src/xpconnect/src/XPCDispInterface.cpp b/js/src/xpconnect/src/XPCDispInterface.cpp
index da4847f09f6..6bd80983806 100644
--- a/js/src/xpconnect/src/XPCDispInterface.cpp
+++ b/js/src/xpconnect/src/XPCDispInterface.cpp
@@ -366,7 +366,7 @@ JSBool XPCDispInterface::Member::GetValue(XPCCallContext& ccx,
             return JS_FALSE;
 
         // Store ourselves and our native interface within the JSObject
-        if(!JS_SetReservedSlot(ccx, funobj, 0, PRIVATE_TO_JSVAL(this)))
+        if(!JS_SetReservedSlot(ccx, funobj, 0, PRIVATE_TO_JSVAL((void *) this)))
             return JS_FALSE;
 
         if(!JS_SetReservedSlot(ccx, funobj, 1, PRIVATE_TO_JSVAL(iface)))
diff --git a/js/src/xpconnect/src/XPCDispTearOff.cpp b/js/src/xpconnect/src/XPCDispTearOff.cpp
index 4c0f30e5517..ad93a2ab702 100644
--- a/js/src/xpconnect/src/XPCDispTearOff.cpp
+++ b/js/src/xpconnect/src/XPCDispTearOff.cpp
@@ -386,7 +386,7 @@ STDMETHODIMP XPCDispatchTearOff::Invoke(DISPID dispIdMember, REFIID riid,
             goto pre_call_clean_up;
         }
 
-        sp = stackbase = args.getvp();
+        sp = stackbase = Jsvalify(args.getvp());
 
         // this is a function call, so push function and 'this'
         *sp++ = fval;
diff --git a/js/src/xpconnect/src/nsXPConnect.cpp b/js/src/xpconnect/src/nsXPConnect.cpp
index eb2a0702d33..f837c0fbcbe 100644
--- a/js/src/xpconnect/src/nsXPConnect.cpp
+++ b/js/src/xpconnect/src/nsXPConnect.cpp
@@ -2804,7 +2804,38 @@ JS_EXPORT_API(void) DumpJSObject(JSObject* obj)
 
 JS_EXPORT_API(void) DumpJSValue(jsval val)
 {
-    js::DumpValue(js::Valueify(val));
+    printf("Dumping 0x%p.\n", (void *) val);
+    if(JSVAL_IS_NULL(val)) {
+        printf("Value is null\n");
+    }
+    else if(JSVAL_IS_OBJECT(val) || JSVAL_IS_NULL(val)) {
+        printf("Value is an object\n");
+        JSObject* obj = JSVAL_TO_OBJECT(val);
+        DumpJSObject(obj);
+    }
+    else if(JSVAL_IS_NUMBER(val)) {
+        printf("Value is a number: ");
+        if(JSVAL_IS_INT(val))
+          printf("Integer %i\n", JSVAL_TO_INT(val));
+        else if(JSVAL_IS_DOUBLE(val))
+          printf("Floating-point value %f\n", JSVAL_TO_DOUBLE(val));
+    }
+    else if(JSVAL_IS_STRING(val)) {
+        printf("Value is a string: ");
+        JSString* string = JSVAL_TO_STRING(val);
+        char* bytes = JS_GetStringBytes(string);
+        printf("<%s>\n", bytes);
+    }
+    else if(JSVAL_IS_BOOLEAN(val)) {
+        printf("Value is boolean: ");
+        printf(JSVAL_TO_BOOLEAN(val) ? "true" : "false");
+    }
+    else if(JSVAL_IS_VOID(val)) {
+        printf("Value is undefined\n");
+    }
+    else {
+        printf("No idea what this value is.\n");
+    }
 }
 JS_END_EXTERN_C
 
diff --git a/modules/plugin/base/src/nsJSNPRuntime.cpp b/modules/plugin/base/src/nsJSNPRuntime.cpp
index 2f3348d7c60..cb98d48e9be 100644
--- a/modules/plugin/base/src/nsJSNPRuntime.cpp
+++ b/modules/plugin/base/src/nsJSNPRuntime.cpp
@@ -197,7 +197,7 @@ static JSClass sNPObjectJSWrapperClass =
 typedef struct NPObjectMemberPrivate {
     JSObject *npobjWrapper;
     jsval fieldValue;
-    jsval methodName;
+    NPIdentifier methodName;
     NPP   npp;
 } NPObjectMemberPrivate;
 
@@ -598,25 +598,23 @@ nsJSObjWrapper::NP_Invalidate(NPObject *npobj)
 }
 
 static JSBool
-GetProperty(JSContext *cx, JSObject *obj, NPIdentifier identifier, jsval *rval)
+GetProperty(JSContext *cx, JSObject *obj, NPIdentifier id, jsval *rval)
 {
-  jsval id = (jsval)identifier;
-
-  if (JSVAL_IS_STRING(id)) {
-    JSString *str = JSVAL_TO_STRING(id);
+  if (NPIdentifierIsString(id)) {
+    JSString *str = NPIdentifierToString(id);
 
     return ::JS_GetUCProperty(cx, obj, ::JS_GetStringChars(str),
                               ::JS_GetStringLength(str), rval);
   }
 
-  NS_ASSERTION(JSVAL_IS_INT(id), "id must be either string or int!\n");
+  NS_ASSERTION(NPIdentifierIsInt(id), "id must be either string or int!\n");
 
-  return ::JS_GetElement(cx, obj, JSVAL_TO_INT(id), rval);
+  return ::JS_GetElement(cx, obj, NPIdentifierToInt(id), rval);
 }
 
 // static
 bool
-nsJSObjWrapper::NP_HasMethod(NPObject *npobj, NPIdentifier identifier)
+nsJSObjWrapper::NP_HasMethod(NPObject *npobj, NPIdentifier id)
 {
   NPP npp = NPPStack::Peek();
   JSContext *cx = GetJSContext(npp);
@@ -639,7 +637,7 @@ nsJSObjWrapper::NP_HasMethod(NPObject *npobj, NPIdentifier identifier)
   AutoJSExceptionReporter reporter(cx);
 
   jsval v;
-  JSBool ok = GetProperty(cx, npjsobj->mJSObj, identifier, &v);
+  JSBool ok = GetProperty(cx, npjsobj->mJSObj, id, &v);
 
   return ok && !JSVAL_IS_PRIMITIVE(v) &&
     ::JS_ObjectIsFunction(cx, JSVAL_TO_OBJECT(v));
@@ -672,7 +670,7 @@ doInvoke(NPObject *npobj, NPIdentifier method, const NPVariant *args,
   JSAutoRequest ar(cx);
   AutoJSExceptionReporter reporter(cx);
 
-  if ((jsval)method != JSVAL_VOID) {
+  if (method != NPIdentifier_VOID) {
     if (!GetProperty(cx, npjsobj->mJSObj, method, &fv) ||
         ::JS_TypeOfValue(cx, fv) != JSTYPE_FUNCTION) {
       return PR_FALSE;
@@ -742,7 +740,7 @@ nsJSObjWrapper::NP_Invoke(NPObject *npobj, NPIdentifier method,
                           const NPVariant *args, uint32_t argCount,
                           NPVariant *result)
 {
-  if ((jsval)method == JSVAL_VOID) {
+  if (method == NPIdentifier_VOID) {
     return PR_FALSE;
   }
 
@@ -754,13 +752,13 @@ bool
 nsJSObjWrapper::NP_InvokeDefault(NPObject *npobj, const NPVariant *args,
                                  uint32_t argCount, NPVariant *result)
 {
-  return doInvoke(npobj, (NPIdentifier)JSVAL_VOID, args, argCount, PR_FALSE,
+  return doInvoke(npobj, NPIdentifier_VOID, args, argCount, PR_FALSE,
                   result);
 }
 
 // static
 bool
-nsJSObjWrapper::NP_HasProperty(NPObject *npobj, NPIdentifier identifier)
+nsJSObjWrapper::NP_HasProperty(NPObject *npobj, NPIdentifier id)
 {
   NPP npp = NPPStack::Peek();
   JSContext *cx = GetJSContext(npp);
@@ -777,22 +775,21 @@ nsJSObjWrapper::NP_HasProperty(NPObject *npobj, NPIdentifier identifier)
   }
 
   nsJSObjWrapper *npjsobj = (nsJSObjWrapper *)npobj;
-  jsval id = (jsval)identifier;
   JSBool found, ok = JS_FALSE;
 
   AutoCXPusher pusher(cx);
   JSAutoRequest ar(cx);
   AutoJSExceptionReporter reporter(cx);
 
-  if (JSVAL_IS_STRING(id)) {
-    JSString *str = JSVAL_TO_STRING(id);
+  if (NPIdentifierIsString(id)) {
+    JSString *str = NPIdentifierToString(id);
 
     ok = ::JS_HasUCProperty(cx, npjsobj->mJSObj, ::JS_GetStringChars(str),
                             ::JS_GetStringLength(str), &found);
   } else {
-    NS_ASSERTION(JSVAL_IS_INT(id), "id must be either string or int!\n");
+    NS_ASSERTION(NPIdentifierIsInt(id), "id must be either string or int!\n");
 
-    ok = ::JS_HasElement(cx, npjsobj->mJSObj, JSVAL_TO_INT(id), &found);
+    ok = ::JS_HasElement(cx, npjsobj->mJSObj, NPIdentifierToInt(id), &found);
   }
 
   return ok && found;
@@ -800,7 +797,7 @@ nsJSObjWrapper::NP_HasProperty(NPObject *npobj, NPIdentifier identifier)
 
 // static
 bool
-nsJSObjWrapper::NP_GetProperty(NPObject *npobj, NPIdentifier identifier,
+nsJSObjWrapper::NP_GetProperty(NPObject *npobj, NPIdentifier id,
                                NPVariant *result)
 {
   NPP npp = NPPStack::Peek();
@@ -824,13 +821,13 @@ nsJSObjWrapper::NP_GetProperty(NPObject *npobj, NPIdentifier identifier,
   AutoJSExceptionReporter reporter(cx);
 
   jsval v;
-  return (GetProperty(cx, npjsobj->mJSObj, identifier, &v) &&
+  return (GetProperty(cx, npjsobj->mJSObj, id, &v) &&
           JSValToNPVariant(npp, cx, v, result));
 }
 
 // static
 bool
-nsJSObjWrapper::NP_SetProperty(NPObject *npobj, NPIdentifier identifier,
+nsJSObjWrapper::NP_SetProperty(NPObject *npobj, NPIdentifier id,
                                const NPVariant *value)
 {
   NPP npp = NPPStack::Peek();
@@ -848,7 +845,6 @@ nsJSObjWrapper::NP_SetProperty(NPObject *npobj, NPIdentifier identifier,
   }
 
   nsJSObjWrapper *npjsobj = (nsJSObjWrapper *)npobj;
-  jsval id = (jsval)identifier;
   JSBool ok = JS_FALSE;
 
   AutoCXPusher pusher(cx);
@@ -858,15 +854,15 @@ nsJSObjWrapper::NP_SetProperty(NPObject *npobj, NPIdentifier identifier,
   jsval v = NPVariantToJSVal(npp, cx, value);
   js::AutoValueRooter tvr(cx, js::Valueify(v));
 
-  if (JSVAL_IS_STRING(id)) {
-    JSString *str = JSVAL_TO_STRING(id);
+  if (NPIdentifierIsString(id)) {
+    JSString *str = NPIdentifierToString(id);
 
     ok = ::JS_SetUCProperty(cx, npjsobj->mJSObj, ::JS_GetStringChars(str),
                             ::JS_GetStringLength(str), &v);
   } else {
-    NS_ASSERTION(JSVAL_IS_INT(id), "id must be either string or int!\n");
+    NS_ASSERTION(NPIdentifierIsInt(id), "id must be either string or int!\n");
 
-    ok = ::JS_SetElement(cx, npjsobj->mJSObj, JSVAL_TO_INT(id), &v);
+    ok = ::JS_SetElement(cx, npjsobj->mJSObj, NPIdentifierToInt(id), &v);
   }
 
   // return ok == JS_TRUE to quiet down compiler warning, even if
@@ -876,7 +872,7 @@ nsJSObjWrapper::NP_SetProperty(NPObject *npobj, NPIdentifier identifier,
 
 // static
 bool
-nsJSObjWrapper::NP_RemoveProperty(NPObject *npobj, NPIdentifier identifier)
+nsJSObjWrapper::NP_RemoveProperty(NPObject *npobj, NPIdentifier id)
 {
   NPP npp = NPPStack::Peek();
   JSContext *cx = GetJSContext(npp);
@@ -893,7 +889,6 @@ nsJSObjWrapper::NP_RemoveProperty(NPObject *npobj, NPIdentifier identifier)
   }
 
   nsJSObjWrapper *npjsobj = (nsJSObjWrapper *)npobj;
-  jsval id = (jsval)identifier;
   JSBool ok = JS_FALSE;
 
   AutoCXPusher pusher(cx);
@@ -901,8 +896,8 @@ nsJSObjWrapper::NP_RemoveProperty(NPObject *npobj, NPIdentifier identifier)
   AutoJSExceptionReporter reporter(cx);
   jsval deleted = JSVAL_FALSE;
 
-  if (JSVAL_IS_STRING(id)) {
-    JSString *str = JSVAL_TO_STRING(id);
+  if (NPIdentifierIsString(id)) {
+    JSString *str = NPIdentifierToString(id);
 
     ok = ::JS_DeleteUCProperty2(cx, npjsobj->mJSObj, ::JS_GetStringChars(str),
                                 ::JS_GetStringLength(str), &deleted);
@@ -923,16 +918,16 @@ nsJSObjWrapper::NP_RemoveProperty(NPObject *npobj, NPIdentifier identifier)
       }
     }
   } else {
-    NS_ASSERTION(JSVAL_IS_INT(id), "id must be either string or int!\n");
+    NS_ASSERTION(NPIdentifierIsInt(id), "id must be either string or int!\n");
 
-    ok = ::JS_DeleteElement2(cx, npjsobj->mJSObj, JSVAL_TO_INT(id), &deleted);
+    ok = ::JS_DeleteElement2(cx, npjsobj->mJSObj, NPIdentifierToInt(id), &deleted);
 
     if (ok && deleted) {
       // FIXME: See bug 425823, we shouldn't need to do this, and once
       // that bug is fixed we can remove this code.
 
       JSBool hasProp;
-      ok = ::JS_HasElement(cx, npjsobj->mJSObj, JSVAL_TO_INT(id), &hasProp);
+      ok = ::JS_HasElement(cx, npjsobj->mJSObj, NPIdentifierToInt(id), &hasProp);
 
       if (ok && hasProp) {
         // The property might have been deleted, but it got
@@ -950,13 +945,13 @@ nsJSObjWrapper::NP_RemoveProperty(NPObject *npobj, NPIdentifier identifier)
 
 //static
 bool
-nsJSObjWrapper::NP_Enumerate(NPObject *npobj, NPIdentifier **identifier,
+nsJSObjWrapper::NP_Enumerate(NPObject *npobj, NPIdentifier **idarray,
                              uint32_t *count)
 {
   NPP npp = NPPStack::Peek();
   JSContext *cx = GetJSContext(npp);
 
-  *identifier = 0;
+  *idarray = 0;
   *count = 0;
 
   if (!cx) {
@@ -982,8 +977,8 @@ nsJSObjWrapper::NP_Enumerate(NPObject *npobj, NPIdentifier **identifier,
   }
 
   *count = ida->length;
-  *identifier = (NPIdentifier *)PR_Malloc(*count * sizeof(NPIdentifier));
-  if (!*identifier) {
+  *idarray = (NPIdentifier *)PR_Malloc(*count * sizeof(NPIdentifier));
+  if (!*idarray) {
     ThrowJSException(cx, "Memory allocation failed for NPIdentifier!");
 
     ::JS_DestroyIdArray(cx, ida);
@@ -995,26 +990,29 @@ nsJSObjWrapper::NP_Enumerate(NPObject *npobj, NPIdentifier **identifier,
     jsval v;
     if (!::JS_IdToValue(cx, ida->vector[i], &v)) {
       ::JS_DestroyIdArray(cx, ida);
-      PR_Free(*identifier);
+      PR_Free(*idarray);
       return PR_FALSE;
     }
 
+    NPIdentifier id;
     if (JSVAL_IS_STRING(v)) {
       JSString *str = JSVAL_TO_STRING(v);
 
       if (!JS_InternUCStringN(cx, ::JS_GetStringChars(str),
                               ::JS_GetStringLength(str))) {
         ::JS_DestroyIdArray(cx, ida);
-        PR_Free(*identifier);
+        PR_Free(*idarray);
 
         return PR_FALSE;
       }
+      id = StringToNPIdentifier(str);
     } else {
       NS_ASSERTION(JSVAL_IS_INT(v),
                    "The element in ida must be either string or int!\n");
+      id = IntToNPIdentifier(JSVAL_TO_INT(v));
     }
 
-    (*identifier)[i] = (NPIdentifier)v;
+    (*idarray)[i] = id;
   }
 
   ::JS_DestroyIdArray(cx, ida);
@@ -1027,8 +1025,7 @@ bool
 nsJSObjWrapper::NP_Construct(NPObject *npobj, const NPVariant *args,
                              uint32_t argCount, NPVariant *result)
 {
-  return doInvoke(npobj, (NPIdentifier)JSVAL_VOID, args, argCount, PR_TRUE,
-                  result);
+  return doInvoke(npobj, NPIdentifier_VOID, args, argCount, PR_TRUE, result);
 }
 
 
@@ -1205,7 +1202,8 @@ NPObjWrapper_AddProperty(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
 
   PluginDestructionGuard pdg(LookupNPP(npobj));
 
-  JSBool hasProperty = npobj->_class->hasProperty(npobj, (NPIdentifier)id);
+  NPIdentifier identifier = JSValToNPIdentifier(id);
+  JSBool hasProperty = npobj->_class->hasProperty(npobj, identifier);
   if (!ReportExceptionIfPending(cx))
     return JS_FALSE;
 
@@ -1214,7 +1212,7 @@ NPObjWrapper_AddProperty(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
 
   // We must permit methods here since JS_DefineUCFunction() will add
   // the function as a property
-  JSBool hasMethod = npobj->_class->hasMethod(npobj, (NPIdentifier)id);
+  JSBool hasMethod = npobj->_class->hasMethod(npobj, identifier);
   if (!ReportExceptionIfPending(cx))
     return JS_FALSE;
 
@@ -1241,8 +1239,10 @@ NPObjWrapper_DelProperty(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
 
   PluginDestructionGuard pdg(LookupNPP(npobj));
 
+  NPIdentifier identifier = JSValToNPIdentifier(id);
+
   if (!NPObjectIsOutOfProcessProxy(npobj)) {
-    JSBool hasProperty = npobj->_class->hasProperty(npobj, (NPIdentifier)id);
+    JSBool hasProperty = npobj->_class->hasProperty(npobj, identifier);
     if (!ReportExceptionIfPending(cx))
       return JS_FALSE;
 
@@ -1250,7 +1250,7 @@ NPObjWrapper_DelProperty(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
       return JS_TRUE;
   }
 
-  if (!npobj->_class->removeProperty(npobj, (NPIdentifier)id))
+  if (!npobj->_class->removeProperty(npobj, identifier))
     *vp = JSVAL_FALSE;
 
   return ReportExceptionIfPending(cx);
@@ -1280,8 +1280,10 @@ NPObjWrapper_SetProperty(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
 
   PluginDestructionGuard pdg(npp);
 
+  NPIdentifier identifier = JSValToNPIdentifier(id);
+
   if (!NPObjectIsOutOfProcessProxy(npobj)) {
-    JSBool hasProperty = npobj->_class->hasProperty(npobj, (NPIdentifier)id);
+    JSBool hasProperty = npobj->_class->hasProperty(npobj, identifier);
     if (!ReportExceptionIfPending(cx))
       return JS_FALSE;
 
@@ -1299,7 +1301,7 @@ NPObjWrapper_SetProperty(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
     return JS_FALSE;
   }
 
-  JSBool ok = npobj->_class->setProperty(npobj, (NPIdentifier)id, &npv);
+  JSBool ok = npobj->_class->setProperty(npobj, identifier, &npv);
   _releasevariantvalue(&npv); // Release the variant
   if (!ReportExceptionIfPending(cx))
     return JS_FALSE;
@@ -1341,6 +1343,8 @@ NPObjWrapper_GetProperty(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
   NPVariant npv;
   VOID_TO_NPVARIANT(npv);
 
+  NPIdentifier identifier = JSValToNPIdentifier(id);
+
 #ifdef MOZ_IPC
   if (NPObjectIsOutOfProcessProxy(npobj)) {
     PluginScriptableObjectParent* actor =
@@ -1350,7 +1354,7 @@ NPObjWrapper_GetProperty(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
     if (!actor)
       return JS_FALSE;
 
-    JSBool success = actor->GetPropertyHelper((NPIdentifier)id, &hasProperty,
+    JSBool success = actor->GetPropertyHelper(identifier, &hasProperty,
                                               &hasMethod, &npv);
     if (!ReportExceptionIfPending(cx)) {
       if (success)
@@ -1375,11 +1379,11 @@ NPObjWrapper_GetProperty(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
   }
 #endif
 
-  hasProperty = npobj->_class->hasProperty(npobj, (NPIdentifier)id);
+  hasProperty = npobj->_class->hasProperty(npobj, identifier);
   if (!ReportExceptionIfPending(cx))
     return JS_FALSE;
 
-  hasMethod = npobj->_class->hasMethod(npobj, (NPIdentifier)id);
+  hasMethod = npobj->_class->hasMethod(npobj, identifier);
   if (!ReportExceptionIfPending(cx))
     return JS_FALSE;
 
@@ -1388,7 +1392,7 @@ NPObjWrapper_GetProperty(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
     return CreateNPObjectMember(npp, cx, obj, npobj, id, nsnull, vp);
 
   if (hasProperty) {
-    if (npobj->_class->getProperty(npobj, (NPIdentifier)id, &npv))
+    if (npobj->_class->getProperty(npobj, identifier, &npv))
       *vp = NPVariantToJSVal(npp, cx, &npv);
 
     _releasevariantvalue(&npv);
@@ -1488,10 +1492,10 @@ CallNPMethodInternal(JSContext *cx, JSObject *obj, uintN argc, jsval *argv,
 
     if (npobj->_class->invoke) {
       JSFunction *fun = (JSFunction *)::JS_GetPrivate(cx, funobj);
-      jsval method = STRING_TO_JSVAL(::JS_GetFunctionId(fun));
+      JSString *name = ::JS_GetFunctionId(fun);
+      NPIdentifier id = StringToNPIdentifier(name);
 
-      ok = npobj->_class->invoke(npobj, (NPIdentifier)method, npargs, argc,
-                                 &v);
+      ok = npobj->_class->invoke(npobj, id, npargs, argc, &v);
     } else {
       ok = JS_FALSE;
 
@@ -1610,7 +1614,8 @@ NPObjWrapper_newEnumerate(JSContext *cx, JSObject *obj, JSIterateOp enum_op,
     enum_value = state->value;
     length = state->length;
     if (state->index != length) {
-      return ::JS_ValueToId(cx, (jsval)enum_value[state->index++], idp);
+      jsval val = NPIdentifierToJSVal(enum_value[state->index++]);
+      return ::JS_ValueToId(cx, val, idp);
     }
 
     // FALL THROUGH
@@ -1643,7 +1648,9 @@ NPObjWrapper_NewResolve(JSContext *cx, JSObject *obj, jsval id, uintN flags,
 
   PluginDestructionGuard pdg(LookupNPP(npobj));
 
-  PRBool hasProperty = npobj->_class->hasProperty(npobj, (NPIdentifier)id);
+  NPIdentifier identifier = JSValToNPIdentifier(id);
+
+  PRBool hasProperty = npobj->_class->hasProperty(npobj, identifier);
   if (!ReportExceptionIfPending(cx))
     return JS_FALSE;
 
@@ -1670,7 +1677,7 @@ NPObjWrapper_NewResolve(JSContext *cx, JSObject *obj, jsval id, uintN flags,
     return JS_TRUE;
   }
 
-  PRBool hasMethod = npobj->_class->hasMethod(npobj, (NPIdentifier)id);
+  PRBool hasMethod = npobj->_class->hasMethod(npobj, identifier);
   if (!ReportExceptionIfPending(cx))
     return JS_FALSE;
 
@@ -2141,6 +2148,8 @@ CreateNPObjectMember(NPP npp, JSContext *cx, JSObject *obj, NPObject* npobj,
 
   ::JS_SetPrivate(cx, memobj, (void *)memberPrivate);
 
+  NPIdentifier identifier = JSValToNPIdentifier(id);
+
   jsval fieldValue;
   NPVariant npv;
   NPBool hasProperty;
@@ -2153,7 +2162,7 @@ CreateNPObjectMember(NPP npp, JSContext *cx, JSObject *obj, NPObject* npobj,
   else {
     VOID_TO_NPVARIANT(npv);
 
-    NPBool hasProperty = npobj->_class->getProperty(npobj, (NPIdentifier)id,
+    NPBool hasProperty = npobj->_class->getProperty(npobj, identifier,
                                                     &npv);
     if (!ReportExceptionIfPending(cx)) {
       ::JS_RemoveValueRoot(cx, vp);
@@ -2178,7 +2187,7 @@ CreateNPObjectMember(NPP npp, JSContext *cx, JSObject *obj, NPObject* npobj,
   memberPrivate->npobjWrapper = obj;
 
   memberPrivate->fieldValue = fieldValue;
-  memberPrivate->methodName = id;
+  memberPrivate->methodName = identifier;
   memberPrivate->npp = npp;
 
   ::JS_RemoveValueRoot(cx, vp);
@@ -2277,9 +2286,10 @@ NPObjectMember_Call(JSContext *cx, JSObject *obj,
     }
   }
 
+
   NPVariant npv;
   JSBool ok;
-  ok = npobj->_class->invoke(npobj, (NPIdentifier)memberPrivate->methodName,
+  ok = npobj->_class->invoke(npobj, memberPrivate->methodName,
                              npargs, argc, &npv);
 
   // Release arguments.
diff --git a/modules/plugin/base/src/nsNPAPIPlugin.cpp b/modules/plugin/base/src/nsNPAPIPlugin.cpp
index 848fc16b72f..c85d2f3596d 100644
--- a/modules/plugin/base/src/nsNPAPIPlugin.cpp
+++ b/modules/plugin/base/src/nsNPAPIPlugin.cpp
@@ -690,7 +690,7 @@ doGetIdentifier(JSContext *cx, const NPUTF8* name)
   if (!str)
     return NULL;
 
-  return (NPIdentifier)STRING_TO_JSVAL(str);
+  return StringToNPIdentifier(str);
 }
 
 #if defined(MOZ_MEMORY_WINDOWS) && !defined(MOZ_MEMORY_WINCE)
@@ -1353,25 +1353,23 @@ _getintidentifier(int32_t intid)
   if (!NS_IsMainThread()) {
     NPN_PLUGIN_LOG(PLUGIN_LOG_ALWAYS,("NPN_getstringidentifier called from the wrong thread\n"));
   }
-  return (NPIdentifier)INT_TO_JSVAL(intid);
+  return IntToNPIdentifier(intid);
 }
 
 NPUTF8* NP_CALLBACK
-_utf8fromidentifier(NPIdentifier identifier)
+_utf8fromidentifier(NPIdentifier id)
 {
   if (!NS_IsMainThread()) {
     NPN_PLUGIN_LOG(PLUGIN_LOG_ALWAYS,("NPN_utf8fromidentifier called from the wrong thread\n"));
   }
-  if (!identifier)
+  if (!id)
     return NULL;
 
-  jsval v = (jsval)identifier;
-
-  if (!JSVAL_IS_STRING(v)) {
+  if (!NPIdentifierIsString(id)) {
     return nsnull;
   }
 
-  JSString *str = JSVAL_TO_STRING(v);
+  JSString *str = NPIdentifierToString(id);
 
   return
     ToNewUTF8String(nsDependentString((PRUnichar *)::JS_GetStringChars(str),
@@ -1379,29 +1377,27 @@ _utf8fromidentifier(NPIdentifier identifier)
 }
 
 int32_t NP_CALLBACK
-_intfromidentifier(NPIdentifier identifier)
+_intfromidentifier(NPIdentifier id)
 {
   if (!NS_IsMainThread()) {
     NPN_PLUGIN_LOG(PLUGIN_LOG_ALWAYS,("NPN_intfromidentifier called from the wrong thread\n"));
   }
-  jsval v = (jsval)identifier;
 
-  if (!JSVAL_IS_INT(v)) {
+  if (!NPIdentifierIsInt(id)) {
     return PR_INT32_MIN;
   }
 
-  return JSVAL_TO_INT(v);
+  return NPIdentifierToInt(id);
 }
 
 bool NP_CALLBACK
-_identifierisstring(NPIdentifier identifier)
+_identifierisstring(NPIdentifier id)
 {
   if (!NS_IsMainThread()) {
     NPN_PLUGIN_LOG(PLUGIN_LOG_ALWAYS,("NPN_identifierisstring called from the wrong thread\n"));
   }
-  jsval v = (jsval)identifier;
 
-  return JSVAL_IS_STRING(v);
+  return NPIdentifierIsString(id);
 }
 
 NPObject* NP_CALLBACK
diff --git a/modules/plugin/base/src/nsNPAPIPlugin.h b/modules/plugin/base/src/nsNPAPIPlugin.h
index ad375649869..3fb55122290 100644
--- a/modules/plugin/base/src/nsNPAPIPlugin.h
+++ b/modules/plugin/base/src/nsNPAPIPlugin.h
@@ -43,6 +43,8 @@
 #include "npfunctions.h"
 #include "nsPluginHost.h"
 
+#include "jsapi.h"
+
 #include "mozilla/PluginLibrary.h"
 
 /*
@@ -114,6 +116,129 @@ namespace mozilla {
 namespace plugins {
 namespace parent {
 
+// On 32-bit platforms, sizeof(jsval) != sizeof(NPIdentifier), so we need to
+// use an alternate encoding scheme. The following inline helpers provide an
+// abstraction for setting and getting the values of NPIdentifiers that should
+// always be used instead of casting an NPIdentifier to a jsval and using the
+// jsapi.
+
+#if JS_BITS_PER_WORD == 64
+
+JS_STATIC_ASSERT(sizeof(NPIdentifier) == sizeof(jsval));
+
+static inline bool
+NPIdentifierIsString(NPIdentifer id)
+{
+    return JSVAL_IS_STRING((jsval)id);
+}
+
+static inline JSString *
+NPIdentifierToString(NPIdentifer id)
+{
+    return JSVAL_TO_STRING((jsval)id);
+}
+
+static inline NPIdentifier
+StringToNPIdentifier(JSString *str)
+{
+    return (NPIdentifier)STRING_TO_JSVAL(str);
+}
+
+static inline bool
+NPIdentifierIsInt(NPIdentifer id)
+{
+    return JSVAL_IS_INT((jsval)id);
+}
+
+static inline jsint
+NPIdentifierToInt(NPIdentifer id)
+{
+    return JSVAL_TO_INT((jsval)id);
+}
+
+static inline bool
+IntToNPIdentifier(JSContext *, jsint i, NPIdentifier *pid)
+{
+    *pid = (NPIdentifier)INT_TO_JSVAL(i);
+    return true;
+}
+
+static inline bool
+NPIdentifierIsVoid(NPIdentifier id)
+{
+    return JSVAL_IS_VOID((NPIdentifier)id);
+}
+
+static const NPIdentifier NPIdentifier_VOID = (NPIdentifier)JSVAL_VOID;
+
+#else  /* JS_BITS_PER_WORD == 32 */
+
+static inline bool
+NPIdentifierIsString(NPIdentifier id)
+{
+    return ((size_t)id & 0x3) == 0;
+}
+
+static inline JSString *
+NPIdentifierToString(NPIdentifier id)
+{
+    NS_ASSERTION(NPIdentifierIsString(id), "id must be string");
+    return (JSString *)id;
+}
+
+static inline NPIdentifier
+StringToNPIdentifier(JSString *str)
+{
+    NS_ASSERTION(((size_t)str & 3) == 0, "Strings are assumed to be at least 4-byte aligned");
+    return (NPIdentifier)str;
+}
+
+static inline bool
+NPIdentifierIsInt(NPIdentifier id)
+{
+    return ((size_t)id & 1) != 0;
+}
+
+static inline jsint
+NPIdentifierToInt(NPIdentifier id)
+{
+    NS_ASSERTION(NPIdentifierIsInt(id), "id must be int");
+    return (jsint)id >> 1;
+}
+
+static inline NPIdentifier
+IntToNPIdentifier(jsint i)
+{
+    NS_ASSERTION(i < (1 << 30) - 1, "integer id is too big, will be truncated");
+    return (NPIdentifier)((i << 1) | 0x1);
+}
+
+static inline bool
+NPIdentifierIsVoid(NPIdentifier id)
+{
+    return (size_t)id == 0x2;
+}
+
+static const NPIdentifier NPIdentifier_VOID = (NPIdentifier)0x2;
+
+#endif
+
+static inline jsval
+NPIdentifierToJSVal(NPIdentifier id)
+{
+    if (NPIdentifierIsString(id))
+        return STRING_TO_JSVAL(NPIdentifierToString(id));
+    return INT_TO_JSVAL(NPIdentifierToInt(id));
+}
+
+static inline NPIdentifier
+JSValToNPIdentifier(jsval val)
+{
+    if (JSVAL_IS_STRING(val))
+        return StringToNPIdentifier(JSVAL_TO_STRING(val));
+    return IntToNPIdentifier(JSVAL_TO_INT(val));
+}
+
 NPObject* NP_CALLBACK
 _getwindowobject(NPP npp);