diff --git a/js/src/jscntxt.cpp b/js/src/jscntxt.cpp
index e4fc1b8553fb..91ee00f02988 100644
--- a/js/src/jscntxt.cpp
+++ b/js/src/jscntxt.cpp
@@ -533,8 +533,6 @@ JSThreadData::purge(JSContext *cx)
 
     /* FIXME: bug 506341. */
     propertyCache.purge(cx);
-
-    dtoaCache.s = NULL;
 }
 
 #ifdef JS_THREADSAFE
diff --git a/js/src/jscntxt.h b/js/src/jscntxt.h
index 18dc62a2a7e5..789ea75f537e 100644
--- a/js/src/jscntxt.h
+++ b/js/src/jscntxt.h
@@ -892,20 +892,6 @@ struct JSThreadData {
     /* State used by dtoa.c. */
     DtoaState           *dtoaState;
 
-    /*
-     * A single-entry cache for some base-10 double-to-string conversions.
-     * This helps date-format-xparb.js.  It also avoids skewing the results
-     * for v8-splay.js when measured by the SunSpider harness, where the splay
-     * tree initialization (which includes many repeated double-to-string
-     * conversions) is erroneously included in the measurement; see bug
-     * 562553.
-     */
-    struct {
-        jsdouble d;
-        jsint    base;
-        JSString *s;        // if s==NULL, d and base are not valid
-    } dtoaCache;
-
     /* Base address of the native stack for the current thread. */
     jsuword             *nativeStackBase;
 
diff --git a/js/src/jscompartment.cpp b/js/src/jscompartment.cpp
index 537cd73bddc1..1a0389f75a3f 100644
--- a/js/src/jscompartment.cpp
+++ b/js/src/jscompartment.cpp
@@ -451,6 +451,7 @@ void
 JSCompartment::purge(JSContext *cx)
 {
     freeLists.purge();
+    dtoaCache.purge();
 
     /* Destroy eval'ed scripts. */
     js_DestroyScriptsToGC(cx, this);
diff --git a/js/src/jscompartment.h b/js/src/jscompartment.h
index a8882adc03e9..8ac777bec301 100644
--- a/js/src/jscompartment.h
+++ b/js/src/jscompartment.h
@@ -332,6 +332,33 @@ class NativeIterCache {
     }
 };
 
+/*
+ * A single-entry cache for some base-10 double-to-string conversions. This
+ * helps date-format-xparb.js.  It also avoids skewing the results for
+ * v8-splay.js when measured by the SunSpider harness, where the splay tree
+ * initialization (which includes many repeated double-to-string conversions)
+ * is erroneously included in the measurement; see bug 562553.
+ */
+class DtoaCache {
+    double   d;
+    jsint    base;
+    JSString *s;        // if s==NULL, d and base are not valid
+  public:
+    DtoaCache() : s(NULL) {}
+    void purge() { s = NULL; }
+
+    JSString *lookup(jsint base, double d) {
+        return this->s && base == this->base && d == this->d ? this->s : NULL;
+    }
+
+    void cache(jsint base, double d, JSString *s) {
+        this->base = base;
+        this->d = d;
+        this->s = s;
+    }
+
+};
+
 } /* namespace js */
 
 struct JS_FRIEND_API(JSCompartment) {
@@ -401,6 +428,8 @@ struct JS_FRIEND_API(JSCompartment) {
 
     void setGCLastBytes(size_t lastBytes);
 
+    js::DtoaCache dtoaCache;
+
   private:
     js::MathCache                *mathCache;
 
diff --git a/js/src/jsnum.cpp b/js/src/jsnum.cpp
index e6c0c0a889c3..7fab6209ae03 100644
--- a/js/src/jsnum.cpp
+++ b/js/src/jsnum.cpp
@@ -603,17 +603,15 @@ js_IntToString(JSContext *cx, int32 si)
     if (si >= 0) {
         if (si < INT_STRING_LIMIT)
             return JSString::intString(si);
-        if (si < 100)
-            return JSString::length2String(si);
         ui = si;
     } else {
         ui = uint32(-si);
         JS_ASSERT_IF(si == INT32_MIN, ui == uint32(INT32_MAX) + 1);
     }
 
-    JSThreadData *data = JS_THREAD_DATA(cx);
-    if (data->dtoaCache.s && data->dtoaCache.base == 10 && data->dtoaCache.d == si)
-        return data->dtoaCache.s;
+    JSCompartment *c = cx->compartment;
+    if (JSString *str = c->dtoaCache.lookup(10, si))
+        return str;
 
     JSShortString *str = js_NewGCShortString(cx);
     if (!str)
@@ -638,9 +636,7 @@ js_IntToString(JSContext *cx, int32 si)
     str->initAtOffsetInBuffer(cp, end - cp);
 
     JSString *ret = str->header();
-    data->dtoaCache.base = 10;
-    data->dtoaCache.d = si;
-    data->dtoaCache.s = ret;
+    c->dtoaCache.cache(10, si, ret);
     return ret;
 }
 
@@ -1156,7 +1152,6 @@ js_NumberToStringWithBase(JSContext *cx, jsdouble d, jsint base)
     ToCStringBuf cbuf;
     char *numStr;
     JSString *s;
-    JSThreadData *data;
 
     /*
      * Caller is responsible for error reporting. When called from trace,
@@ -1166,6 +1161,8 @@ js_NumberToStringWithBase(JSContext *cx, jsdouble d, jsint base)
     if (base < 2 || base > 36)
         return NULL;
 
+    JSCompartment *c = cx->compartment;
+
     int32_t i;
     if (JSDOUBLE_IS_INT32(d, &i)) {
         if (base == 10 && jsuint(i) < INT_STRING_LIMIT)
@@ -1176,16 +1173,14 @@ js_NumberToStringWithBase(JSContext *cx, jsdouble d, jsint base)
             return JSString::unitString(jschar('a' + i - 10));
         }
 
-        data = JS_THREAD_DATA(cx);
-        if (data->dtoaCache.s && data->dtoaCache.base == base && data->dtoaCache.d == d)
-            return data->dtoaCache.s;
+        if (JSString *str = c->dtoaCache.lookup(base, d))
+            return str;
 
         numStr = IntToCString(&cbuf, i, base);
         JS_ASSERT(!cbuf.dbuf && numStr >= cbuf.sbuf && numStr < cbuf.sbuf + cbuf.sbufSize);
     } else {
-        data = JS_THREAD_DATA(cx);
-        if (data->dtoaCache.s && data->dtoaCache.base == base && data->dtoaCache.d == d)
-            return data->dtoaCache.s;
+        if (JSString *str = c->dtoaCache.lookup(base, d))
+            return str;
 
         numStr = FracNumberToCString(cx, &cbuf, d, base);
         if (!numStr) {
@@ -1200,10 +1195,7 @@ js_NumberToStringWithBase(JSContext *cx, jsdouble d, jsint base)
 
     s = js_NewStringCopyZ(cx, numStr);
 
-    data->dtoaCache.base = base;
-    data->dtoaCache.d = d;
-    data->dtoaCache.s = s;
-
+    c->dtoaCache.cache(base, d, s);
     return s;
 }