diff --git a/js/src/jscntxt.h b/js/src/jscntxt.h
index 70ae1ccc0d09..80cf29f8a84e 100755
--- a/js/src/jscntxt.h
+++ b/js/src/jscntxt.h
@@ -126,6 +126,7 @@ struct VMFragment;
 #ifdef __cplusplus
 struct REHashKey;
 struct REHashFn;
+class FrameInfoCache;
 typedef nanojit::HashMap<REHashKey, nanojit::Fragment*, REHashFn> REHashMap;
 #endif
 
@@ -177,6 +178,7 @@ struct JSTraceMonitor {
     CLS(nanojit::Assembler) assembler;
     CLS(nanojit::LirBuffer) lirbuf;
     CLS(nanojit::LirBuffer) reLirBuf;
+    CLS(FrameInfoCache)     frameCache;
 #ifdef DEBUG
     CLS(nanojit::LabelMap)  labels;
 #endif
diff --git a/js/src/jstracer.cpp b/js/src/jstracer.cpp
index af8c5b62ff5f..8ff252b55e6e 100644
--- a/js/src/jstracer.cpp
+++ b/js/src/jstracer.cpp
@@ -1142,6 +1142,94 @@ IsSlotUndemotable(JSContext* cx, TreeInfo* ti, unsigned slot)
     return oracle.isGlobalSlotUndemotable(cx, gslots[slot - ti->nStackTypes]);
 }
 
+class FrameInfoCache
+{
+    struct Entry : public JSDHashEntryHdr
+    {
+        FrameInfo *fi;
+    };
+
+    static JSBool
+    MatchFrameInfo(JSDHashTable *table, const JSDHashEntryHdr *entry, const void *key) {
+        const FrameInfo* fi1 = ((const Entry*)entry)->fi;
+        const FrameInfo* fi2 = (const FrameInfo*)key;
+        if (memcmp(fi1, fi2, sizeof(FrameInfo)) != 0)
+            return JS_FALSE;
+        return memcmp(fi1->get_typemap(), fi2->get_typemap(),
+                      fi1->callerHeight * sizeof(JSTraceType)) == 0;
+    }
+
+    static JSDHashNumber
+    HashFrameInfo(JSDHashTable *table, const void *key) {
+        FrameInfo* fi = (FrameInfo*)key;
+        size_t len = sizeof(FrameInfo) + fi->callerHeight * sizeof(JSTraceType);
+
+        JSDHashNumber h = 0;
+        const unsigned char *s = (const unsigned char*)fi;
+        for (size_t i = 0; i < len; i++, s++)
+            h = JS_ROTATE_LEFT32(h, 4) ^ *s;
+        return h;
+    }
+
+    static const JSDHashTableOps FrameCacheOps;
+
+    JSDHashTable *table;
+    VMAllocator *allocator;
+
+  public:
+    FrameInfoCache(VMAllocator *allocator) : allocator(allocator) {
+        init();
+    }
+
+    ~FrameInfoCache() {
+        clear();
+    }
+
+    void clear() {
+        if (table) {
+            JS_DHashTableDestroy(table);
+            table = NULL;
+        }
+    }
+
+    bool reset() {
+        clear();
+        return init();
+    }
+
+    bool init() {
+        table = JS_NewDHashTable(&FrameCacheOps, NULL, sizeof(Entry),
+                                 JS_DHASH_DEFAULT_CAPACITY(32));
+        return table != NULL;
+    }
+
+    FrameInfo *memoize(const FrameInfo *fi) {
+        Entry *entry = (Entry*)JS_DHashTableOperate(table, fi, JS_DHASH_ADD);
+        if (!entry)
+            return NULL;
+        if (!entry->fi) {
+            FrameInfo* n = (FrameInfo*)
+                allocator->alloc(sizeof(FrameInfo) + fi->callerHeight * sizeof(JSTraceType));
+            memcpy(n, fi, sizeof(FrameInfo) + fi->callerHeight * sizeof(JSTraceType));
+            entry->fi = n;
+        }
+        return entry->fi;
+    }
+};
+
+const JSDHashTableOps FrameInfoCache::FrameCacheOps =
+{
+    JS_DHashAllocTable,
+    JS_DHashFreeTable,
+    FrameInfoCache::HashFrameInfo,
+    FrameInfoCache::MatchFrameInfo,
+    JS_DHashMoveEntryStub,
+    JS_DHashClearEntryStub,
+    JS_DHashFinalizeStub,
+    NULL
+};
+
+
 struct PCHashEntry : public JSDHashEntryStub {
     size_t          count;
 };
@@ -2566,6 +2654,7 @@ JSTraceMonitor::flush()
             js_FragProfiling_FragFinalizer(f->head, this);
     )
 
+    frameCache->reset();
     dataAlloc->reset();
     traceAlloc->reset();
     codeAlloc->reset();
@@ -2817,12 +2906,12 @@ public:
 class FlushNativeStackFrameVisitor : public SlotVisitorBase
 {
     JSContext *mCx;
-    JSTraceType *mTypeMap;
+    const JSTraceType *mTypeMap;
     double *mStack;
     jsval *mStop;
 public:
     FlushNativeStackFrameVisitor(JSContext *cx,
-                                 JSTraceType *typeMap,
+                                 const JSTraceType *typeMap,
                                  double *stack,
                                  jsval *stop) :
         mCx(cx),
@@ -2831,7 +2920,7 @@ public:
         mStop(stop)
     {}
 
-    JSTraceType* getTypeMap()
+    const JSTraceType* getTypeMap()
     {
         return mTypeMap;
     }
@@ -3121,7 +3210,7 @@ GetClosureVar(JSContext* cx, JSObject* callee, const ClosureVarInfo* cv, double*
  * @return the number of things we popped off of np.
  */
 static JS_REQUIRES_STACK int
-FlushNativeStackFrame(JSContext* cx, unsigned callDepth, JSTraceType* mp, double* np,
+FlushNativeStackFrame(JSContext* cx, unsigned callDepth, const JSTraceType* mp, double* np,
                       JSStackFrame* stopFrame)
 {
     jsval* stopAt = stopFrame ? &stopFrame->argv[-2] : NULL;
@@ -6301,7 +6390,7 @@ LeaveTree(InterpState& state, VMSideExit* lr)
          * type map pointer on the native call stack.
          */
         SynthesizeFrame(cx, *fi, callee);
-        int slots = FlushNativeStackFrame(cx, 1 /* callDepth */, (JSTraceType*)(fi + 1),
+        int slots = FlushNativeStackFrame(cx, 1 /* callDepth */, (*callstack)->get_typemap(),
                                           stack, cx->fp);
 #ifdef DEBUG
         JSStackFrame* fp = cx->fp;
@@ -7164,6 +7253,7 @@ js_InitJIT(JSTraceMonitor *tm)
     tm->tempAlloc = new VMAllocator();
     tm->reTempAlloc = new VMAllocator();
     tm->codeAlloc = new CodeAlloc();
+    tm->frameCache = new FrameInfoCache(tm->dataAlloc);
     tm->flush();
     verbose_only( tm->branches = NULL; )
 
@@ -7271,6 +7361,11 @@ js_FinishJIT(JSTraceMonitor *tm)
     delete[] tm->reservedDoublePool;
     tm->reservedDoublePool = tm->reservedDoublePoolPtr = NULL;
 
+    if (tm->frameCache) {
+        delete tm->frameCache;
+        tm->frameCache = NULL;
+    }
+
     if (tm->codeAlloc) {
         delete tm->codeAlloc;
         tm->codeAlloc = NULL;
@@ -11614,9 +11709,8 @@ TraceRecorder::interpretedFunctionCall(jsval& fval, JSFunction* fun, uintN argc,
     // Generate a type map for the outgoing frame and stash it in the LIR
     unsigned stackSlots = NativeStackSlots(cx, 0 /* callDepth */);
     FrameInfo* fi = (FrameInfo*)
-        traceMonitor->traceAlloc->alloc(sizeof(FrameInfo) +
-                                        stackSlots * sizeof(JSTraceType));
-    JSTraceType* typemap = reinterpret_cast<JSTraceType *>(fi + 1);
+        traceMonitor->tempAlloc->alloc(sizeof(FrameInfo) + stackSlots * sizeof(JSTraceType));
+    JSTraceType* typemap = (JSTraceType*)(fi + 1);
 
     DetermineTypesVisitor detVisitor(*this, typemap);
     VisitStackSlots(detVisitor, cx, 0);
@@ -11638,6 +11732,9 @@ TraceRecorder::interpretedFunctionCall(jsval& fval, JSFunction* fun, uintN argc,
     if (callDepth >= treeInfo->maxCallDepth)
         treeInfo->maxCallDepth = callDepth + 1;
 
+    fi = traceMonitor->frameCache->memoize(fi);
+    if (!fi)
+        RETURN_STOP("out of memory");
     lir->insStorei(INS_CONSTPTR(fi), lirbuf->rp, callDepth * sizeof(FrameInfo*));
 
     atoms = fun->u.i.script->atomMap.vector;
diff --git a/js/src/jstracer.h b/js/src/jstracer.h
index fac1fdffb12a..f8b1cdbc50bd 100755
--- a/js/src/jstracer.h
+++ b/js/src/jstracer.h
@@ -574,7 +574,7 @@ struct FrameInfo {
     bool   is_constructing() const { return (argc & CONSTRUCTING_FLAG) != 0; }
 
     // The typemap just before the callee is called.
-    JSTraceType* get_typemap() { return (JSTraceType*) (this+1); }
+    const JSTraceType* get_typemap() const { return (JSTraceType*) (this+1); }
 };
 
 struct UnstableExit