diff --git a/lib/Analysis/MemoryDependenceAnalysis.cpp b/lib/Analysis/MemoryDependenceAnalysis.cpp
index 3b2102955f3..091b256cfc8 100644
--- a/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -731,10 +731,22 @@ getNonLocalPointerDepFromBB(Value *Pointer, uint64_t PointeeSize,
     // If we do need to do phi translation, then there are a bunch of different
     // cases, because we have to find a Value* live in the predecessor block. We
     // know that PtrInst is defined in this block at least.
+
+    // We may have added values to the cache list before this PHI translation.
+    // If so, we haven't done anything to ensure that the cache remains sorted.
+    // Sort it now (if needed) so that recursive invocations of
+    // getNonLocalPointerDepFromBB and other routines that could reuse the cache
+    // value will only see properly sorted cache arrays.
+    if (Cache && NumSortedEntries != Cache->size()) {
+      std::sort(Cache->begin(), Cache->end());
+      NumSortedEntries = Cache->size();
+    }
     
     // If this is directly a PHI node, just use the incoming values for each
     // pred as the phi translated version.
     if (PHINode *PtrPHI = dyn_cast<PHINode>(PtrInst)) {
+      Cache = 0;
+      
       for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
         BasicBlock *Pred = *PI;
         Value *PredPtr = PtrPHI->getIncomingValueForBlock(Pred);
@@ -759,15 +771,6 @@ getNonLocalPointerDepFromBB(Value *Pointer, uint64_t PointeeSize,
           goto PredTranslationFailure;
         }
 
-        // We may have added values to the cache list before this PHI
-        // translation.  If so, we haven't done anything to ensure that the
-        // cache remains sorted.  Sort it now (if needed) so that recursive
-        // invocations of getNonLocalPointerDepFromBB that could reuse the cache
-        // value will only see properly sorted cache arrays.
-        if (Cache && NumSortedEntries != Cache->size())
-          std::sort(Cache->begin(), Cache->end());
-        Cache = 0;
-        
         // FIXME: it is entirely possible that PHI translating will end up with
         // the same value.  Consider PHI translating something like:
         // X = phi [x, bb1], [y, bb2].  PHI translating for bb1 doesn't *need*
@@ -779,7 +782,7 @@ getNonLocalPointerDepFromBB(Value *Pointer, uint64_t PointeeSize,
                                         Result, Visited))
           goto PredTranslationFailure;
       }
-
+      
       // Refresh the CacheInfo/Cache pointer so that it isn't invalidated.
       CacheInfo = &NonLocalPointerDeps[CacheKey];
       Cache = &CacheInfo->second;
@@ -806,11 +809,8 @@ getNonLocalPointerDepFromBB(Value *Pointer, uint64_t PointeeSize,
       CacheInfo = &NonLocalPointerDeps[CacheKey];
       Cache = &CacheInfo->second;
       NumSortedEntries = Cache->size();
-    } else if (NumSortedEntries != Cache->size()) {
-      std::sort(Cache->begin(), Cache->end());
-      NumSortedEntries = Cache->size();
     }
-
+    
     // Since we did phi translation, the "Cache" set won't contain all of the
     // results for the query.  This is ok (we can still use it to accelerate
     // specific block queries) but we can't do the fastpath "return all
diff --git a/test/Transforms/GVN/2009-07-13-MemDepSortFail.ll b/test/Transforms/GVN/2009-07-13-MemDepSortFail.ll
new file mode 100644
index 00000000000..f87370427ca
--- /dev/null
+++ b/test/Transforms/GVN/2009-07-13-MemDepSortFail.ll
@@ -0,0 +1,67 @@
+; RUN: llvm-as < %s | opt -gvn | llvm-dis
+; PR4256
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32"
+target triple = "i386-linux-gnu"
+	%llvm.dbg.anchor.type = type { i32, i32 }
+	%struct.cset = type { i8*, i8, i8, i32, i8* }
+	%struct.lmat = type { %struct.re_guts*, i32, %llvm.dbg.anchor.type*, i8*, i8*, i8*, i8*, i8**, i32, i8*, i8*, i8*, i8*, i8* }
+	%struct.re_guts = type { i32*, %struct.cset*, i8*, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i8*, i8*, i32, i32, i32, i32, [1 x i8] }
+
+define i8* @lbackref(%struct.lmat* %m, i8* %start, i8* %stop, i32 %startst, i32 %stopst, i32 %lev, i32 %rec) nounwind {
+entry:
+	br label %bb63
+
+bb:		; preds = %bb63
+	switch i32 0, label %bb62 [
+		i32 268435456, label %bb2
+		i32 805306368, label %bb9
+		i32 -1610612736, label %bb51
+	]
+
+bb2:		; preds = %bb
+	br label %bb62
+
+bb9:		; preds = %bb
+	%0 = load i8* %sp.1, align 1		; <i8> [#uses=0]
+	br label %bb62
+
+bb51:		; preds = %bb
+	%1 = load i8* %sp.1, align 1		; <i8> [#uses=0]
+	ret i8* null
+
+bb62:		; preds = %bb9, %bb2, %bb
+	br label %bb63
+
+bb63:		; preds = %bb84, %bb69, %bb62, %entry
+	%sp.1 = phi i8* [ null, %bb62 ], [ %sp.1.lcssa, %bb84 ], [ %start, %entry ], [ %sp.1.lcssa, %bb69 ]		; <i8*> [#uses=3]
+	br i1 false, label %bb, label %bb65
+
+bb65:		; preds = %bb63
+	%sp.1.lcssa = phi i8* [ %sp.1, %bb63 ]		; <i8*> [#uses=4]
+	br i1 false, label %bb66, label %bb69
+
+bb66:		; preds = %bb65
+	ret i8* null
+
+bb69:		; preds = %bb65
+	switch i32 0, label %bb108.loopexit2.loopexit.loopexit [
+		i32 1342177280, label %bb63
+		i32 1476395008, label %bb84
+		i32 1879048192, label %bb104
+		i32 2013265920, label %bb93
+	]
+
+bb84:		; preds = %bb69
+	%2 = tail call i8* @lbackref(%struct.lmat* %m, i8* %sp.1.lcssa, i8* %stop, i32 0, i32 %stopst, i32 0, i32 0) nounwind		; <i8*> [#uses=0]
+	br label %bb63
+
+bb93:		; preds = %bb69
+	ret i8* null
+
+bb104:		; preds = %bb69
+	%sp.1.lcssa.lcssa33 = phi i8* [ %sp.1.lcssa, %bb69 ]		; <i8*> [#uses=0]
+	unreachable
+
+bb108.loopexit2.loopexit.loopexit:		; preds = %bb69
+	ret i8* null
+}