diff --git a/lib/Transforms/Scalar/ScalarReplAggregates.cpp b/lib/Transforms/Scalar/ScalarReplAggregates.cpp
index 5343600..c245b14 100644
--- a/lib/Transforms/Scalar/ScalarReplAggregates.cpp
+++ b/lib/Transforms/Scalar/ScalarReplAggregates.cpp
@@ -193,6 +193,22 @@
 };
 } // end anonymous namespace.
 
+
+/// IsVerbotenVectorType - Return true if this is a vector type ScalarRepl isn't
+/// allowed to form.  We do this to avoid MMX types, which is a complete hack,
+/// but is required until the backend is fixed.
+static bool IsVerbotenVectorType(const VectorType *VTy) {
+  // Reject all the MMX vector types.
+  switch (VTy->getNumElements()) {
+  default: return false;
+  case 1: return VTy->getElementType()->isIntegerTy(64);
+  case 2: return VTy->getElementType()->isIntegerTy(32);
+  case 4: return VTy->getElementType()->isIntegerTy(16);
+  case 8: return VTy->getElementType()->isIntegerTy(8);
+  }
+}
+
+
 /// TryConvert - Analyze the specified alloca, and if it is safe to do so,
 /// rewrite it to be a new alloca which is mem2reg'able.  This returns the new
 /// alloca if possible or null if not.
@@ -209,7 +225,8 @@
   // we just get a lot of insert/extracts.  If at least one vector is
   // involved, then we probably really do have a union of vector/array.
   const Type *NewTy;
-  if (VectorTy && VectorTy->isVectorTy() && HadAVector) {
+  if (VectorTy && VectorTy->isVectorTy() && HadAVector &&
+      !IsVerbotenVectorType(cast<VectorType>(VectorTy))) {
     DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n  TYPE = "
           << *VectorTy << '\n');
     NewTy = VectorTy;  // Use the vector type.
@@ -1662,6 +1679,12 @@
 /// HasPadding - Return true if the specified type has any structure or
 /// alignment padding, false otherwise.
 static bool HasPadding(const Type *Ty, const TargetData &TD) {
+  if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty))
+    return HasPadding(ATy->getElementType(), TD);
+  
+  if (const VectorType *VTy = dyn_cast<VectorType>(Ty))
+    return HasPadding(VTy->getElementType(), TD);
+  
   if (const StructType *STy = dyn_cast<StructType>(Ty)) {
     const StructLayout *SL = TD.getStructLayout(STy);
     unsigned PrevFieldBitOffset = 0;
@@ -1691,12 +1714,8 @@
       if (PrevFieldEnd < SL->getSizeInBits())
         return true;
     }
-
-  } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
-    return HasPadding(ATy->getElementType(), TD);
-  } else if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) {
-    return HasPadding(VTy->getElementType(), TD);
   }
+  
   return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
 }
 
diff --git a/test/Transforms/ScalarRepl/vector_promote.ll b/test/Transforms/ScalarRepl/vector_promote.ll
index dd4251b..5287cbe 100644
--- a/test/Transforms/ScalarRepl/vector_promote.ll
+++ b/test/Transforms/ScalarRepl/vector_promote.ll
@@ -85,3 +85,17 @@
 ; CHECK-NEXT: ret i32
 }
 
+
+;; should not turn into <1 x i64> - It is a banned MMX datatype.
+;; rdar://8380055
+define i64 @test6(<2 x float> %X) {
+	%X_addr = alloca <2 x float>
+        store <2 x float> %X, <2 x float>* %X_addr
+	%P = bitcast <2 x float>* %X_addr to i64*
+	%tmp = load i64* %P
+	ret i64 %tmp
+; CHECK: @test6
+; CHECK-NEXT: bitcast <2 x float> %X to i64
+; CHECK-NEXT: ret i64
+}
+