Index: llvm/trunk/lib/CodeGen/InterleavedAccessPass.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/InterleavedAccessPass.cpp
+++ llvm/trunk/lib/CodeGen/InterleavedAccessPass.cpp
@@ -174,7 +174,7 @@
 /// I.e. <0, LaneLen, ... , LaneLen*(Factor - 1), 1, LaneLen + 1, ...>
 /// E.g. For a Factor of 2 (LaneLen=4): <0, 4, 1, 5, 2, 6, 3, 7>
 static bool isReInterleaveMask(ArrayRef<int> Mask, unsigned &Factor,
-                               unsigned MaxFactor) {
+                               unsigned MaxFactor, unsigned OpNumElts) {
   unsigned NumElts = Mask.size();
   if (NumElts < 4)
     return false;
@@ -246,6 +246,9 @@
 
       if (StartMask < 0)
         break;
+      // We must stay within the vectors; This case can happen with undefs.
+      if (StartMask + LaneLen > OpNumElts*2)
+        break;
     }
 
     // Found an interleaved mask of current factor.
@@ -406,7 +409,8 @@
 
   // Check if the shufflevector is RE-interleave shuffle.
   unsigned Factor;
-  if (!isReInterleaveMask(SVI->getShuffleMask(), Factor, MaxFactor))
+  unsigned OpNumElts = SVI->getOperand(0)->getType()->getVectorNumElements();
+  if (!isReInterleaveMask(SVI->getShuffleMask(), Factor, MaxFactor, OpNumElts))
     return false;
 
   DEBUG(dbgs() << "IA: Found an interleaved store: " << *SI << "\n");
Index: llvm/trunk/test/Transforms/InterleavedAccess/AArch64/interleaved-accesses.ll
===================================================================
--- llvm/trunk/test/Transforms/InterleavedAccess/AArch64/interleaved-accesses.ll
+++ llvm/trunk/test/Transforms/InterleavedAccess/AArch64/interleaved-accesses.ll
@@ -547,3 +547,21 @@
   store <12 x i32> %interleaved.vec, <12 x i32>* %ptr, align 4
   ret void
 }
+
+@g = external global <4 x float>
+
+; The following does not give a valid interleaved store
+; NEON-LABEL: define void @no_interleave
+; NEON-NOT: call void @llvm.aarch64.neon.st2
+; NEON: shufflevector
+; NEON: store
+; NEON: ret void
+; NO_NEON-LABEL: define void @no_interleave
+; NO_NEON: shufflevector
+; NO_NEON: store
+; NO_NEON: ret void
+define void @no_interleave(<4 x float> %a0) {
+  %v0 = shufflevector <4 x float> %a0, <4 x float> %a0, <4 x i32> <i32 0, i32 3, i32 7, i32 undef>
+  store <4 x float> %v0, <4 x float>* @g, align 16
+  ret void
+}
Index: llvm/trunk/test/Transforms/InterleavedAccess/ARM/interleaved-accesses.ll
===================================================================
--- llvm/trunk/test/Transforms/InterleavedAccess/ARM/interleaved-accesses.ll
+++ llvm/trunk/test/Transforms/InterleavedAccess/ARM/interleaved-accesses.ll
@@ -626,3 +626,21 @@
   store <12 x i32> %interleaved.vec, <12 x i32>* %ptr, align 4
   ret void
 }
+
+@g = external global <4 x float>
+
+; The following does not give a valid interleaved store
+; NEON-LABEL: define void @no_interleave
+; NEON-NOT: call void @llvm.arm.neon.vst2
+; NEON: shufflevector
+; NEON: store
+; NEON: ret void
+; NO_NEON-LABEL: define void @no_interleave
+; NO_NEON: shufflevector
+; NO_NEON: store
+; NO_NEON: ret void
+define void @no_interleave(<4 x float> %a0) {
+  %v0 = shufflevector <4 x float> %a0, <4 x float> %a0, <4 x i32> <i32 0, i32 7, i32 1, i32 undef>
+  store <4 x float> %v0, <4 x float>* @g, align 16
+  ret void
+}