Index: llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
===================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -1209,7 +1209,6 @@
   if (isShuffleExtractingFromLHS(SVI, Mask)) {
     Value *V = LHS;
     unsigned MaskElems = Mask.size();
-    unsigned BegIdx = Mask.front();
     VectorType *SrcTy = cast<VectorType>(V->getType());
     unsigned VecBitWidth = SrcTy->getBitWidth();
     unsigned SrcElemBitWidth = DL.getTypeSizeInBits(SrcTy->getElementType());
@@ -1223,6 +1222,7 @@
           // Only visit bitcasts that weren't previously handled.
           BCs.push_back(BC);
     for (BitCastInst *BC : BCs) {
+      unsigned BegIdx = Mask.front();
       Type *TgtTy = BC->getDestTy();
       unsigned TgtElemBitWidth = DL.getTypeSizeInBits(TgtTy);
       if (!TgtElemBitWidth)
Index: llvm/trunk/test/Transforms/InstCombine/shufflevec-bitcast.ll
===================================================================
--- llvm/trunk/test/Transforms/InstCombine/shufflevec-bitcast.ll
+++ llvm/trunk/test/Transforms/InstCombine/shufflevec-bitcast.ll
@@ -0,0 +1,16 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+define void @test(<16 x i8> %w, i32* %o1, float* %o2) {
+
+; CHECK:       %v.bc = bitcast <16 x i8> %w to <4 x i32>
+; CHECK-NEXT:  %v.extract = extractelement <4 x i32> %v.bc, i32 3
+; CHECK-NEXT:  %v.bc{{[0-9]*}} = bitcast <16 x i8> %w to <4 x float>
+; CHECK-NEXT:  %v.extract{{[0-9]*}} = extractelement <4 x float> %v.bc{{[0-9]*}}, i32 3
+
+  %v = shufflevector <16 x i8> %w, <16 x i8> undef, <4 x i32> <i32 12, i32 13, i32 14, i32 15>
+  %f = bitcast <4 x i8> %v to float
+  %i = bitcast <4 x i8> %v to i32
+  store i32 %i, i32* %o1, align 4
+  store float %f, float* %o2, align 4
+  ret void
+}