diff --git a/lib/Transforms/Utils/BasicBlockUtils.cpp b/lib/Transforms/Utils/BasicBlockUtils.cpp
index a2e82f337b9..12de9eed4b8 100644
--- a/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -400,8 +400,12 @@ static void UpdatePHINodes(BasicBlock *OrigBB, BasicBlock *NewBB,
       // If all incoming values for the new PHI would be the same, just don't
       // make a new PHI.  Instead, just remove the incoming values from the old
       // PHI.
-      for (unsigned i = 0, e = Preds.size(); i != e; ++i)
-        PN->removeIncomingValue(Preds[i], false);
+      for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
+        // Explicitly check the BB index here to handle duplicates in Preds.
+        int Idx = PN->getBasicBlockIndex(Preds[i]);
+        if (Idx >= 0)
+          PN->removeIncomingValue(Idx, false);
+      }
     } else {
       // If the values coming into the block are not the same, we need a PHI.
       // Create the new PHI node, insert it into NewBB at the end of the block
diff --git a/test/Transforms/LoopSimplify/dup-preds.ll b/test/Transforms/LoopSimplify/dup-preds.ll
new file mode 100644
index 00000000000..3d1f1499b11
--- /dev/null
+++ b/test/Transforms/LoopSimplify/dup-preds.ll
@@ -0,0 +1,46 @@
+; RUN: opt -loop-simplify -S %s | FileCheck %s
+target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f128:128:128-v128:128:128-n32:64"
+target triple = "powerpc64-bgq-linux"
+
+define fastcc void @do_update_md([3 x float]* nocapture readonly %x) #0 {
+entry:
+  br i1 undef, label %if.end365, label %lor.lhs.false134
+
+lor.lhs.false134:                                 ; preds = %entry
+  br i1 undef, label %lor.lhs.false138, label %if.end365
+
+lor.lhs.false138:                                 ; preds = %lor.lhs.false134
+  br i1 undef, label %lor.lhs.false142, label %if.end365
+
+lor.lhs.false142:                                 ; preds = %lor.lhs.false138
+  br i1 undef, label %for.body276.lr.ph, label %if.end365
+
+for.body276.lr.ph:                                ; preds = %lor.lhs.false142
+  switch i16 undef, label %if.then288 [
+    i16 4, label %for.body344
+    i16 2, label %for.body344
+  ]
+
+if.then288:                                       ; preds = %for.body276.lr.ph
+  br label %for.body305
+
+for.body305:                                      ; preds = %for.body305, %if.then288
+  br label %for.body305
+
+for.body344:                                      ; preds = %for.body344, %for.body276.lr.ph, %for.body276.lr.ph
+  %indvar = phi i64 [ %indvar.next, %for.body344 ], [ 0, %for.body276.lr.ph ]
+  %indvars.iv552 = phi i64 [ %indvars.iv.next553, %for.body344 ], [ 0, %for.body276.lr.ph ], [ 0, %for.body276.lr.ph ]
+  %indvars.iv.next553 = add nuw nsw i64 %indvars.iv552, 1
+  %indvar.next = add i64 %indvar, 1
+  br label %for.body344
+
+; CHECK-LABEL: @do_update_md
+; CHECK: %indvars.iv552 = phi i64 [ %indvars.iv.next553, %for.body344 ], [ 0, %for.body344.preheader ]
+; CHECK: ret
+
+if.end365:                                        ; preds = %lor.lhs.false142, %lor.lhs.false138, %lor.lhs.false134, %entry
+  ret void
+}
+
+attributes #0 = { nounwind }
+