diff --git a/lib/Transforms/Vectorize/SLPVectorizer.cpp b/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 9312b4bb4b0..22a2519d67f 100644
--- a/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -1187,10 +1187,21 @@ Value *BoUpSLP::vectorizeTree(TreeEntry *E) {
       PHINode *NewPhi = Builder.CreatePHI(VecTy, PH->getNumIncomingValues());
       E->VectorizedValue = NewPhi;
 
+      // PHINodes may have multiple entries from the same block. We want to
+      // visit every block once.
+      SmallSet<BasicBlock*, 4> VisitedBBs;
+
       for (unsigned i = 0, e = PH->getNumIncomingValues(); i < e; ++i) {
         ValueList Operands;
         BasicBlock *IBB = PH->getIncomingBlock(i);
 
+        if (VisitedBBs.count(IBB)) {
+          NewPhi->addIncoming(NewPhi->getIncomingValueForBlock(IBB), IBB);
+          continue;
+        }
+
+        VisitedBBs.insert(IBB);
+
         // Prepare the operand vector.
         for (unsigned j = 0; j < E->Scalars.size(); ++j)
           Operands.push_back(cast<PHINode>(E->Scalars[j])->
diff --git a/test/Transforms/SLPVectorizer/X86/crash_netbsd_decompress.ll b/test/Transforms/SLPVectorizer/X86/crash_netbsd_decompress.ll
new file mode 100644
index 00000000000..8da3c34a027
--- /dev/null
+++ b/test/Transforms/SLPVectorizer/X86/crash_netbsd_decompress.ll
@@ -0,0 +1,41 @@
+; RUN: opt < %s -basicaa -slp-vectorizer -dce -S -mtriple=x86_64-apple-macosx10.8.0 -mcpu=corei7
+
+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-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.8.0"
+
+%struct.DState = type { i32, i32 }
+
+@b = common global %struct.DState zeroinitializer, align 4
+@d = common global i32 0, align 4
+@c = common global i32 0, align 4
+@a = common global i32 0, align 4
+@e = common global i32 0, align 4
+
+define i32 @fn1() {
+entry:
+  %0 = load i32* getelementptr inbounds (%struct.DState* @b, i32 0, i32 0), align 4
+  %1 = load i32* getelementptr inbounds (%struct.DState* @b, i32 0, i32 1), align 4
+  %2 = load i32* @d, align 4
+  %cond = icmp eq i32 %2, 0
+  br i1 %cond, label %sw.bb, label %save_state_and_return
+
+sw.bb:                                            ; preds = %entry
+  %3 = load i32* @c, align 4
+  %and = and i32 %3, 7
+  store i32 %and, i32* @a, align 4
+  switch i32 %and, label %if.end [
+    i32 7, label %save_state_and_return
+    i32 0, label %save_state_and_return
+  ]
+
+if.end:                                           ; preds = %sw.bb
+  br label %save_state_and_return
+
+save_state_and_return:                            ; preds = %sw.bb, %sw.bb, %if.end, %entry
+  %t.0 = phi i32 [ 0, %if.end ], [ %0, %entry ], [ %0, %sw.bb ], [ %0, %sw.bb ]
+  %f.0 = phi i32 [ 0, %if.end ], [ %1, %entry ], [ 0, %sw.bb ], [ 0, %sw.bb ]
+  store i32 %t.0, i32* getelementptr inbounds (%struct.DState* @b, i32 0, i32 0), align 4
+  store i32 %f.0, i32* getelementptr inbounds (%struct.DState* @b, i32 0, i32 1), align 4
+  ret i32 undef
+}
+