diff --git a/lib/Analysis/VectorUtils2.cpp b/lib/Analysis/VectorUtils2.cpp
index b8cac7a9a6..97bae15abe 100644
--- a/lib/Analysis/VectorUtils2.cpp
+++ b/lib/Analysis/VectorUtils2.cpp
@@ -42,6 +42,10 @@ llvm::Value *llvm::findScalarElement(llvm::Value *V, unsigned EltNo) {
     if (EltNo == IIElt)
       return III->getOperand(1);
 
+    // Guard against infinite loop on malformed, unreachable IR.
+    if (III == III->getOperand(0))
+      return nullptr;
+
     // Otherwise, the insertelement doesn't modify the value, recurse on its
     // vector input.
     return findScalarElement(III->getOperand(0), EltNo);
diff --git a/tools/clang/test/CodeGenHLSL/minimal2.ll b/tools/clang/test/CodeGenHLSL/minimal2.ll
new file mode 100644
index 0000000000..846ce51f06
--- /dev/null
+++ b/tools/clang/test/CodeGenHLSL/minimal2.ll
@@ -0,0 +1,49 @@
+; RUN: opt -simplify-inst -S < %s | FileCheck %s
+
+%"class.Texture3D<unsigned int>" = type { i32, %"class.Texture3D<unsigned int>::mips_type" }
+%"class.Texture3D<unsigned int>::mips_type" = type { i32 }
+%dx.types.Handle = type { i8* }
+%dx.types.ResourceProperties = type { i32, i32 }
+
+@"\01?t1@@3V?$Texture3D@I@@A" = external global %"class.Texture3D<unsigned int>", align 4
+
+; Function Attrs: nounwind
+define void @main(<2 x i32> %dtid, i32 %laneID) #0 {
+"\01?f1@@s1@@U1@@Z.exit":
+  br label %if.end.13
+
+while.cond.6.preheader:                           ; No predecessors!
+  ; CHECK: %0 = extractelement <2 x i32> %1, i32 1
+  %0 = extractelement <2 x i32> %2, i32 1
+  %cmp7.14 = icmp ne i32 %0, 0
+  br i1 %cmp7.14, label %while.body, label %if.end.13
+
+while.body:                                       ; preds = %while.cond.6.preheader
+  %1 = extractelement <2 x i32> %2, i32 0
+  ; CHECK: %sub = sub i32 %sub, 1
+  ; CHECK: %1 = insertelement <2 x i32> %1, i32 %sub, i32 0
+  %sub = sub i32 %1, 1
+  %2 = insertelement <2 x i32> %2, i32 %sub, i32 0
+  br label %if.end.13
+
+if.end.13:                                        ; preds = %while.body, %while.cond.6.preheader, %"\01?f1@@s1@@U1@@Z.exit"
+  ret void
+}
+
+; Function Attrs: nounwind
+declare void @llvm.lifetime.start(i64, i8* nocapture) #0
+
+; Function Attrs: nounwind
+declare void @llvm.lifetime.end(i64, i8* nocapture) #0
+
+; Function Attrs: nounwind readnone
+declare i1 @"dx.hl.op.rn.i1 (i32, i1)"(i32, i1) #1
+
+; Function Attrs: nounwind readonly
+declare i32 @"dx.hl.op.ro.i32 (i32, %dx.types.Handle, <4 x i32>)"(i32, %dx.types.Handle, <4 x i32>) #2
+
+; Function Attrs: nounwind readnone
+declare %dx.types.Handle @"dx.hl.createhandle..%dx.types.Handle (i32, %\22class.Texture3D<unsigned int>\22)"(i32, %"class.Texture3D<unsigned int>") #1
+
+; Function Attrs: nounwind readnone
+declare %dx.types.Handle @"dx.hl.annotatehandle..%dx.types.Handle (i32, %dx.types.Handle, %dx.types.ResourceProperties, %\22class.Texture3D<unsigned int>\22)"(i32, %dx.types.Handle, %dx.types.ResourceProperties, %"class.Texture3D<unsigned int>") #1