[PhiValues] Adjust unit test to invalidate instructions before deleting them

This should fix a sanitizer buildbot failure.

llvm-svn: 335862
diff --git a/llvm/unittests/Analysis/PhiValuesTest.cpp b/llvm/unittests/Analysis/PhiValuesTest.cpp
index 9a1b5d7..303b0df 100644
--- a/llvm/unittests/Analysis/PhiValuesTest.cpp
+++ b/llvm/unittests/Analysis/PhiValuesTest.cpp
@@ -194,8 +194,8 @@
 
   // Check that replacing an incoming phi then deleting it works
   Phi3->setIncomingValue(1, Val2);
-  Phi2->eraseFromParent();
   PV.invalidateValue(Phi2);
+  Phi2->eraseFromParent();
   PV.invalidateValue(Phi3);
   Vals = PV.getValuesForPhi(Phi1);
   EXPECT_EQ(Vals.size(), 2u);