Relax an assert a bit to avoid a crash on unreachable code.

Patch by Duncan Exon Smith with a small tweak by me.

llvm-svn: 222984
diff --git a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
index 187eada..ad72421 100644
--- a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -1361,7 +1361,7 @@
       if (I->getBB() != BB)
         continue;
 
-      assert(I->getResult().isNonLocal() &&
+      assert((I->getResult().isNonLocal() || !DT->isReachableFromEntry(BB)) &&
              "Should only be here with transparent block");
       I->setResult(MemDepResult::getUnknown());
       Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(),