Ignore unreachable blocks when doing memory dependence analysis on non-local

loads. It's not really profitable and may result in GVN going into an infinite
loop when it hits constructs like this:

     %x = gep %some.type %x, ...

Found via an LTO build of LLVM.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166490 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/MemoryDependenceAnalysis.cpp

@@ -983,7 +983,7 @@ getNonLocalPointerDepFromBB(const PHITransAddr &Pointer,
     for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
          I != E; ++I) {
       Visited.insert(std::make_pair(I->getBB(), Addr));
-      if (!I->getResult().isNonLocal())
+      if (!I->getResult().isNonLocal() && DT->isReachableFromEntry(I->getBB()))
         Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(), Addr));
     }
     ++NumCacheCompleteNonLocalPtr;
@@ -1029,7 +1029,7 @@ getNonLocalPointerDepFromBB(const PHITransAddr &Pointer,
                                                  NumSortedEntries);
       
       // If we got a Def or Clobber, add this to the list of results.
-      if (!Dep.isNonLocal()) {
+      if (!Dep.isNonLocal() && DT->isReachableFromEntry(BB)) {
         Result.push_back(NonLocalDepResult(BB, Dep, Pointer.getAddr()));
         continue;
       }