Revert r137655. There is some question about whether the 'landingpad'
instruction should be marked as potentially reading and/or writing memory.

llvm-svn: 137863
diff --git a/llvm/lib/Analysis/LoopInfo.cpp b/llvm/lib/Analysis/LoopInfo.cpp
index 9a7c50d..36fd598 100644
--- a/llvm/lib/Analysis/LoopInfo.cpp
+++ b/llvm/lib/Analysis/LoopInfo.cpp
@@ -99,6 +99,9 @@
     return false;
   if (I->mayReadFromMemory())
     return false;
+  // The landingpad instruction is immobile.
+  if (isa<LandingPadInst>(I))
+    return false;
   // Determine the insertion point, unless one was given.
   if (!InsertPt) {
     BasicBlock *Preheader = getLoopPreheader();