Move assert as early as possible.

[sanjoy]

lgtm with a comment inline

llvm/include/llvm/Analysis/LoopInfoImpl.h

249

Since you're touching this code, can you (in a separate change) change this loop to use std::any_of? Even better would be if you add a children function (that directly returns a range) and use llvm::any_of.

[sebpop]

llvm/include/llvm/Analysis/LoopInfoImpl.h

249

Cleanup committed in https://reviews.llvm.org/rL276835

llvm/include/llvm/Analysis/LoopInfoImpl.h

#ifndef NDEBUG
   for ( ; BI != BE; ++BI) {
     BlockT *BB = *BI;
     bool HasInsideLoopSuccs = false;
     bool HasInsideLoopPreds = false;
     SmallVector<BlockT *, 2> OutsideLoopPreds;
 
     typedef GraphTraits<BlockT*> BlockTraits;
     for (typename BlockTraits::ChildIteratorType SI =
            BlockTraits::child_begin(BB), SE = BlockTraits::child_end(BB);
          SI != SE; ++SI)
       if (contains(*SI)) {
         HasInsideLoopSuccs = true;
         break;
       }
+    assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!");
+
     typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
     for (typename InvBlockTraits::ChildIteratorType PI =
            InvBlockTraits::child_begin(BB), PE = InvBlockTraits::child_end(BB);
          PI != PE; ++PI) {
       BlockT *N = *PI;
       if (contains(N))
         HasInsideLoopPreds = true;
       else
         OutsideLoopPreds.push_back(N);
     }
+    assert(HasInsideLoopPreds && "Loop block has no in-loop predecessors!");
 
     if (BB == getHeader()) {
         assert(!OutsideLoopPreds.empty() && "Loop is unreachable!");
     } else if (!OutsideLoopPreds.empty()) {
       // A non-header loop shouldn't be reachable from outside the loop,
       // though it is permitted if the predecessor is not itself actually
       // reachable.
       BlockT *EntryBB = &BB->getParent()->front();
       for (BlockT *CB : depth_first(EntryBB))
         for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i)
           assert(CB != OutsideLoopPreds[i] &&
                  "Loop has multiple entry points!");
     }
-    assert(HasInsideLoopPreds && "Loop block has no in-loop predecessors!");
-    assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!");
     assert(BB != &getHeader()->getParent()->front() &&
            "Loop contains function entry block!");
 
     NumVisited++;
   }
 
   assert(NumVisited == getNumBlocks() && "Unreachable block in loop");