3 files changed, 19 insertions, 10 deletions
diff --git a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
index c2adb7caad6..305122511f5 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
@@ -1160,7 +1160,8 @@ PreservedAnalyses LoopUnrollPass::run(Loop &L, LoopAnalysisManager &AM,
 #endif
 
   // Unrolling can do several things to introduce new loops into a loop nest:
-  // - Partial unrolling clones child loops within the current loop.
+  // - Partial unrolling clones child loops within the current loop. If it
+  //   uses a remainder, then it can also create any number of sibling loops.
   // - Full unrolling clones child loops within the current loop but then
   //   removes the current loop making all of the children appear to be new
   //   sibling loops.
diff --git a/llvm/lib/Transforms/Utils/LoopUnroll.cpp b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
index 7cd69d2b847..5c3c94008d3 100644
--- a/llvm/lib/Transforms/Utils/LoopUnroll.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
@@ -199,11 +199,14 @@ const Loop* llvm::addClonedBlockToLoopInfo(BasicBlock *OriginalBB,
     assert(OriginalBB == OldLoop->getHeader() &&
            "Header should be first in RPO");
 
+    NewLoop = new Loop();
     Loop *NewLoopParent = NewLoops.lookup(OldLoop->getParentLoop());
-    assert(NewLoopParent &&
-           "Expected parent loop before sub-loop in RPO");
-    NewLoop = new Loop;
-    NewLoopParent->addChildLoop(NewLoop);
+
+    if (NewLoopParent)
+      NewLoopParent->addChildLoop(NewLoop);
+    else
+      LI->addTopLevelLoop(NewLoop);
+
     NewLoop->addBasicBlockToLoop(ClonedBB, *LI);
     return OldLoop;
   } else {
diff --git a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
index d5d54cf1d84..8406c563a9c 100644
--- a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -311,17 +311,22 @@ static void CloneLoopBlocks(Loop *L, Value *NewIter,
   }
 
   NewLoopsMap NewLoops;
-  NewLoops[L] = NewLoop;
+  if (NewLoop)
+    NewLoops[L] = NewLoop;
+  else if (ParentLoop)
+    NewLoops[L] = ParentLoop;
+
   // For each block in the original loop, create a new copy,
   // and update the value map with the newly created values.
   for (LoopBlocksDFS::RPOIterator BB = BlockBegin; BB != BlockEnd; ++BB) {
     BasicBlock *NewBB = CloneBasicBlock(*BB, VMap, "." + suffix, F);
     NewBlocks.push_back(NewBB);
-
-    if (NewLoop) {
+   
+    // If we're unrolling the outermost loop, there's no remainder loop,
+    // and this block isn't in a nested loop, then the new block is not
+    // in any loop. Otherwise, add it to loopinfo.
+    if (CreateRemainderLoop || LI->getLoopFor(*BB) != L || ParentLoop)
       addClonedBlockToLoopInfo(*BB, NewBB, LI, NewLoops);
-    } else if (ParentLoop)
-      ParentLoop->addBasicBlockToLoop(NewBB, *LI);
 
     VMap[*BB] = NewBB;
     if (Header == *BB) {