[LoopUnroll] Properly update loopinfo for runtime unrolling by 2

Even when we don't create a remainder loop (that is, when we unroll by 2), we
may duplicate nested loops into the remainder. This is complicated by the fact
the remainder may itself be either inserted into an outer loop, or at the top
level. In the latter case, we may need to create new top-level loops.

Differential Revision: https://reviews.llvm.org/D29156

llvm-svn: 293124

1 files changed, 10 insertions, 5 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
index d5d54cf..8406c56 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) {