1 files changed, 22 insertions, 3 deletions
diff --git a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
index 085d910..86b2eb0 100644
--- a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -758,12 +758,22 @@ BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
 
   // The new block unconditionally branches to the old block.
   BranchInst *BI = BranchInst::Create(BB, NewBB);
+
+  Loop *L = nullptr;
+  BasicBlock *OldLatch = nullptr;
   // Splitting the predecessors of a loop header creates a preheader block.
-  if (LI && LI->isLoopHeader(BB))
+  if (LI && LI->isLoopHeader(BB)) {
+    L = LI->getLoopFor(BB);
     // Using the loop start line number prevents debuggers stepping into the
     // loop body for this instruction.
-    BI->setDebugLoc(LI->getLoopFor(BB)->getStartLoc());
-  else
+    BI->setDebugLoc(L->getStartLoc());
+
+    // If BB is the header of the Loop, it is possible that the loop is
+    // modified, such that the current latch does not remain the latch of the
+    // loop. If that is the case, the loop metadata from the current latch needs
+    // to be applied to the new latch.
+    OldLatch = L->getLoopLatch();
+  } else
     BI->setDebugLoc(BB->getFirstNonPHIOrDbg()->getDebugLoc());
 
   // Move the edges from Preds to point to NewBB instead of BB.
@@ -798,6 +808,15 @@ BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
     UpdatePHINodes(BB, NewBB, Preds, BI, HasLoopExit);
   }
 
+  if (OldLatch) {
+    BasicBlock *NewLatch = L->getLoopLatch();
+    if (NewLatch != OldLatch) {
+      MDNode *MD = OldLatch->getTerminator()->getMetadata("llvm.loop");
+      NewLatch->getTerminator()->setMetadata("llvm.loop", MD);
+      OldLatch->getTerminator()->setMetadata("llvm.loop", nullptr);
+    }
+  }
+
   return NewBB;
 }