1 files changed, 15 insertions, 4 deletions
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 4fac5d3..b03fb62 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1866,10 +1866,19 @@ bool SimplifyCFGOpt::hoistCommonCodeFromSuccessors(Instruction *TI,
   // If either of the blocks has it's address taken, then we can't do this fold,
   // because the code we'd hoist would no longer run when we jump into the block
   // by it's address.
-  for (auto *Succ : successors(BB))
-    if (Succ->hasAddressTaken() || !Succ->getSinglePredecessor())
+  for (auto *Succ : successors(BB)) {
+    if (Succ->hasAddressTaken())
       return false;
-
+    if (Succ->getSinglePredecessor())
+      continue;
+    // If Succ has >1 predecessors, continue to check if the Succ contains only
+    // one `unreachable` inst. Since executing `unreachable` inst is an UB, we
+    // can relax the condition based on the assumptiom that the program would
+    // never enter Succ and trigger such an UB.
+    if (isa<UnreachableInst>(*Succ->begin()))
+      continue;
+    return false;
+  }
   // The second of pair is a SkipFlags bitmask.
   using SuccIterPair = std::pair<BasicBlock::iterator, unsigned>;
   SmallVector<SuccIterPair, 8> SuccIterPairs;
@@ -7623,7 +7632,9 @@ static bool simplifySwitchOfPowersOfTwo(SwitchInst *SI, IRBuilder<> &Builder,
     auto *DefaultCaseBB = SI->getDefaultDest();
     BasicBlock *SplitBB = SplitBlock(OrigBB, SI, DTU);
     auto It = OrigBB->getTerminator()->getIterator();
-    BranchInst::Create(SplitBB, DefaultCaseBB, IsPow2, It);
+    auto *BI = BranchInst::Create(SplitBB, DefaultCaseBB, IsPow2, It);
+    // BI is handling the default case for SI, and so should share its DebugLoc.
+    BI->setDebugLoc(SI->getDebugLoc());
     It->eraseFromParent();
 
     addPredecessorToBlock(DefaultCaseBB, OrigBB, SplitBB);