[SimplifyCFG] Preserve metadata when unconditionalizing branches (constant condition).

When replacing a conditional branch by an unconditional one because the condition is a constant, transfer the metadata to the new branch instruction.

Part of fix for llvm.org/PR50060

Reviewed By: lebedev.ri

Differential Revision: https://reviews.llvm.org/D101141

1 files changed, 6 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 255bb8d..b61c369 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -167,7 +167,12 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions,
       OldDest->removePredecessor(BB);
 
       // Replace the conditional branch with an unconditional one.
-      Builder.CreateBr(Destination);
+      BranchInst *NewBI = Builder.CreateBr(Destination);
+
+      // Transfer the metadata to the new branch instruction.
+      NewBI->copyMetadata(*BI, {LLVMContext::MD_loop, LLVMContext::MD_dbg,
+                                LLVMContext::MD_annotation});
+
       BI->eraseFromParent();
       if (DTU)
         DTU->applyUpdates({{DominatorTree::Delete, BB, OldDest}});