[llvm] [DebugInfo][SimpleLoopUnswitch] Fix missing debug location updates (PR #97662)

[Orlando Cazalet-Hyams via llvm-commits]

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@@ -2334,21 +2338,25 @@ static void unswitchNontrivialInvariants(
   // nuke the initial terminator placed in the split block.
   SplitBB->getTerminator()->eraseFromParent();
   if (FullUnswitch) {
-    // Splice the terminator from the original loop and rewrite its
-    // successors.
-    TI.moveBefore(*SplitBB, SplitBB->end());
-
     // Keep a clone of the terminator for MSSA updates.
     Instruction *NewTI = TI.clone();
     NewTI->insertInto(ParentBB, ParentBB->end());
 
+    // Splice the terminator from the original loop and rewrite its
+    // successors.
+    TI.moveBefore(*SplitBB, SplitBB->end());
+    TI.dropLocation();
+
     // First wire up the moved terminator to the preheaders.
     if (BI) {
       BasicBlock *ClonedPH = ClonedPHs.begin()->second;
       BI->setSuccessor(ClonedSucc, ClonedPH);
       BI->setSuccessor(1 - ClonedSucc, LoopPH);
       Value *Cond = skipTrivialSelect(BI->getCondition());
       if (InsertFreeze)
+        // We don't give any debug location to the new freeze, because the
+        // BI (`dyn_cast<BranchInst>(TI)`) is an in-loop instruction hoisted
+        // out of the loop.
----------------
OCHyams wrote:

nit: Please either add braces around this or hoist the comment out the if statement (see second para [here](https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements)).

https://github.com/llvm/llvm-project/pull/97662