Index: llvm/lib/Transforms/Scalar/LoopDistribute.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LoopDistribute.cpp
+++ llvm/lib/Transforms/Scalar/LoopDistribute.cpp
@@ -785,6 +785,8 @@
       return fail("HeuristicDisabled", "distribution heuristic disabled");
 
     LLVM_DEBUG(dbgs() << "\nDistributing loop: " << *L << "\n");
+
+    bool Modified = false;
     // We're done forming the partitions set up the reverse mapping from
     // instructions to partitions.
     Partitions.setupPartitionIdOnInstructions();
@@ -792,8 +794,10 @@
     // To keep things simple have an empty preheader before we version or clone
     // the loop.  (Also split if this has no predecessor, i.e. entry, because we
     // rely on PH having a predecessor.)
-    if (!PH->getSinglePredecessor() || &*PH->begin() != PH->getTerminator())
+    if (!PH->getSinglePredecessor() || &*PH->begin() != PH->getTerminator()) {
+      Modified = true;
       SplitBlock(PH, PH->getTerminator(), DT, LI);
+    }
 
     // If we need run-time checks, version the loop now.
     auto PtrToPartition = Partitions.computePartitionSetForPointers(*LAI);
@@ -804,7 +808,8 @@
 
     if (LAI->hasConvergentOp() && !Checks.empty()) {
       return fail("RuntimeCheckWithConvergent",
-                  "may not insert runtime check with convergent operation");
+                  "may not insert runtime check with convergent operation",
+                  Modified);
     }
 
     if (!Pred.isAlwaysTrue() || !Checks.empty()) {
@@ -835,6 +840,7 @@
     // Create identical copies of the original loop for each partition and hook
     // them up sequentially.
     Partitions.cloneLoops();
+    Modified = true;
 
     // Now, we remove the instruction from each loop that don't belong to that
     // partition.
@@ -854,11 +860,11 @@
                                 L->getHeader())
              << "distributed loop";
     });
-    return true;
+    return Modified;
   }
 
-  /// Provide diagnostics then \return with false.
-  bool fail(StringRef RemarkName, StringRef Message) {
+  /// Provide diagnostics then \return with Modified.
+  bool fail(StringRef RemarkName, StringRef Message, bool Modified=false) {
     LLVMContext &Ctx = F->getContext();
     bool Forced = isForced().getValueOr(false);
 
@@ -887,7 +893,7 @@
           *F, L->getStartLoc(), "loop not distributed: failed "
                                 "explicitly specified loop distribution"));
 
-    return false;
+    return Modified;
   }
 
   /// Return if distribution forced to be enabled/disabled for the loop.