D132199 alternative

llvm/include/llvm/Transforms/Scalar/LoopPassManager.h

#endif
   void revisitCurrentLoop() {
     // Tell the currently in-flight pipeline to stop running.
     SkipCurrentLoop = true;
 
     // And insert ourselves back into the worklist.
     Worklist.insert(CurrentL);
   }
 
+  void markLoopNestChanged() {
+    SkipCurrentLoop = true;
+
+    Loop *L = CurrentL;
+    while (auto *PL = L->getParentLoop())
+      L = PL;
+    Worklist.insert(L);
+  }
+
 private:
   friend class llvm::FunctionToLoopPassAdaptor;
 
   /// The \c FunctionToLoopPassAdaptor's worklist of loops to process.
   SmallPriorityWorklist<Loop *, 4> &Worklist;
 
   /// The analysis manager for use in the current loop nest.
   LoopAnalysisManager &LAM;

llvm/lib/Transforms/Scalar/LoopInterchange.cpp

 #include "llvm/InitializePasses.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Scalar/LoopPassManager.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/LoopUtils.h"
 #include <cassert>
 #include <utility>
 #include <vector>
 
 using namespace llvm;
 
PreservedAnalyses LoopInterchangePass::run(LoopNest &LN,
   Function &F = *LN.getParent();
 
   DependenceInfo DI(&F, &AR.AA, &AR.SE, &AR.LI);
   std::unique_ptr<CacheCost> CC =
       CacheCost::getCacheCost(LN.getOutermostLoop(), AR, DI);
   OptimizationRemarkEmitter ORE(&F);
   if (!LoopInterchange(&AR.SE, &AR.LI, &DI, &AR.DT, CC, &ORE).run(LN))
     return PreservedAnalyses::all();
+  U.markLoopNestChanged();
   return getLoopPassPreservedAnalyses();
 }

llvm/lib/Transforms/Scalar/LoopPassManager.cpp

if (!PassPA)
       continue;
 
     // If the loop was deleted, abort the run and return to the outer walk.
     if (U.skipCurrentLoop()) {
       PA.intersect(std::move(*PassPA));
       break;
     }
 
+    assert(L.isOutermost());
+
     // Update the analysis manager as each pass runs and potentially
     // invalidates analyses.
     AM.invalidate(L, *PassPA);
 
     // Finally, we intersect the final preserved analyses to compute the
     // aggregate preserved set for this pass manager.
     PA.intersect(std::move(*PassPA));