Index: llvm/lib/Transforms/Scalar/LoopPassManager.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LoopPassManager.cpp
+++ llvm/lib/Transforms/Scalar/LoopPassManager.cpp
@@ -84,6 +84,7 @@
   // invalid when encountering a loop-nest pass.
   std::unique_ptr<LoopNest> LoopNestPtr;
   bool IsLoopNestPtrValid = false;
+  Loop *OuterMostLoop = &L;
 
   for (size_t I = 0, E = IsLoopNestPass.size(); I != E; ++I) {
     Optional<PreservedAnalyses> PassPA;
@@ -98,9 +99,12 @@
       // If the loop-nest object calculated before is no longer valid,
       // re-calculate it here before running the loop-nest pass.
       if (!IsLoopNestPtrValid) {
-        LoopNestPtr = LoopNest::getLoopNest(L, AR.SE);
+        while (auto *ParentLoop = OuterMostLoop->getParentLoop())
+          OuterMostLoop = ParentLoop;
+        LoopNestPtr = LoopNest::getLoopNest(*OuterMostLoop, AR.SE);
         IsLoopNestPtrValid = true;
       }
+
       PassPA = runSinglePass(*LoopNestPtr, Pass, AM, AR, U, PI);
     }
 
@@ -118,7 +122,7 @@
 
     // Update the analysis manager as each pass runs and potentially
     // invalidates analyses.
-    AM.invalidate(L, *PassPA);
+    AM.invalidate(IsLoopNestPass[I] ? *OuterMostLoop : L, *PassPA);
 
     // Finally, we intersect the final preserved analyses to compute the
     // aggregate preserved set for this pass manager.
@@ -130,7 +134,7 @@
     // After running the loop pass, the parent loop might change and we need to
     // notify the updater, otherwise U.ParentL might gets outdated and triggers
     // assertion failures in addSiblingLoops and addChildLoops.
-    U.setParentLoop(L.getParentLoop());
+    U.setParentLoop((IsLoopNestPass[I] ? *OuterMostLoop : L).getParentLoop());
   }
   return PA;
 }
Index: llvm/test/Transforms/LoopInterchange/interchanged-loop-nest-4.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/LoopInterchange/interchanged-loop-nest-4.ll
@@ -0,0 +1,53 @@
+; REQUIRES: asserts
+; RUN: opt < %s -passes="loop(loop-interchange,loop-interchange)" -cache-line-size=8 -verify-dom-info -verify-loop-info \
+; RUN:  -debug-only=loop-interchange 2>&1 | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+@g_75 = external global i32, align 1
+@g_78 = external global [6 x ptr], align 1
+
+; Loop interchange as a loopnest pass should always construct the loop nest from
+; the outermost loop. This test case runs loop interchange twice. In the loop pass
+; manager, it might occur that after the first loop interchange transformation 
+; the original outermost loop becomes a inner loop hence the loop nest constructed 
+; afterwards for the second loop interchange pass turns out to be a loop list of size
+; 2 and is not valid. This causes functional issues.
+;
+; Make sure we always construct the valid and correct loop nest at the beginning 
+; of execution of a loopnest pass.
+
+; CHECK: Processing LoopList of size = 3
+; CHECK: Processing LoopList of size = 3
+define void @loopnest_01() {
+entry:
+  br label %for.cond5.preheader.i.i.i
+
+for.cond5.preheader.i.i.i:                        ; preds = %for.end16.i.i.i, %entry
+  %storemerge11.i.i.i = phi i32 [ 4, %entry ], [ %sub18.i.i.i, %for.end16.i.i.i ]
+  br label %for.cond8.preheader.i.i.i
+
+for.cond8.preheader.i.i.i:                        ; preds = %for.inc14.i.i.i, %for.cond5.preheader.i.i.i
+  %l_105.18.i.i.i = phi i16 [ 0, %for.cond5.preheader.i.i.i ], [ %add15.i.i.i, %for.inc14.i.i.i ]
+  br label %for.body10.i.i.i
+
+for.body10.i.i.i:                                 ; preds = %for.body10.i.i.i, %for.cond8.preheader.i.i.i
+  %storemerge56.i.i.i = phi i16 [ 5, %for.cond8.preheader.i.i.i ], [ %sub.i.i.i, %for.body10.i.i.i ]
+  %arrayidx.i.i.i = getelementptr [6 x ptr], ptr @g_78, i16 0, i16 %storemerge56.i.i.i
+  store ptr @g_75, ptr %arrayidx.i.i.i, align 1
+  %sub.i.i.i = add nsw i16 %storemerge56.i.i.i, -1
+  br i1 true, label %for.inc14.i.i.i, label %for.body10.i.i.i
+
+for.inc14.i.i.i:                                  ; preds = %for.body10.i.i.i
+  %add15.i.i.i = add nuw nsw i16 %l_105.18.i.i.i, 1
+  %exitcond.not.i.i.i = icmp eq i16 %add15.i.i.i, 6
+  br i1 %exitcond.not.i.i.i, label %for.end16.i.i.i, label %for.cond8.preheader.i.i.i
+
+for.end16.i.i.i:                                  ; preds = %for.inc14.i.i.i
+  %sub18.i.i.i = add nsw i32 %storemerge11.i.i.i, -1
+  %cmp.i10.not.i.i = icmp eq i32 %storemerge11.i.i.i, 0
+  br i1 %cmp.i10.not.i.i, label %func_4.exit.i, label %for.cond5.preheader.i.i.i
+
+func_4.exit.i:                                    ; preds = %for.end16.i.i.i
+  unreachable
+}