Index: llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h
===================================================================
--- llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h
+++ llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h
@@ -224,6 +224,10 @@
   /// Plan how to best vectorize, return the best VF and its cost.
   VectorizationFactor plan(bool OptForSize, unsigned UserVF);
 
+  /// Build VPlan with VF = 1 for interleaving without vectorization, if no
+  /// VPlans have been created earlier.
+  void planForInterleaving();
+
   /// Use the VPlan-native path to plan how to best vectorize, return the best
   /// VF and its cost.
   VectorizationFactor planInVPlanNativePath(bool OptForSize, unsigned UserVF);
Index: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -6161,6 +6161,18 @@
   return CM.selectVectorizationFactor(MaxVF);
 }
 
+void  LoopVectorizationPlanner::planForInterleaving() {
+  // Already created VPlans.
+  if (!VPlans.empty())
+    return;
+
+  assert(OrigLoop->empty() && "Inner loop expected.");
+  // Collect Uniform and Scalar instructions after vectorization.
+  CM.collectUniformsAndScalars(1);
+  buildVPlansWithVPRecipes(1, 1);
+  LLVM_DEBUG(printPlans(dbgs()));
+}
+
 void LoopVectorizationPlanner::setBestPlan(unsigned VF, unsigned UF) {
   LLVM_DEBUG(dbgs() << "Setting best plan to VF=" << VF << ", UF=" << UF
                     << '\n');
@@ -7319,15 +7331,15 @@
   // Get user vectorization factor.
   unsigned UserVF = Hints.getWidth();
 
+  // Get user interleave count.
+  unsigned UserIC = Hints.getInterleave();
+
   // Plan how to best vectorize, return the best VF and its cost.
   VectorizationFactor VF = LVP.plan(OptForSize, UserVF);
 
   // Select the interleave count.
   unsigned IC = CM.selectInterleaveCount(OptForSize, VF.Width, VF.Cost);
 
-  // Get user interleave count.
-  unsigned UserIC = Hints.getInterleave();
-
   // Identify the diagnostic messages that should be produced.
   std::pair<StringRef, std::string> VecDiagMsg, IntDiagMsg;
   bool VectorizeLoop = true, InterleaveLoop = true;
@@ -7388,6 +7400,9 @@
     });
     return false;
   } else if (!VectorizeLoop && InterleaveLoop) {
+    // We might reach this code path without building VPlans in LVP.plan().
+    // Make sure we have a plan with VF == 1, for interleaving.
+    LVP.planForInterleaving();
     LLVM_DEBUG(dbgs() << "LV: Interleave Count is " << IC << '\n');
     ORE->emit([&]() {
       return OptimizationRemarkAnalysis(VAPassName, VecDiagMsg.first,
Index: llvm/test/Transforms/LoopVectorize/interleave-need-vplan.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/LoopVectorize/interleave-need-vplan.ll
@@ -0,0 +1,47 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -loop-vectorize -S | FileCheck %s
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+define void @inc(i32 %n) #0 {
+; CHECK-LABEL: @inc(
+; CHECK-NEXT:    br i1 false, label [[DOTLR_PH_PREHEADER:%.*]], label [[DOT_CRIT_EDGE:%.*]]
+; CHECK:       .lr.ph.preheader:
+; CHECK-NEXT:    br i1 true, label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
+; CHECK:       vector.ph:
+; CHECK-NEXT:    br label [[VECTOR_BODY:%.*]]
+; CHECK:       vector.body:
+; CHECK-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[INDUCTION:%.*]] = add i64 [[INDEX]], 0
+; CHECK-NEXT:    [[INDUCTION1:%.*]] = add i64 [[INDEX]], 1
+; CHECK-NEXT:    [[INDEX_NEXT]] = add i64 [[INDEX]], 2
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq i64 [[INDEX_NEXT]], 0
+; CHECK-NEXT:    br i1 [[TMP1]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop !0
+; CHECK:       middle.block:
+; CHECK-NEXT:    [[CMP_N:%.*]] = icmp eq i64 1, 0
+; CHECK-NEXT:    br i1 [[CMP_N]], label [[DOT_CRIT_EDGE_LOOPEXIT:%.*]], label [[SCALAR_PH]]
+; CHECK:       scalar.ph:
+; CHECK-NEXT:    [[BC_RESUME_VAL:%.*]] = phi i64 [ 0, [[MIDDLE_BLOCK]] ], [ 0, [[DOTLR_PH_PREHEADER]] ]
+; CHECK-NEXT:    br label [[DOTLR_PH:%.*]]
+; CHECK:       .lr.ph:
+; CHECK-NEXT:    [[INDVARS_IV:%.*]] = phi i64 [ [[INDVARS_IV_NEXT:%.*]], [[DOTLR_PH]] ], [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ]
+; CHECK-NEXT:    [[INDVARS_IV_NEXT]] = add i64 [[INDVARS_IV]], 1
+; CHECK-NEXT:    br i1 true, label [[DOT_CRIT_EDGE_LOOPEXIT]], label [[DOTLR_PH]], !llvm.loop !3
+; CHECK:       ._crit_edge.loopexit:
+; CHECK-NEXT:    br label [[DOT_CRIT_EDGE]]
+; CHECK:       ._crit_edge:
+; CHECK-NEXT:    ret void
+;
+  br i1 false, label %.lr.ph, label %._crit_edge
+
+.lr.ph:                                           ; preds = %.lr.ph, %0
+  %indvars.iv = phi i64 [ %indvars.iv.next, %.lr.ph ], [ 0, %0 ]
+  %indvars.iv.next = add i64 %indvars.iv, 1
+  br i1 true, label %._crit_edge, label %.lr.ph, !llvm.loop !0
+
+._crit_edge:                                      ; preds = %.lr.ph, %0
+  ret void
+}
+
+!0 = distinct !{!0, !1}
+!1 = !{!"llvm.loop.interleave.count", i32 2}