diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -5179,11 +5179,53 @@
   bool ReSchedule = false;
   LLVM_DEBUG(dbgs() << "SLP:  bundle: " << *S.OpValue << "\n");
 
+  auto &&TryScheduleBundle = [this, OldScheduleEnd, SLP](bool ReSchedule,
+                                                         ScheduleData *Bundle) {
+    // The scheduling region got new instructions at the lower end (or it is a
+    // new region for the first bundle). This makes it necessary to
+    // recalculate all dependencies.
+    // It is seldom that this needs to be done a second time after adding the
+    // initial bundle to the region.
+    if (ScheduleEnd != OldScheduleEnd) {
+      for (auto *I = ScheduleStart; I != ScheduleEnd; I = I->getNextNode())
+        doForAllOpcodes(I, [](ScheduleData *SD) { SD->clearDependencies(); });
+      ReSchedule = true;
+    }
+    if (ReSchedule) {
+      resetSchedule();
+      initialFillReadyList(ReadyInsts);
+    }
+    if (Bundle) {
+      LLVM_DEBUG(dbgs() << "SLP: try schedule bundle " << *Bundle
+                        << " in block " << BB->getName() << "\n");
+      calculateDependencies(Bundle, /*InsertInReadyList=*/true, SLP);
+    }
+
+    // Now try to schedule the new bundle or (if no bundle) just calculate
+    // dependencies. As soon as the bundle is "ready" it means that there are no
+    // cyclic dependencies and we can schedule it. Note that's important that we
+    // don't "schedule" the bundle yet (see cancelScheduling).
+    while (((!Bundle && ReSchedule) || (Bundle && !Bundle->isReady())) &&
+           !ReadyInsts.empty()) {
+      ScheduleData *Picked = ReadyInsts.pop_back_val();
+      if (Picked->isSchedulingEntity() && Picked->isReady())
+        schedule(Picked, ReadyInsts);
+    }
+  };
+
   // Make sure that the scheduling region contains all
   // instructions of the bundle.
   for (Value *V : VL) {
-    if (!extendSchedulingRegion(V, S))
+    if (!extendSchedulingRegion(V, S)) {
+      // If the scheduling region got new instructions at the lower end (or it
+      // is a new region for the first bundle). This makes it necessary to
+      // recalculate all dependencies.
+      // Otherwise the compiler may crash trying to incorrectly calculate
+      // dependencies and emit instruction in the wrong order at the actual
+      // scheduling.
+      TryScheduleBundle(/*ReSchedule=*/false, nullptr);
       return None;
+    }
   }
 
   for (Value *V : VL) {
@@ -5212,42 +5254,8 @@
     BundleMember->FirstInBundle = Bundle;
     PrevInBundle = BundleMember;
   }
-  if (ScheduleEnd != OldScheduleEnd) {
-    // The scheduling region got new instructions at the lower end (or it is a
-    // new region for the first bundle). This makes it necessary to
-    // recalculate all dependencies.
-    // It is seldom that this needs to be done a second time after adding the
-    // initial bundle to the region.
-    for (auto *I = ScheduleStart; I != ScheduleEnd; I = I->getNextNode()) {
-      doForAllOpcodes(I, [](ScheduleData *SD) {
-        SD->clearDependencies();
-      });
-    }
-    ReSchedule = true;
-  }
-  if (ReSchedule) {
-    resetSchedule();
-    initialFillReadyList(ReadyInsts);
-  }
   assert(Bundle && "Failed to find schedule bundle");
-
-  LLVM_DEBUG(dbgs() << "SLP: try schedule bundle " << *Bundle << " in block "
-                    << BB->getName() << "\n");
-
-  calculateDependencies(Bundle, true, SLP);
-
-  // Now try to schedule the new bundle. As soon as the bundle is "ready" it
-  // means that there are no cyclic dependencies and we can schedule it.
-  // Note that's important that we don't "schedule" the bundle yet (see
-  // cancelScheduling).
-  while (!Bundle->isReady() && !ReadyInsts.empty()) {
-
-    ScheduleData *pickedSD = ReadyInsts.pop_back_val();
-
-    if (pickedSD->isSchedulingEntity() && pickedSD->isReady()) {
-      schedule(pickedSD, ReadyInsts);
-    }
-  }
+  TryScheduleBundle(ReSchedule, Bundle);
   if (!Bundle->isReady()) {
     cancelScheduling(VL, S.OpValue);
     return None;
diff --git a/llvm/test/Transforms/SLPVectorizer/X86/crash_exceed_scheduling.ll b/llvm/test/Transforms/SLPVectorizer/X86/crash_exceed_scheduling.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Transforms/SLPVectorizer/X86/crash_exceed_scheduling.ll
@@ -0,0 +1,100 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -slp-vectorizer -slp-min-tree-size=2 -slp-threshold=-1000 -slp-max-look-ahead-depth=1 -slp-look-ahead-users-budget=1 -slp-schedule-budget=27 -S -mtriple=x86_64-unknown-linux-gnu | FileCheck %s
+
+define void @exceed(double %0, double %1) {
+; CHECK-LABEL: @exceed(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP2:%.*]] = insertelement <2 x double> poison, double [[TMP0:%.*]], i32 0
+; CHECK-NEXT:    [[TMP3:%.*]] = insertelement <2 x double> [[TMP2]], double [[TMP0]], i32 1
+; CHECK-NEXT:    [[TMP4:%.*]] = insertelement <2 x double> poison, double [[TMP1:%.*]], i32 0
+; CHECK-NEXT:    [[TMP5:%.*]] = insertelement <2 x double> [[TMP4]], double [[TMP1]], i32 1
+; CHECK-NEXT:    [[TMP6:%.*]] = fdiv fast <2 x double> [[TMP3]], [[TMP5]]
+; CHECK-NEXT:    [[TMP7:%.*]] = extractelement <2 x double> [[TMP6]], i32 1
+; CHECK-NEXT:    [[IX:%.*]] = fmul double [[TMP7]], undef
+; CHECK-NEXT:    [[IXX0:%.*]] = fsub double undef, undef
+; CHECK-NEXT:    [[IXX1:%.*]] = fsub double undef, undef
+; CHECK-NEXT:    [[IXX2:%.*]] = fsub double undef, undef
+; CHECK-NEXT:    [[IXX3:%.*]] = fsub double undef, undef
+; CHECK-NEXT:    [[IXX4:%.*]] = fsub double undef, undef
+; CHECK-NEXT:    [[IXX5:%.*]] = fsub double undef, undef
+; CHECK-NEXT:    [[IX1:%.*]] = fmul double [[TMP7]], undef
+; CHECK-NEXT:    [[IXX10:%.*]] = fsub double undef, undef
+; CHECK-NEXT:    [[IXX11:%.*]] = fsub double undef, undef
+; CHECK-NEXT:    [[IXX12:%.*]] = fsub double undef, undef
+; CHECK-NEXT:    [[IXX13:%.*]] = fsub double undef, undef
+; CHECK-NEXT:    [[IXX14:%.*]] = fsub double undef, undef
+; CHECK-NEXT:    [[IXX15:%.*]] = fsub double undef, undef
+; CHECK-NEXT:    [[IXX20:%.*]] = fsub double undef, undef
+; CHECK-NEXT:    [[IXX21:%.*]] = fsub double undef, undef
+; CHECK-NEXT:    [[IXX22:%.*]] = fsub double undef, undef
+; CHECK-NEXT:    [[TMP8:%.*]] = extractelement <2 x double> [[TMP6]], i32 0
+; CHECK-NEXT:    [[IX2:%.*]] = fmul double [[TMP8]], [[TMP8]]
+; CHECK-NEXT:    [[TMP9:%.*]] = insertelement <2 x double> [[TMP2]], double [[TMP1]], i32 1
+; CHECK-NEXT:    [[TMP10:%.*]] = fadd fast <2 x double> [[TMP6]], [[TMP9]]
+; CHECK-NEXT:    [[TMP11:%.*]] = fadd fast <2 x double> [[TMP3]], [[TMP5]]
+; CHECK-NEXT:    [[TMP12:%.*]] = fmul fast <2 x double> [[TMP10]], [[TMP11]]
+; CHECK-NEXT:    [[IXX101:%.*]] = fsub double undef, undef
+; CHECK-NEXT:    [[TMP13:%.*]] = insertelement <2 x double> poison, double [[TMP7]], i32 0
+; CHECK-NEXT:    [[TMP14:%.*]] = insertelement <2 x double> [[TMP13]], double undef, i32 1
+; CHECK-NEXT:    [[TMP15:%.*]] = insertelement <2 x double> <double undef, double poison>, double [[TMP1]], i32 1
+; CHECK-NEXT:    [[TMP16:%.*]] = fmul fast <2 x double> [[TMP14]], [[TMP15]]
+; CHECK-NEXT:    switch i32 undef, label [[BB1:%.*]] [
+; CHECK-NEXT:    i32 0, label [[BB2:%.*]]
+; CHECK-NEXT:    ]
+; CHECK:       bb1:
+; CHECK-NEXT:    br label [[LABEL:%.*]]
+; CHECK:       bb2:
+; CHECK-NEXT:    [[TMP17:%.*]] = extractelement <2 x double> [[TMP16]], i32 0
+; CHECK-NEXT:    [[TMP18:%.*]] = insertelement <2 x double> poison, double [[TMP17]], i32 0
+; CHECK-NEXT:    [[TMP19:%.*]] = extractelement <2 x double> [[TMP16]], i32 1
+; CHECK-NEXT:    [[TMP20:%.*]] = insertelement <2 x double> [[TMP18]], double [[TMP19]], i32 1
+; CHECK-NEXT:    br label [[LABEL]]
+; CHECK:       label:
+; CHECK-NEXT:    [[TMP21:%.*]] = phi <2 x double> [ [[TMP12]], [[BB1]] ], [ [[TMP20]], [[BB2]] ]
+; CHECK-NEXT:    ret void
+;
+entry:
+  %i10 = fdiv fast double %0, %1
+  %ix = fmul double %i10, undef
+  %ixx0 = fsub double undef, undef
+  %ixx1 = fsub double undef, undef
+  %ixx2 = fsub double undef, undef
+  %ixx3 = fsub double undef, undef
+  %ixx4 = fsub double undef, undef
+  %ixx5 = fsub double undef, undef
+  %ix1 = fmul double %i10, undef
+  %ixx10 = fsub double undef, undef
+  %ixx11 = fsub double undef, undef
+  %ixx12 = fsub double undef, undef
+  %ixx13 = fsub double undef, undef
+  %ixx14 = fsub double undef, undef
+  %ixx15 = fsub double undef, undef
+  %ixx20 = fsub double undef, undef
+  %ixx21 = fsub double undef, undef
+  %ixx22 = fsub double undef, undef
+  %i11 = fdiv fast double %0, %1
+  %ix2 = fmul double %i11, %i11
+  %tmp1 = fadd fast double %i11, %0
+  %tmp2 = fadd fast double %0, %1
+  %tmp5 = fmul fast double %tmp1, %tmp2
+  %tmp15 = fadd fast double %i10, %1
+  %tmp25 = fadd fast double %0, %1
+  %tmp6 = fmul fast double %tmp15, %tmp25
+  %tmp555 = fmul fast double %i10, undef
+  %ixx101 = fsub double undef, undef
+  %tmp666 = fmul fast double %1, undef
+  switch i32 undef, label %bb1 [
+  i32 0, label %bb2
+  ]
+
+bb1:                                              ; preds = %entry
+  br label %label
+
+bb2:                                              ; preds = %entry
+  br label %label
+
+label:                                            ; preds = %bb2, %bb1
+  %phi1 = phi double [ %tmp5, %bb1 ], [ %tmp555, %bb2 ]
+  %phi2 = phi double [ %tmp6, %bb1 ], [ %tmp666, %bb2 ]
+  ret void
+}