Index: llvm/lib/Analysis/IVDescriptors.cpp
===================================================================
--- llvm/lib/Analysis/IVDescriptors.cpp
+++ llvm/lib/Analysis/IVDescriptors.cpp
@@ -1025,6 +1025,18 @@
       // Previous. Nothing left to do.
       if (DT->dominates(Previous, OtherPrev) || Previous == OtherPrev)
         return true;
+
+      // If there are other instructions to be sunk after SinkCandidate, remove
+      // and re-insert SinkCandidate can break those instructions. Bail out for
+      // simplicity.
+      const auto SuccIt = find_if(
+          SinkAfter,
+          [SinkCandidate](const std::pair<Instruction *, Instruction *> &P) {
+            return P.second == SinkCandidate;
+          });
+      if (SuccIt != std::end(SinkAfter))
+        return false;
+
       // Otherwise, Previous comes after OtherPrev and SinkCandidate needs to be
       // re-sunk to Previous, instead of sinking to OtherPrev. Remove
       // SinkCandidate from SinkAfter to ensure it's insert position is updated.
Index: llvm/test/Transforms/LoopVectorize/sinkafter.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/LoopVectorize/sinkafter.ll
@@ -0,0 +1,36 @@
+; RUN: opt -loop-vectorize -S %s | FileCheck %s
+
+; Make sure LLVM doesn't generate wrong data in SinkAfter, and causes crash in
+; loop vectorizer.
+
+; CHECK-LABEL: @foo
+; CHECK:       ret
+define void @foo(i64 %count, double %d1, double %d2, ptr %p1, ptr %p2) {
+Entry:
+  br label %Loop
+
+Loop:
+  %v792 = phi double [ %v806, %Loop ], [ %d1, %Entry ]
+  %v793 = phi double [ %v813, %Loop ], [ %d1, %Entry ]
+  %v794 = phi double [ %v793, %Loop ], [ %d2, %Entry ]
+  %v795 = phi i64 [ %v811, %Loop ], [ 1, %Entry ]
+  %v802 = fdiv double %v794, %v792
+  %v803 = getelementptr inbounds [4 x double], ptr %p1, i64 %v795
+  %v804 = fdiv double 1.000000e+00, %v792
+  %v805 = getelementptr inbounds double, ptr %p2, i64 %v795
+  %v806 = load double, ptr %v805, align 8
+  %v807 = fdiv double 1.000000e+00, %v806
+  %v808 = fadd double %v804, %v807
+  %v809 = fmul double %v793, %v808
+  %v810 = fsub double %v802, %v809
+  %v811 = add nuw nsw i64 %v795, 1
+  %v812 = getelementptr inbounds [4 x double], ptr %p1, i64 %v811, i64 2
+  %v813 = load double, ptr %v812, align 8
+  %v815 = fadd double %v813, %v810
+  store double %v815, ptr %v803, align 8
+  %v818 = icmp eq i64 %v811, %count
+  br i1 %v818, label %End, label %Loop
+
+End:
+  ret void
+}