Index: include/llvm/Transforms/Utils/LoopUtils.h
===================================================================
--- include/llvm/Transforms/Utils/LoopUtils.h
+++ include/llvm/Transforms/Utils/LoopUtils.h
@@ -184,9 +184,14 @@
   /// Returns true if Phi is a first-order recurrence. A first-order recurrence
   /// is a non-reduction recurrence relation in which the value of the
   /// recurrence in the current loop iteration equals a value defined in the
-  /// previous iteration.
-  static bool isFirstOrderRecurrence(PHINode *Phi, Loop *TheLoop,
-                                     DominatorTree *DT);
+  /// previous iteration. \p SinkAfter includes pairs of instructions where the
+  /// first will be rescheduled to appear after the second if/when the loop is
+  /// vectorized. It may be augmented with additional pairs if needed in order
+  /// to handle Phi as a first-order recurrence.
+  static bool
+  isFirstOrderRecurrence(PHINode *Phi, Loop *TheLoop,
+                         DenseMap<Instruction *, Instruction *> &SinkAfter,
+                         DominatorTree *DT);
 
   RecurrenceKind getRecurrenceKind() { return Kind; }
 
Index: lib/Transforms/Utils/LoopUtils.cpp
===================================================================
--- lib/Transforms/Utils/LoopUtils.cpp
+++ lib/Transforms/Utils/LoopUtils.cpp
@@ -528,8 +528,9 @@
   return false;
 }
 
-bool RecurrenceDescriptor::isFirstOrderRecurrence(PHINode *Phi, Loop *TheLoop,
-                                                  DominatorTree *DT) {
+bool RecurrenceDescriptor::isFirstOrderRecurrence(
+    PHINode *Phi, Loop *TheLoop,
+    DenseMap<Instruction *, Instruction *> &SinkAfter, DominatorTree *DT) {
 
   // Ensure the phi node is in the loop header and has two incoming values.
   if (Phi->getParent() != TheLoop->getHeader() ||
@@ -551,12 +552,22 @@
   // Get the previous value. The previous value comes from the latch edge while
   // the initial value comes form the preheader edge.
   auto *Previous = dyn_cast<Instruction>(Phi->getIncomingValueForBlock(Latch));
-  if (!Previous || !TheLoop->contains(Previous) || isa<PHINode>(Previous))
+  if (!Previous || !TheLoop->contains(Previous) || isa<PHINode>(Previous) ||
+      SinkAfter.count(Previous)) // Cannot rely on dominance due to motion.
     return false;
 
   // Ensure every user of the phi node is dominated by the previous value.
   // The dominance requirement ensures the loop vectorizer will not need to
   // vectorize the initial value prior to the first iteration of the loop.
+  if (Phi->hasOneUse()) {
+    auto *I = Phi->user_back();
+    if (I->isCast() && (I->getParent() == Phi->getParent()) && I->hasOneUse() &
+        DT->dominates(Previous, I->user_back())) {
+      SinkAfter[I] = Previous;
+      return true;
+    }
+  }
+    
   for (User *U : Phi->users())
     if (auto *I = dyn_cast<Instruction>(U)) {
       if (!DT->dominates(Previous, I))
Index: lib/Transforms/Vectorize/LoopVectorize.cpp
===================================================================
--- lib/Transforms/Vectorize/LoopVectorize.cpp
+++ lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -1591,6 +1591,9 @@
   /// Return the first-order recurrences found in the loop.
   RecurrenceSet *getFirstOrderRecurrences() { return &FirstOrderRecurrences; }
 
+  /// Return the set of instructions to sink to handle first-order recurrences.
+  DenseMap<Instruction *, Instruction *> &getSinkAfter() { return SinkAfter; }
+
   /// Returns the widest induction type.
   Type *getWidestInductionType() { return WidestIndTy; }
 
@@ -1793,6 +1796,9 @@
   InductionList Inductions;
   /// Holds the phi nodes that are first-order recurrences.
   RecurrenceSet FirstOrderRecurrences;
+  /// Holds instructions that need to sink past other instructions to handle
+  /// first-order recurrences.
+  DenseMap<Instruction *, Instruction *> SinkAfter;
   /// Holds the widest induction type encountered.
   Type *WidestIndTy;
 
@@ -3895,6 +3901,15 @@
   //
   //===------------------------------------------------===//
 
+  // Move instructions to handle first-order recurrences.
+  DenseMap<Instruction *, Instruction *> SinkAfter = Legal->getSinkAfter();
+  for (auto &Entry : SinkAfter) {
+    Entry.first->removeFromParent();
+    Entry.first->insertAfter(Entry.second);
+    DEBUG(dbgs() << "Sinking" << *Entry.first << " after" << *Entry.second
+                 << " to vectorize a 1st order recurrence.\n");
+  }
+
   // Collect instructions from the original loop that will become trivially dead
   // in the vectorized loop. We don't need to vectorize these instructions. For
   // example, original induction update instructions can become dead because we
@@ -5376,7 +5391,8 @@
           continue;
         }
 
-        if (RecurrenceDescriptor::isFirstOrderRecurrence(Phi, TheLoop, DT)) {
+        if (RecurrenceDescriptor::isFirstOrderRecurrence(Phi, TheLoop,
+                                                         SinkAfter, DT)) {
           FirstOrderRecurrences.insert(Phi);
           continue;
         }
Index: test/Transforms/LoopVectorize/first-order-recurrence.ll
===================================================================
--- test/Transforms/LoopVectorize/first-order-recurrence.ll
+++ test/Transforms/LoopVectorize/first-order-recurrence.ll
@@ -2,6 +2,7 @@
 ; RUN: opt < %s -loop-vectorize -force-vector-width=4 -force-vector-interleave=2 -dce -instcombine -S | FileCheck %s --check-prefix=UNROLL
 ; RUN: opt < %s -loop-vectorize -force-vector-width=4 -force-vector-interleave=2 -S | FileCheck %s --check-prefix=UNROLL-NO-IC
 ; RUN: opt < %s -loop-vectorize -force-vector-width=1 -force-vector-interleave=2 -S | FileCheck %s --check-prefix=UNROLL-NO-VF
+; RUN: opt < %s -loop-vectorize -force-vector-width=4 -force-vector-interleave=1 -S | FileCheck %s --check-prefix=SINK-AFTER
 
 target datalayout = "e-m:e-i64:64-i128:128-n32:64-S128"
 
@@ -396,3 +397,32 @@
 for.end:
   ret i32 %val.phi
 }
+; SINK-AFTER-LABEL: sink_after
+; SINK-AFTER: vector.body
+; void sink_after(short *a, int n, int *b) {
+;   for(int i = 0; i < n; i++)
+;     b[i] = (a[i] * a[i + 1]);
+;}
+define void @sink_after(i16* %a, i32* %b, i64 %n) {
+entry:
+  %.pre = load i16, i16* %a
+  br label %for.body
+
+for.body:
+  %0 = phi i16 [ %.pre, %entry ], [ %1, %for.body ]
+  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+  %conv = sext i16 %0 to i32
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %arrayidx2 = getelementptr inbounds i16, i16* %a, i64 %indvars.iv.next
+  %1 = load i16, i16* %arrayidx2
+  %conv3 = sext i16 %1 to i32
+  %add = add nsw i32 %conv3, %conv
+  %arrayidx5 = getelementptr inbounds i32, i32* %b, i64 %indvars.iv
+  store i32 %add, i32* %arrayidx5
+  %exitcond = icmp eq i64 %indvars.iv.next, %n
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:
+  ret void
+}
+