Index: lib/Analysis/ScalarEvolutionExpander.cpp
===================================================================
--- lib/Analysis/ScalarEvolutionExpander.cpp
+++ lib/Analysis/ScalarEvolutionExpander.cpp
@@ -1822,6 +1822,21 @@
   return NumElim;
 }
 
+// If S contains Base, return true. This function is called by
+// findExistingExpansion.
+static bool IsExistExpr(const SCEV *S, const SCEV *Base) {
+  if (S == Base)
+    return true;
+
+  if (const SCEVNAryExpr *NAry = dyn_cast<SCEVNAryExpr>(S)) {
+    for (auto *Op : NAry->operands()) {
+      if (IsExistExpr(Op, Base))
+        return true;
+    }
+  }
+  return false;
+}
+
 Value *SCEVExpander::findExistingExpansion(const SCEV *S,
                                            const Instruction *At, Loop *L) {
   using namespace llvm::PatternMatch;
@@ -1833,18 +1848,45 @@
   for (BasicBlock *BB : ExitingBlocks) {
     ICmpInst::Predicate Pred;
     Instruction *LHS, *RHS;
+    ConstantInt *CRHS;
     BasicBlock *TrueBB, *FalseBB;
 
-    if (!match(BB->getTerminator(),
-               m_Br(m_ICmp(Pred, m_Instruction(LHS), m_Instruction(RHS)),
-                    TrueBB, FalseBB)))
-      continue;
-
-    if (SE.getSCEV(LHS) == S && SE.DT.dominates(LHS, At))
-      return LHS;
+    bool IsMatchCmpII =
+        match(BB->getTerminator(),
+              m_Br(m_ICmp(Pred, m_Instruction(LHS), m_Instruction(RHS)), TrueBB,
+                   FalseBB));
+    bool IsMatchCmpIC = false;
+    if (!IsMatchCmpII) {
+      IsMatchCmpIC =
+          match(BB->getTerminator(),
+                m_Br(m_ICmp(Pred, m_Instruction(LHS), m_ConstantInt(CRHS)),
+                     TrueBB, FalseBB));
+    }
 
-    if (SE.getSCEV(RHS) == S && SE.DT.dominates(RHS, At))
-      return RHS;
+    if (!IsMatchCmpII && !IsMatchCmpIC) {
+      continue;
+    }
+    if (IsMatchCmpII) {
+      if (SE.getSCEV(LHS) == S && SE.DT.dominates(LHS, At))
+        return LHS;
+
+      if (SE.getSCEV(RHS) == S && SE.DT.dominates(RHS, At))
+        return RHS;
+    } else if (IsMatchCmpIC) {
+      if (IsExistExpr(SE.getSCEV(LHS), S) && SE.DT.dominates(LHS, At)) {
+        if (const SCEVAddRecExpr *AR =
+                dyn_cast<SCEVAddRecExpr>(SE.getSCEVAtScope(LHS, L))) {
+          if (AR->getStepRecurrence(SE)->getSCEVType() == scConstant) {
+            if (const SCEVConstant *SCConst =
+                    cast<SCEVConstant>(AR->getOperand(1))) {
+              if (SCConst->getValue()->isOne() ||
+                  SCConst->getValue()->isMinusOne())
+                return LHS;
+            }
+          }
+        }
+      }
+    }
   }
 
   // There is potential to make this significantly smarter, but this simple
Index: lib/Transforms/Utils/LoopUnrollRuntime.cpp
===================================================================
--- lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -313,7 +313,10 @@
   BasicBlock *Header = L->getHeader();
   const DataLayout &DL = Header->getModule()->getDataLayout();
   SCEVExpander Expander(*SE, DL, "loop-unroll");
-  if (!AllowExpensiveTripCount && Expander.isHighCostExpansion(TripCountSC, L))
+  BranchInst *ExtingBlockBR =
+      cast<BranchInst>(L->getExitingBlock()->getTerminator());
+  if (!AllowExpensiveTripCount &&
+      Expander.isHighCostExpansion(TripCountSC, L, ExtingBlockBR))
     return false;
 
   // We only handle cases when the unroll factor is a power of 2.
Index: test/Transforms/LoopUnroll/high-cost-trip-count-computation.ll
===================================================================
--- test/Transforms/LoopUnroll/high-cost-trip-count-computation.ll
+++ test/Transforms/LoopUnroll/high-cost-trip-count-computation.ll
@@ -24,4 +24,30 @@
   ret i32 0
 }
 
+;; We expect this loop to be unrolled, because IV's step is minus one.
+;; In this case, we don't need to generate dvision for computing trip count.
+
+define i32 @test2(i64* %loc, i64 %conv7) {
+; CHECK-LABEL: @test2(
+; CHECK-LABEL: for.body.prol
+entry:
+  %rem0 = load i64, i64* %loc, align 8, !tbaa !0
+  %div11 = udiv i64 %rem0, %conv7
+  %cmp.i38 = icmp ugt i64 %div11, 1
+  %div12 = select i1 %cmp.i38, i64 %div11, i64 1
+  br label %for.body
+for.body:
+  %rem1 = phi i64 [ %rem0, %entry ], [ %rem2, %for.body ]
+  %k1 = phi i64 [ %div12, %entry ], [ %dec, %for.body ]
+  %mul1 = mul i64 %rem1, 48271
+  %rem2 = urem i64 %mul1, 2147483647
+  %dec = add i64 %k1, -1
+  %cmp = icmp eq i64 %dec, 0
+  br i1 %cmp, label %exit, label %for.body
+exit:
+  %rem3 = phi i64 [ %rem2, %for.body ]
+  store i64 %rem3, i64* %loc, align 8, !tbaa !0
+  ret i32 0
+}
+
 !0 = !{i64 1, i64 100}