Index: lib/Transforms/Scalar/LoopUnrollPass.cpp
===================================================================
--- lib/Transforms/Scalar/LoopUnrollPass.cpp
+++ lib/Transforms/Scalar/LoopUnrollPass.cpp
@@ -278,8 +278,9 @@
 public:
   UnrolledInstAnalyzer(unsigned Iteration,
                        DenseMap<Value *, Constant *> &SimplifiedValues,
+                       SmallSet<Instruction *, 16> &DeadInstructions,
                        const Loop *L, ScalarEvolution &SE)
-      : Iteration(Iteration), SimplifiedValues(SimplifiedValues), L(L), SE(SE) {
+      : Iteration(Iteration), SimplifiedValues(SimplifiedValues), DeadInstructions(DeadInstructions), L(L), SE(SE) {
       IterationNumber = SE.getConstant(APInt(64, Iteration));
   }
 
@@ -316,6 +317,17 @@
   /// post-unrolling.
   DenseMap<Value *, Constant *> &SimplifiedValues;
 
+  /// \brief Keeps track of all instructions known to become dead.
+  ///
+  /// After one operand in an instruction is constant-folded and the
+  /// instruction is simplified, the other operand might become dead.
+  /// For example:
+  ///   X = <...>
+  ///   A[i] = X * B[i]
+  /// If at one iteration B[i] becomes 0, A[i] also becomes 0, and we no longer
+  /// need to compute X (assuming it has no other uses).
+  SmallSet<Instruction *, 16> &DeadInstructions;
+
   const Loop *L;
   ScalarEvolution &SE;
 
@@ -542,6 +554,7 @@
 
   SmallSetVector<BasicBlock *, 16> BBWorklist;
   DenseMap<Value *, Constant *> SimplifiedValues;
+  SmallSet<Instruction *, 16> DeadInstructions;
 
   // The estimated cost of the unrolled form of the loop. We try to estimate
   // this by simplifying as much as we can while computing the estimate.
@@ -559,7 +572,8 @@
   // we literally have to go through all loop's iterations.
   for (unsigned Iteration = 0; Iteration < TripCount; ++Iteration) {
     SimplifiedValues.clear();
-    UnrolledInstAnalyzer Analyzer(Iteration, SimplifiedValues, L, SE);
+    DeadInstructions.clear();
+    UnrolledInstAnalyzer Analyzer(Iteration, SimplifiedValues, DeadInstructions, L, SE);
 
     BBWorklist.clear();
     BBWorklist.insert(L->getHeader());
@@ -620,6 +634,25 @@
     // won't find them on later ones too.
     if (UnrolledCost == RolledDynamicCost)
       return None;
+
+    for (unsigned Idx = BBWorklist.size() - 1; Idx != 0; --Idx) {
+      BasicBlock *BB = BBWorklist[Idx];
+      if (BB->empty())
+        continue;
+      for (BasicBlock::reverse_iterator I = BB->rbegin(), E = BB->rend(); I != E; ++I) {
+        if (SimplifiedValues.count(&*I))
+          continue;
+        if (DeadInstructions.count(&*I))
+          continue;
+        if (std::all_of(I->user_begin(), I->user_end(), [&](User *U) {
+              return SimplifiedValues.count(cast<Instruction>(U)) +
+                     DeadInstructions.count(cast<Instruction>(U));
+              })) {
+          UnrolledCost -= TTI.getUserCost(&*I);
+          DeadInstructions.insert(&*I);
+        }
+      }
+    }
   }
   return {{UnrolledCost, RolledDynamicCost}};
 }
Index: test/Transforms/LoopUnroll/full-unroll-heuristics-dce.ll
===================================================================
--- /dev/null
+++ test/Transforms/LoopUnroll/full-unroll-heuristics-dce.ll
@@ -0,0 +1,38 @@
+; RUN: opt < %s -S -loop-unroll -unroll-max-iteration-count-to-analyze=100 -unroll-dynamic-cost-savings-discount=1000 -unroll-threshold=20 -unroll-percent-dynamic-cost-saved-threshold=50 | FileCheck %s
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+@known_constant = internal unnamed_addr constant [10 x i32] [i32 0, i32 0, i32 0, i32 0, i32 1, i32 0, i32 0, i32 0, i32 0, i32 0], align 16
+
+; If a load becomes a constant after loop unrolling, we sometimes can simplify
+; CFG. This test verifies that we handle such cases.
+; After one operand in an instruction is constant-folded and the
+; instruction is simplified, the other operand might become dead.
+; In this test we have::
+; for i in 1..10:
+;   r += A[i] * B[i]
+; A[i] is 0 almost at every iteration, so there is no need in loading B[i] at
+; all.
+
+
+; CHECK-LABEL: @unroll_dce
+; CHECK-NOT:   br i1 %exitcond, label %for.end, label %for.body
+define i32 @unroll_dce(i32* noalias nocapture readonly %b) {
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %for.body, %entry
+  %iv.0 = phi i64 [ 0, %entry ], [ %iv.1, %for.body ]
+  %r.0 = phi i32 [ 0, %entry ], [ %r.1, %for.body ]
+  %arrayidx1 = getelementptr inbounds [10 x i32], [10 x i32]* @known_constant, i64 0, i64 %iv.0
+  %x1 = load i32, i32* %arrayidx1, align 4
+  %arrayidx2 = getelementptr inbounds i32, i32* %b, i64 %iv.0
+  %x2 = load i32, i32* %arrayidx2, align 4
+  %mul = mul i32 %x1, %x2
+  %r.1 = add i32 %mul, %r.0
+  %iv.1 = add nuw nsw i64 %iv.0, 1
+  %exitcond = icmp eq i64 %iv.1, 10
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.body
+  ret i32 %r.1
+}