Index: lib/Transforms/Utils/LoopUnrollRuntime.cpp
===================================================================
--- lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -899,13 +899,13 @@
     // Update counter in loop for unrolling.
     // I should be multiply of Count.
     IRBuilder<> B2(NewPreHeader->getTerminator());
-    Value *TestVal = B2.CreateSub(TripCount, ModVal, "unroll_iter");
+    Value *TestVal = B2.CreateNUWSub(TripCount, ModVal, "unroll_iter");
     BranchInst *LatchBR = cast<BranchInst>(Latch->getTerminator());
     B2.SetInsertPoint(LatchBR);
     PHINode *NewIdx = PHINode::Create(TestVal->getType(), 2, "niter",
                                       Header->getFirstNonPHI());
     Value *IdxSub =
-        B2.CreateSub(NewIdx, ConstantInt::get(NewIdx->getType(), 1),
+        B2.CreateNUWSub(NewIdx, ConstantInt::get(NewIdx->getType(), 1),
                      NewIdx->getName() + ".nsub");
     Value *IdxCmp;
     if (LatchBR->getSuccessor(0) == Header)
Index: test/Transforms/LoopUnroll/nuw-backedge.ll
===================================================================
--- /dev/null
+++ test/Transforms/LoopUnroll/nuw-backedge.ll
@@ -0,0 +1,47 @@
+; RUN: opt -loop-unroll -unroll-runtime -unroll-count=4 %s -S -o - | FileCheck %s
+
+; CHECK-LABEL: nuw_trip_count
+; CHECK: entry:
+; CHECK: [[LOOP_GUARD:%[^ ]+]] = icmp eq i32 %N, 0
+; CHECK: br i1 [[LOOP_GUARD]], label {{.*}}, label %for.body.preheader
+
+; CHECK: for.body.preheader:
+; CHECK: [[BECOUNT:%[^ ]+]] = add i32 %N, -1
+; CHECK: %xtraiter = and i32 %N, 3
+; CHECK: [[UNROLL_GUARD:%[^ ]+]] = icmp ult i32 [[BECOUNT]], 3
+; CHECK: br i1 [[UNROLL_GUARD]], label {{.*}}, label %for.body.preheader.new
+
+; CHECK: for.body.preheader.new:
+; CHECK: %unroll_iter = sub nuw i32 %N, %xtraiter
+; CHECK: br label %for.body
+
+; CHECK: for.body:
+; CHECK: %niter = phi i32 [ %unroll_iter, %for.body.preheader.new ], [ [[NSUB3:%[^ ]+]], %for.body ]
+; CHECK: [[NSUB:%[^ ]+]] = sub nuw i32 %niter, 1
+; CHECK: [[NSUB1:%[^ ]+]] = sub nuw i32 [[NSUB]], 1
+; CHECK: [[NSUB2:%[^ ]+]] = sub nuw i32 [[NSUB1]], 1
+; CHECK: [[NSUB3:%[^ ]+]] = sub nuw i32 [[NSUB2]], 1
+; CHECK: [[NCMP:%[^ ]+]] = icmp eq i32 [[NSUB3]], 0
+; CHECK: br i1 [[NCMP]], label {{.*}}, label %for.body
+
+define void @nuw_trip_count(i32* nocapture readonly %a, i32* nocapture readonly %b, i32* noalias nocapture %c, i32 %N) {
+entry:
+  %cmp8 = icmp eq i32 %N, 0
+  br i1 %cmp8, label %for.cond.cleanup, label %for.body
+
+for.cond.cleanup:
+  ret void
+
+for.body:
+  %i.09 = phi i32 [ %inc, %for.body ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i32, i32* %a, i32 %i.09
+  %0 = load i32, i32* %arrayidx, align 4
+  %arrayidx1 = getelementptr inbounds i32, i32* %b, i32 %i.09
+  %1 = load i32, i32* %arrayidx1, align 4
+  %mul = mul nsw i32 %1, %0
+  %arrayidx2 = getelementptr inbounds i32, i32* %c, i32 %i.09
+  store i32 %mul, i32* %arrayidx2, align 4
+  %inc = add nuw i32 %i.09, 1
+  %exitcond = icmp eq i32 %inc, %N
+  br i1 %exitcond, label %for.cond.cleanup, label %for.body
+}
Index: test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll
===================================================================
--- test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll
+++ test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll
@@ -19,7 +19,7 @@
 ; EPILOG-NEXT:    [[TMP1:%.*]] = icmp ult i64 [[TMP0]], 7
 ; EPILOG-NEXT:    br i1 [[TMP1]], label %exit2.loopexit.unr-lcssa, label [[ENTRY_NEW:%.*]]
 ; EPILOG:       entry.new:
-; EPILOG-NEXT:    [[UNROLL_ITER:%.*]] = sub i64 [[TRIP]], [[XTRAITER]]
+; EPILOG-NEXT:    [[UNROLL_ITER:%.*]] = sub nuw i64 [[TRIP]], [[XTRAITER]]
 ; EPILOG-NEXT:    br label [[LOOP_HEADER:%.*]]
 ; EPILOG:  loop_latch.epil:
 ; EPILOG-NEXT:     %epil.iter.sub = add i64 %epil.iter, -1
@@ -147,7 +147,7 @@
 ; EPILOG-NEXT:    [[TMP1:%.*]] = icmp ult i64 [[TMP0]], 7
 ; EPILOG-NEXT:    br i1 [[TMP1]], label %exit2.loopexit.unr-lcssa, label [[ENTRY_NEW:%.*]]
 ; EPILOG:       entry.new:
-; EPILOG-NEXT:    %unroll_iter = sub i64 [[TRIP]], [[XTRAITER]]
+; EPILOG-NEXT:    %unroll_iter = sub nuw i64 [[TRIP]], [[XTRAITER]]
 ; EPILOG-NEXT:    br label [[LOOP_HEADER:%.*]]
 ; EPILOG:  loop_header:
 ; EPILOG-NEXT:     %sum = phi i64 [ 0, %entry.new ], [ %sum.next.7, %loop_latch.7 ]
Index: test/Transforms/LoopUnroll/runtime-unroll-remainder.ll
===================================================================
--- test/Transforms/LoopUnroll/runtime-unroll-remainder.ll
+++ test/Transforms/LoopUnroll/runtime-unroll-remainder.ll
@@ -21,7 +21,7 @@
 ; CHECK: br i1 [[CMP]], label %[[CLEANUP:.*]], label %for.body.lr.ph.new
 
 ; CHECK-LABEL: for.body.lr.ph.new:
-; CHECK: %unroll_iter = sub nsw i64 %wide.trip.count, %xtraiter
+; CHECK: %unroll_iter = sub nuw nsw i64 %wide.trip.count, %xtraiter
 ; CHECK: br label %for.body
 
 ; CHECK: [[CLEANUP]]: