Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -11200,10 +11200,19 @@
                                   FirstInChain->getAlignment());
 
   // Replace the last store with the new store
+  DEBUG(dbgs() << "NewStore: "; NewStore->dump(); dbgs() << "NewChain: ";
+        NewChain->dump());
+  unsigned MaxIROrder = 0;
+  for (unsigned i = 0; i < NumStores; ++i)
+    MaxIROrder = std::max(MaxIROrder, StoreNodes[i].MemNode->getIROrder());
+
   CombineTo(LatestOp, NewStore);
   // Erase all other stores.
   for (unsigned i = 0; i < NumStores; ++i) {
-    if (StoreNodes[i].MemNode == LatestOp)
+    DEBUG(dbgs() << "Merged Store [" << i << "]:";
+          StoreNodes[i].MemNode->dump());
+    if (StoreNodes[i].MemNode == LatestOp ||
+        StoreNodes[i].MemNode->getOpcode() == ISD::DELETED_NODE)
       continue;
     StoreSDNode *St = cast<StoreSDNode>(StoreNodes[i].MemNode);
     // ReplaceAllUsesWith will replace all uses that existed when it was
@@ -11216,11 +11225,36 @@
     // When we change it's chain to be St's chain they become identical,
     // get CSEed and the net result is that X is now a use of St.
     // Since we know that St is redundant, just iterate.
-    while (!St->use_empty())
+    // For cases like
+    //   TokF / St1
+    //        \ St2 -> another st
+    // When St1 and St2 are combined to NewStore, we need to make sure that
+    // "another st" is chained to NewStore instead of TokF. There are cases
+    // where one merged st is a use of another merged st directly or
+    // indirectly. Those uses should be replaced with St's chain to avoid
+    // cycles. So all uses of merged store that are topologically strictly
+    // after all merged stores should be replaced with NewStore and the rest
+    // uses be replaced with St's chain.
+    // FIXME: Since we don't have topological order here, we use IROrder.
+    for (auto U : St->uses()) {
+      DEBUG(dbgs() << "Checking User:"; U->dump(););
+      if (U->getIROrder() <= MaxIROrder || U->getOpcode() == ISD::TokenFactor)
+        continue;
+      if (U->getOperand(0) == NewStore)
+        continue;
+      std::vector<SDValue> Ops;
+      for (auto &o : U->ops())
+        Ops.push_back(o);
+      Ops[0] = NewStore; // Change to chain to NewStore.
+      DEBUG(dbgs() << "Morphing : "; U->dump(); dbgs() << " To: ";);
+      DAG.MorphNodeTo(U, U->getOpcode(), U->getVTList(), Ops);
+      DEBUG(U->dump());
+    }
+    if (St->getOpcode() != ISD::DELETED_NODE) {
       DAG.ReplaceAllUsesWith(SDValue(St, 0), St->getChain());
-    deleteAndRecombine(St);
+      deleteAndRecombine(St);
+    }
   }
-
   return true;
 }
 
Index: test/CodeGen/AArch64/merge-store.ll
===================================================================
--- test/CodeGen/AArch64/merge-store.ll
+++ test/CodeGen/AArch64/merge-store.ll
@@ -1,5 +1,6 @@
 ; RUN: llc -march aarch64 %s -o - | FileCheck %s
 ; RUN: llc < %s -mtriple=aarch64-unknown-unknown  -mcpu=cyclone  | FileCheck %s --check-prefix=CYCLONE
+; RUN: llc -mcpu cortex-a53 -march aarch64 %s -o - | FileCheck %s --check-prefix=A53
 
 @g0 = external global <3 x float>, align 16
 @g1 = external global <3 x float>, align 4
@@ -48,3 +49,66 @@
 ; CYCLONE-NEXT:     str   d1, [x0, #32]
 ; CYCLONE-NEXT:     ret
 }
+
+
+; PR26827 - Merge stores causes wrong dependency.
+%struct1 = type { %struct1*, %struct1*, i32, i32, i16, i16, void (i32, i32, i8*)*, i8* }
+@gv0 = internal unnamed_addr global i32 0, align 4
+@gv1 = internal unnamed_addr global %struct1** null, align 8
+
+define void @test(%struct1* %fde, i32 %fd, void (i32, i32, i8*)* %func, i8* %arg)  {
+;CHECK-LABEL: test
+entry:
+;A53: mov [[DATA:w[0-9]+]], w1
+;A53: str q{{[0-9]+}}, {{.*}}
+;A53: str q{{[0-9]+}}, {{.*}}
+;A53: str [[DATA]], {{.*}}
+
+  %0 = bitcast %struct1* %fde to i8*
+  tail call void @llvm.memset.p0i8.i64(i8* %0, i8 0, i64 40, i32 8, i1 false)
+  %state = getelementptr inbounds %struct1, %struct1* %fde, i64 0, i32 4
+  store i16 256, i16* %state, align 8
+  %fd1 = getelementptr inbounds %struct1, %struct1* %fde, i64 0, i32 2
+  store i32 %fd, i32* %fd1, align 8
+  %force_eof = getelementptr inbounds %struct1, %struct1* %fde, i64 0, i32 3
+  store i32 0, i32* %force_eof, align 4
+  %func2 = getelementptr inbounds %struct1, %struct1* %fde, i64 0, i32 6
+  store void (i32, i32, i8*)* %func, void (i32, i32, i8*)** %func2, align 8
+  %arg3 = getelementptr inbounds %struct1, %struct1* %fde, i64 0, i32 7
+  store i8* %arg, i8** %arg3, align 8
+  %call = tail call i32 (i32, i32, ...) @fcntl(i32 %fd, i32 4, i8* %0) #6
+  %1 = load i32, i32* %fd1, align 8
+  %cmp.i = icmp slt i32 %1, 0
+  br i1 %cmp.i, label %if.then.i, label %while.body.i.preheader
+if.then.i:
+  unreachable
+
+while.body.i.preheader:
+  %2 = load i32, i32* @gv0, align 4
+  %3 = icmp eq i32* %fd1, @gv0
+  br i1 %3, label %while.body.i.split, label %while.body.i.split.ver.us.preheader
+
+while.body.i.split.ver.us.preheader:
+  br label %while.body.i.split.ver.us
+
+while.body.i.split.ver.us:
+  %.reg2mem21.0 = phi i32 [ %mul.i.ver.us, %while.body.i.split.ver.us ], [ %2, %while.body.i.split.ver.us.preheader ]
+  %mul.i.ver.us = shl nsw i32 %.reg2mem21.0, 1
+  %4 = icmp sgt i32 %mul.i.ver.us, %1
+  br i1 %4, label %while.end.i, label %while.body.i.split.ver.us
+
+while.body.i.split:
+  br label %while.body.i.split
+
+while.end.i:
+  %call.i = tail call i8* @foo()
+  store i8* %call.i, i8** bitcast (%struct1*** @gv1 to i8**), align 8
+  br label %exit
+
+exit:
+  ret void
+}
+
+declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1)
+declare i32 @fcntl(i32, i32, ...)
+declare noalias i8* @foo()