Index: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -11226,26 +11226,34 @@
                                   false, false,
                                   FirstInChain->getAlignment());
 
-  // Replace the last store with the new store
-  CombineTo(LatestOp, NewStore);
-  // Erase all other stores.
-  for (unsigned i = 0; i < NumStores; ++i) {
-    if (StoreNodes[i].MemNode == LatestOp)
-      continue;
-    StoreSDNode *St = cast<StoreSDNode>(StoreNodes[i].MemNode);
-    // ReplaceAllUsesWith will replace all uses that existed when it was
-    // called, but graph optimizations may cause new ones to appear. For
-    // example, the case in pr14333 looks like
-    //
-    //  St's chain -> St -> another store -> X
-    //
-    // And the only difference from St to the other store is the chain.
-    // 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())
-      DAG.ReplaceAllUsesWith(SDValue(St, 0), St->getChain());
-    deleteAndRecombine(St);
+  bool UseAA = CombinerAA.getNumOccurrences() > 0 ? CombinerAA
+                                                  : DAG.getSubtarget().useAA();
+  if (UseAA) {
+    // Replace all merged stores with the new store.
+    for (unsigned i = 0; i < NumStores; ++i)
+      CombineTo(StoreNodes[i].MemNode, NewStore);
+  } else {
+    // Replace the last store with the new store.
+    CombineTo(LatestOp, NewStore);
+    // Erase all other stores.
+    for (unsigned i = 0; i < NumStores; ++i) {
+      if (StoreNodes[i].MemNode == LatestOp)
+        continue;
+      StoreSDNode *St = cast<StoreSDNode>(StoreNodes[i].MemNode);
+      // ReplaceAllUsesWith will replace all uses that existed when it was
+      // called, but graph optimizations may cause new ones to appear. For
+      // example, the case in pr14333 looks like
+      //
+      //  St's chain -> St -> another store -> X
+      //
+      // And the only difference from St to the other store is the chain.
+      // 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())
+        DAG.ReplaceAllUsesWith(SDValue(St, 0), St->getChain());
+      deleteAndRecombine(St);
+    }
   }
 
   return true;
@@ -11778,16 +11786,22 @@
                                   SDValue(NewLoad.getNode(), 1));
   }
 
-  // Replace the last store with the new store.
-  CombineTo(LatestOp, NewStore);
-  // Erase all other stores.
-  for (unsigned i = 0; i < NumElem ; ++i) {
-    // Remove all Store nodes.
-    if (StoreNodes[i].MemNode == LatestOp)
-      continue;
-    StoreSDNode *St = cast<StoreSDNode>(StoreNodes[i].MemNode);
-    DAG.ReplaceAllUsesOfValueWith(SDValue(St, 0), St->getChain());
-    deleteAndRecombine(St);
+  if (UseAA) {
+    // Replace the all stores with the new store.
+    for (unsigned i = 0; i < NumElem; ++i)
+      CombineTo(StoreNodes[i].MemNode, NewStore);
+  } else {
+    // Replace the last store with the new store.
+    CombineTo(LatestOp, NewStore);
+    // Erase all other stores.
+    for (unsigned i = 0; i < NumElem; ++i) {
+      // Remove all Store nodes.
+      if (StoreNodes[i].MemNode == LatestOp)
+        continue;
+      StoreSDNode *St = cast<StoreSDNode>(StoreNodes[i].MemNode);
+      DAG.ReplaceAllUsesOfValueWith(SDValue(St, 0), St->getChain());
+      deleteAndRecombine(St);
+    }
   }
 
   return true;
Index: llvm/trunk/test/CodeGen/AArch64/merge-store.ll
===================================================================
--- llvm/trunk/test/CodeGen/AArch64/merge-store.ll
+++ llvm/trunk/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()