Index: llvm/trunk/lib/Target/AMDGPU/SILoadStoreOptimizer.cpp
===================================================================
--- llvm/trunk/lib/Target/AMDGPU/SILoadStoreOptimizer.cpp
+++ llvm/trunk/lib/Target/AMDGPU/SILoadStoreOptimizer.cpp
@@ -344,7 +344,8 @@
       }
 
       if (MBBI->mayLoadOrStore() &&
-        !memAccessesCanBeReordered(*CI.I, *MBBI, TII, AA)) {
+        (!memAccessesCanBeReordered(*CI.I, *MBBI, TII, AA) ||
+         !canMoveInstsAcrossMemOp(*MBBI, CI.InstsToMove, TII, AA))) {
         // We fail condition #1, but we may still be able to satisfy condition
         // #2.  Add this instruction to the move list and then we will check
         // if condition #2 holds once we have selected the matching instruction.
Index: llvm/trunk/test/CodeGen/AMDGPU/merge-load-store.mir
===================================================================
--- llvm/trunk/test/CodeGen/AMDGPU/merge-load-store.mir
+++ llvm/trunk/test/CodeGen/AMDGPU/merge-load-store.mir
@@ -0,0 +1,70 @@
+# RUN: llc -march=amdgcn -verify-machineinstrs -run-pass si-load-store-opt -o - %s | FileCheck %s
+
+# Check that SILoadStoreOptimizer honors memory dependencies between moved
+# instructions.
+#
+# The following IR snippet would usually be optimized by the peephole optimizer.
+# However, an equivalent situation can occur with buffer instructions as well.
+
+# CHECK-LABEL: name: mem_dependency
+# CHECK: DS_READ2_B32 %0, 0, 1,
+# CHECK: DS_WRITE_B32 %0, killed %1, 64,
+# CHECK: DS_READ2_B32 %0, 16, 17,
+# CHECK: DS_WRITE_B32 killed %0, %5, 0
+
+--- |
+  define amdgpu_kernel void @mem_dependency(i32 addrspace(3)* %ptr.0) nounwind {
+    %ptr.4 = getelementptr i32, i32 addrspace(3)* %ptr.0, i32 1
+    %ptr.64 = getelementptr i32, i32 addrspace(3)* %ptr.0, i32 16
+    %1 = load i32, i32 addrspace(3)* %ptr.0
+    store i32 %1, i32 addrspace(3)* %ptr.64
+    %2 = load i32, i32 addrspace(3)* %ptr.64
+    %3 = load i32, i32 addrspace(3)* %ptr.4
+    %4 = add i32 %2, %3
+    store i32 %4, i32 addrspace(3)* %ptr.0
+    ret void
+  }
+...
+---
+name:            mem_dependency
+alignment:       0
+exposesReturnsTwice: false
+legalized:       false
+regBankSelected: false
+selected:        false
+tracksRegLiveness: true
+liveins:
+  - { reg: '%vgpr0', virtual-reg: '%1' }
+frameInfo:
+  isFrameAddressTaken: false
+  isReturnAddressTaken: false
+  hasStackMap:     false
+  hasPatchPoint:   false
+  stackSize:       0
+  offsetAdjustment: 0
+  maxAlignment:    0
+  adjustsStack:    false
+  hasCalls:        false
+  maxCallFrameSize: 0
+  hasOpaqueSPAdjustment: false
+  hasVAStart:      false
+  hasMustTailInVarArgFunc: false
+body:             |
+  bb.0:
+    liveins: %vgpr0
+
+    %1:vgpr_32 = COPY %vgpr0
+    %m0 = S_MOV_B32 -1
+    %2:vgpr_32 = DS_READ_B32 %1, 0, 0, implicit %m0, implicit %exec :: (load 4 from %ir.ptr.0)
+    DS_WRITE_B32 %1, killed %2, 64, 0, implicit %m0, implicit %exec :: (store 4 into %ir.ptr.64)
+
+    ; Make this load unmergeable, to tempt SILoadStoreOptimizer into merging the
+    ; other two loads.
+    %6:vreg_64 = DS_READ2_B32 %1, 16, 17, 0, implicit %m0, implicit %exec :: (load 8 from %ir.ptr.64, align 4)
+    %3:vgpr_32 = COPY %6.sub0
+    %4:vgpr_32 = DS_READ_B32 %1, 4, 0, implicit %m0, implicit %exec :: (load 4 from %ir.ptr.4)
+    %5:vgpr_32 = V_ADD_I32_e32 killed %3, killed %4, implicit-def %vcc, implicit %exec
+    DS_WRITE_B32 killed %1, %5, 0, 0, implicit killed %m0, implicit %exec :: (store 4 into %ir.ptr.0)
+    S_ENDPGM
+
+...