diff --git a/llvm/lib/Target/ARM/ARMTargetMachine.cpp b/llvm/lib/Target/ARM/ARMTargetMachine.cpp
index bd29a052c372..e794fb71af63 100644
--- a/llvm/lib/Target/ARM/ARMTargetMachine.cpp
+++ b/llvm/lib/Target/ARM/ARMTargetMachine.cpp
@@ -402,6 +402,9 @@ void ARMPassConfig::addPreEmitPass() {
   if (getARMSubtarget().isThumb2())
     addPass(&UnpackMachineBundlesID);
 
-  addPass(createARMOptimizeBarriersPass());
+  // Don't optimize barriers at -O0.
+  if (getOptLevel() != CodeGenOpt::None)
+    addPass(createARMOptimizeBarriersPass());
+
   addPass(createARMConstantIslandPass());
 }
diff --git a/llvm/test/CodeGen/ARM/noopt-dmb-v7.ll b/llvm/test/CodeGen/ARM/noopt-dmb-v7.ll
new file mode 100644
index 000000000000..56a29c8a17e8
--- /dev/null
+++ b/llvm/test/CodeGen/ARM/noopt-dmb-v7.ll
@@ -0,0 +1,15 @@
+; Ensure that adjacent duplicated barriers are not removed at -O0.
+; RUN: llc -O0 < %s -mtriple=armv7 -mattr=+db | FileCheck %s
+
+define i32 @t1() {
+entry:
+  fence seq_cst
+  fence seq_cst
+  fence seq_cst
+  ret i32 0
+}
+
+; CHECK: @ BB#0: @ %entry
+; CHECK-NEXT: dmb ish
+; CHECK-NEXT: dmb ish
+; CHECK-NEXT: dmb ish
diff --git a/llvm/test/CodeGen/ARM/optimize-dmbs-v7.ll b/llvm/test/CodeGen/ARM/optimize-dmbs-v7.ll
index 64f5e202d36a..34a55aa718a3 100644
--- a/llvm/test/CodeGen/ARM/optimize-dmbs-v7.ll
+++ b/llvm/test/CodeGen/ARM/optimize-dmbs-v7.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -mtriple=armv7 -mattr=+db | FileCheck %s
+; RUN: llc -O1 < %s -mtriple=armv7 -mattr=+db | FileCheck %s
 
 @x1 = global i32 0, align 4
 @x2 = global i32 0, align 4