diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -2468,10 +2468,28 @@
 
 // Fence instruction simplification
 Instruction *InstCombinerImpl::visitFenceInst(FenceInst &FI) {
-  // Remove identical consecutive fences.
-  Instruction *Next = FI.getNextNonDebugInstruction();
-  if (auto *NFI = dyn_cast<FenceInst>(Next))
-    if (FI.isIdenticalTo(NFI))
+  auto *NFI = dyn_cast<FenceInst>(FI.getNextNonDebugInstruction());
+  // This check is solely here to handle arbitrary target-dependent syncscopes.
+  // TODO: Can remove if does not matter in practice.
+  if (NFI && FI.isIdenticalTo(NFI))
+    return eraseInstFromFunction(FI);
+
+  // Returns true if FI1 is identical or stronger fence than FI2.
+  auto isIdenticalOrStrongerFence = [](FenceInst *FI1, FenceInst *FI2) {
+    auto FI1SyncScope = FI1->getSyncScopeID();
+    // Consider same scope, where scope is global or single-thread.
+    if (FI1SyncScope != FI2->getSyncScopeID() ||
+        (FI1SyncScope != SyncScope::System &&
+         FI1SyncScope != SyncScope::SingleThread))
+      return false;
+
+    return isAtLeastOrStrongerThan(FI1->getOrdering(), FI2->getOrdering());
+  };
+  if (NFI && isIdenticalOrStrongerFence(NFI, &FI))
+    return eraseInstFromFunction(FI);
+
+  if (auto *PFI = dyn_cast_or_null<FenceInst>(FI.getPrevNonDebugInstruction()))
+    if (isIdenticalOrStrongerFence(PFI, &FI))
       return eraseInstFromFunction(FI);
   return nullptr;
 }
diff --git a/llvm/test/Transforms/InstCombine/consecutive-fences.ll b/llvm/test/Transforms/InstCombine/consecutive-fences.ll
--- a/llvm/test/Transforms/InstCombine/consecutive-fences.ll
+++ b/llvm/test/Transforms/InstCombine/consecutive-fences.ll
@@ -4,7 +4,7 @@
 
 ; CHECK-LABEL: define void @tinkywinky
 ; CHECK-NEXT:   fence seq_cst
-; CHECK-NEXT:   fence syncscope("singlethread") acquire
+; CHECK-NEXT:   fence syncscope("singlethread") acquire 
 ; CHECK-NEXT:   ret void
 ; CHECK-NEXT: }
 
@@ -18,6 +18,17 @@
   ret void
 }
 
+; Arbitrary target dependent scope
+; Is this transform really needed?
+; CHECK-LABEL: test_target_dependent_scope
+; CHECK-NEXT: fence syncscope("MSP430") acquire
+; CHECK-NEXT: ret void
+define void @test_target_dependent_scope() {
+  fence syncscope("MSP430") acquire
+  fence syncscope("MSP430") acquire
+  ret void
+}
+
 ; CHECK-LABEL: define void @dipsy
 ; CHECK-NEXT:   fence seq_cst
 ; CHECK-NEXT:   fence syncscope("singlethread") seq_cst
@@ -31,9 +42,6 @@
 }
 
 ; CHECK-LABEL: define void @patatino
-; CHECK-NEXT:   fence acquire
-; CHECK-NEXT:   fence seq_cst
-; CHECK-NEXT:   fence acquire
 ; CHECK-NEXT:   fence seq_cst
 ; CHECK-NEXT:   ret void
 ; CHECK-NEXT: }
@@ -46,6 +54,47 @@
   ret void
 }
 
+; CHECK-LABEL: define void @weaker_fence_1
+; CHECK-NEXT: fence seq_cst
+; CHECK-NEXT: ret void
+define void @weaker_fence_1() {
+  fence seq_cst
+  fence release
+  fence seq_cst
+  ret void
+}
+
+; CHECK-LABEL: define void @weaker_fence_2
+; CHECK-NEXT: fence seq_cst
+; CHECK-NEXT: ret void
+define void @weaker_fence_2() {
+  fence seq_cst
+  fence release
+  fence seq_cst
+  fence acquire 
+  ret void
+}
+
+; Although acquire is a weaker ordering than seq_cst, it has a system scope,
+; compare to singlethread scope in seq_cst.
+; CHECK-LABEL: acquire_global_neg_test
+; CHECK-NEXT: fence acquire
+; CHECK-NEXT: fence syncscope("singlethread") seq_cst
+define void @acquire_global_neg_test() {
+  fence acquire 
+  fence acquire 
+  fence syncscope("singlethread") seq_cst 
+  ret void
+}
+
+; CHECK-LABEL: acquire_single_thread_scope
+; CHECK-NEXT: fence syncscope("singlethread") seq_cst 
+define void @acquire_single_thread_scope() {
+  fence syncscope("singlethread") acquire 
+  fence syncscope("singlethread") seq_cst 
+  ret void
+}
+
 ; CHECK-LABEL: define void @debug
 ; CHECK-NOT: fence
 ; CHECK: call void @llvm.dbg.value