diff --git a/llvm/include/llvm/CodeGen/MachineMemOperand.h b/llvm/include/llvm/CodeGen/MachineMemOperand.h
--- a/llvm/include/llvm/CodeGen/MachineMemOperand.h
+++ b/llvm/include/llvm/CodeGen/MachineMemOperand.h
@@ -282,17 +282,7 @@
   /// success and failure orderings for an atomic operation.  (For operations
   /// other than cmpxchg, this is equivalent to getSuccessOrdering().)
   AtomicOrdering getMergedOrdering() const {
-    AtomicOrdering Ordering = getSuccessOrdering();
-    AtomicOrdering FailureOrdering = getFailureOrdering();
-    if (FailureOrdering == AtomicOrdering::SequentiallyConsistent)
-      return AtomicOrdering::SequentiallyConsistent;
-    if (FailureOrdering == AtomicOrdering::Acquire) {
-      if (Ordering == AtomicOrdering::Monotonic)
-        return AtomicOrdering::Acquire;
-      if (Ordering == AtomicOrdering::Release)
-        return AtomicOrdering::AcquireRelease;
-    }
-    return Ordering;
+    return getMergedAtomicOrdering(getSuccessOrdering(), getFailureOrdering());
   }
 
   bool isLoad() const { return FlagVals & MOLoad; }
diff --git a/llvm/include/llvm/Support/AtomicOrdering.h b/llvm/include/llvm/Support/AtomicOrdering.h
--- a/llvm/include/llvm/Support/AtomicOrdering.h
+++ b/llvm/include/llvm/Support/AtomicOrdering.h
@@ -133,6 +133,16 @@
   return isAtLeastOrStrongerThan(AO, AtomicOrdering::Release);
 }
 
+/// Return a single atomic ordering that is at least as strong as both the \p A0
+/// and \p Other orderings for an atomic operation.
+inline AtomicOrdering getMergedAtomicOrdering(AtomicOrdering AO,
+                                              AtomicOrdering Other) {
+  if (((AO == AtomicOrdering::Acquire) && (Other == AtomicOrdering::Release)) ||
+      ((AO == AtomicOrdering::Release) && (Other == AtomicOrdering::Acquire)))
+    return AtomicOrdering::AcquireRelease;
+  return isStrongerThan(AO, Other) ? AO : Other;
+}
+
 inline AtomicOrderingCABI toCABI(AtomicOrdering AO) {
   static const AtomicOrderingCABI lookup[8] = {
       /* NotAtomic */ AtomicOrderingCABI::relaxed,
diff --git a/llvm/lib/Target/AMDGPU/SIMemoryLegalizer.cpp b/llvm/lib/Target/AMDGPU/SIMemoryLegalizer.cpp
--- a/llvm/lib/Target/AMDGPU/SIMemoryLegalizer.cpp
+++ b/llvm/lib/Target/AMDGPU/SIMemoryLegalizer.cpp
@@ -126,8 +126,7 @@
            (OrderingAddrSpace & SIAtomicAddrSpace::ATOMIC) !=
                SIAtomicAddrSpace::NONE &&
            (InstrAddrSpace & SIAtomicAddrSpace::ATOMIC) !=
-               SIAtomicAddrSpace::NONE &&
-           !isStrongerThan(FailureOrdering, Ordering));
+               SIAtomicAddrSpace::NONE);
 
     // There is also no cross address space ordering if the ordering
     // address space is the same as the instruction address space and
@@ -651,14 +650,11 @@
       }
 
       SSID = IsSyncScopeInclusion.getValue() ? SSID : MMO->getSyncScopeID();
-      Ordering = isStrongerThan(Ordering, OpOrdering)
-                     ? Ordering
-                     : MMO->getSuccessOrdering();
+      Ordering = getMergedAtomicOrdering(Ordering, OpOrdering);
       assert(MMO->getFailureOrdering() != AtomicOrdering::Release &&
              MMO->getFailureOrdering() != AtomicOrdering::AcquireRelease);
       FailureOrdering =
-          isStrongerThan(FailureOrdering, MMO->getFailureOrdering()) ?
-              FailureOrdering : MMO->getFailureOrdering();
+          getMergedAtomicOrdering(FailureOrdering, MMO->getFailureOrdering());
     }
   }