Index: lib/Target/ARM/ARMLoadStoreOptimizer.cpp
===================================================================
--- lib/Target/ARM/ARMLoadStoreOptimizer.cpp
+++ lib/Target/ARM/ARMLoadStoreOptimizer.cpp
@@ -1580,7 +1580,8 @@
   const MachineMemOperand &MMO = **MI.memoperands_begin();
 
   // Don't touch volatile memory accesses - we may be changing their order.
-  if (MMO.isVolatile())
+  // TODO: Unclear whether we need to be as defense about atomic operations.
+  if (MMO.isVolatile() || MMO.isAtomic())
     return false;
 
   // Unaligned ldr/str is emulated by some kernels, but unaligned ldm/stm is
@@ -2144,7 +2145,8 @@
   // At the moment, we ignore the memoryoperand's value.
   // If we want to use AliasAnalysis, we should check it accordingly.
   if (!Op0->hasOneMemOperand() ||
-      (*Op0->memoperands_begin())->isVolatile())
+      (*Op0->memoperands_begin())->isVolatile() ||
+      (*Op0->memoperands_begin())->isAtomic())
     return false;
 
   unsigned Align = (*Op0->memoperands_begin())->getAlignment();
Index: lib/Target/Hexagon/HexagonExpandCondsets.cpp
===================================================================
--- lib/Target/Hexagon/HexagonExpandCondsets.cpp
+++ lib/Target/Hexagon/HexagonExpandCondsets.cpp
@@ -733,7 +733,7 @@
     HasDef = true;
   }
   for (auto &Mo : MI->memoperands())
-    if (Mo->isVolatile())
+    if (Mo->isVolatile() || Mo->isAtomic())
       return false;
   return true;
 }
Index: lib/Target/Hexagon/HexagonFrameLowering.cpp
===================================================================
--- lib/Target/Hexagon/HexagonFrameLowering.cpp
+++ lib/Target/Hexagon/HexagonFrameLowering.cpp
@@ -2101,7 +2101,7 @@
         }
         if (!Bad) {
           for (auto *Mo : In.memoperands()) {
-            if (!Mo->isVolatile())
+            if (!Mo->isVolatile() && !Mo->isAtomic())
               continue;
             Bad = true;
             break;
Index: lib/Target/Hexagon/HexagonSplitDouble.cpp
===================================================================
--- lib/Target/Hexagon/HexagonSplitDouble.cpp
+++ lib/Target/Hexagon/HexagonSplitDouble.cpp
@@ -152,8 +152,8 @@
 }
 
 bool HexagonSplitDoubleRegs::isVolatileInstr(const MachineInstr *MI) const {
-  for (auto &I : MI->memoperands())
-    if (I->isVolatile())
+  for (auto &MO : MI->memoperands())
+    if (MO->isVolatile() || MO->isAtomic())
       return true;
   return false;
 }
Index: lib/Target/Lanai/LanaiMemAluCombiner.cpp
===================================================================
--- lib/Target/Lanai/LanaiMemAluCombiner.cpp
+++ lib/Target/Lanai/LanaiMemAluCombiner.cpp
@@ -158,7 +158,8 @@
   const MachineMemOperand *MemOperand = *MI.memoperands_begin();
 
   // Don't move volatile memory accesses
-  if (MemOperand->isVolatile())
+  // TODO: unclear if we need to be as conservative about atomics
+  if (MemOperand->isVolatile() || MemOperand->isAtomic())
     return false;
 
   return true;
Index: lib/Target/SystemZ/SystemZInstrInfo.cpp
===================================================================
--- lib/Target/SystemZ/SystemZInstrInfo.cpp
+++ lib/Target/SystemZ/SystemZInstrInfo.cpp
@@ -1188,7 +1188,7 @@
   // MVCs that turn out to be redundant.
   if (OpNum == 0 && MI.hasOneMemOperand()) {
     MachineMemOperand *MMO = *MI.memoperands_begin();
-    if (MMO->getSize() == Size && !MMO->isVolatile()) {
+    if (MMO->getSize() == Size && !MMO->isVolatile() && !MMO->isAtomic()) {
       // Handle conversion of loads.
       if (isSimpleBD12Move(&MI, SystemZII::SimpleBDXLoad)) {
         return BuildMI(*InsertPt->getParent(), InsertPt, MI.getDebugLoc(),