Implement optional turbofan UnalignedLoad and UnalignedStore operators

src/compiler/machine-operator-reducer.cc

Index: src/compiler/machine-operator-reducer.cc
diff --git a/src/compiler/machine-operator-reducer.cc b/src/compiler/machine-operator-reducer.cc
index 19ea06205361fef01f29d5a2dc22e6067de10554..1ab438c22c09cb2104891c3977b3c6a5cd25b20c 100644
--- a/src/compiler/machine-operator-reducer.cc
+++ b/src/compiler/machine-operator-reducer.cc
@@ -439,6 +439,8 @@ Reduction MachineOperatorReducer::Reduce(Node* node) {
       return ReduceFloat64InsertHighWord32(node);
     case IrOpcode::kStore:
       return ReduceStore(node);
+    case IrOpcode::kUnalignedStore:
+      return ReduceUnalignedStore(node);
     case IrOpcode::kFloat64Equal:
     case IrOpcode::kFloat64LessThan:
     case IrOpcode::kFloat64LessThanOrEqual:
@@ -712,6 +714,41 @@ Reduction MachineOperatorReducer::ReduceStore(Node* node) {
   return NoChange();
 }
 
+Reduction MachineOperatorReducer::ReduceUnalignedStore(Node* node) {
+  MachineRepresentation const rep = UnalignedStoreRepresentationOf(node->op());
+  Node* const value = node->InputAt(2);
+  switch (value->opcode()) {
+    case IrOpcode::kWord32And: {
+      Uint32BinopMatcher m(value);
+      if (m.right().HasValue() && ((rep == MachineRepresentation::kWord8 &&
+                                    (m.right().Value() & 0xff) == 0xff) ||
+                                   (rep == MachineRepresentation::kWord16 &&
+                                    (m.right().Value() & 0xffff) == 0xffff))) {
+        node->ReplaceInput(2, m.left().node());
+        return Changed(node);
+      }
+      break;
+    }
+    case IrOpcode::kWord32Sar: {
+      Int32BinopMatcher m(value);
+      if (m.left().IsWord32Shl() && ((rep == MachineRepresentation::kWord8 &&
+                                      m.right().IsInRange(1, 24)) ||
+                                     (rep == MachineRepresentation::kWord16 &&
+                                      m.right().IsInRange(1, 16)))) {
+        Int32BinopMatcher mleft(m.left().node());
+        if (mleft.right().Is(m.right().Value())) {
+          node->ReplaceInput(2, mleft.left().node());
+          return Changed(node);
+        }
+      }
+      break;
+    }
+    default:
+      break;
+  }
+  return NoChange();
+}
+
 
 Reduction MachineOperatorReducer::ReduceProjection(size_t index, Node* node) {
   switch (node->opcode()) {