Revert of [Atomics] Remove Atomics code stubs; use TF ops

src/compiler/mips/code-generator-mips.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/ast/scopes.h"
 #include "src/compiler/code-generator.h"
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/osr.h"
@@ skipping 1306 matching lines @@
     case kCheckedStoreFloat32:
       ASSEMBLE_CHECKED_STORE_FLOAT(Single, swc1);
       break;
     case kCheckedStoreFloat64:
       ASSEMBLE_CHECKED_STORE_FLOAT(Double, sdc1);
       break;
     case kCheckedLoadWord64:
     case kCheckedStoreWord64:
       UNREACHABLE();  // currently unsupported checked int64 load/store.
       break;
-    case kAtomicLoadInt8:
-    case kAtomicLoadUint8:
-    case kAtomicLoadInt16:
-    case kAtomicLoadUint16:
-    case kAtomicLoadWord32:
-      UNIMPLEMENTED();
-      break;
   }
 }  // NOLINT(readability/fn_size)
 
 
 #define UNSUPPORTED_COND(opcode, condition)                                  \
   OFStream out(stdout);                                                      \
   out << "Unsupported " << #opcode << " condition: \"" << condition << "\""; \
   UNIMPLEMENTED();
 
 static bool convertCondition(FlagsCondition condition, Condition& cc) {
@@ skipping 594 matching lines @@
       padding_size -= v8::internal::Assembler::kInstrSize;
     }
   }
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8