PPC/s390: [Atomics] Make Atomics.exchange a builtin using TF

src/compiler/s390/code-generator-s390.cc

 // Copyright 2015 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/compiler/code-generator.h"
 
 #include "src/compilation-info.h"
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
@@ skipping 2242 matching lines @@
       break;
     case kAtomicStoreWord8:
       __ StoreByte(i.InputRegister(0), i.MemoryOperand(NULL, 1));
       break;
     case kAtomicStoreWord16:
       __ StoreHalfWord(i.InputRegister(0), i.MemoryOperand(NULL, 1));
       break;
     case kAtomicStoreWord32:
       __ StoreW(i.InputRegister(0), i.MemoryOperand(NULL, 1));
       break;
+    case kAtomicExchangeInt8:
+    case kAtomicExchangeUint8:
+    case kAtomicExchangeInt16:
+    case kAtomicExchangeUint16:
+    case kAtomicExchangeWord32:
+      UNREACHABLE();
+      break;
     default:
       UNREACHABLE();
       break;
   }
   return kSuccess;
 }  // NOLINT(readability/fn_size)
 
 // Assembles branches after an instruction.
 void CodeGenerator::AssembleArchBranch(Instruction* instr, BranchInfo* branch) {
   S390OperandConverter i(this, instr);
@@ skipping 525 matching lines @@
       padding_size -= 2;
     }
   }
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8