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

src/compiler/ppc/code-generator-ppc.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/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 1960 matching lines @@
 
     case kAtomicStoreWord8:
       ASSEMBLE_ATOMIC_STORE_INTEGER(stb, stbx);
       break;
     case kAtomicStoreWord16:
       ASSEMBLE_ATOMIC_STORE_INTEGER(sth, sthx);
       break;
     case kAtomicStoreWord32:
       ASSEMBLE_ATOMIC_STORE_INTEGER(stw, stwx);
       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) {
@@ skipping 590 matching lines @@
       padding_size -= v8::internal::Assembler::kInstrSize;
     }
   }
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8