Reland: Introduce a V8_NORETURN macro and use it to make GCC 4.9.2 happy again.

test/cctest/interpreter/test-bytecode-generator.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/v8.h"
 
 #include "src/compiler.h"
 #include "src/interpreter/bytecode-array-iterator.h"
 #include "src/interpreter/bytecode-generator.h"
 #include "src/interpreter/interpreter.h"
@@ skipping 139 matching lines @@
         // one we use to specify an unknown byte.
         CHECK_NE(raw_operand, _);
         if (expected.bytecode[operand_index] == _) {
           continue;
         }
       }
       uint32_t expected_operand;
       switch (Bytecodes::SizeOfOperand(operand_type)) {
         case OperandSize::kNone:
           UNREACHABLE();
+          return;
         case OperandSize::kByte:
           expected_operand =
               static_cast<uint32_t>(expected.bytecode[operand_index]);
           break;
         case OperandSize::kShort:
           expected_operand = Bytecodes::ShortOperandFromBytes(
               &expected.bytecode[operand_index]);
           break;
+        default:
+          UNREACHABLE();
+          return;
       }
       if (raw_operand != expected_operand) {
         std::ostringstream stream;
         stream << "Check failed: expected operand [" << j << "] for bytecode ["
                << bytecode_index << "] to be "
                << static_cast<unsigned int>(expected_operand) << " but got "
                << static_cast<unsigned int>(raw_operand);
         FATAL(stream.str().c_str());
       }
     }
@@ skipping 1078 matching lines @@
   for (size_t i = 0; i < arraysize(snippets); i++) {
     Handle<BytecodeArray> bytecode_array =
         helper.MakeBytecodeForFunctionBody(snippets[i].code_snippet);
     CheckBytecodeArrayEqual(snippets[i], bytecode_array);
   }
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8