[turbofan] Handle void returns in instruction selector.

test/cctest/compiler/test-run-machops.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 <cmath>
 #include <functional>
 #include <limits>
 
 #include "src/base/bits.h"
 #include "src/base/utils/random-number-generator.h"
@@ skipping 64 matching lines @@
         Node* a = Int32Input(&m, j);
         Node* b = Int32Input(&m, k);
         m.Return(m.NewNode(kOps[i], a, b));
         m.GenerateCode();
       }
     }
   }
 }
 
 
+TEST(CodeGenNop) {
+  RawMachineAssemblerTester<void> m;
+  m.Return(m.Int32Constant(0));
+  m.GenerateCode();
+}
+
+
 #if V8_TURBOFAN_BACKEND_64
 static Node* Int64Input(RawMachineAssemblerTester<int64_t>* m, int index) {
   switch (index) {
     case 0:
       return m->Parameter(0);
     case 1:
       return m->Parameter(1);
     case 2:
       return m->Int64Constant(0);
     case 3:
@@ skipping 5174 matching lines @@
                             param, param, param, param));
   FOR_INT32_INPUTS(i) {
     int32_t const x = *i;
     CHECK_EQ(x * 8, m.Call(x));
   }
 }
 
 #endif  // USE_SIMULATOR
 
 #endif  // V8_TURBOFAN_TARGET