Fix warnings on Win64.

src/x64/codegen-x64.cc

 // Copyright 2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 7741 matching lines @@
 
 #ifdef _WIN64
 typedef double (*ModuloFunction)(double, double);
 // Define custom fmod implementation.
 ModuloFunction CreateModuloFunction() {
   size_t actual_size;
   byte* buffer = static_cast<byte*>(OS::Allocate(Assembler::kMinimalBufferSize,
                                                  &actual_size,
                                                  true));
   CHECK(buffer);
-  Assembler masm(buffer, actual_size);
+  Assembler masm(buffer, static_cast<int>(actual_size));
   // Generated code is put into a fixed, unmovable, buffer, and not into
   // the V8 heap. We can't, and don't, refer to any relocatable addresses
   // (e.g. the JavaScript nan-object).
 
   // Windows 64 ABI passes double arguments in xmm0, xmm1 and
   // returns result in xmm0.
   // Argument backing space is allocated on the stack above
   // the return address.
 
   // Compute x mod y.
@@ skipping 62 matching lines @@
   masm.GetCode(&desc);
   // Call the function from C++.
   return FUNCTION_CAST<ModuloFunction>(buffer);
 }
 
 #endif
 
 #undef __
 
 } }  // namespace v8::internal