Fix Windows build.

src/x64/lithium-codegen-x64.cc

 // Copyright 2012 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 927 matching lines @@
     Register reg1 = ToRegister(instr->TempAt(0));
     Register reg2 = ToRegister(instr->result());
 
     // Find b which: 2^b < divisor_abs < 2^(b+1).
     unsigned b = 31 - CompilerIntrinsics::CountLeadingZeros(divisor_abs);
     unsigned shift = 32 + b;  // Precision +1bit (effectively).
     double multiplier_f =
         static_cast<double>(static_cast<uint64_t>(1) << shift) / divisor_abs;
     int64_t multiplier;
     if (multiplier_f - floor(multiplier_f) < 0.5) {
-        multiplier = floor(multiplier_f);
+        multiplier = static_cast<int64_t>(floor(multiplier_f));
     } else {
-        multiplier = floor(multiplier_f) + 1;
+        multiplier = static_cast<int64_t>(floor(multiplier_f)) + 1;
     }
     // The multiplier is a uint32.
     ASSERT(multiplier > 0 &&
            multiplier < (static_cast<int64_t>(1) << 32));
     // The multiply is int64, so sign-extend to r64.
     __ movsxlq(reg1, dividend);
     if (divisor < 0 &&
         instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
       __ neg(reg1);
       DeoptimizeIf(zero, instr->environment());
@@ skipping 4070 matching lines @@
                                FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64