X64: Convert doubles to int32 inline (without calling runtime).

src/x64/macro-assembler-x64.h

 // 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
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   // function register will be untouched; the other register may be
   // clobbered.
   void TryGetFunctionPrototype(Register function,
                                Register result,
                                Label* miss);
 
   // Generates code for reporting that an illegal operation has
   // occurred.
   void IllegalOperation(int num_arguments);
 
+
+  // Converts a double precission floating point number to a 32-bit
+  // integer. It is equivalent to first converting the double to an
+  // integer by truncation (dropping decimals) and then finding the
+  // remainder modulo 2^32 of the result. Non-numbers like infinites
+  // and NaN are converted to zero.
+  // Uses rcx register as well, and dst can be same register as scratch,
+  // or same register as src, but src and scracth cannot be the same.
+  void DoubleToInteger32(Register dst, Register src, Register scratch);
+
   // ---------------------------------------------------------------------------
   // Runtime calls
 
   // Call a code stub.
   void CallStub(CodeStub* stub);
 
   // Return from a code stub after popping its arguments.
   void StubReturn(int argc);
 
   // Call a runtime routine.
@@ skipping 152 matching lines @@
   }                                                                       \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_MACRO_ASSEMBLER_X64_H_