Add roundsd instruction to ia32 and use it in optimized Math.floor.

src/ia32/assembler-ia32.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // 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.
 //
@@ skipping 923 matching lines @@
   void subsd(XMMRegister dst, XMMRegister src);
   void mulsd(XMMRegister dst, XMMRegister src);
   void divsd(XMMRegister dst, XMMRegister src);
   void xorpd(XMMRegister dst, XMMRegister src);
   void xorps(XMMRegister dst, XMMRegister src);
   void sqrtsd(XMMRegister dst, XMMRegister src);
 
   void andpd(XMMRegister dst, XMMRegister src);
 
   void ucomisd(XMMRegister dst, XMMRegister src);
+
+  enum RoundingMode {
+    kRoundToNearest = 0x0,
+    kRoundDown      = 0x1,
+    kRoundUp        = 0x2,
+    kRoundToZero    = 0x3
+  };
+
+  void roundsd(XMMRegister dst, XMMRegister src, RoundingMode mode);
+
   void movmskpd(Register dst, XMMRegister src);
 
   void cmpltsd(XMMRegister dst, XMMRegister src);
 
   void movaps(XMMRegister dst, XMMRegister src);
 
   void movdqa(XMMRegister dst, const Operand& src);
   void movdqa(const Operand& dst, XMMRegister src);
   void movdqu(XMMRegister dst, const Operand& src);
   void movdqu(const Operand& dst, XMMRegister src);
@@ skipping 184 matching lines @@
  private:
   Assembler* assembler_;
 #ifdef DEBUG
   int space_before_;
 #endif
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_ASSEMBLER_IA32_H_